Aims. This study aimed to investigate the clinical characteristics and outcomes associated with culture-negative limb osteomyelitis patients. Methods. A total of 1,047 limb osteomyelitis patients aged 18 years or older who underwent debridement and intraoperative culture at our clinic centre from 1 January 2011 to 31 December 2020 were included. Patient characteristics, infection eradication, and complications were analyzed between culture-negative and culture-positive cohorts. Results. Of these patients, 264 (25.2%) had negative cultures. Patients with a culture-negative compared with a culture-positive status were more likely to have the following characteristics: younger age (≤ 40 years) (113/264 (42.8%) vs 257/783 (32.8%); p = 0.004), a haematogenous aetiology (75/264 (28.4%) vs 150/783 (19.2%); p = 0.002), Cierny-Mader host A (79/264 (29.9%) vs 142/783 (18.1%); p < 0.001), antibiotic use before sampling (34/264 (12.9%) vs 41/783 (5.2%); p＜0.001), fewer taken samples (n＜3) (48/264 (18.2%) vs 60/783 (7.7%); p＜0.001), and less frequent presentation with a sinus (156/264 (59.1%) vs 665/783 (84.9%); p < 0.001). After initial treatments of first-debridement and antimicrobial, infection eradication was inferior in culture-positive osteomyelitis patients, with a 2.24-fold increase (odds ratio 2.24 (95% confidence interval 1.42 to 3.52)) in the redebridement rate following multivariate analysis. No statistically significant differences were found in long-term recurrence and complications within the two-year follow-up. Conclusion. We identified several factors being associated with the culture-negative result in osteomyelitis patients. In addition, the data also indicate that culture negativity is a positive prognostic factor in early infection eradication. These results constitute the basis of optimizing clinical management and patient consultations. Cite this article: Bone Joint J 2024;106-B(7):720–727

Aims. In the absence of an identified organism, single-stage revision is contraindicated in prosthetic joint infection (PJI). However, no studies have examined the use of intra-articular antibiotics in combination with single-stage revision in these cases. In this study, we present the results of single-stage revision using intra-articular antibiotic infusion for treating culture-negative (CN) PJI. Methods. A retrospective analysis between 2009 and 2016 included 51 patients with CN PJI who underwent single-stage revision using intra-articular antibiotic infusion; these were compared with 192 culture-positive (CP) patients. CN patients were treated according to a protocol including intravenous vancomycin and a direct intra-articular infusion of imipenem and vancomycin alternately used in the morning and afternoon. In the CP patients, pathogen-sensitive intravenous (IV) antibiotics were administered for a mean of 16 days (12 to 21), and for resistant cases, additional intra-articular antibiotics were used. The infection healing rate, Harris Hip Score (HHS), and Hospital for Special Surgery (HSS) knee score were compared between CN and CP groups. Results. Of 51 CN patients, 46 (90.2%) required no additional medical treatment for recurrent infection at a mean of 53.2 months (24 to 72) of follow-up. Impaired kidney function occurred in two patients, and one patient had a local skin rash. No significant difference in the infection control rate was observed between CN and CP PJIs (90.2% (46/51) versus 94.3% (181/192); p = 0.297). The HHS of the CN group showed no substantial difference from that of CP cases (79 versus 81; p = 0.359). However, the CN group showed a mean HSS inferior to that of the CP group (76 versus 80; p = 0.027). Conclusion. Single-stage revision with direct intra-articular antibiotic infusion can be effective in treating CN PJI, and can achieve an infection control rate similar to that in CP patients. However, in view of systemic toxicity, local adverse reactions, and higher costs, additional strong evidence is needed to verify these treatment regimens. Cite this article: Bone Joint J 2020;102-B(3):336–344

Aims. The aim of this study was to analyze the prevalence of culture-negative periprosthetic joint infections (PJIs) when adequate methods of culture are used, and to evaluate the outcome in patients who were treated with antibiotics for a culture-negative PJI compared with those in whom antibiotics were withheld. Methods. A multicentre observational study was undertaken: 1,553 acute and 1,556 chronic PJIs, diagnosed between 2013 and 2018, were retrospectively analyzed. Culture-negative PJIs were diagnosed according to the Muskuloskeletal Infection Society (MSIS), International Consensus Meeting (ICM), and European Bone and Joint Society (EBJIS) definitions. The primary outcome was recurrent infection, and the secondary outcome was removal of the prosthetic components for any indication, both during a follow-up period of two years. Results. None of the acute PJIs and 70 of the chronic PJIs (4.7%) were culture-negative; a total of 36 culture-negative PJIs (51%) were treated with antibiotics, particularly those with histological signs of infection. After two years of follow-up, no recurrent infections occurred in patients in whom antibiotics were withheld. The requirement for removal of the components for any indication during follow-up was not significantly different in those who received antibiotics compared with those in whom antibiotics were withheld (7.1% vs 2.9%; p = 0.431). Conclusion. When adequate methods of culture are used, the incidence of culture-negative PJIs is low. In patients with culture-negative PJI, antibiotic treatment can probably be withheld if there are no histological signs of infection. In all other patients, diagnostic efforts should be made to identify the causative microorganism by means of serology or molecular techniques. Cite this article: Bone Joint J 2022;104-B(1):183–188

Aims. Removal of infected components and culture-directed antibiotics are important for the successful treatment of chronic periprosthetic joint infection (PJI). However, as many as 27% of chronic PJI patients yield negative culture results. Although culture negativity has been thought of as a contraindication to one-stage revision, data supporting this assertion are limited. The aim of our study was to report on the clinical outcomes for one-stage and two-stage exchange arthroplasty performed in patients with chronic culture-negative PJI. Methods. A total of 105 consecutive patients who underwent revision arthroplasty for chronic culture-negative PJI were retrospectively evaluated. One-stage revision arthroplasty was performed in 30 patients, while 75 patients underwent two-stage exchange, with a minimum of one year's follow-up. Reinfection, re-revision for septic and aseptic reasons, amputation, readmission, mortality, and length of stay were compared between the two treatment strategies. Results. The patient demographic characteristics did not differ significantly between the groups. At a mean follow-up of 4.2 years, the treatment failure for reinfection for one-stage and two-stage revision was five (16.7%) and 15 patients (20.0%) (p = 0.691), and for septic re-revision was four (13.3%) and 11 patients (14.7%) (p = 0.863), respectively. No significant differences were observed between one-stage and two-stage revision for 30- 60- and 90-day readmissions (10.0% vs 8.0%; p = 0.714; 16.7% vs 9.3%; p = 0.325; and 26.7% vs 10.7%; p = 0.074), one-year mortality (3.3% vs 4.0%; p > 0.999), and amputation (3.3% vs 1.3%; p = 0.496). Conclusion. In this non-randomized study, one-stage revision arthroplasty demonstrated similar outcomes including reinfection, re-revision, and readmission rates for the treatment of chronic culture-negative PJI after TKA and THA compared to two-stage revision. This suggests culture negativity may not be a contraindication to one-stage revision arthroplasty for chronic culture-negative PJI in selected patients. Cite this article: Bone Joint J 2021;103-B(3):515–521

Background. Recent reports demonstrate that Next Generation Sequencing (NGS) facilitates pathogen identification in the context of culture-negative PJI; however the clinical relevance of the polymicrobial genomic signal often generated remains unknown. This study was conceived to explore: (1) the ability of NGS to identify pathogens in culture-negative PJI; and (2) determine whether organisms detected by NGS, as part of a prospective observational study, had any role in later failure of patients undergoing surgical treatment for PJI. Methods. In this prospective study samples were collected in 238 consecutive patients undergoing revision total hip and knee arthroplasties. Of these 83 patients (34.9%) had PJI, as determined using the Musculoskeletal Infection Society (MSIS) criteria, and of these 20 were culture-negative (CN-PJI). Synovial fluid, deep tissue and swabs were obtained at the time of surgery and sent for NGS and culture/MALDI-TOF. Patients undergoing reimplantation were excluded. Treatment failure was assessed using the previously described Delphi criteria. In cases of re-operation, organisms present were confirmed by culture and MALDI-TOF. Concordance of the infecting pathogen(s) at failure with the NGS analysis at the initial stage CN- PJI procedure was determined. Results. Twenty cases of culture-negative PJI were identified (Figure 1). CNPJI rate in our samples was 24%. NGS was positive in 18 cases. Two cases were both culture and NGS negative. Eight CN-PJIs (8/20; 40%) failed by re-operation with infection recurrence confirmed on culture. In 7 of these 8 cases (88%), the organism at failure was present on NGS at the time of the initial CN-PJI procedure. The remaining case failed with a new organism, via likely hematogenous seeding from an inter-current infection (Figure 2). NGS detected several organisms in CN-PJI cases (Figure 3). Discussion. CN-PJI is often associated with polymicrobial genomic organism profile. Furthermore, most of the failures by infection recurrence were due to an organism previously detected by NGS. Our findings suggest some cases of PJI may be polymicrobial and escape detection using conventional culture. Further multi-institutional work with larger numbers and longer clinical follow-up is required for validation

Aim. Identification of the causal pathogen is crucial in the management of periprosthetic joint infection (PJI) of the hip. Unfortunately, it was often difficult and negative culture could be a common findings. This situation made the treatment of PJI of the hip became more challenging. The negative culture finding resulted in a doubtful diagnosis of infection, and poses difficulty in choosing the appropriate antibiotics. Here we compared the treatment outcome of two-stage revision arthroplasty for culture-negative versus culture-positive PJI of the hip. Method. We retrospectively reviewed patients who received two-stage revision for PJI of the hip between January 2010 to June 2015. All patients was planned to received articulated antibiotic cement-spacer as the first stage and revision total hip arthroplasty (THA) as the second stage of the procedure. Out of total 94 patients, 10 patients was loss to follow-up and excluded from the study. We devided the rest of 84 patients into two groups: culture-negative group (n: 27) and culture-positive group (n: 57). We compared all relevant medical records and the treatment outcome between the two groups. Results. The mean of follow-up was 29.5 months (range, 12–78) in culture-negative group and 30.9 months (range, 12–71) in culture-positive group (p = 0.74). The overall negative culture finding rate was 30.8%. There was no significant difference on baseline data between the two groups including: age, gender, body mass index, preoperative C-reactive protein (CRP), preoperative erythrocyte sedimentation rate and preoperative white blood count, type of hip arthroplasty, previous history of irrigation and debridement (I & D), and preoperative Harris hip score (HHS). However, culture-negative group has significantly higher number on history of preoperative antibiotic use (p = 0.003). The reimplantation rate was 96.3% and 91.2% in culture-negative and culture-positive group, respectively (p= 0.39). The infection recurrency rate after reimplantation was 7.7% and 15.4% in culture-negative and culture-positive group, respectively (p= 0.33). The overall infection control rate was 92.6% (25/27) and 82.4% (47/57) in culture-negative and culture-positive group, respectively (p = 0.21). We also observed no significant difference on the time interval between stage, time to normal CRP, time to recurrency and complications rate between the two groups. A higher postoperative HHS was obtained in culture-negative group (p = 0.04). Conclusions. Negative culture finding was not resulted in an inferior treatment outcome compared to culture-positive group in periprosthetic joint infection of the hip which treated with two-stage revision arthroplasty

Periprosthetic joint infection (PJI) remains a challenging complication following Total Hip Arthroplasty (THA). It is associated with high levels of morbidity, mortality and is time consuming and expensive to treat. Our management generally relies on identification of the infecting organism(s) in order to define the appropriate treatment strategy. Patients with culture-negative PJI poses a greater challenge to surgeons and to the wider multidisciplinary team. This study compares the outcomes of 50 consecutive complex culture-positive (deemed unsuitable for single stage exchange) and 50 culture-negative THAs managed with two-stage revision arthroplasty with a minimum of five years follow-up. Culture-negative PJIs were associated with older age, smoking, external referral source and greater use of preoperative antibiotics. There was however no significant difference in outcome between these groups of patients with a similar complication rates and reinfection rates of 6% at 5 years. Culture negative periprosthetic sepsis generates concern, and is often considered a poor prognostic indicator. This study suggests that a strict 2 stage protocol is associated with satisfactory outcomes in such cases

Aim. To date, the value of culture results after a debridement, antibiotics and implant retention (DAIR) for early (suspected) prosthetic joint infection (PJI) as risk indicators in terms of prosthesis retention is not clear. At one year follow-up, the relative risk of prosthesis removal was determined for culture-positive and culture-negative DAIRs after primary total hip or knee arthroplasty. The secondary aim was to explore differences in patient characteristics, infection characteristics and outcomes between these two groups. Methods. A retrospective regional registry study was performed in a group of 359 patients (positive cultures: n = 299, negative cultures n = 60) undergoing DAIR for high suspicion of early PJI in the period from 2014 to 2019. Differences in patient characteristics, deceased patients and number of subsequent DAIRs between the positive and negative DAIR groups were analyzed using independent t-tests, Mann-Whitney, Pearson's Chi-square tests and Fisher's Exact tests. Results. Overall implant survival rate following DAIR was 89%. The relative risk for prosthesis removal was 7.4 times higher (95% confidence interval (CI) 1.0–53.1) in the positive DAIR group (37/299, 12.4%) compared to the negative DAIR group (1/60, 1.7%). The positive group had a higher body mass index (p = 0.034), rate of wound leakage of >10 days (p = 0.016) and more subsequent DAIRs (p = 0.006). Conclusion. Since implant survival results after DAIR are favorable, the threshold to perform a DAIR procedure in early PJI should be low in order to retain the prosthesis. A DAIR procedure in case of negative cultures does not seem to have unfavorable results in terms of prosthesis retention

Purpose. Unexpected-positive-intraoperative-cultures (UPIC) in presumed aseptic revision-total-knee-arthroplasties (rTKA) are common, and the clinical significance is not entirely clear. In contrast, in some presumably septic rTKA, an identification of an underlying pathogen was not possible, so called unexpected-negative-intraoperative-cultures (UNIC). The purpose of this study was to evaluate alpha defensin (AD) levels in these patient populations. Methods. In this retrospective analysis of our prospectively maintained biobank, we evaluated synovial AD levels from 143 rTKAs. The 2018-Musculoskeletal Infection Society score (MSIS) was used to define our study groups. Overall, 20 rTKA with UPIC with a minimum of one positive intraoperative culture with MSIS 2-≥6 and 14 UNIC samples with MSIS≥6 were compared to 34 septic culture-positive samples (MSIS ≥6) and 75 aseptic culture-negative (MSIS 0–1) rTKAs. Moreover, we compared the performance of both AD-lateral-flow-assay (ADLF) and an enzyme-linked-immunosorbent-assay (ELISA) to test the presence of AD in native and centrifuged synovial fluid. Concentration of AD determined by ELISA and ADLF methods, as well as microbiological, and histopathological results, serum and synovial parameters along with demographic factors were considered. Results. AD was detected in 31/34 (91.2%) samples from the infected-group and in 14/14 (100%) samples in the UNIC group. All UPIC samples showed a negative AD result. Positive AD samples were highly (p<0.001) associated with culture positive and infection related histopathological results. Moreover, we found significantly (p=0.001) more high-virulent microorganisms 19/34 (55.9%) in the infected-group compared to the UPIC-group (0/20). Samples from the infected group with high virulent microorganisms 17/19 (89.5%) showed a positive AD. The presence of methicillin resistant Staphylococcus epidermis (MRSE) led to increased AD (p=0.003) levels when compared to those determined in samples positive for methicillin susceptible S. epidermdis (MSSE). ELISA and ADLF tests were positive with centrifuged (8/8) and native (8/8) synovial fluid. Conclusion. AD showed a solid diagnostic performance in infected and non-infected revisions, and it provided an additional value in the diagnostic of UPIC and UNIC associated to rTKAs. AD levels produced by patients with PJIs caused by high-virulent microorganisms and MRSE are significantly higher compared to those in patients with PJIs caused by either low-virulent or antibiotic susceptible microorganisms. Centrifugation of synovial fluid had no influence in the outcome of ADLF quantification. Keywords: Alpha-defensin, UPIC, UNIC, revision-knee-arthroplasty

Aims. The diagnosis of periprosthetic joint infection can be difficult due to the high rate of culture-negative infections. The aim of this study was to assess the use of next-generation sequencing for detecting organisms in synovial fluid. Materials and Methods. In this prospective, single-blinded study, 86 anonymized samples of synovial fluid were obtained from patients undergoing aspiration of the hip or knee as part of the investigation of a periprosthetic infection. A panel of synovial fluid tests, including levels of C-reactive protein, human neutrophil elastase, total neutrophil count, alpha-defensin, and culture were performed prior to next-generation sequencing. Results. Of these 86 samples, 30 were alpha-defensin-positive and culture-positive (Group I), 24 were alpha-defensin-positive and culture-negative (Group II) and 32 were alpha-defensin-negative and culture-negative (Group III). Next-generation sequencing was concordant with 25 results for Group I. In four of these, it detected antibiotic resistant bacteria whereas culture did not. In another four samples with relatively low levels of inflammatory biomarkers, culture was positive but next-generation sequencing was negative. A total of ten samples had a positive next-generation sequencing result and a negative culture. In five of these, alpha-defensin was positive and the levels of inflammatory markers were high. In the other five, alpha-defensin was negative and the levels of inflammatory markers were low. While next-generation sequencing detected several organisms in each sample, in most samples with a higher probability of infection, there was a predominant organism present, while in those presumed not to be infected, many organisms were identified with no predominant organism. Conclusion. Pathogens causing periprosthetic infection in both culture-positive and culture-negative samples of synovial fluid could be identified by next-generation sequencing. Cite this article: Bone Joint J 2018;100-B:127–33

Introduction

Pulmonary Tuberculosis (TB) can be detected by sputum cultures. However, Extra Pulmonary Spinal Tuberculosis (EPSTB), diagnosis is challenging as it relies on retrieving a sample. It is usually discovered in the late stages of presentation due to its slow onset and vague early presentation. Difficulty in detecting Mycobacterium Tuberculosis bacteria from specimens is well documented and therefore often leads to culture negative results. Diagnostic imaging is helpful to initiate empirical therapy, but growing incidence of multidrug resistant TB adds further challenges.

Aim

Culture negative (CN) prosthetic joint infections (PJI) account for approximately 10% of all PJIs and present significant challenges for clinicians. We aimed to explore the significance of CN PJI within a large prospective cohort study, and to compare their characteristics and outcomes with culture positive cases.

Aim

To analyse the prevalence of culture negative periprosthetic joint infections (PJI) when adequate culture techniques are applied, and to evaluate the outcome of patients who were treated with antibiotics for a culture negative PJI versus those in whom treatment was withheld.

Aims. This aim of this study was to analyze the detection rate of rare pathogens in bone and joint infections (BJIs) using metagenomic next-generation sequencing (mNGS), and the impact of mNGS on clinical diagnosis and treatment. Methods. A retrospective analysis was conducted on 235 patients with BJIs who were treated at our hospital between January 2015 and December 2021. Patients were divided into the no-mNGS group (microbial culture only) and the mNGS group (mNGS testing and microbial culture) based on whether mNGS testing was used or not. Results. A total of 147 patients were included in the no-mNGS group and 88 in the mNGS group. The mNGS group had a higher detection rate of rare pathogens than the no-mNGS group (21.6% vs 10.2%, p = 0.016). However, the mNGS group had lower rates of antibiotic-related complications, shorter hospital stays, and higher infection control rates compared with the no-mNGS group (p = 0.017, p = 0.003, and p = 0.028, respectively), while there was no significant difference in the duration of antibiotic use (p = 0.957). In culture-negative cases, the mNGS group had lower rates of antibiotic-related complications, shorter hospital stays, and a higher infection control rate than the no-mNGS group (p = 0.036, p = 0.033, p = 0.022, respectively), while there was no significant difference in the duration of antibiotic use (p = 0.748). Conclusion. mNGS improves detection of rare pathogens in BJIs. mNGS testing reduces antibiotic-related complications, shortens hospital stay and antibiotic use duration, and improves treatment success rate, benefits which are particularly evident in culture-negative cases. Cite this article: Bone Joint Res 2024;13(8):401–410

Aim. While 16S rRNA PCR - Sanger sequencing has paved the way for the diagnosis of culture-negative bacterial infections, it does not provide the composition of polymicrobial infections. We aimed to evaluate the performance of the Nanopore-based 16S rRNA metagenomic approach using partial-length amplification of the gene, and to explore its feasibility and suitability as a routine diagnostic tool for bone and joint infections (BJI) in a clinical laboratory. Method. Sixty-two clinical samples from patients with BJI were sequenced on MinION* using the in-house partial amplification of the 16S rRNA gene. BJI were defined based on the ICM Philly 2018 and EBJIS 2021 criteria. Among the 62 samples, 16 (26%) were culture-positive, including 6 polymicrobial infections, and 46 (74%) were culture-negative from mono- and polymicrobial infections based on Sanger-sequencing. Contamination, background noise definition, bacterial identification, and time-effectiveness issues were addressed. Results. Results were obtained within one day. Setting a threshold at 1% of total reads overcame the background noise issue and eased interpretation of clinical samples. The partial 16S rRNA metagenomics approach had a greater sensitivity compared both to the culture method and the Sanger sequencing. All the 16 culture-positive samples were confirmed with the metagenomic sequencing. Bacterial DNA was detected in 32 culture-negative samples (70%), with pathogens consistent with BJI. The 14 Nanopore negative samples included 7 negative results confirmed after implementation of other molecular techniques and 7 false-negative MinION results: 3 Kingella kingae infections detected after targeted-PCR only, 2 Staphylococcus aureus infections and 2 Pseudomonas aeruginosa infections sterile on agar plate media and detected only after implementation of blood culture media, advocating for the very low inoculum. Conclusions. The results discriminated polymicrobial samples, and gave accurate bacterial identifications compared to Sanger-based results. They confirmed that Nanopore technology is user-friendly as well as cost- and time-effective. They also indicated that 16S rRNA targeted metagenomics is a suitable approach to be implemented for routine diagnosis of culture-negative samples in clinical laboratories. * Oxford Nanopore Technologies

Aims. The microbiological detection of microorganisms plays a crucial role in the diagnosis as well as in the targeted systemic and local antibiotic therapy of periprosthetic infections (PJI). Despite extensive efforts to improve the sensitivity of current culture methods, the rate of culture-negative infections is approximately 10–20% of all PJI. This study investigates an preanalytical algorithm (culture collection and direct processing in the OR) to potentially increasing culture yield in patients with PJI. Methods. Patients undergoing staged revision arthroplasty for PJI in our hospital between October 2021 and 2022 were included in this prospective pilot study. Intraoperatively twenty tissue samples were collected and distributed among 4 groups. Tissue samples were prepared according to standard without medium and in thioglycolate medium at 3 different temperatures (room temperature, 4°C, 37° for 24h before transport to microbiology) directly in the OR. The removed implants were sonicated. Cultures were investigated on days 1, 3, 7, 12, 14 for possible growth. All grown organism, the number of positive samples and the time to positivity were recorded and compared. Results. 71 patients were included (age, gender). Compared to the standard procedure the thioglycolate broth at 37°C was significantly more often culture-negative (p=0.031). No significant differences in the frequency of culture-negative samples were detected in the other groups. 8.4% (6/71) patients were culture negative in the standard culture but positive in the thioglycolate samples. In contrast, 7% (5/71) were culture negative in the thioglycolate samples but had bacterial detection in the standard approach. In 4.7% (3/63) of the patients, only the sonication showed growth, whereas 25.4% (16/63) had no growth in sonication fluid but in one of the cultures. For S. caprae, there was a significantly different distribution (p=0.026) with more frequent detection in the group with thioglycolate at 37°C. The standard procedure (p=0.005) and sonication (p=0.023) showed a shorter time to positivity of the culture compared to the thioglycolate approach at 4°C. Conclusions. No general differences could be shown between the standard preparation and the thioglycolate preparation; in particular, storage at different temperatures does not seem to result in any difference. For individual cases (8% in this study), bacterial growth was detected in the thioglycolate group that would have been culture-negative otherwise. There might be organism dependent differences in growth in different media

Aims. Periprosthetic joint infection (PJI) is a devastating complication following total knee arthroplasty (TKA). Two-stage revision has traditionally been considered the gold standard of treatment for established infection, but increasing evidence is emerging in support of one-stage exchange for selected patients. The objective of this study was to determine the outcomes of single-stage revision TKA for PJI, with mid-term follow-up. Methods. A total of 84 patients, with a mean age of 68 years (36 to 92), underwent single-stage revision TKA for confirmed PJI at a single institution between 2006 and 2016. In all, 37 patients (44%) were treated for an infected primary TKA, while the majority presented with infected revisions: 31 had undergone one previous revision (36.9%) and 16 had multiple prior revisions (19.1%). Contraindications to single-stage exchange included systemic sepsis, extensive bone or soft-tissue loss, extensor mechanism failure, or if primary wound closure was unlikely to be achievable. Patients were not excluded for culture-negative PJI or the presence of a sinus. Results. Overall, 76 patients (90.5%) were infection-free at a mean follow-up of seven years, with eight reinfections (9.5%). Culture-negative PJI was not associated with a higher reinfection rate (p = 0.343). However, there was a significantly higher rate of recurrence in patients with polymicrobial infections (p = 0.003). The mean Oxford Knee Score (OKS) improved from 18.7 (SD 8.7) preoperatively to 33.8 (SD 9.7) at six months postoperatively (p < 0.001). The Kaplan-Meier implant survival rate for all causes of reoperation, including reinfection and aseptic failure, was 95.2% at one year (95% confidence interval (CI) 87.7 to 98.2), 83.5% at five years (95% CI 73.2 to 90.3), and 78.9% at 12 years (95% CI 66.8 to 87.2). Conclusion. One-stage exchange, using a strict debridement protocol and multidisciplinary input, is an effective treatment option for the infected TKA. This is the largest single-surgeon series of consecutive cases reported to date, with broad inclusion criteria. Cite this article: Bone Jt Open 2021;2(5):305–313

Aims. This study aimed to explore the diagnostic value of synovial fluid neutrophil extracellular traps (SF-NETs) in periprosthetic joint infection (PJI) diagnosis, and compare it with that of microbial culture, serum ESR and CRP, synovial white blood cell (WBC) count, and polymorphonuclear neutrophil percentage (PMN%). Methods. In a single health centre, patients with suspected PJI were enrolled from January 2013 to December 2021. The inclusion criteria were: 1) patients who were suspected to have PJI; 2) patients with complete medical records; and 3) patients from whom sufficient synovial fluid was obtained for microbial culture and NET test. Patients who received revision surgeries due to aseptic failure (AF) were selected as controls. Synovial fluid was collected for microbial culture and SF-WBC, SF-PNM%, and SF-NET detection. The receiver operating characteristic curve (ROC) of synovial NET, WBC, PMN%, and area under the curve (AUC) were obtained; the diagnostic efficacies of these diagnostic indexes were calculated and compared. Results. The levels of SF-NETs in the PJI group were significantly higher than those of the AF group. The AUC of SF-NET was 0.971 (95% confidence interval (CI) 0.903 to 0.996), the sensitivity was 93.48% (95% CI 82.10% to 98.63%), the specificity was 96.43% (95% CI 81.65% to 99.91%), the accuracy was 94.60% (95% CI 86.73% to 98.50%), the positive predictive value was 97.73%, and the negative predictive value was 90%. Further analysis showed that SF-NET could improve the diagnosis of culture-negative PJI, patients with PJI who received antibiotic treatment preoperatively, and fungal PJI. Conclusion. SF-NET is a novel and ideal synovial fluid biomarker for PJI diagnosis, which could improve PJI diagnosis greatly. Cite this article: Bone Joint Res 2023;12(2):113–120

Aims. Metal particles detached from metal-on-metal hip prostheses (MoM-THA) have been shown to cause inflammation and destruction of tissues. To further explore this, we investigated the histopathology (aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL) score) and metal concentrations of the periprosthetic tissues obtained from patients who underwent revision knee arthroplasty. We also aimed to investigate whether accumulated metal debris was associated with ALVAL-type reactions in the synovium. Methods. Periprosthetic metal concentrations in the synovia and histopathological samples were analyzed from 230 patients from our institution from October 2016 to December 2019. An ordinal regression model was calculated to investigate the effect of the accumulated metals on the histopathological reaction of the synovia. Results. Median metal concentrations were as follows: cobalt: 0.69 μg/g (interquartile range (IQR) 0.10 to 6.10); chromium: 1.1 μg/g (IQR 0.27 to 4.10); and titanium: 1.6 μg/g (IQR 0.90 to 4.07). Moderate ALVAL scores were found in 30% (n = 39) of the revised knees. There were ten patients with an ALVAL score of 6 or more who were revised for suspected periprosthetic joint infection (PJI), aseptic loosening, or osteolysis. R2 varied between 0.269 and 0.369 for the ordinal regression models. The most important variables were model type, indication for revision, and cobalt and chromium in the ordinal regression models. Conclusion. We found that metal particles released from the knee prosthesis can accumulate in the periprosthetic tissues. Several patients revised for suspected culture-negative PJI had features of an ALVAL reaction, which is a novel finding. Therefore, ALVAL-type reactions can also be found around knee prostheses, but they are mostly mild and less common than those found around metal-on-metal prostheses. Cite this article: Bone Joint Res 2024;13(4):149–156

Aims. Single-stage revision is not widely pursued due to restrictive inclusion criteria. In this study, we evaluated the results of single-stage revision of chronically infected total hip arthroplasty (THA) using broad inclusion criteria and cementless implants. Patients and Methods. Between 2010 and 2016, 126 patients underwent routine single-stage revision with cementless reconstruction with powdered vancomycin or imipenem poured into the medullary cavity and re-implantation of cementless components. For patients with a culture-negative hip, fungal infections, and multidrug-resistant organisms, a direct intra-articular infusion of pathogen-sensitive antibiotics was performed postoperatively. Recurrence of infection and clinical outcomes were evaluated. Three patients died and 12 patients (none with known recurrent infection) were lost to follow-up. There were 111 remaining patients (60 male, 51 female) with a mean age of 58.7 (. sd. 12.7; 20 to 79). Results. Of these 111 patients, 99 (89.2%) were free of infection at a mean follow-up time of 58 months (24 to 107). A recurrent infection was observed in four of the 23 patients (17.4%) with culture-negative infected hip. The success rate in patients with multidrug-resistant organisms was 84.2% (16/19). The mean postoperative Harris hip score was 79.6 points (63 to 92) at the most recent assessment. Conclusion. Routine single-stage revision with cementless reconstruction can be a viable option for the treatment of chronically infected THA. The results of this study will add to the growing body of evidence supporting routine use of single-stage revision for the treatment of chronically infected THA. Cite this article: Bone Joint J 2019;101-B:396–402

Aims. Periprosthetic joint infection (PJI) remains a challenging complication following total hip arthroplasty (THA). It is associated with high levels of morbidity, mortality and expense. Guidelines and protocols exist for the management of culture-positive patients. Managing culture-negative patients with a PJI poses a greater challenge to surgeons and the wider multidisciplinary team as clear guidance is lacking. Patients and Methods. We aimed to compare the outcomes of treatment for 50 consecutive culture-negative and 50 consecutive culture-positive patients who underwent two-stage revision THA for chronic infection with a minimum follow-up of five years. Results. There was no significant difference in the outcomes between the two groups of patients, with a similar rate of re-infection of 6%, five years post-operatively. Culture-negative PJIs were associated with older age, smoking, referral from elsewhere and pre-operative antibiotic treatment. The samples in the culture-negative patients were negative before the first stage (aspiration), during the first-stage (implant removal) and second-stage procedures (re-implantation). Conclusion. Adherence to strict protocols for selecting and treating culture-negative patients with a PJI using the same two-stage revision approach that we employ for complex culture-positive PJIs is important in order to achieve control of the infection in this difficult group of patients. Cite this article: Bone Joint J 2018;(1 Supple A)100-B:3–8

Aims. The aim of this study was to evaluate the performance of metagenomic next-generation sequencing (mNGS) in detecting pathogens from synovial fluid of prosthetic joint infection (PJI) patients. Methods. A group of 75 patients who underwent revision knee or hip arthroplasties were enrolled prospectively. Ten patients with primary arthroplasties were included as negative controls. Synovial fluid was collected for mNGS analysis. Optimal thresholds were determined to distinguish pathogens from background microbes. Synovial fluid, tissue, and sonicate fluid were obtained for culture. Results. A total of 49 PJI and 21 noninfection patients were finally included. Of the 39 culture-positive PJI cases, mNGS results were positive in 37 patients (94.9%), and were consistent with culture results at the genus level in 32 patients (86.5%) and at the species level in 27 patients (73.0%). Metagenomic next-generation sequencing additionally identified 15 pathogens from five culture-positive and all ten culture-negative PJI cases, and even one pathogen from one noninfection patient, while yielding no positive findings in any primary arthroplasty. However, seven pathogens identified by culture were missed by mNGS. The sensitivity of mNGS for diagnosing PJI was 95.9%, which was significantly higher than that of comprehensive culture (79.6%; p = 0.014). The specificity is similar between mNGS and comprehensive culture (95.2% and 95.2%, respectively; p = 1.0). Conclusion. Metagenomic next-generation sequencing can effectively identify pathogens from synovial fluid of PJI patients, and demonstrates high accuracy in diagnosing PJI. Cite this article: Bone Joint Res 2020;9(7):440–449

Aims. Microbiological culture is a key element in the diagnosis of periprosthetic joint infection (PJI). However, cultures of periprosthetic tissue do not have optimal sensitivity. One of the main reasons for this is that microorganisms are not released from the tissues, either due to biofilm formation or intracellular persistence. This study aimed to optimize tissue pretreatment methods in order to improve detection of microorganisms. Methods. From December 2017 to September 2019, patients undergoing revision arthroplasty in a single centre due to PJI and aseptic failure (AF) were included, with demographic data and laboratory test results recorded prospectively. Periprosthetic tissue samples were collected intraoperatively and assigned to tissue-mechanical homogenization (T-MH), tissue-manual milling (T-MM), tissue-dithiothreitol (T-DTT) treatment, tissue-sonication (T-S), and tissue-direct culture (T-D). The yield of the microbial cultures was then analyzed. Results. A total of 46 patients were enrolled, including 28 patients in the PJI group and 18 patients in the AF group. In the PJI group, 23 cases had positive culture results via T-MH, 22 cases via T-DTT, 20 cases via T-S, 15 cases via T-MM, and 13 cases via T-D. Three cases under ongoing antibiotic treatment remained culture-negative. Five tissue samples provided the optimal yield. Any ongoing antibiotic treatment had a relevant influence on culture sensitivity, except for T-DTT. Conclusion. T-MH had the highest sensitivity. Combining T-MH with T-DTT, which requires no special equipment, may effectively improve bacterial detection in PJI. A total of five periprosthetic tissue biopsies should be sampled in revision arthroplasty for optimal detection of PJI. Cite this article: Bone Joint Res 2021;10(2):96–104

Although single-stage revision has attracted a lot of attention due to less socioeconomic cost, this technique is not widely used throughout the world due to strict indications. In this situation, we report our outcome on single-stage revision combined with selective direct intra-articular antibiotic infusion for chronic infected THA, especially for patients with culture-negative hip, fungal infections and multidrug-resistant organism. We retrospectively reviewed 131 patients with chronic infected THA between January 2010 and February 2017 who underwent single-stage revision, including soakage of surgical area with 0.5% aqueous betadine, pouring powdered vancomycin or imipenem into the medullary cavity. For patients with culture-negative hip, fungal infections and multidrug-resistant organism, a direct intra-articular infusion of pathogens-sensitive antibiotics via three-branch catheter were performed postoperatively. Recurrence of infection and clinical outcomes were evaluated. One hundred and fifteen patients were followed-up for an average of 4.5 years (range, 1.2–8 years). Of the 115 patients, 103 patients (89.6%) required no additional surgical or medical treatment for recurrence of infection. A recurrent infection was observed in 4 of the 23 patients (17.4%) with culture-negative infected hip. One of 4 fungal infections was relapse and the success rate in patients with multidrug-resistant organism was 84.2% (16/19). The mean postoperative Harris hip score was 81 points (63 to 92; p < 0.05) at the most recent assessment. Treatment of chronic infected THA by single-stage revision combined with selective direct intra-articular antibiotic infusion can be fairly effective, even for patients with relative “contraindication” of this approach

Aim. The gold standard treatment for late acute hematogenous (LAH) periprosthetic joint infection (PJI) is surgical debridement, antibiotics and implant retention (DAIR). However, this strategy is still controversial in the case of total knee arthroplasty (TKA) as some studies report a higher failure rate. The aim of the present study is to report the functional outcomes and cure rate of LAH PJI following TKA treated by means of DAIR at a long-term follow-up. Method. A consecutive prospective cohort consisting of 2,498 TKA procedures was followed for a minimum of 10 years (implanted between 2005 and 2009). The diagnosis of PJI and classification into LAH was done in accordance with the Zimmerli criteria (NEJM 2004). The primary outcome was the failure rate, defined as death before the end of antibiotic treatment, a further surgical intervention for treatment of infection was needed and life-long antibiotic treatment or chronic infection. The Knee Society Score (KSS) was used to evaluate clinical outcomes. Surgical management, antibiotic treatment, the source of infection (primary focus) and the microorganisms isolated were also assessed. Results. Among the 2,498 TKA procedures, 10 patients were diagnosed with acute hematogenous PJI during the study period (0.4%). All those 10 patients were operated by means of DAIR, which of course included the polyethylene exchange. They were performed by a knee surgeon and/or PJI surgeon. The failure rate was 0% at the 8.5 years (SD, 2.4) follow-up mark. The elapsed time between primary total knee replacement surgery and the DAIR intervention was 4.7 years (SD, 3.6). DAIR was performed at 2.75 days (SD 1.8) of the onset of symptoms. The most common infecting organism was S. aureus (30%) and E. coli (30%). There were 2 infections caused by coagulase-negative staphylococci and 2 culture-negative PJI. All culture-positive PJI microorganisms were susceptible to anti-biofilm antibiotics. The source of infection was identified in only 3 cases. The mean duration of antibiotic treatment was 11.4 weeks (SD 1.9). The postoperative clinical outcomes were excellent, with a mean KSS of 84.1 points (SD, 14.6). Conclusions. Although the literature suggests that TKA DAIR for acute hematogenous periprosthetic joint infection is associated with high rates of failure, the results presented here suggest a high cure rate with good functional outcomes. Some explanations for this disparity in results may be the correct diagnosis of LHA, not misdiagnosing acute chronic PJI, and a thorough debridement by surgeons specialized in PJI

Introduction. The burden of prosthetic joint infection (PJI) in total knee arthroplasty (TKA) has been rising in line with the number of primary operations performed. Current estimates suggest an infection rate of 1–2.4%. Two-stage revision has traditionally been considered the gold standard of treatment; however, some studies suggest comparable results can be achieved with single-stage procedures. The potential advantages include less time in hospital, a single anaesthetic, reduced costs, and greater patient satisfaction. Methods. We reviewed data for 72 patients (47 males, 25 females), with a mean age of 71 years (range, 49 to 94), who underwent single-stage revision TKA for confirmed PJI between 2006 and 2016. A standardized debridement protocol was performed with immediate single-stage exchange. All cases were discussed preoperatively at multidisciplinary team (MDT) meetings, which included input from a senior musculoskeletal microbiologist. Patients were not excluded for previous revisions, culture-negative PJI, or the presence of a sinus. Results. The average length of follow-up was 8 years (range, 2 to 13). In total, 65 patients (90.3%) were infection free at most recent follow-up, with seven reinfections (9.7%). Three of these patients with recurrent infections underwent arthrodesis, two underwent re-revision, and two received long-term antibiotics following debridement and implant retention (DAIR). No amputations were undertaken. Conclusions. Single-stage revision for the infected TKA, according to a strict debridement protocol with MDT input, demonstrates reinfection rates comparable with two-stage revision procedures. This is the largest single-surgeon series to date, with extensive follow-up, and supports a growing evidence base for one-stage exchange

Aim. Clear differentiation between aseptic failure and prosthetic joint infection remains one of the goals of modern orthopaedic surgery. New diagnostic methods can provide more precise evaluation of the etiology of prosthetic joint failure. With the introduction of sonication an increasing number of culture-negative prosthetic joint infection were detected. The aim of our study was to evaluate culture-negative prosthetic joint infections in patients who were preoperatively evaluated as aseptic failure. Method. For the purpose of the study we included patients planed for revision surgery for presumed aseptic failure. Intraoperatively acquired samples of periprosthetic tissue and explanted prosthesis were microbiologically evaluated using standard microbiologic methods and sonication. If prosthetic joint infection was discovered, additional therapy was introduced. Results. Between October 2010 and till the end of 2014 151 cases were operated (38 revision knee arthroplasty, 113 revision hip arthroplasty). 40 (26,5%) cases had positive sonication and negative periprosthetic tissue samples (knee 7 cases, hips 33 cases), 13 (8,6%) cases had positive tissue samples but negative sonication (knee 7 cases, hips 6 cases), in 13 (8,6%) cases both tests were positive (knee none, hips 13 cases) and in 85 (56,3%) cases all microbiologic tests were negative (knee 24 cases, hips 61 cases). In both groups cases coagulase-negative staphylococci and P.acnes were most common, followed by mixed flora. Conclusions. With the increasing number of patients requiring revision arthroplasty, a clear differentiation between aseptic failure and prosthetic joint infection is crucial for the optimal treatment. Sonication of explanted material is more successful in the isolation of pathogens compared to periprosthetic tissue cultures. Sonication of explanted prosthetic material is helpful in the detection of culture-negative prosthetic joint infections

Aim. Fracture-related infection (FRI) is a challenging complication. This study aims to investigate (1) microbial patterns in fracture-related infection (FRI), (2) the comparison of isolated pathogens in FRI patients with early, delayed, and late onset of infection and (3) antibiotic susceptibility profiles to identify effective empiric antibiotic therapy for FRI. Method. Patients treated for FRI from 2013 to 2020 were grouped into early (< 2 weeks), delayed (2– 10 weeks) and late (> 10 weeks) onset of infection. Pathogens detected during treatment were evaluated for pathogens. Antibiotic susceptibility profiles were examined with respect to broadly used antibiotics and antibiotic combinations. Results. In total 117 patients (early n=19, delated n=60, late n=38) were included in the study. Infection was polymicrobial in 10 cases (8.6%) and culture-negative in 11 cases (9.4%). Staphylococcus aureus was the most frequently detected pathogen (40.5%), followed by Staphylococcus epidermidis (17.2%) and gram-negative bacteria (16.4%). Pathogen distribution did not differ statistically significant between the groups. Highest effectiveness could be achieved by the combination of meropenem + vancomycin (95.7%) and gentamycin + vancomycin (94.0%). More than 90% of all patients would have also been covered by co-amoxiclav + glycopeptide (93.2%), ciprofloxacin + glycopeptide and piperacillin/tazobactam + glycopeptide (92.3% each) as well as ceftriaxone + glycopeptide (91.5%). Comparing the predicted efficacy of empiric antimicrobial regimens between the subgroups only revealed a statistically significant difference regarding the combination ciprofloxacin with a glycopeptide (F= 3.304, p=.04), for which more patients with an early onset of infection would have been susceptible. Conclusions. Microbiological pattern for the causative microorganism between early, delayed, and late FRI are comparable. Empiric therapy combinations such as meropenem + vancomycin, gentamycin +vancomycin or co-amoxiclav + glycopeptide are effective antibiotic strategies. To bypass unwanted side effects of systemic antibiotics and reduce the risk of antimicrobial resistance, the administration of local antibiotic carriers should be implemented in clinical practice

Clear differentiation between aseptic failure and prosthetic joint infection remains one of the goals of modern orthopaedic surgery. The development of new diagnostic methods enabled more precise evaluation of the etiology of prosthetic joint failure. With the introduction of sonication an increasing number of culture-negative prosthetic joint infection were detected. The aim of our study was to evaluate culture-negative prosthetic joint infections in patients who were preoperatively evaluated as aseptic failure. For the purpose of the study we included patients planed for revision surgery for aseptic failure. Intraoperatively acquired samples of periprosthetic tissue and explanted prosthesis were microbiologicaly evaluated using standard microbiologic methods and sonication. If prosthetic joint infection was discovered, additional therapy was introduced. Between October 2010 and April 2013 54 patients were operated (12 revision knee arthroplasty, 42 revision hip arthroplasty). 10 (18,6%) patients had positive sonication and negative periprosthetic tissue sample, 5 (9,2%) patients had positive tissue samples, but negative sonication, in 9 (16,7%) patients both tests were positive and in 30 (55,5%) patients all microbiologic tests were negative. The microbiologic isolates of sonicate fluid were in 12 cases coagulase-negative staphylococci, in 3 cases P.acnes in 3 cases mixed flora, in 1 case enterococcus and in 1 case SA. From periprosthetic tissue cultures 5 samples have yielded coagulase-negative staphylococci in 5 cases P.acnes in 2 cases mixed flora, in 1 case enterococcus and in 1 case SA were isolated. With the increasing number of patients requiring revision arthroplasty, a clear differentiation between aseptic failure and prosthetic joint infection is crucial for the optimal treatment. Sonication of explanted material is more successful in the isolation of pathogens compared to periprosthetic tissue cultures. Sonication of explanted prosthetic material is helpful in the detection of culture-negative prosthetic joint infections

Aim. To compare pre-referral microbiology and previous bone excision in long bone osteomyelitis with intra-operative microbiology from a specialist centre. Method. A prospective observational cohort study of patients referred to a single tertiary centre who met the following criteria: (i) aged ≥18 years, (ii) received surgery for long bone osteomyelitis and (iii) met diagnostic criteria for long bone osteomyelitis. Patient demographics, referral microbiology and previous surgical history were collected at the time of initial clinic appointment. During surgery, a minimum of 5 intra-operative deep tissue samples were sent for microbiology. Antimicrobial options were classified from the results of susceptibility testing using the BACH classification of long bone osteomyelitis as either Ax (unknown or culture negative), A1 (good options available) or A2 (limited options available). The cultures and susceptibility of pre-referral microbiology were compared to the new intra-operative sampling results. In addition, an association between previous osteomyelitis excision and antimicrobial options were investigated. Results. 79 patients met inclusion criteria during the study period. From these, 39 (49.4%) patients had information available at referral regarding microbiology obtained from either sinus swab (n=16), bone biopsy (n=11), previous osteomyelitis excision sampling (n=7), aspiration (n=4) or blood culture (n=1). From these 39 patients, microbiology information at referral fully matched microbiology samples taken at operation in 8 cases (20.5%). Fifteen of the 39 patients (38.5%) had a different species isolated at surgery compared to referral microbiology. The remaining 16 patients (41.0%) had a culture-negative osteomyelitis on surgical sampling. Based on the microbiology obtained in our centre, 35 patients were classified as A1 (44.3%), 15 as A2 (18.9%) and 29 as culture negative, Ax (36.7%). Patients who had received previous excision of osteomyelitis before referral (n=32, 40.5%) had an increased odds ratio (OR) of having microbiology with limited antimicrobial options compared to those undergoing primary osteomyelitis excision (OR: 3.8, 95% CI 1.2 – 11.2, P=0.023, Fisher's exact test). Conclusions. Patients are frequently referred with limited microbiological information. Pre-referral microbiology in long bone osteomyelitis correlated with intra-operative samples taken at our centre in less than one quarter of cases. Pre-referral microbiology data should be used with caution for planning treatment in osteomyelitis. Previous surgery for osteomyelitis was associated with microbiology culture with limited antimicrobial treatment options

Aim. It is traditionally stated that around 80% of all periprosthetic joint infections (PJI) are caused by well-known gram-positive organisms such as Staphylococcus aureus. With the advances in diagnostic modalities and improved abilities to isolate infective organisms, we believe the organism profile causing PJI has changed over time and includes numerous other organisms that were either not recognized as pathogens and/or considered as contaminants. Method. We retrospectively reviewed the medical records of 1,363 patients with confirmed PJI (559 THA and 804 TKA) who received treatment at our institution between 2000 and 2019. Pertinent data related to demographics, microbiological findings, and outcome of treatment were collected. Organisms were differentiated using culture or confirmed by Matrix-Assisted Laser Desorption Ionization-time of flight (MALDI-tof) mass spectrometry. Statistical analysis included logistic regressions. Results. There was a total of 26 different species of organisms that resulted in PJI in our cohort. The rate of PJI caused by slow growing organisms, that are catalase negative, such as Streptococcal viridans (OR 1.244; 95% CI 1.036–1.494), Streptococcus agalactiae (OR 1.513; 95% CI 1.207–1.898), and Staphylococcus epidermidis (OR 1.321; 95% CI 1.191–1.466) has been increasing over time. In contrast, the incidence of PJI caused by coagulase-negative Staphylococcus (OR 0.954; 95% CI 0.927–0.981); resistant species (OR 0.962, 95% CI 0.931–0.995), and Gram-positive species (OR 0.94, 95% CI 0.914–0.966) decreased over time. Notably, there was a higher prevalence of Streptococcal PJI (OR 0.551, 95% CI 0.374–0.812) and culture-negative PJI (OR 0.652, 95% CI 0.478–0.890) seen in knees versus hips. The rate of culture negative PJI also increased from 20% in 2000 to 28% in 2019. In the latter years of the study, very unusual list of organisms causing PJI were also identified. Conclusions. This study reveals that the list of organisms causing PJI has expanded in recent years. The study also finds that some the slow growing organisms that were previously believed to be “contaminants” can and do cause PJI in a considerable number of patients. The number of culture negative cases of PJI has also increased at our institution over the years. There are a number of explanations for the latter finding, perhaps with the most important reason being liberal use of antibiotics that interferes with isolation of the infective organism

Aim. A two-stage exchange of an infected prosthetic joint (PJI) is considered the most effective surgical treatment of chronic PJIs, particularly in North America. However, reinfection rates are unacceptably high (10–20%). This could be the consequence of a persistent infection or a new infection introduced during the first or second stage of the exchange arthroplasty. We aimed to determine: i) the prevalence of positive cultures at reimplantation, ii) whether there is an association between positive cultures at reimplantation and reinfection during follow-up, and iii) if there is a microbiological correlation between primary infections, reimplantations and reinfections. Method. We retrospectively evaluated all two-stage exchange procedures performed at two academic centers between 2000 and 2015. Primary culture-negative PJIs and cases in whom no intraoperative cultures were obtained during reimplantation were excluded from the analysis. One or more positive intraoperative cultures during reimplantation were considered positive for infection. Reinfection was defined as the need for additional surgical intervention after reimplantation or the need for antibiotic suppressive therapy due to persistent clinical signs of infection. Results. A total of 424 cases were included in the final analysis with a mean follow-up of 48 months (SD 37). Eighty-eight cases (20.8%) had positive cultures during reimplantation (second stage) of which 68.1% (n=60) grew a different microorganism than during the first stage of the procedure. The percentage of positive cultures during reimplantation was higher for hips than for knees (26.5% vs 17.1%, p 0.02). For the total group, the reinfection rate during follow-up was 18.4% (78/424), which was 29.5% for the positive-culture group versus 15.5% for the culture-negative group at reimplantation (p=0.002). A positive culture during reimplantation was an independent risk factor for reinfection during follow-up in the multivariate analysis (OR 2.2 (95% CI 1.2 – 3.8), p 0.007). Reinfection was caused by a different microorganism than the primary infection (first stage) in 64.1% of cases (50/78). Conclusions. There is a very high rate of positive cultures at reimplantation, which are mostly attributed to a different microorganism than the primary infection and is associated with a worse outcome. These results stress the importance of developing treatment strategies for this particular population

Aim. Metagenomic nanopore sequencing is demonstrating potential as a tool for diagnosis of infections directly from clinical samples. We have previously shown nanopore sequencing can be used to determine the causative bacterial species in prosthetic joint infections (PJI). However, to make predictions regarding antimicrobial resistance, human DNA contamination must be reduced so a greater proportion of sequence data corresponds to the microbial portion of the DNA extract. Here, we utilise selective DNA extraction from sonication fluid samples to begin to make predictions regarding antimicrobial resistance in PJI. Method. We investigated host cell DNA depletion with 5% saponin selective human cell lysis followed by nuclease digestion. Subsequently, bacterial cells were mechanically lysed before DNA extraction. Sequencing libraries from samples treated with and without saponin were prepared with a Rapid PCR Barcoding Kit. 1. and sequenced in multiplexes of 2–8 samples/flowcell on a GridION. Sequencing reads were analysed using the CRuMPIT pipeline and thresholds to indicate presence of a specific bacterial genus/species were investigated. Antimicrobial resistance determinants were detected using previously published sequences specifically for Staphylococcus aureus, as an example organism frequently causing PJI. Results. 247 DNA extracts from 115 sonication fluids plus controls were subjected to metagenomic sequencing, comprising extracts from 67 culture-positive (10 of which were culture-positive at <50 CFU/ml) and 48 culture-negative samples. 5% saponin depleted human DNA contamination, reducing the number of human sequenced bases to a median 12% from 98% in comparison to 5μm filtration without saponin. In 11 samples 5% saponin depleted human bases by <12% in comparison to 5μm filtration, which may be indicative of incomplete depletion. Bacteria observed in sonication fluid culture were identified to species-level in 49/65 (75%) cases, and to genus-level in 51/65 (78%). Specificity of sequencing was 103/114 (90%). Sequencing made a completely successful prediction of antimicrobial susceptibility in 8/19 S. aureus culture-positive samples treated with 5% saponin, and a partial prediction in 5/19 for the 8 antibiotics investigated. Without 5% saponin treatment sequencing could only detect a limited number of AMR determinants in 3/19 samples. Sequencing correctly predicted 13/15 (87%) resistant and 74/74 (100%) susceptible phenotypes where sufficient sequence data were available. Conclusions. Nanopore metagenomic sequencing can provide species identification in PJI. Additionally, depletion of human DNA improves depth of coverage and allows detection of antimicrobial resistance determinants, demonstrating as a proof of principle that nanopore sequencing could potentially provide a complete diagnostic tool in PJI. 1. Oxford Nanopore Technologies

Aim. Empiric antibiotic therapy for suspected pyogenic spondylodiscitis (SD) should be initiated immediately with severely ill patients and may also be necessary for culture-negative SD. The aim of this study was to infer an appropriate empiric antibiotic regimen by analyzing the antimicrobial susceptibility of isolated pathogens from microbiologically proven pyogenic spondylodiscitis. Method. We performed a retrospective review of adult patients with clinically proven SD treated at our level 1 trauma center between 2013 and 2020. Demographic data, radiologic findings, and treatment modalities were evaluated. The appropriateness of empiric antibiotic regimens was assessed based on the antibiograms of the isolated pathogens. Anamneses were used to distinguish between community-acquired (CA) and healthcare-associated (HA) pathogens, which included cases that had a hospital stay or invasive intervention in the past 6 months. Results. A total of 155 patients (male: N=88; female: N=67; mean age 66.1 ± 12.4 years) with SD were identified. In n= 74 (47.7%) cases, the infections were associated with the healthcare system (HA). N=34 (21.9%) patients suffered from sepsis. The lumbar spine was involved in 47.1% of the cases, the thoracic spine in 37.3%, and the cervical spine in 7.8%. In 7.8% of the cases, SD occurred in multiple spinal segments. N=96 (62.0%) patients were treated surgically. The mean hospital stay was 36.4 ± 36.3 days. Antibiograms of n=45 patients (HA: N=22; CA: N=23) could be retrospectively evaluated: The most frequently identified pathogens were Staphylococcus aureus (46.7%), Coagulase-negative Staphylococci (17.8%), Enterobacteriaceae (15.6%) and Streptococcus species (15.6%). Overall, 82.2% (HA: 68.2%; CA: 95.5%) of the isolated pathogens were sensitive to piperacillin/tazobactam, 77.8% (HA: 81.8%; CA: 72.2%) to vancomycin, 64.4% (HA: 68.2%; CA: 59.1%) to clindamycin, and 55.6% (HA: 36.4%; CA: 72.7%) to ceftriaxone. To a combination of vancomycin plus meropenem 97.8% of pathogens were sensitive (HA: 95.5%; CA: 100.0%), to vancomycin plus ciprofloxacin 91.1% (HA: 86.4%; CA: 95.7%), and to vancomycin plus cefotaxime 93.3% (HA: 90.9%; CA: 95.7%). In 14 cases, empiric antibiosis was adjusted based on the results of the antibiogram. Conclusions. Antibiotic resistance of CA SD pathogens differed significantly from HA SD. The identification of the pathogen and the analysis of its susceptibility guides the antibiotic therapy. Vancomycin in combination with a carbapenem, broad-spectrum cephalosporin, or fluoroquinolone may be appropriate for empiric treatment of HA SD

Aim. The aim of our study was to evaluate culture-negative prosthetic joint infections in patients who were pre-operatively evaluated as aseptic failure. Method. For the purpose of the study we included patients planed for revision surgery for presumed aseptic failure. Intraoperatively acquired samples of periprosthetic tissue and explanted prosthesis were microbiologicaly evaluated using standard microbiologic methods and sonication. If prosthetic joint infection was discovered, additional therapy was introduced. Results. Between October 2010 and June 2016 265 cases were operated as aseptic loosenings (66 revision knee arthroplasty, 199 revision hip arthroplasty). 69 (26,0%) cases had positive sonication and negative periprosthetic tissue sample, 24 (9,1%) cases had positive tissue samples, but negative sonication, in 27 (10,2%) cases both tests were positive and in 145 (54,7%) cases all microbiologic tests were negative. In both groups coagulase-negative staphylococci and P.acnes were most common, followed by mixed flora. Conclusions. With the increasing number of patients requiring revision arthroplasty, a clear differentiation between aseptic failure and prosthetic joint infection is crucial for the optimal treatment. Sonication of explanted material is more successful in the isolation of pathogens compared to periprosthetic tissue cultures. Sonication of explanted prosthetic material is helpful in the detection of culture-negative prosthetic joint infections

We aim to describe the microbiological spectrum and relevant antibiotic susceptibility profile of PJI in our institution over a five-year period(2009–2013) and determine its evolution considering the preceding six years(2003–2008) thus evaluating the adequacy of our empirical antibiotic regimen. We retrospectively reviewed the records of 96 consecutive PJI (51 hips:45 knees) treated from May 2009-December 2013. Demographics, microbial species and antibiotic susceptibility were recorded. These results were then compared to those previously obtained by studying the 2003–2008 time period. Infections were polymicrobial in 27 cases(28.1%) and only two cases(2.1%) were culture-negative accounting for a total of 132 different culture results. S.aureus grew in 37 samples(28.0%) being the most frequently isolated microorganism. Coagulase-negative staphylococci grew in 32 samples(24.2%) and gram negative bacteria in 35 samples(26.5%). Other Gram positive species (most commonly enterococci and streptococci) were isolated in 26 samples(19.7%). Comparing 2009–2013 to 2003–2008, there was a significant increase of polymicrobial infections – 28% vs. 8%(OR=4.6, 95%CI [1.9–11.3]) and a significant decrease of culture-negative cases – 2% vs. 18%(OR=0.1, 95%CI [0.02–0.4]). It is also noteworthy that the prevalence of gram negative isolates was significantly increased – 26.5% vs. 13.3%(OR=1.3, 95%CI [1.1–1.6]). Antibiotic susceptibilities study showed a 41.4% methicillin resistance among S.aureus and even higher among coagulase-negative staphylococci isolates(57.7%). This is a not quite significant decrease compared to the earlier period(p=0.10). We also found a high rate antibiotic resistance among gram negative: ampiciline(81.8%), amoxicilin/clavulanate(59.1%), ciprofloxacin(19.2%), aminoglycosides(17%), third generation cephalosporins(14.6%) and even carbapenems(13.6%). These results show that our sampling protocol has improved considerably as the proportion of culture-negative cases has dramatically decreased. On the other hand this may also help explain the increase in polymicrobial infections. We have no clear explanation for the increase in gram negative bacteria. Despite the downward trend we still face a very significant proportion of methicillin-resistant staphylococci infections. The antibiotic resistance profile among gram negative bacteria is also worrying. As such we believe a regimen consisting of vancomycin and gram-negative coverage such as aminoglycosides or a third generation cephalosporin is still warranted in our institution

Introduction. Despite recent advances in the diagnosis of periprosthetic joint infection(PJI), identifying the infecting organism continues to be a challenge, with up to a third of PJIs reported to have negative cultures. Current molecular techniques have thus far been unable to replace culture as the gold standard for isolation of the infecting pathogen. Next- generation sequencing(NGS) is a well-established technique for comprehensively sequencing the entire pathogen DNA in a given sample and has recently gained much attention in many fields of medicine. Our aim was to evaluate the ability of NGS in identifying the causative organism(s) in patients with PJI. Methods. After obtaining Institutional Review Board approval and informed consent for all study participants, samples were prospectively collected from 148 revision total joint arthroplasty procedures (83 knees, 65 hips). Synovial fluid, deep tissue and swabs were obtained at the time of surgery and shipped to the laboratory for NGS analysis (MicroGenDx). Deep tissue specimens were also sent to the institutional laboratory(Thomas Jefferson University Hospital) for culture. PJI was diagnosed using the Musculoskeletal Infection Society(MSIS) definition of PJI. Statistical analysis was performed using SPSS software. Results. Fifty-five revisions were considered infected; culture was positive in 40 of these (40/55, 72.7%), while NGS was positive in 47 (47/55, 85.5%). Among the positive cultures, complete concordance between NGS and culture was observed in 33 cases (33/40, 82.5%). One case was partially discordant between NGS and culture, with culture detecting three organisms as opposed to one organism on NGS. One case showed complete discordance with NGS and culture detecting different organisms. Three patients with negative NGS results had positive cultures. In another two cases culture simply reported the gross morphology of the organism but the phenotype was not identified, while NGS was able to definitively identify an organism. Among the 15 cases of culture-negative PJI, NGS was able to identify an organism in 10 cases (10/15, 66.7%). These data are summarized in Figure 1. Ninety-three revisions were considered to be aseptic; NGS exclusively identified microbes in 15 of 93 “aseptic” revisions (16.1%) and culture exclusively isolated an organism in 4 of 93 cases(5.3%). One case was positive on both NGS and culture, however the results were discordant from each other. The remaining cases (73/93, 78.5%) were both NGS and culture negative. NGS detected several organisms in most positive samples, with a greater number of organisms detected in aseptic compared to septic cases (6.8 vs. 4.0, respectively). Discussion. NGS was able to detect a pathogen in two-thirds of culture-negative cases and demonstrated a high rate of concordance with culture in culture-positive cases. The rate of false positives was low compared to earlier studies using molecular techniques. Our findings also suggest that some cases of PJI may be polymicrobial and escape detection using conventional culture. NGS may be a useful adjunct for identifying the causative organism(s) in PJI, particularly in the setting of negative cultures. Further study is required to determine the significance of isolated organisms in samples from patients who are not thought to be infected

Aims. The aim of this study was to identify the incidence of positive cultures during the second stage of a two-stage revision arthroplasty and to analyse the association between positive cultures and an infection-free outcome. Patients and Methods. This single-centre retrospective review of prospectively collected data included patients with a periprosthetic joint infection (PJI) of either the hip or the knee between 2013 and 2015, who were treated using a standardised diagnostic and therapeutic algorithm with two-stage exchange. Failure of treatment was assessed according to a definition determined by a Delphi-based consensus. Logistic regression analysis was performed to assess the predictors of positive culture and risk factors for failure. The mean follow-up was 33 months (24 to 48). Results. A total of 163 two-stage revision arthroplasties involving 84 total hip arthroplasties (THAs) and 79 total knee arthroplasties (TKAs) were reviewed. In 27 patients (16.6%), ≥ 1 positive culture was identified at re-implantation and eight (29.6%) of these subsequently failed compared with 20 (14.7%) patients who were culture-negative. The same initially infecting organism was isolated at re-implantation in nine of 27 patients (33.3%). The organism causing re-infection in none of the patients was the same as that isolated at re-implantation. The risk of the failure of treatment was significantly higher in patients with a positive culture (odds ratio (OR) 1.7; 95% confidence interval (CI) 1.0 to 3.0; p = 0.049) and in patients with a higher Charlson Comorbidity Index (OR 1.5; 95% CI 1.6 to 1.8; p = 0.001). Conclusion. Positive culture at re-implantation was independently associated with subsequent failure. Surgeons need to be aware of this association and should consider the medical optimisation of patients with severe comorbidities both before and during treatment. Cite this article: Bone Joint J 2017;99-B:1490–5

Introduction. Patients with long-bone osteomyelitis are frequently referred with limited microbiological information. This study compared pre-referral microbiology in long bone osteomyelitis with intra-operative microbiology from a specialist centre. Materials and Methods. All patients referred to a single tertiary centre between February 2019 and February 2020, aged ≥18 years and received surgery for confirmed long-bone osteomyelitis were included. Patient demographics, referral microbiology and previous surgical history were collected at the time of initial clinic appointment. During surgery, a minimum of 5 intra-operative deep tissue samples were sent for microbiology. Antimicrobial options were classified from the results of susceptibility testing using the BACH classification of long bone osteomyelitis as either Ax (unknown or culture negative), A1 (good options available) or A2 (limited options available). The cultures and susceptibility of pre-referral microbiology were compared to the new intra-operative sampling results. In addition, an association between previous osteomyelitis excision and antimicrobial options were investigated. Results. 79 patients met inclusion criteria during the study period. From these, 39 (49.4%) patients had information available at referral regarding microbiology obtained from either sinus swab (n–16), bone biopsy (n–11), previous osteomyelitis excision sampling (n–7), aspiration (n–4) or blood culture (n–1). From these 39 patients, microbiology information at referral fully matched microbiology samples taken at operation in 8 cases (20.5%). Fifteen of the 39 patients (38.5%) had a different species isolated at surgery compared to referral microbiology. The remaining 16 patients (41.0%) had a culture-negative osteomyelitis on surgical sampling. Based on the microbiology obtained in our centre, 35 patients were classified as A1 (44.3%), 15 as A2 (18.9%) and 29 as culture negative, Ax (36.7%). Patients who had received previous excision of osteomyelitis before referral (n–32, 40.5%) had an increased odds ratio (OR) of having microbiology with limited antimicrobial options compared to those undergoing primary osteomyelitis excision (OR: 3.8, 95% CI 1.2–11.2, P–0.023, Fisher's exact test). Conclusions. Pre-referral microbiology correlated with intra-operative samples taken at our centre in less than one quarter of cases of long-bone osteomyelitis. Previous failed surgery for osteomyelitis was associated with increased antimicrobial resistance, reducing options for effective treatment

Aim. When treating periprosthetic joint infections with a two-stage procedure, antibiotic-impregnated spacers are used in the interval between removal of prosthesis and reimplantation. The spacer provides local antibiotics; however, it may also act as foreign-body that can be colonized by microorganisms. According to our experience, cultures of sonicated spacers are most often negative. The objective of our study was to investigate whether PCR analysis would improve the detection of bacteria in the spacer sonication fluid. Method. A prospective monocentric study was performed at Lausanne University Hospital from September 2014 until January 2016. Inclusion criteria were two-stage procedure for prosthetic infection and agreement of the patient to participate in the study. For a two-stage procedure the interval before reimplantation ranged between 2 and 8 weeks. Spacers were made of cement impregnated with gentamycin, tobramycin and vancomycin. Cultures of intraoperative deep tissues samples from first and second stage procedures, prosthesis sonication and spacer sonication were analyzed. Multiplex-PCR. *. , pan-bacterial PCR (16S), and a Staphylococcus-specific PCR analysis were performed on the sonicated spacer fluid. Results. 23 patients were identified (12 hip, 10 knee and 1 ankle replacements). Initial infection was caused by Staphylococcus aureus (27%), Streptococcus epidermidis (27%), S. dysgalactiae (13%), S. milleri (9%), S. pneumoniae (4%), S. capitis (4%), S. salivarus (4%), P. acnes (4%), E. faecalis (4%) and C. fetus (4%). At reimplantation, cultures of tissue samples and spacer sonication fluid were all negative. Of culture-negative samples, the PCR analyses were negative except for 5 cases. 4 cases of infection recurrence were observed, with bacteria different than for the initial infection in 3 cases. For these cases, no germs were detected in the spacer sonication fluid by neither cultures nor PCR. Conclusions. The 3 different PCR analyses performed did not detect any bacteria in spacer sonication fluid that was culture-negative. In our study, PCR did not improve the bacterial detection and did not help to predict whether the patient will present a recurrence of infection. Prosthetic 2-stage exchange with short interval and antibiotic-impregnated spacer is an efficient treatment to eradicate infection as both culture- and molecular-based methods were unable to detect bacteria in spacer sonication fluid after reimplantation

Literature debates whether fluid aspirates for suspected PJI should undergo prolonged incubation for cultures. We looked at sensitivity and specificity of 14-day cultures, compared to 7-days, for aspirates from prosthetic hips and knees. Design and methods. Conducted at a quaternary referral centre for PJIs from Jan 2017 to July 2019. Suspected PJIs who underwent aspiration, incubated 14 days and later surgical intervention with minimum three tissue samples were included. Results. 176 aspirates were included. This is an increased number compared to our historic figures (average 88 Vs 48 pts/yr). 47 patients had fluid and tissue positive (true positive), 20 fluid +ive but tissue -ive (false positive), 98 fluid and tissue -ive (true negative) and 15 fluid negative but tissue +ive (False negative). Thus, sensitivity 76%, specificity 83%, positive predictive value70% and negative predictive value 87%. Of 88 positive aspirates, only 75% were within 7-day cultures. Low virulence organisms as Propionibacterium acnes and coagulase negative staph were grown later. Of 48 with only one tissue sample positive, 38 were culture-negative on aspiration and 6 grew different organisms on aspirate and tissues. Also, as many were cultured later, it suggests contamination. Conclusion. Increased numbers reflect quaternary referral nature of institution and increasing PJI load. Modest drop in sensitivity and specificity of 14-day cultures compared to 7-day(84 and 85% respectively) is due to higher false negatives. Contamination contributes to false-ive as more tissue samples become positive (there were 1076 tissue samples due to multiple sampling Vs 176 aspirates). Higher tissue yield may also be because they are more representative. Effect of antibiotic use between samples cannot be determined. Organism profile suggest14-day culture produces more contaminant growth despite a well-equipped microbiology lab with laminar airflow for subcultures. Caution in interpreting 14-day results in diagnosis of PJI of Hip and Knee is advised

Optimal sampling for culture-based or molecular diagnosis remains highly contested for patients suspected of prosthetic joint infection (PJI). Most existing studies have a retrospective design without a standardized sampling strategy. Therefore, the results are difficult to translate into guidelines. We have conducted a 2-year prospective study with a sampling strategy adaptable to the specific procedure in patients with either hip or knee alloplasty. Thus, comparisons of results obtained with different specimen types and diagnostic methods are possible. The study enrolled patients with a painful hip or knee alloplasty. The sampling strategy for microbiological diagnosis included multiple specimens of each type (joint fluid, tissue biopsies, bone biopsies, and swabs taken from the prosthesis in situ), and prosthetic components (if removed). Prepacked boxes with containers and accessories for sampling, transport and storage were provided. Microbial culture and bacterial 16S rDNA screening were carried out for all specimen types. Whenever positive upon 16S rDNA screening, samples were analyzed further by sequencing. Peptide nucleic acid-fluorescence in situ hybridization (optimized using filtrations; Filter-PNA-FISH) was limited to a subset thereof. An overall completeness of ∼90% was obtained by the sampling strategy in 164 procedures (‘cases’) in 131 patients. In 58 cases PJI was suspected, and a revision was carried out. 42 cases were culture-positive, and 16 were culture-negative; one culture-negative case was positive by 16S rDNA sequencing of a corresponding specimen. The contribution to a microbiological diagnosis was high for periprosthetic tissue biopsies (≥ 3 positive out of 5) 90%, prosthetic component(s) 90%, and joint fluid 94%. Conversely, the contribution was sparse for prosthetic swabs 50% and bone biopsies 40%, respectively. Filter-PNA-FISH was used to confirm findings by culture and to demonstrate biofilm formation. With the described sampling strategy we reached high completeness of complex specimen sets. The sampling strategy may be adapted to other clinical settings with microbiological sampling of similar complexity. We found multiple periprosthetic tissue biopsies, prosthetic component(s) and joint fluid to form the optimal specimen set for culture-based diagnosis. The contribution by 16S rDNA sequencing is still under investigations but the contributions seems moderate probably because of a low rate of antibiotic therapy before the procedure, use of effective culture methods and prolonged incubation (14 days)

Introduction. Antibiotic loaded absorbable calcium sulphate beads (ALCSB) are an increasingly popular adjunct in the treatment of musculoskeletal infections including osteomyelitis and peri-prosthetic joint infections (PJI). Limited data exist regarding the clinical indications and biochemical outcomes of ALCSB in PJI cases. Aims. To determine the proportion of organisms that were sensitive to the gentamicin and vancomycin that we add to the ALCSB as a part of our treatment protocol and to determine the prevalence of postoperative hypercalcaemia when used for treatment of hip and knee DAIR (debridement and implant retention) and revision arthroplasty for PJI. Methods. A retrospective review of 160 hip and knee revisions using ALCSB performed between June 2015 and May 2018 at a tertiary unit was performed. 10–40 cc of ALCSB was used for each case containing vancomycin and gentamicin. Data recorded included patient demographics, comorbidities, indication for surgery, operative intervention, microbiological results and serum biochemistry for calcium levels. Results. The cohort consisted of 91 males and 69 females, with a mean age of 69.0 years (21.3 to 93.1) and mean BMI of 34.7(12.6 to 48.1). 56 (35%) had single-stage revision, 45 (28.1%) had first stage revision, 35 (21.9) had DAIR, 19 (11.9%) had second stage revision and 5 (3.1%) other procedures. Organisms included staphylococcus aureus (30.0%), culture-negative (27.5%), staphylococcus epidermidis (18.1%), and pseudomonas aeruginosa (3.1%). 54.3% were sensitive to both vancomycin and gentamicin, 25.0% to vancomycin only and 8.6% to gentamicin only. 11.9% (19/160) of patients had transient post-operative hypercalcaemia (normal range 2.2–2.7mmol/L), peaking at day 6–7 and resolved with hydration by day 10 postoperatively. Preoperatively, 26.9% had albumin <35 g/L and 49.3% had some degree of renal impairment with an eGFR <90 ml/min. Conclusion. The use of ALCSB allows local delivery of vancomycin and gentamicin in lower limb PJI. Organisms were sensitive to this antibiotic combination in 88% cases. Care must be taken to monitor calcium for 10 days post-operatively

Aims. To identify the most common infecting organisms associated with deep infection and infected non-union of the tibia, as well as the rate of ‘culture-negative’ infections, at a tertiary referral trauma centre dealing with military and civilian trauma. Method. Between 2008 and 2010 all patients with a confirmed clinical diagnosis of implant-related infection or infected non-union of the tibia were identified retrospectively from a database and their records analysed. After a period of at least 10–14 days without antibiotics, all patients underwent surgical debridement in which ‘clean’ samples were went for microbiological analysis. Skeletal stablity was achieved with a circular frame and intravenous antibiotics were started pending culture and sensitivity results. Results. There were 31 patients; 28 male, 3 female. Mean age 41yrs. 21 patients (68%) had sustained open fractures. In 11 patients, tissue cultures were negative. In the remainder, 8 patients cultured one organism, 6 two organisms, 2 three organisms, and 2 four organisms. Only those with open fractures grew more than 2 organisms. A total of 15 different infecting organisms (all of which were bacteria) were identified. The most common organisms isolated were Staphylococcus aureus, coagulase-negative Staphylococcus, Bacillus and Enterobacter cloacae. There were 3 cases of MRSA infection, all in open fractures. The most frequently used antibiotics for definitive therapy were ciprofloxacin, rifampicin and vancomycin. Conclusions. The majority of patients had sustained open fractures. Patient with open fractures were more likely to have polymicrobial infections. There was a high rate of culture-negative infections, particularly in the closed fracture group. Meticulous sampling and processing of microbiology samples is essential to minimise the number of culture-negative infections. Laboratory techniques such as polymerase chain reaction may help improve culture yields

Objectives. The risk of infection after type III° open fractures is high (10–50%). Preemptive antibiotic therapy may prevent posttraumatic infection and improve the outcome. Recommendations about the type and duration of antibiotic vary among the institutions and it remains unclear whether gram-negative bacilli or anaerobs need to be covered. In Europe, the most commonly recommended antibiotic is amoxicillin/clavulanic acid. We retrospectively analyzed microbiology, characteristics and outcome of patients with open type III° fractures treated at our institution. Methods. Between 01/2005 and 12/2009 we retrospectively included all type III grade open fractures of the leg at our institution classified after Gustilo (JBJS Am 1976) into type IIIA (adequate soft-tissue coverage of bone with extensive soft-tissue laceration or flaps), IIIB (extensive soft-tissue loss with periosteal stripping and bone exposure), and IIIC (requiring arterial injury repair). Demographic characteristics, clinical presentation, microbiology, surgical and antibiotic treatment and patient outcome were recorded using a standardized case-report form. Results. 30 cases of patients with type III° open fractures were included (25 males, mean age was 40.5 years, range 17–67 years). 27 fractures (90%) were located on the lower leg and 3 (10%) on the upper leg. 24 cases (80%) were high-energy and almost half of the patients (n=16, 53%) had a polytrauma. Microbiology at initial surgery was available for 19 cases (63%), of which 10 grew at least one organism (including 8 amoxicillin/clavulanic acid-resistant gram-negative bacilli [GNB], 7 amoxicillin/clavulanic acid-resistant Bacillus cereus), 11 were culture-negative. Preemptive antibiotics were given in all cases (100%) for an average duration of 8.5 days (range 1–53 days), the most common antibiotic was amoxicillin/clavulanic acid in 60 % (n=18). 11 cases just received preemptive antibiotic treatment, in 19 of 30 cases the antibiotic therapy was changed and prolonged. Microbiology at revision surgery was available for 25 cases and 22 grew at least one pathogen (including 32 amoxicillin/clavulanic acid-resistant gram-negative bacilli and 10 amoxicillin/clavulanic acid-resistant Bacillus cereus), 3 were culture-negative. Conclusions. At initial surgery, most common isolated organisms were coagulase-negative staphylococci (43%), Bacillus cereus (23%), and gram-negative bacilli (27%), and others (7%) of which 48% were resistant to amoxicillin/clavulanic acid. At revision surgery, isolated organisms were gram-negative bacilli (64%), Bacillus cereus (20%), and others (16%) of which 88% were resistant to amoxicillin/clavulanic acid. The spectrum of amoxicillin/clavulanic does not cover the most common isolated organisms

Aim. Here we describe a cohort study to determine the performance of a commercially available Fluorescence In Situ Hybridization (FISH)-kit on samples of 65 consecutive patients suspected of orthopedic implant associated infections (IAI). Culture is routinely used and has a high specificity and sensitivity but requires days to more than a week for slow growing bacteria. FISH results are available within 45–60 minutes and thus specific treatment can start immediately. In addition, previous antibiotic therapy may hinder culture while bacteria may still be detected by FISH. Method. The hemoFISH-kit from Miacom diagnostics (Dusseldorf, Germany) was used on a total of 82 joint aspirates, sonication fluids and tissue samples of 65 consecutive patients to detect and identify possible microorganisms. This FISH-kit contains a universal 16S rRNA probe and species-specific probes for bacteria commonly encountered in blood infections. FISH and culture were compared to the clinical definition of IAI. These definitions were based on the criteria described by Pro-Implant Foundation criteria for IAI after fracture fixation or prosthetic joint infection. If no criteria were described in the literature for a specific IAI then MSIS criteria were used. Results. FISH and culture was done in 33 plain tissue samples, 43 sonication fluid samples and 6 joint aspirates of 65 patients. Results are shown in table 1. In clinical infections FISH provided earlier results in 7 and 2 extra for culture-negative. In 5 IAI-negative cases FISH was false-positive. Conclusions. Faster diagnosis by FISH is appealing, however with a PPV of 64% the hemoFISH-kit is not accurate enough for clinical use. Also, blood and orthopedic infections have different common pathogens, therefor FISH could not identify all of the bacterial strains due to a lack of specific probes. An orthopedic FISH-kit could solve this problem

Introduction. Next generation sequencing (NGS) has been shown to facilitate detection of microbes in a clinical sample, particularly in the setting of culture-negative periprosthetic joint infection (PJI). However, it is unknown whether every microbial DNA signal detected by NGS is clinically relevant. This multi-institutional study was conceived to 1) identify species detected by NGS that may predict PJI, then 2) build a predictive model for PJI in a developmental cohort; and 3) validate the predictive utility of the model in a separate multi-institutional cohort. Methods. This multicenter investigation involving 15 academic institutions prospectively collected samples from 194 revision total knee arthroplasties (TKA) and 184 revision hip arthroplasties (THA) between 2017–2019. Patients undergoing reimplantation or spacer exchange procedures were excluded. Synovial fluid, deep tissue and swabs were obtained at the time of surgery and shipped to MicrogenDx (Lubbock, TX) for NGS analysis. Deep tissue specimens were also sent to the institutional labs for culture. All patients were classified per the 2018 Consensus definition of PJI. Microbial DNA analysis of community similarities (ANCOM) was used to identify 17 candidate bacterial species out of 294 (W-value >50) for differentiating infected vs. noninfected cases. Logistic Regression with LASSO model selection and random forest algorithms were then used to build a model for predicting PJI. For this analysis, ICM classification was the response variable (gold standard) and the species identified through ANCOM were the predictor variables. Recruited cases were randomly split in half, with one half designated as the training set, and the other half as the validation set. Using the training set, a model for PJI diagnosis was generated. The optimal resulting model was then tested for prediction ability with the validation set. The entire model-building procedure and validation was iterated 1000 times. From the model set, distributions of overall assignment rate, specificity, sensitivity, positive predictive value (PPV) and negative predicative value (NPV) were assessed. Results. The overall predictive accuracy achieved in the model was 75.9% (Figure 1). There was a high accuracy in true-negative and false-negative classification of patients using this predictive model (Figure 2), which has previously been a criticism of NGS interpretation and reporting. Specificity was 97.1%, PPV was 75.0%, and NPV was 76.2%. On comparison of the distribution of abundances between ICM-positive and ICM-negative patients, Staphylococcus aureus was the strongest contributor (F=0.99) to the predictive power of the model (Figure 3). In contrast, Cutibacterium acnes was less predictive (F=0.309) and noted to be abundant across both infected and noninfected revision TJA samples. Discussion. This study is the first to utilize predictive modeling algorithms on a large prospective multicenter database in order to transform analytic NGS data into a clinically relevant diagnostic signal. Our collaborative findings suggest the microbial DNA signal identified on NGS may be an independent useful adjunct for the diagnosis of PJI, as well as help identify causative organisms. Further work applying artificial intelligence tools will improve accuracy, predictive power and clinical utility of high-throughput sequencing technology. For figures, tables, or references, please contact authors directly

Aims

This study aimed to evaluate the BioFire Joint Infection (JI) Panel in cases of hip and knee periprosthetic joint infection (PJI) where conventional microbiology is unclear, and to assess its role as a complementary intraoperative diagnostic tool.

Aim. This study quantified changes in the microbiology of osteomyelitis in a single specialist centre within the UK. The rate of infection with multi-drug-resistant (MDR) bacteria was measured over a ten year period in 388 patients. Method. Patients with confirmed osteomyelitis who received curative surgery from 2013–2017 were included (n=222). Microbiology was compared to patients from a cohort between 2001–2004, using the same diagnostic criteria (n=166). 1. The proportion of MDR bacterial pathogens. 2. from deep tissue culture in these cohorts were compared. Pathogens were analysed according to aetiology and the presence of metal-work. Results. Both cohorts had similar baseline characteristics. A median of five tissue samples were submitted for each patient. The proportions of specific pathogens remained unchanged between the two cohorts, with the exception of a decrease in the proportion of coagulase-negative Staphylococcus (CoNS) (12.7% vs 5.3%, p<0.05). Although the overall proportion of Staphylococcus aureus remained similar, the rate of MRSA infection decreased in the 2013–2017 cohort when compared to the 2001–2004 cohort (30.7% vs. 10.5% of Staphylococcus aureus, p<0.05). However, the proportion of MDR Enterococcus, Pseudomonas and Enterobacteriaceae did not differ between the two cohorts (37.3% vs. 35.7%). There were no differences in microbiology of the 2013–2017 cohort that related to presence of metal-work or aetiology of infection. A higher proportion of haematogenous osteomyelitis were culture-negative compared to other aetiologies (37.1% versus 20.3%). Conclusions. In this UK centre over the past 10 years, rates of MRSA osteomyelitis have fallen by two thirds, which is in line with the reducing rate of MRSA bacteraemia nationally. However, the proportion of other MDR bacteria remained unchanged. A decrease in the proportion of CoNS may reflect improved sampling technique and culture. Furthermore, this study demonstrated that classification by aetiology or the presence of metal-work does not predict the pathogen in adults with chronic osteomyelitis

Aims

Gram-negative periprosthetic joint infection (PJI) has been poorly studied despite its rapidly increasing incidence. Treatment with one-stage revision using intra-articular (IA) infusion of antibiotics may offer a reasonable alternative with a distinct advantage of providing a means of delivering the drug in high concentrations. Carbapenems are regarded as the last line of defense against severe Gram-negative or polymicrobial infection. This study presents the results of one-stage revision using intra-articular carbapenem infusion for treating Gram-negative PJI, and analyzes the characteristics of bacteria distribution and drug sensitivity.