Aim. Antimicrobial peptides occur naturally in our intrinsic immune system. PLG0206 is a novel, engineered, 24-amino acid peptide which has broad-spectrum antimicrobial activity, including in biofilm and against multi-drug resistant pathogens (1,2). This is the first clinical study to evaluate the safety and tolerability of PLG0206 when administered via an irrigation solution in patients with periprosthetic joint infections (PJI) following total knee arthroplasty (TKA) during debridement, antibiotics, and implant retention (DAIR). Secondary objectives were to evaluate pharmacokinetics (PK), biomarkers and initial clinical efficacy at one year post-DAIR procedure. Method. This prospective, multicenter, open-label, interventional study assessed two dose levels of PLG0206. Fourteen patients underwent revision for PJI after TKA. At the end of debridement, they received a single intra-articular irrigation of PLG0206 into the wound cavity lasting 15 minutes at concentrations of 3 mg/mL (n=7) or 10 mg/mL (n=7). Patients received post-operative care and intravenous/oral antimicrobial therapy as per their institutional guidelines. Patients were monitored for safety and signs of relapse or persistent infection for 12 months post study drug administration and PK and blood biomarkers were assessed. Results. All patients completed their final study assessment at Day 365. Over the 1-year follow-up, only one recurrence (7%) was noted at Day 169 in the low-dose cohort. Following dosing, nine patients (64.3%) had limited systemic exposure; maximum plasma concentration occurred 1-hour post-administration and declined rapidly to undetectable levels by 24 hours following treatment in all patients. The incidence of drug related treatment-emergent adverse events (TEAEs) was low. Two patients, both in the higher dose cohort, experienced a transient drug related TEAE; one of hypertransaminasaemia and one of neuralgia. Both events were moderate in severity and resolved within two weeks of onset. Conclusions. A single 15-minute irrigation of PLG0206 into the wound cavity of patients undergoing a DAIR procedure for PJI following TKA, is safe and well tolerated by patients. This new antimicrobial peptide offers a promising therapeutic option in musculoskeletal infection. The initial clinical efficacy is encouraging but now needs to be investigated in a much larger clinical trial

Aim. Two types of national registers surveil infections after primary total hip arthroplasty (THA) in Norway: The National surveillance system for surgical site infections (NOIS) that surveil all primary THAs 30 days postoperatively for surgical site infections (SSI), and the Norwegian Arthroplasty Register (NAR) that follow all THAs until any surgical reoperation/revision or the death of the patient. Since these registers report on the same THAs we assessed correspondence between and time trends for the two registers in period 2013 to 2022. All reported THAs were included. Method. The THAs were matched on a group level according to sex, age and ASA-class. In addition to descriptive statistics, adjusted Cox regression analyses were performed with adjustment for sex, age group (<45, 45-54, 55-64, 65-74, 75-84, >85 years) and ASA-class (1, 2, 3, 4 and missing). Changes in annual incidence and adjusted hazard rate (aHR) was calculated. Endpoints in the NOIS were 30-Days SSI and 30-Days reoperation for SSI. Endpoints in the NAR were 30-Days and 1-Year reoperation for periprosthetic joint infection (PJI). Results. The NOIS had registered 87,923 THAs with 1,393 (1.58%) SSIs and 765 (0.87%) reoperations for SSI within 30 postoperatively. The NAR had registered 91,194 THAs with 725 (0.80%) reoperations for infection after 30 days, and 1,019 (1.21%) reoperations for infections after one year. The distribution of sex, age and ASA-class was near identical in the two registers. There was a mean annual reduction in risk of both SSI (aHR 0.92 (95% CI 0.90-0.93)) and reoperation for SSI (0.95(0.92-0.97)) and PJI (30-Days: 0.96 (0.94-0.99), 1-Year: 0.95-0.99)) over the period 2013-2022. Conclusions. The NOIS and the NAR have excellent completeness and the registrations in both registers may be considered representative for the Norwegian population. Not all SSI are reoperated. The incidence and risk of SSI (NOIS) and reoperation for PJI (NAR) is declining and may reflect a true reduction in incidence of PJI after primary THA

Aim. An instrumented blood culture system automatically flags when growth within the culture medium has been detected (‘work in progress’), and subsequently when the organism has been identified. We explore using this data to switch patients to oral therapy within 72 hours post-surgery, reducing costs and improving antimicrobial stewardship. Method. This retrospective review focused on clinically significant culture-positive bone and joint infections over a 5-month period in 2022. Two cohorts were defined as either having positive intraoperative microbiology at <72 hours or at ≥72 hours. Results. 150 patients were included. 133/150(88%) exhibited microbial growth <72hours. Of these, 98/133(74%) had all organisms identified <72-hours, and 34/133(26%) had additional organisms ≥72 hours. 19/151(12%) patients had their first positive cultures ≥72hrs from sampling. The most common isolates identified within 72 hours were S. aureus(30%), Enterobacteriaceae (26%), and Coagulase-negative Staphylococcus (CoNS)(19%). If no growth was observed by 48 hours, there was a 69.6% probability that subsequent growth wouldn't occur; this probability increases to 81.9% by 72 hours, 88.7% by 96 hours, 91.0% by 120 hours, and 95.0% by 144 hours (see figure 1). The most common isolates identified ≥72 hours were CoNS(28%), Cutibacterium acnes(16%) and S. aureus(12%). Assessing oral antibiotic regimes for isolates identified after 72 hours demonstrated that linezolid would cover isolates from 96% of patients, tetracyclines 92% of patients, clindamycin 85% of patients, and ciprofloxacin and rifampicin would cover 80% of patients. Vancomycin and meropenem, our standard empirical therapy, gave the best cover at 96% of patients. Conclusions. This study suggests there is sufficient microbiological information at 72 hours for most patients to allow transition to a targeted regimen. If there has been no detection of growth when using an instrumented blood culture system by 72 hours, it is likely that there will be no growth. For any tables or figures, please contact the authors directly

Aim. Periprosthetic Joint Infection (PJI) is a devastating complication in hip and knee joint arthroplasty. The “JS BACH” classification system was developed in 2021 to stratify the complexity of PJI, and more importantly, to act as a tool to guide referrals to specialist centers. The “JS BACH” classification has not been validated in an external cohort. This study aimed to do so using a large prospective cohort from Australia and New Zealand. Method. We applied the JS-BACH classification to the Prosthetic Joint Infection in Australia and New Zealand Observational (PIANO) cohort. This prospective study of newly diagnosed PJI collected 2-year outcome data from 653 participants enrolled in 27 hospitals. The definition of PJI treatment failure at 24 months was any of the following: death, clinical or microbiological signs of infection, destination prosthesis removed, or ongoing antibiotic use. Results. Individual cases were classified as per JS-BACH into “1 - uncomplicated” (n = 268), “2 - complex” (n = 330), and “3 - limited options” (n = 55). This cohort was similar to the original JS-BACH population in terms of baseline characteristics. However, there was a difference in complexity, with more DAIR procedures, fewer revision procedures, and a higher proportion of uncomplicated patients in the PIANO cohort. The risk of treatment failure correlated strongly with the JS-BACH category, with odds ratios (95% CI [confidence interval]) for category 2 versus 1 of 1.75 (1.24 to 2.47) and for category 3 versus 1 of 7.12 (3.42 to 16.02). Conclusions. Despite the PIANO study population being less complicated than the original derivation cohort, the JS-BACH classification showed a clear association with treatment failure in this large external cohort

Background. Two-stage revision arthroplasty is the standard treatment for chronic hip and knee periprosthetic joint infections (PJI). Accurate diagnosis of persistent infections at 2nd stage using established biomarkers and diagnostic criteria is of paramount importance. This study aimed to evaluate the diagnostic value of synovial calprotectin and alpha-defensin, and compare established diagnostic criteria from the International Consensus Meeting (ICM 2018) and the European Bone and Joint Infection Society (EBJIS 2021) to determine persistent PJI at the 2nd stage of a two-stage revision arthroplasty. Methods. We retrospectively analyzed 97 patients who underwent 100 two-stage revisions (hip: 39, knee: 61). Synovial fluid samples were assessed for calprotectin and alpha-defensin levels. ICM 2018 and EBJIS 2021 were applied to all patients undergoing 2nd stage revision. Receiver operating characteristic (ROC) curves and Youden Index were utilized to determine optimal cut-off values, and correlations between biomarkers were evaluated. The microbiological spectrum was analyzed at 2nd stage and re-revision surgery. Results. Calprotectin levels showed a sensitivity of 66.7%, specificity of 32.9%, and accuracy of 38.0% in predicting septic failure. Alpha-defensin showed sensitivity of 28.6%, specificity of 87.8%, and accuracy of 79.2%. Significant correlations included: calprotectin with PMN% (r = 0.471, p = 0.05) and alpha-defensin with WBC (r = 0.830, p < 0.01) in the successful cohort. For septic re-revisions, calprotectin and alpha-defensin were highly correlated (r = 0.969, p < 0.01). ICM correctly diagnosed persistent PJI in 26.7%, while EBJIS diagnosed 24.2%. The microbial spectrum shifted from gram-positive to gram-negative bacteria between reimplantation and re-revision surgeries. Conclusion. Synovial calprotectin and alpha-defensin demonstrated limited accuracy in ruling out persistent PJI at reimplantation. The low sensitivity of current diagnostic criteria, combined with the observed shift in microbial spectrum, underscores the challenges in diagnosing persistent PJI during 2nd stage of a two-stage revisions arthroplasty

Aim. The SOLARIO trial is a randomised controlled non-inferiority trial of antibiotic strategy for bone and joint infection. SOLARIO compares short or long post-operative systemic antibiotic duration, for patients with confirmed infections, who had local antibiotics implanted and no infected metalwork retained when undergoing surgery. This analysis compared systemic antibiotic use in the short (intervention) and long (standard of care) arms of the trial, in the 12 months after index surgery. Method. Data was collected prospectively from study randomisation, within 7 days of index surgery. All systemic antibiotics prescribed for the index infection were recorded, from health records and patient recall, at randomisation, 6 weeks, 3-6 months and 12 months after study entry. Start and end dates for each antibiotic were recorded. Results. 251 patients were randomised to short systemic antibiotics (up to 7 post-operative days) and 249 patients, to long systemic antibiotics. 5 participants in the short group and 2 participants in the long group withdrew from study follow-up. Complete data for all systemic antibiotics taken in the 12 months following surgery, were available for 237 participants in the short group and 236 participants in the long group. 80 participants across both groups were noted as having deviated from their assigned treatment strategy. Both groups received empiric antibiotics, predominantly vancomycin and meropenem, for up to 7 days after surgery. Considering each prescribed antibiotic as a separate duration (even when administered concurrently), participants assigned to standard care received a mean of 74.9 antibiotic-days. Participants assigned to short systemic antibiotics received a mean of 27.5 antibiotic-days in the 12 months after surgery. The most commonly prescribed antibiotics in both treatment groups were vancomycin and meropenem: these antibiotics accounted for 7.1 days prescribed per participant in the long group, and 6.3 days in the short group (p=0.37). Reasons for post-randomisation antibiotic prescribing in the short treatment group included later planned surgery, identification of bacteria requiring additional systemic antibiotics, and treatment of superficial wound infections. WHO AWaRe classification ‘watch’ and ‘reserve’ group antibiotics, such as ciprofloxacin, rifampicin, vancomycin and meropenem, accounted for 39.4 antibiotic-days per long group participant, and 16.5 antibiotic-days per short group participant. Conclusions. Considering the combined duration of all systemic antibiotics prescribed over 12 months, including those co-administered, participants in the short arm of the SOLARIO trial received considerably fewer days of all antibiotic classes, and particularly those antibiotics restricted in the WHO AWaRe classification (2021)

Aim. This study aims to evaluate the effectiveness of a pre-formulated irrigation solution. 1. (containing ethanol, acetic acid, sodium acetate, benzalkonium chloride, and sterile water) compared to saline solution in managing acute periprosthetic joint infections (A-PJI) during Debridement, Antibiotic, and Implant Retention (DAIR) surgeries. The primary objective is to assess the healing rate using this solution. 1. versus saline in A-PJI patients, with “cure” defined by a set of criteria including no recurrence, wound issues, or need for ongoing suppressive antibiotics after 1 year. Principio del formularioFinal del formulario. Method. This single-center, randomized controlled trial will involve patients with acute periprosthetic infections undergoing standard DAIR surgery, divided into two groups: one receiving saline solution and the other receiving pre-formulated solution. 1. The study is single-blinded, with patients unaware of their group assignment. The study is registered at ISRCTN: https://doi.org/10.1186/ISRCTN10873696. Inclusion criteria include patients over 18 with hip or knee prostheses suffering from acute or hematogenous periprosthetic infections, while exclusion criteria include a history of prior debridement or multiple infected implants, among others. Principio del formularioFinal del formulario A total of 50 subjects are needed for statistical significance, with a 5% dropout rate anticipated. An interim safety analysis will assess early effectiveness and adverse effects, and the results are presented in this study. Data will be managed in online databases and analyzed using SPSS software, with a significance level of p<0.05. Results. Twenty-four patients were eligible for analysis, twelve in each group. The overall average age was 75 years, and the gender distribution was predominantly female (9 F and 3 M in each group). No significant differences were found at the baseline characteristics level between the two groups (p>0.05). The minimum follow-up of 1 year was achieved in all cases except three due to deaths not related to periprosthetic infection. Regarding efficacy, a non-statistically significant difference was observed (p>0.05), with 58% in the serum group and 42% in the pre-formulated irrigation solution. 1. group (X. 2. = 0.17, p=0.683). The average hospital stay was 38.42 days (SD 26.32) in the pre-formulated irrigation solution group. 1. and 24.42 days (SD 18.72) in the serum group, with this difference being not significant (t=1.5, p=0.148). Conclusions. While the current analysis indicates no significant differences between both groups in terms of efficacy, the study's ongoing progress and the inclusion of a larger sample size could potentially yield more definitive results

Aim. Daptomycin plus fosfomycin combination therapy is a valuable strategy for treating staphylococcal osteoarticular infections. Considernig that each gram of fosfomycin contains 330 mg of sodium, electrolytic imbalance due to sodium overload could pose safety issues, especially in the cardiopatic patients and/or in the frail elderly. The aim of this study was to compare the efficacy of using reduced vs. standard daily dose fosfomycin in combination with daptomycin in a cohort of patients with osteoarticular infections. Method. This analysis included adult patients with osteoarticular infections admitted to the Infectious Diseases Unit of our University hospital in the period Nov 2022 – Feb 2024 and who were treated with daptomycin (8-10 mg/kg/daily) plus 24h-continuous infusion (CI) fosfomycin at the standard-dose of 16 g daily (standard-dose group) or at the reduced-dose of 8-12 g daily (reduced-dose group). All the patients underwent therapeutic drug monitoring (TDM) of fosfomycin for granting a pharmacodynamic target attainment of 24h-area under the concentration-time curve over minimum inhibitory concentration (AUC24h/MIC) >95 against Staphylococcus aureus with an MIC value up to 32 mg/L and of 70%t>MIC. Estimated glomerular filtration rate (eGFR) was assessed at each TDM session. Patient clinical outcome was assessed. Results. The standard- and the reduced-dose groups included 43 (29 males, 67.4%) and 21 (11 males, 52.4%) patients, respectively. No differences in median age (54 vs. 63 years, p=36), weight (80 vs. 76 kg, p=0.13) and type of diagnosis [prosthetic joint infections (16 vs. 29, p=0.38), osteomyelitis (2 vs. 9, p=0.72), septic arthritis (3 vs. 3, p=0.39) and spondilodiscitis (0 vs. 2, p=1.0)] were observed between the two groups. Median eGFR was similar in the standard vs. the reduced-dose group (109 vs. 98 mL/min/1.73m2, p=0.004). In the reduced-dose group, CI fosfomycin was administerd at 8 and 12 g/daily in 12 and 9 patients, respectively. There was no difference between the standard- and reduced-dose groups in attainment of the pharmacodynamic targets of AUC24h/MIC>95 (41/43 vs. 20/21, p=1.0), of 70%t>MIC (43/43 vs. 21/21 p=1.0) and of clinical cure (39/43 vs. 19/21, p=1.0). Conclusions. Combination therapy of 8-10 mg/kg/daily daptomycin plus 8-12 g/daily CI fosfomycin may be as effective as that of 8-10 mg/kg/daily daptomycin plus 16 g/daily CI fosfomycin. The fosfomycin reduced-dose strategy allows to decrease the daily sodium load by 25-50% compared to the standard dose, thus reducing the risk of cardiac adverse events. TDM may be a valuable strategy for individualizing fosfomycin dose in patients with osteoarticular infections

Aim. Periprosthetic joint infection (PJI) is one of the main reasons for revision surgery after primary unicompartmental knee arthroplasty (UKA), total knee arthroplasty (TKA) or total hip arthroplasty (THA). Currently the MSIS and EBJIS criteria sets are considered to be the gold standards in determining PJI. These criteria sets are complex and contain tests that are time-consuming and many are rather costly. Therefore, further research is indicated to find a simpler but equally reliable diagnostic test. In this study we evaluated the additional value of calprotectine measurement in synovial fluid in patients undergoing hip and knee (revision) arthroplasty following routine work-up. Method. In a retrospective cohort study, we analyzed 182 synovial fluid samples from 143 patients with suspected PJI after UKA, TKA, THA or revision arthroplasty. Twenty-six of those cases were classified as PJI according to the MSIS and EBJIS criteria. Subsequently, synovial calprotectin was determined, using a lateral flow assay and two cut-off thresholds of ≥14 mg/L and ≥50 mg/L. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of synovial calprotectin was determined. Results. When applying the MSIS and EBJIS criteria and a calprotectin level ≥14 mg/L, synovial calprotectin revealed an area under the curve of 0.96 (95% CI 0.90-1.00), with 92.3% sensitivity and 100% specificity. The PPV and NPV were 100% and 92.9% respectively. When applying the MSIS and EBJIS criteria and a calprotectin level ≥ 50 mg/L, synovial calprotectin revealed an area under the curve of 0.94 (95% CI 0.87-1.00), with 88.5% sensitivity and 100% specificity. The PPV and NPV were 100% and 89.7% respectively. Conclusions. The value of calprotectin in synovial fluid gives valuable information with a single test result, resulting in high predictive value in the diagnosis of PJI after hip or knee arthroplasty and should seriously be considered as part of PJI diagnostics in an outpatient clinical setting. The high specificity can help rule in patients that are suspected of PJI. Therefor this test can be helpful in a preop diagnostic work-up to avoid unnecessary revisions in patients with well-placed and well-fixed arthroplasties with a suspected PJI. These conclusions are independent of which criteria set was used as a gold standard

Aim. Suppressive antimicrobial therapy (SAT) is used worldwide for patients with a prosthetic joint infection (PJI but clear definitions or guidelines regarding the indications, antimicrobial strategy or treatment duration are currently lacking in the literature. The aim of this study was to identify the global differences in the clinical practice of SAT for PJI. Method. An online survey was designed to investigate the current opinion on indication and treatment goals, preferred antimicrobial drugs, dosing and treatment duration and follow-up of patients with PJI on suppression. The survey was distributed using e-mail lists of several international bone and joint infection societies and study groups. Recipients were asked to share the survey with colleagues who were not a member of one of the societies but who were involved in PJI care. Results. The questionnaire was fully completed by 330 physicians from 43 different countries on six continents (Europe, n=134, 41%; Oceania n=112, 34%; North America, n=51, 16%; other, n=33, 10%; total response rate 14%). Antimicrobial treatment for PJI was discussed in a multidisciplinary team in Europe (90%), Oceania (42%) and North America (12%). In six of eight (75%) different clinical scenarios, respondents from North America would most often place a patient on SAT. In seven of eight (88%) scenarios, SAT was started least often by European respondents. The presence of a fistula was considered a contra-indication for suppression by 74 respondents (22%). First choices of SAT for staphylococcal PJI were: oral cephalosporins (39%) and tetracyclines (31%) in North America; anti-staphylococcal penicillins (55%) and oral cephalosporins (24%) in Oceania; tetracyclines (27%) and anti-staphylococcal penicillins (22%) in Europe. For streptococcal PJI, most clinicians preferred penicillins (91% in Oceania, 67% in Europe, and 53% in North America). Preferred SAT for gram negative PJI was: fluoroquinolones and a penicillin/betalactamase inhibitor in North America (26% and 18%, respectively) and Oceania (23% and 27%, respectively); fluoroquinolones (31%) and Cotrimoxazole (28%) in Europe. The dosage of SAT was never lowered (n=126, 38%), standardly lowered for all antibiotics (n=79, 24%) or only lowered for specific antibiotics (n=125, 38%). SAT was prescribed for an indefinite duration (n=43, 13%), as fixed duration between six months and three years (n=104, 32%) or for an undetermined prespecified duration (n=154, 47%). Conclusions. Substantial variation in the practice of SAT for PJI exists between physicians worldwide and throughout the different continents. This reflects the paucity of data regarding the indication and treatment of PJI with SAT

Aim. Accurate diagnosis is key in correctly managing prosthetic joint infection(PJI). Shoulder PJI definition and diagnosis is challenging. Current PJI definitions, based overwhelmingly in hip/knee research, may not accurately diagnose shoulder PJI. Our aim is to compare the preoperative performance of two PJI definitions comparing it to definitive postoperative classification. Method. This is a retrospective study of patients who have undergone total shoulder revision surgery for infection between 2005 and 2022. Cases were classified using two different PJI definitions: a)the European Bone and Joint Infection Society (EBJIS) and; 2)the 2018 International Consensus Meeting(ICM) PJI specific shoulder definition. Preoperative classification was based on clinical features, inflammatory markers and synovial fluid leukocyte count and definitive classification also considered microbiology and histology results. Results. Preoperative and definitive PJI classification status of the 21 patients included were evaluated and is summarized in table 1. The shoulder specific 2018 ICM definition showed the highest agreement between preoperative and definitive classification (76.2%, k=0.153, p=0.006) compared to EBJIS (52.4%, k=0.205, p=0.006). In all cases, the classification was changed because of positive intraoperative microbiology (at least two identical isolates). Microbiology findings showed coagulase negative staphylococci, Staphyloccocus aureus and Cutibacterium acnes to be the most frequent. Four patients had polymicrobial infections. Conclusions. Both the EBJIS 2021 and 2018 ICM definitions have low accuracy in predicting shoulder PJI preoperatively. Clearly further studies with larger cohorts are in dire need focusing specifically on shoulder revision arthroplasty to improve on existing definitions. Caution is advised while extrapolating of criteria/thresholds recommended for hip/knee joints. For any tables or figures, please contact the authors directly

Aim. The current recommendation in Norway is to use four doses of a first-generation cephalosporin (cefazolin or cephalotin) as systemic antibiotic prophylaxis (SAP) the day of surgery in primary joint arthroplasty. Due to shortage of supply, scientific development, changed courses of treatment and improved antibiotic stewardship, this recommendation has been disputed. We therefore wanted to assess if one dose of SAP was non-inferior to four doses in preventing periprosthetic joint infection (PJI) in primary joint arthroplasty. Method. We included patients with primary hip- and knee arthroplasties from the Norwegian Arthroplasty Register and the Norwegian Hip Fracture Register for the period 2005-2023. We included the most used SAPs (cephalotin, cefazolin, cefuroxime, cloxacillin and clindamycin), administered as the only SAP in 1-4 doses, starting preoperatively. Risk of revision (Hazard rate ratio; HRR) for PJI was estimated by Cox regression analyses with adjustment for sex, age, ASA class, duration of surgery, reason for- and type of arthroplasty, and year of primary arthroplasty. The outcome was 1-year reoperation or revision for PJI. Non-inferiority margins were calculated for 1, 2 and 3 doses versus reference of 4 doses of SAP at the day of surgery, against a predetermined limit of 15% increased risk of PJI. Results. In total 274,188 primary arthroplasties (total hip 133,985, hemi hip 51,442, and total knee 88,761) were included. Of these primary arthroplasties, 2,996 (1.1%) had subsequent revisions for PJI during the first postoperative year. One dose of SAP was given in 9,603 arthroplasties, two doses in 10,068, three doses in 18,351, and four doses in 236,166 arthroplasties. With the recommended four doses as reference, the HRR (95% CI) for 1-year revision for infection was 0.9 (0.7-1.1) for one dose, 1.0 (0.8-1.2) for two doses, and 0.9 (0.8-1.1) for three doses. The corresponding adjusted 1-year revision incidences for PJI was 0.9 (0.7-1.1), 1.0 (0.8-1.2), 0.9 (0. 8-1.1) and 1.0 (1.0-1.1) for one, two, three and four doses respectively, and less than four doses was found to be non-inferior. Conclusions. One preoperative dose of SAP in primary joint arthroplasty surgery seems to be non-inferior to the current recommendation of four doses of a first-generation cephalosporin as PJI-prophylaxis. This finding may simplify the course of treatment for arthroplasty patients, save costs, and improve antibiotic stewardship

Aim. Fast and accurate identification of pathogens causing periprosthetic joint infections (PJI) is essential to initiate effective antimicrobial treatment. Culture-based approaches frequently yield false negative results, despite clear signs of infection. This may be due to the use of general growth media, which do not mimic the conditions at site of infection. Possible alternative approaches include DNA-based techniques, the use of in vivo-like media and isothermal microcalorimetry (ITC). We developed a synthetic synovial fluid (SSF) medium that closely resembles the in vivo microenvironment and allows to grow and study PJI pathogens in physiologically relevant conditions. In this study we investigated whether the use of ITC in combination with the SSF medium can improve accuracy and time to detection in the context of PJI. Methods. In this study, 120 synovial fluid samples were included, aspirated from patients with clinical signs of PJI. For these samples microbiology data (obtained in the clinical microbiology lab using standard procedures) and next generation sequencing (NGS) data, were available. The samples were incubated in the SSF medium at different oxygen levels (21% O. 2. , 3% O. 2. and 0% O. 2. ) for 10 days. Every 24h, the presence of growth was checked. From positive samples, cultures were purified on Columbia blood agar and identified using MALDI-TOF. In parallel, heat produced by metabolically active microorganisms present in the samples was measured using ITC (calScreener, Symcel), (96h at 37°C, in SSF, BHI and thioglycolate). From the resulting thermograms the ‘time to activity’ could be derived. The accuracy and time to detection were compared between the different detection methods. Results. So far, seven samples were investigated. Using conventional culture-based techniques only 14.3% of the samples resulted in positive cultures, whereas NGS indicated the presence of microorganisms in 57.1% of the samples (with 3/7 samples being polymicrobial). Strikingly, 100% of the samples resulted in positive cultures after incubation in the SSF medium, with time to detection varying from 1 to 9 days. MALDI-TOF revealed all samples to be polymicrobial after cultivation in SSF, identifying organisms not detected by conventional techniques or NGS. For the samples investigated so far, signals obtained with ITC were low, probably reflecting the low microbial load in the first set of samples. Conclusion. These initial results highlight the potential of the SSF medium as an alternative culture medium to detect microorganisms in PJI context. Further studies with additional samples are ongoing; in addition, the microcalorimetry workflow is being optimized

Aim. The management of PJIs is slowed down by the presence of bacteria forming biofilms where they may withstand antibiotic therapy. The use of adjuvant strategies, such as hydrolytic enzymes cocktail targeting biofilm matrices and facilitating their dispersion, is a promising option to limit impact of biofilms. Our aim was to evaluate the effect of enzymes cocktail combined with antibiotic dual therapy of rifampicin and vancomycin in a relevant in-vitro model. Method. Mature methicillin-resistant Staphylococcus aureus biofilms were grown on Ti-6Al-4V coupons by adding 1mL of a 8Log10 ATCC 33591 suspension in TGN (TSB + 1% glucose + 2% NaCl) to 24-wells plates containing the coupons and incubating the plates for 24h at 37°C with a continuous 50rpm agitation. The samples were rinsed and placed in 6 wells plates containing 1ml of the enzymatic cocktail (C.D.D.) solution (tris-buffered (pH 7.0) solution of 400 U/ml of aspecific DNA/RNA endonuclease, 50 U/ml of endo-1,4-b-D-glucanase, and 0.06 U/ml of β-N-acetylhexosaminidase). 9ml of TGN or TGN containing antibiotics RIF/VAN (rifampicin 5µg/mL + vancomycin 8µg/mL) at clinically relevant concentrations found locally in bone or joints, was then added and the samples were incubated in identical conditions for 24h. The samples were then recovered and rinsed. CFU counts were obtained by recovering the bacteria with sonication, serial dilutions, and TSA plating. Biomass was determined via crystal violet staining, followed by dye solubilization in acetic acid, and absorbance measurement using a spectrophotometer. Results. Significant reductions in bacterial counts were observed in biofilms exposed to either RIF/VAN or RIF/VAN+CDD, by respectively 2,6 and 3,7Log10 when compared to samples reincubated with TGN alone (p <0.05). Additionally, CFU counts in samples exposed to RIF/VAN+CDD were reduced by 1,1Log10 when compared to those exposed to RIF/VAN (p<0,05). Significant reduction in biomass (-29,8%, p<0.05) was observed for coupons exposed to RIF/VAN+CDD when compared to C.D.D alone (figure 1). Conclusions. The concurrent utilization of enzymes with rifampicin and vancomycin, holds promise as a feasible method to address periprosthetic joint infections (PJIs). For any tables or figures, please contact the authors directly

Aim. Periprosthetic joint infection (PJI) and periprosthetic fracture (PF) are one of the most devastating complications in arthroplasty. Each complication by itself is challenging to solve. Yet, simultaneously, both complications are inconceivably complex to deal with, while the treatment regimen of PJI and PF are contradictory. Chronic PJI most often requires implant removal, while PF requires stability, regularly achieved by stable osteosynthesis. This study aims to (1) analyse the success rate of PJI with following concomitant PF during the treatment course in total hip arthroplasties (THA) and (2) to determine the risk factors for reinfection and subsequent revision surgery after treatment of PJI and PF. Method. This restrospective study analyzed 41 patients with concomitant PJI and PF during the PJI treatment period from 2013 to 2022 involving THA. Patients were divided in two cohorts termed success and failure and were statistically compared. The median follow-up time was 66 months (>12 months). All patients were considered individually and treated according to their individual needs in fracture and infection treatment. Re-arthroplasty survival was analyzed using the Kaplan-Meier method. Relevant risk factors were analyzed using the Mann-Whitney test or Chi-square, depending on the variable's scale. Results. The overall success rate of our cohort was 70,7%. Twelve patients required re-operation due to reinfection, resulting in a cumulative 12-month-reinfection rate of 19,5%. The estimated cumulative reinfection free survival rate was 68,3%. Significance in risk factors for failure were found in pathogen virulence grade, Difficult to treat pathogen and number of debridement during interval. On average the Harris Hip score was 66 in the group of reinfection compared to 77 in the group of success. Conclusions. Reoperation and re-infection rate remains high in patients with simultaneous PJI and PF in THA. Due to the heterogeneity of the fractures, soft tissue conditions and pathogens found, treatment must be individualised to salvage the limb. However, small cohorts impact the statistical strength negatively due to instances of two rare complications

Aims. Bone and joint infections cause significant morbidity, often requiring combination medical and surgical treatment. The presence of foreign material reduces the number of organisms required to cause an infection. The aim of this study was to assess whether there was a difference in the species of organism identified on culture in osteomyelitis compared to prosthetic joint infection. Method. This was a retrospective observational cohort study of patients that had surgical intervention for prosthetic joint infection or osteomyelitis with positive microbial culture between 2019 and 2022. Data including patient demographics, site of injury, BACH score for osteomyelitis and JS-BACH score for prosthetic joint infection, organism classification and antibiotic resistance to vancomycin and gentamicin were extracted from the medical record. Logistic and multiple regressions were used to adjust for potential confounding variables. Results. A total of 445 patients were included in the study; 267 patients with osteomyelitis or fracture-related infection and 177 patients with prosthetic joint infection. The patients with prosthetic joint infection were older (Mean age 70 for PJI; IQR 60-77 vs 56 for OM/FRI; IQR 39-64), more likely to be female (55.6% vs 26.2%) and had a higher BMI and ASA compared to those with osteomyelitis. Symptom duration tended to be longer in osteomyelitis/FRI (p<0.001). Staphylococcus aureus was the most common pathogen isolated in both osteomyelitis (155/267 (58.1%)) and prosthetic joint infection (85/177 (48.9%), followed by other Gram negative pathogens with 77/267 (28.8%) in osteomyelitis and 48/177 (27.1%) in prosthetic joint infection. On multivariate analysis, there was no difference between the rate of Staphylococcus aureus infection between the two groups. The rate of polymicrobial infection was higher in patients with osteomyelitis (92/267 (34.5%)) compared to prosthetic joint infection (38/177 (23.7%), however after adjustment for confounders there was no difference, p = 0.842. There was no difference in the presence of gentamicin resistant organisms or vancomycin resistant Gram positive organisms in osteomyelitis compared to prosthetic joint infection. Conclusion. Causative pathogens are similar in these two common forms of bone and joint infection. There was no significant difference in the identification, presence of polymicrobial infection or gentamicin and vancomycin resistance in organisms isolated in osteomyelitis compared to prosthetic joint infection. This may have implications for empiric antibiotic choice and local antibiotic therapy in the management of bone and joint infection

Aim. The primary objective is to evaluate the diagnostic performance of inoculating homogenized tissue and bone biopsies in blood culture bottles (BCB) for patients with (suspected) orthopaedic device-related infections. As secondary objective the time to positivity (TTP) of BCB and Wilkins-Chalgren broth (conventional method) will be evaluated. Method. Patients undergoing revision surgery due to suspected or proven fracture-related infection (FRI) or periprosthetic joint infection (PJI) according to respectively Consensus definition and EBJIS definition are included. 1,2. A minimal of three macroscopic infected/inflamed tissue/bone samples are collected in a container with saline and glass beads. 1.5 mL of the homogenized suspension is inoculated in BacT/ALERT FA and FN Plus bottles for 14 days. The remaining suspension is inoculated in Wilkins-Chalgren broth for 10 days and subcultured when cloudy or after 10 days. TTP is defined as the time until definite identification of the pathogen in the Laboratory Information System. Results. Up to now, 25 patients have been included, 11 (44%) had concordant results in BCB and the CM. In 11 patients cultures showed negative results for both methods. Three patients tested positive with BCB but remained negative with the same pathogen in CM. In the first patient, the CM failed to identify anaerobic bacteria (i.e. Fusobacterium nucleatum). In the second patient, three BCB were positive with Staphylococcus capitis. The third patient showed an infection with Escherichia coli, which was detected in all samples from the BCB, while all cultures obtained with the CM remained negative. A possible explanation for this discrepancy could be that this patient already received antibiotic therapy. BCB contain resins, which are capable of neutralizing antibiotic activity. Another case illustrating superiority of BCB involved an infection with Cutibacterium acnes, which showed positivity in six BCB, while only three were positive using the CM. We observed the shortest TTP with BCB. The median TTP of BCB was 32.0 hours (IQR 29.8) compared to a median TTP of 77.5 hours (IQR 107.6) when culturing with the CM. Contamination was seen in three patients with both methods, in eight patients contamination was only seen with the CM. For the remaining 14 patients no contamination was found. Conclusions. The results in this ongoing study indicate that the recovery of pathogens and TTP is better using BCB compared to CM. In addition, contamination occurs less frequently with the BCB method. Culturing tissue or bone biopsies in BCB seems a promising and faster detection method

Aim. Periprosthetic joint infections follow 1-3% of arthroplasty surgeries, with the biofilm nature of these infections presenting a significant treatment challenge. 1. Prevention strategies include antibiotic-loaded bone cement; however, increases in cementless procedures means there is an urgent need for alternative local antimicrobial delivery methods. 2. A novel, ultrathin, silica-based sol-gel technology is evaluated in this research as an anti-infective coating for orthopaedic prosthetic devices, providing local antibiotic release following surgery. Method. Reduction in clinically relevant microbial activity and biofilm reduction by antimicrobial sol-gel coatings, containing a selection of antibiotics, were assessed via disc diffusion and microdilution culture assays using the Calgary biofilm device. 3. Proliferation, morphology, collagen, and calcium production by primary bovine osteoblasts cultured upon antibiotic sol-gel surfaces were examined, and cytotoxicity evaluated using Alamar blue staining and lactate dehydrogenase assays. Concentrations of silica, calcium and phosphorus compounds within the cell layer cultured on sol-gel coatings and concentrations eluted into media, were quantified using ICP-OES. Furthermore, cellular phenotype was assessed using alkaline phosphatase activity with time in culture. Results. Low antibiotic concentrations within sol-gel had an inhibitory effect on clinically relevant biofilm growth, for example 0.8 mg ml. -1. tobramycin inhibited clinically isolated S. aureus (MRSA) growth with an 8-log reduction in viable colony forming units. There was no significant difference in metabolic activity between untreated and sol-gel exposed primary bovine osteoblasts in elution-based assays. Reduction (2-fold) in metabolic activity in direct contact assays after 48 hours exposure was likely to be due to increased osteoinduction, whereas no impact upon cell proliferation were observed (p=0.92 at 14 days culture). The morphology of primary osteoblasts was unaffected by culture on sol-gel coatings and collagen production was maintained. Calcium containing nodule production within bovine osteoblastic cells was increased 16-fold after 14 days culture upon sol-gel. Conclusions. The ultrathin sol-gel coating showed low cytotoxicity, strong biofilm reducing activity and antimicrobial activity, which was comparable to antibiotics alone, demonstrating that sol-gel delivery of antibiotics could provide local antimicrobial effects to inhibit PJI growth without the need for bone cement. Future work will develop and evaluate sol-gel performance in an ex vivo explant bone infection model which will reduce the need for animal experimentation

Aim. Periprosthetic joint infection (PJI) is one of the most serious and frequent complications in prosthetic surgery. Despite significant improvements in the criteria for diagnosis of PJI, the diagnostic workflow remains complex and, sometimes, inconclusive. Host immune factors hold great potential as diagnostic biomarkers in bone and joint infections. We have recently reported that the synovial concentration of the humoral pattern recognition molecule long pentraxin 3 (PTX3) is a sensitive and specific marker of PJI in total hip and knee arthroplasty patients (THA and TKA) undergoing revision surgery [1]. However, the contribution to risk and diagnosis of PJI of the genetic variation in PTX3 and inflammatory genes that are known to affect its expression (IL-1b, IL-6, IL-10, and IL-17A) has not been addressed. Therefore, we assessed these relationships in a cohort of THA and TKA patients who underwent prosthesis revision by focusing on a panel of single nucleotide polymorphisms (SNPs) in the PTX3, IL-1β, IL-6, IL-10 and IL-17A genes. Method. A case-control retrospective study was conducted on an historic cohort of patients that received THA or TKA revision and were diagnosed with PJI (cases) or aseptic complications (controls) [1]. Samples of saliva were collected from 93 subjects and used for extraction of genomic DNA to perform genotyping of the PTX3, IL-1β, IL-6, IL-10 and IL-17A polymorphisms. Moreover, whenever available, samples of synovial fluid and plasma [1] were used to measure the concentration of the IL-1β, IL-10, and IL-6 proteins by immunoassay. Uni-and multivariate analyses were performed to evaluate the relationships between genetic, biochemical, and clinical variables. Results. The rs3024491 (IL-10) and rs2853550 (IL-1b) SNPs were found to be strongly associated with the risk of PJI. The synovial levels of PTX3, IL-1β, IL-10, and IL-6 were higher in cases than in controls, and a clear correlation emerged between the synovial concentration of PTX3 and IL-1b in cases only. Also, we identified a causal relationship between rs2853550, synovial concentration of IL-1b and that of PTX3 (that is induced by IL-1b). Conclusions. Our findings suggest that SNPs in the IL-10 and IL-1b genes could be used for early identification of THA and TKA patients with high risk of PJI. It is therefore conceivable that integrating genetic data into current diagnostic criteria would improve diagnosis of PJI

Aim. Periprosthetic joint infection (PJI) is a devasting complication after total hip arthroplasty. Joint aspiration and preoperative biopsy can be helpful diagnostics for PJI. The aim of this study is to evaluate the diagnostic value of preoperative biopsies after inconclusive or dry tap aspiration of the hip in patients undergoing revision hip arthroplasty. Secondarily we will evaluate the diagnostic value of synovial fluid aspiration cultures and peroperative tissue cultures for diagnosing or ruling out PJI. Methods. Patients who underwent diagnostic aspiration and subsequent preoperative biopsy and/or revision surgery between January 2015 and January 2024 were included in the study. Synovial fluid aspirations and tissue samples obtained from biopsy and revision surgery were interpreted using the European Bone and Joint Infection Society criteria for PJI and in close consultation with the microbiologist. Results. 207 Patients were included with 231 synovial fluid aspirations. Sensitivity and specificity of synovial fluid aspiration cultures were 76% and 98%. In 62 patients tissue biopsies were performed, of which 40 after a dry tap. The tissue biopsies after a dry tap aspiration had a sensitivity of 50.0% and a specificity of 95.8%. In 21% tissue biopsies led to the confirmation of PJI in patient with a high suspicion of PJI after dry tap aspiration. In patients with an inconclusive synovial fluid aspiration result the addition of tissue biopsies led to a change in treatment in 14%. In 212 cases revision surgery was performed, intraoperative tissue cultures had a sensitivity and specificity of 83.3% and 99.3%. Conclusions. Diagnosing PJI can be troublesome, especially if synovial fluid aspiration provides a dry tap. Tissue biopsy cultures in patients with a high suspicion of PJI after dry tap aspiration is a feasible way to confirm PJI, in 21% of patients PJI could be confirmed after dry tap aspiration. Ruling out PJI by means of a biopsy after a dry tap aspiration is less successful due to its low sensitivity. Tissue biopsies after an inconclusive aspiration leads to clinically important treatment changes