Aims. Cutibacterium acnes (C. acnes; previously known as Propionibacterium acnes or P. acnes) periprosthetic hip and knee infections are under-reported. While culture contamination with C. acnes occurs, true infections are important to recognize and treat. We sought to describe the demographics and treatment outcomes of patients with C. acnes periprosthetic joint infections (PJIs) of the hip and knee. Methods. Patients with C. acnes PJI between January 2005 and December 2018 were retrospectively reviewed utilizing the institutional total joint registry. Patients with monomicrobial PJI and two or more positive cultures were considered to have true C. acnes PJI. Patients with polymicrobial infection or with only one positive culture were excluded. This resulted in 35 PJIs (21 hips and 14 knees); the patients’ mean age was 63 years (35 to 84) and 15 (43%) were female. Mean follow-up was five years (1 to 14). Results. The median time to positive culture was five days (IQR 5 to 6) and median synovial fluid cell count was 22,583 cells (IQR 15,200 to 53,231). The median ESR was 25 mm/hr (IQR 7 to 37), and CRP was 15 mg/l (IQR 3 to 29). Of the 35 PJIs, 18 (51%) were treated with chronic antibiotic suppression without surgical intervention, and the remainder were treated with two-stage exchange arthroplasty. The two-year survival free of any revision was 94%. Four patients failed treatment due to symptomatic infection, with three treated with two-stage exchange and one treated with irrigation and debridement with modular component exchange for a survival rate of 89% and 83% at two and five years, respectively. Conclusion. Laboratory evidence of C. acnes PJI in this cohort was typical compared to more conventional organisms. Cultures grew more quickly than previously thought in patients with C. acnes PJI. Treatment with two-stage exchange or chronic antibiotic suppression alone both had few treatment failures at mid-term follow-up. Cite this article: Bone Joint J 2024;106-B(12):1426–1430

Aims. Our aim was to investigate the prevalence of Propionibacterium (P.) acnes in the subcutaneous fat and capsule of patients undergoing shoulder surgery for frozen shoulder or instability. Patients and Methods. A total of 46 patients undergoing either an arthroscopic capsular release or stabilisation had biopsies taken from the subcutaneous fat and capsule of the shoulder at the time of surgery. These samples were sent for culture in enrichment, and also for Nucleic Acid Amplification testing. The prevalence of P. acnes and other microbes was recorded. Fisher's exact test of binary variables was used to calculate the association with significance set at p < 0.05. Assessment of influence of independent variables including a pre-operative glenohumeral injection, fat colonisation and gender, was undertaken using binary linear regression. Results. A total of 25 patients (53%) had P. acnes in one or more tissue samples and 35 (74%) had other bacterial species. The same microbe was found in the subcutaneous fat and the capsule in 13 patients (28%). There was no statistically significant association between the surgical pathology and capsular colonisation with P. acnes (p = 0.18) or mixed identified bacterial species (p = 0.77). Male gender was significantly associated with an increased capsular colonisation of P. acnes (odds ratio (OR) 12.38, 95% confidence interval (CI) 1.43 to 106.77, p = 0.02). A pre-operative glenohumeral injection was significantly associated with capsular P. acnes colonisation (OR 5.63, 95% CI 1.07 to 29.61, p = 0.04. Positive fat colonisation with P. acnes was significantly associated with capsular P. acnes (OR 363, 95% CI 20.90 to 6304.19, p < 0.01). Regression models pseudo R. 2. found fat colonisation with P. acnes to explain 70% of the variance of the model. Patients who had a pre-operative glenohumeral injection who were found intra-operatively to have fat colonisation with P. acnes had a statistically significant association with colonisation of their capsule with P. acnes (OR 165, 95% CI 13.51 to 2015.24, p < 0.01). Conclusion. These results show a statistically significant association between subcutaneous skin P. acnes culture and P. acnes capsular culture, especially when the patient has undergone a previous injection. The results refute the hypothesis that P. acnes causes frozen shoulder. Cite this article: Bone Joint J 2017;99-B:1067–72

Aim. Propionibacterium acnes is a skin commensal colonizing the deeper structures of the pilous bulb. It is responsible for 5–10% of lower limb prosthetic joint infections (PJI) but accounts for as many as 50% of shoulder arthroplasty infections. P. acnes PJIs characteristically feature limited systemic inflammation, limited polymorphonuclear infiltration and clinical signs compatible with aseptic loosening. All current microbiological definitions of PJI require two or more identical commensal isolates to be recovered from the same procedure to diagnose PJI to increase specificity and rule out contamination. Whereas the antimicrobial susceptibility patterns of coagulase negative staphylococci are highly polymorphic and commonly allow the ready distinction of unrelated strains, P. acnes shows a highly stereotypical susceptibility profile and it is impossible to phenotypically assess the clonal relationship of isolates. In order to determine the clonal relationship of multiple P. acnes isolates recovered from arthroplasty revisions, we analyzed by multi-locus sequence typing (MLST) P. acnes isolates grown from PJI in a reference center for bone and joint infection. Method. We retrospectively selected all cases of microbiologically documented monomicrobial PJI caused by P. acnes diagnosed in our center from January 2009 to January 2014. Microorganisms were identified by MALDI-TOF mass spectrometry (Bruker Daltonics). All corresponding P.acnes isolates biobanked in cryovials frozen at −80°C were subcultured on anaerobic blood agar, DNA extracted by freeze-thawing and bead-milling, and typed according to the 9 gene MLST scheme proposed by Lomholt HB. and al. Results. Over the 5-year period, 39 cases of PJI positive with P. acnes were diagnosed in our center. Three to ten intraoperative samples were sent for microbiological analysis per surgery. Overall, 113 P. acnes isolates were grown from 210 samples. On average, four samples were positive out of six. In 34/39 cases, all isolates belonged to the same ST. In 5 cases, multiples STs were found among the P.acnes isolates. In 3/39 cases (7.7%), a single ST was found to be microbiologically significant, with a single isolate of the alternate ST. In 2/39 cases (5.1%), we found that each isolate belonged to a different ST. Conclusions. P. acnes PJI were found to be polyclonal by MLST in 12.8% of cases in our experience, with more than 5% of cases not fulfilling the requirements for microbiological significance. The criteria for microbiological significance do not necessarily apply to commensal agents with no antimicrobial susceptibility pattern variation such as P. acnes

Propionibacterium acnes infection of the shoulder after arthroplasty is a common complication. Current detection methodologies for P. acnes involve prolonged anaerobic cultures that can take up to three weeks before findings can be reported. Our aim was to develop a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) approach that is both sensitive and specific to P. acnes that would enable a 24-hour turnaround between biopsy and results. Comparisons between the 16S ribosomal sequences of P. acnes and closely related bacteria identified two unique regions in P.acnes to which PCR primers were designed. Additionally, two unique restriction enzyme cut sites for HaeIII were identified within this amplicon. To test the PCR method, arthroscopic surgical biopsies were mechanically homogenised and boiled for 20 minutes to lyse the cellular membranes. PCR was performed using standard conditions followed by a one hour HaeIII enzymatic digest of the PCR product. Resultant fragments were visualised on polyacrylamide gels stained with ethidium bromide. All experiments included no-template controls to rule out reagent contamination and independently confirmed P. acnes DNA as a positive control. Serial dilutions of P. acnes cultures in Robertson's cooked-meat broth and spectrophotometric analysis of cellular concentration were used to assess the sensitivity of the PCR reaction. A unique 564 base-pair PCR amplicon was derived from different strains of P. acnes. This amplicon was confirmed as P. acnes DNA by gel excision and DNA sequencing. HaeIII digests of the amplicon yielded 3 restriction fragments at the sizes predicted by in silico analyses. Sensitivity testing confirmed that as few as 10 P. acnes cells in a 50µl reaction volume could be detected using this assay. P. acnes was also detected in surgical biopsy samples. P. acnes infections following shoulder arthroplasty are a serious complication placing a burden on the healthcare system and the patient due to the lengthy surgical revision process that follows. The infections are also difficult to diagnose. This unique assay combines the sensitivity of PCR with the specificity of RFLP mapping to specifically identify P. acnes in surgical isolates. We anticipate that this assay will allow us to determine if a biopsy is P. acnes positive within 24-hours of sampling, allowing for more aggressive antibiotic therapy and monitoring to avoid implant failure and revision surgery. Additionally, this PCR-RFLP method may decrease the false positive rate of extended length cultures due to P. acnes contamination

The routine use of intraoperative vancomycin powder to prevent postoperative wound infections has not been borne out in the literature in the pediatric spine population. The goal of this study is to determine the impact of vancomycin powder on postoperative wound infection rates and determine its potential impact on microbiology. A retrospective analysis of the Harms Study Group database of 1269 adolescent idiopathic scoliosis patients was performed. Patients that underwent a posterior fusion from 2004-2018 were analyzed. A comparative analysis of postoperative infection rates was done between patients that received vancomycin powder to those who did not. Statistical significance was determined using Chi-squared test. Additionally, the microbiology of infected patients was examined. In total, 765 patients in the vancomycin group (VG) were compared to 504 patients in the non-vancomycin group (NVG). NVG had a significantly higher rate of deep wound infection (p<0.0001) and associated reoperation rate compared to VG (p<0.0001). Both groups were compared for age, gender, race, weight, surgical time, blood loss, number of levels instrumented, and preop curve magnitude. There were significant differences between the groups for race (p<0.0001); surgical time (p=0.0033), and blood loss (p=0.0021). In terms of microbiology, VG grew p.acnes (n=2), and serratia (n=1), whereas NVG grew p.acnes (n=1) and gram positive bacilli (n=1). The remaining cultures were negative. The use of intraoperative vancomycin powder in adolescent idiopathic scoliosis appears to contribute significantly to deep wound infection prevention and reduction of associated reoperations. Based on this study's limited culture data, Vancomycin does not seem to alter the microbiology of deep wound infections

Aim. Propionibacterium acnes is an emerging pathogen especially in orthopedic implant infection. Interestingly, we previously reported a difference in the distribution of the clades involved in spine versus hip or knee prosthetic infection. To date, no study has previously explored the direct impact and close relationship of P. acnes on bone cells according to their own genetic background. The aim of this study was to investigate this interaction of P. acnes clinical strains involved in spine material infections, arthroplasty infections and acne lesions with bone cells. Method. From a large collection of 88 P. acnes clinical isolates collected between January 2003 and December 2014, a subset of 11 isolates was studied. Four isolates were recovered from spine infections, two from prosthetic infections (knee and hip), three from acne lesions and two reference strains (ATCC11827 and ATCC6919). Implant-associated infections were confirmed according to Infectious Diseases Society of America guidelines for bone and joint infections. Multi-Locus Sequence Typing (MLST) was carried out on all isolates as described by Lomholt et al. PLoS ONE 2010. Bacterial internalization experiments with MG63 osteosarcoma cells were adapted from Crémet et al. Pathog Dis 2015. Results. Among the nine clinical isolates, three isolates belonged to clonal complexes (CCs) 18; three to CC28 and three to CC36. ATCC isolates belonged to CC18. Bacterial internalization experiments revealed that CC36 P. acnes strains were less invasive than CC18 and CC28 P. acnes strains towards osteoblasts (mean percentage of internalized bacteria (< 0.01% for the CC36 P. acnes strains versus more than 1% for the CC18 and CC28 P. acnes strains). Surprisingly, the ATCC11827 CC18 P. acnes strain exhibited invasiveness similar to CC36 isolates. Conclusions. Evasion mechanism observed for CC36 P. acnes isolates could allow this clade to leave the site of infection, disseminate into deeper tissue layers and beget arthroplasty infection. Inside the deeper tissue, close to the material, the local immune defect fosters the low-grade infections observed with P. acnes clinical strains. On the another hand, for CC18 et CC28 clades, mostly involved in spine infection, the internalization process observed could allow these clades to escape from the numerous immune cells located under the skin and generate an infection locally, favored by the spine instrumentation close to the skin, especially during long spine surgeries

Propionibacterium acnes is an emerging pathogen especially in orthopedic implant infection. Aim of this study was to investigate P. acnes phylogeny and to screen for virulence factors among a large collection of clinical isolates involved in spine material infections, arthroplasty infections and acne lesions. 88 P. acnes clinical isolates were collected between January 2003 and December 2014 at Nantes University Hospital (France). Fifty-eight isolates came from spine infections, 14 from prosthetic infections (knee, hip or shoulder), 14 from acne lesions and two reference strains (ATCC11827 and ATCC6919). Implant associated infections were confirmed using Infectious Diseases Society of America criteria for bone and joint infections. Phylotypes and Multi-Locus Sequence Typing (MLST) was carried out on all isolates as described by Lomholt et al. All isolates were tested by established PCR-based assays for 21 putative virulence factor genes characteristic of P. acnes. MLST analysis revealed an association between clonal complexes (CCs) and origin of P. acnes isolates (p = 0,027). Regarding CCs distribution between different origins, CC36 and phylotype II P. acnes isolates are more frequently observed in prosthetic joint infections. On the other hand, CC18 (IA) and CC28 (IB) P. acnes isolates are more frequently involved in spine infections and acne lesions. Among all virulence factors screened, hyaluronate lyase gene was only present in CC36 and phylotype II P acnes isolates. Other virulence factors were present in all isolates, whatever their origin or CC. Regarding molecular typing results, P. acnes involved in spine infections seem to have a skin origin (same CC as isolates from acne lesion). Interestingly, the origin of prosthetic joint infection isolates seems different and they all carry one more virulence factor. Hyaluronate lyase (Hyl) is a major surface protein of P. acnes with potential antigenetically variable properties that might be essential for P. acnes virulence. Increased tissue permeability caused by the action of hyaluronidase on the extracellular matrix appears to play a role in wound infections, pneumonia, and other sepsis such as bacteremia and meningitis. It could be also take a prominent part in P. acnes prosthetic joint infection pathogenesis

Introduction: Propionibacterium acnes (P. acnes), a common anaerobic skin commensal, has been implicated in biomaterial-related infections (BRI). Bacteria can adhere to biomaterial surfaces and grow as a bio-film held together by exopolymer, exhibiting increased antimicrobial resistance. To our knowledge, images of P. acnes biofilms have not previously been published. We have demonstrated the ability of P. acnes to adhere to surgical steel and to develop a biofilm on this material. However its ability to adhere to and develop a biofilm on titanium, a commonly used surgical implant material, has not been fully investigated. Aims:. To determine the quantitative adherence and biofilm development of P. acnes on titanium compared to surgical steel. To assess the subsequent effect of penicillin, the therapeutic drug of choice, on mature P. acnes biofilms. Method: Six clinical isolates of P. acnes were assayed for adherence to materials with and without plasma glycoprotein conditioning film by chemiluminescence and culture. Biofilm development was assessed by chemiluminescence, fluorescence microscopy, environmental (ESEM) and scanning electron microscopy (SEM). Mature biofilms were exposed to plasma concentrations of penicillin and quantified by chemiluminescence and culture. Unpaired student’s t tests and univariate linear regression models were calculated using SPSS software (version 12). Results: Univariate linear regression showed that P. acnes adherence to titanium was 18% (p=0.001) greater than to steel. Adherence was reduced by the presence of the conditioning film on titanium by 28% (p=0.001), but this made no significant difference to P. acnes adherence to steel. P. acnes biofilms were clearly demonstrated, along with bacterial expolymer, showing an interesting similarity to biofilms of S. epidermidis. P. acnes grows as a thick biofilm on both materials held together by exopolymer and our preliminary results suggest that biofilms on titanium might be less susceptible to antimicrobials after 24 hours of penicillin treatment; a reduction of 94% on steel and 81% on titanium (p=0.057, p=0.39 resp). Conclusions: P. acnes adheres to steel and titanium, a crucial first step in BRI. Greater numbers of P. acnes adhere to titanium than to steel. The naked surface of titanium is microporous, assisting adhesion. A conditioning film reduces P. acnes adherence to titanium but not to steel. P. acnes develops as a biofilm on steel and titanium. Results indicate that pathogenesis of P. acnes infection on titanium is more successful than on steel. P. acnes biofilms on titanium may be harder to eradicate with antimicrobial agents

Aim. The purpose of this study was to compare the presence of P.acnes on the skin after topical pre-operative application with benzoyl peroxide (BPO) to chlorhexidine soap (CHS) and whether this also affected skin recolonization after surgical preparation and draping. Method. Forty volunteers – twenty-four men and sixteen women were randomized to pre-operative topical treatment at home with either CHS or BPO in the area of a delto-pectoral approach of their left shoulder. The right served as a control. Five skin swabs were taken in a standardized manner on different occasions: before and after topical treatment, after surgical skin preparation and sterile draping and 120 minutes after draping. A fifth sample was taken on the contralateral untreated side as a control when the patient was draped. The draping took place in an operating room with laminar air flow and skin preparation was performed for 2 minutes with 0.5% chlorhexidine solution in 70% ethanol according to the recommendations of the Swedish National Board of Health and Welfare. Bacterial colonies were then analyzed on agar plates by colony forming units (CFU) and surface characteristics. P.acnes were identified with matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry. Results. Topical treatment with BPO significantly reduced the presence of P.acnes as CFU on the skin after surgical preparation. P.acnes was found in 1/20 subjects of the BPO group, and 7/20 in the CHS-group (p<0.044). The results remained after two hours (p<0.048). Topical treatment with BPO before surgical skin preparation significantly decreased the presence of CFU (p-value 0.035). Conclusions. Topical preparation with BPO before shoulder surgery may be effective in reducing P.acnes on the skin and prevent recolonization

Background: Proprionibacterium acnes (P. acnes) is a skin commensal which is often interpreted as a contaminant when found in cultures of surgical specimens. However, recent reports suggest that P. acnes can be identified as the causative micro-organism of infection. Furthermore P. acnes infections occur more often after shoulder surgery than after surgery of the lower extremities or spine. The aim of this study was to identify how frequent P. acnes was responsible for infection after orthopaedic surgery of the shoulder, lower extremity and spine in a single centre. Patients and Methods: Inclusion criteria were the occurrence of infection after surgery of the shoulder, lower extremity (hip and knee), or spine in a 100-bed orthopaedic hospital. The inclusion period was between January 2000 and May 2008. Infection was defined when two or more cultures were positive with the same microorganism in the presence of clinical signs and symptoms. The first goal was to identify the incidence of infection due to P. acnes amongst all infections. The secondary outcome was the incidence of infection versus contamination amongst all cases with positive cultures for P. acnes. Both outcomes were compared for surgery of the shoulder, lower extremity and spine. Results: A total of 3703 surgeries of the shoulder were performed, compared to 19906 lower extremity- and 5687 spine surgeries. The incidence of infection after surgery of the shoulder was 1.4% (52 cases; prosthesis [n=23], fractures [n=5], soft tissue surgery [n=16] and others [n=8]). After surgery of the lower extremity and spine this was 2.8% (548 cases) and 3.1% (177 cases), respectively. The incidence of infection due to P. acnes after shoulder surgery (23%) was significantly greater then after surgery of the lower extremity (1.3%; p < 0.001) or spine (0%; p < 0.001). Furthermore, in cases where P. acnes was cultured after surgery of the shoulder it was more often identified as the causative pathogen of infection than when P. acnes was cultured after surgery of the lower extremity or spine (71% vs 22%; p < 0.05 and 71% vs 0%; p < 0.01). Conclusion: The low virulent P. acnes can cause orthopaedic surgical infections and should not be regarded a priori as a contaminant in cultures. This is especially true for shoulder surgery, where P. acnes infections occur frequently and significantly more often than in surgery of other joints

Aim. Recent studies have indicated that the presence of P. acnes in the skin of the shoulder and around the acromion is higher than other body regions like the knee or the hip. The aim of this study was to estimate the presence of P. acnes in a real set of primary shoulder arthroplasty, after skin preparation with chlorhexidine and administration of empirical antibiotic therapy. Method. A prospective observational study involving 63 patients undergoing primary shoulder arthroplasty was designed. In all patients two skin biopsies with a 3 mm dermal punch and one subcutaneous tissue sample after surgical incision were obtained. Skin biopsies were obtained at the most anterior part of the surgical wound in case of superior approach and at the upper part in the deltopectoral approach. All patients underwent preoperative antibiotic prophylaxis with cefazolin 2g ev and skin preparation with 2% chlorhexidine alcoholic tinted before the start of surgery twice. The aerobic cultures were incubated at 37ºC for 7 days whereas the anaerobic ones incubated for 14 days. Results. A total of 63 consecutive patients who underwent shoulder arthroplasty (58 reverse shoulder arthroplasty and 5 anatomical) were analysed. 54 women and 9 men, mean age of 73.94 (SD 6.19). The indication for arthroplasty was a secondary arthropathy cuff injury in 42 cases, primary osteoarthritis in 3, acute fracture in 9 and fracture sequelae in 9. We obtained 189 tissue cultures (126 skin cultures and 63 subcutaneous) and 4 cultures were positive (2.02%) for P. acnes in 3 different patients. A first patient (female) had both positive skin cultures, the second patient (male) only had positive the subcutaneous tissue cultures and the third patient had positive also the subcutaneous tissue culture. The first patient underwent anatomical shoulder arthroplasty whereas the second and third patients underwent reverse shoulder arthroplasty. The time to grow was 15 days in first patient and 14 days in the second and third patient (mean 14.5 days). Conclusions. In a real setting of patients undergoing shoulder arthroplasty using antibiotic prophylaxis and standard preoperative skin preparation with chlorhexidine we found a low rate of positive cultures for P. acnes (2.02 %). The higher rate of P. acnes positive cultures in skin reported in previous studies may be caused by a different population study group (healthy and younger volunteers without antibiotic prophylaxis) or suboptimal culture technique (use of swaps)

Objective: To determine whether Propionibacterium acnes is able to adhere to implant materials, and to develop biofilms. Background: Most orthopaedic implant infections are caused by staphylococci, which express adhesins and can adhere to biomaterials and to plasma glycoprotein conditioning films. They then produce exopolymers and develop biofioms. P acnes, being anaerobic, is often missed as a cause of implant infection and might be more common than is realised, yet little is known about its virulence factors (ability to adhere to biomaterials or conditioning film and biofilm development). Materials & Methods: Surgical steel or silicone coupons, with and without plasma conditioning film, were exposed to three clinical isolates of P acnes and examined by cultural methods and chemiluminescence for adherence. In further experiments, the coupons were incubated anaerobically with the P acnes strains for several days. They were then rinsed, fixed and processed for scanning electron microscopy (SEM). In a third set of experiments, coupons were again incubated anaerobically with P acnes and examined by laser confocal microscopy (LCM) for biofilm development. Results: All three isolates of P acnes were able to adhere to the biomaterials, to a degree similar to that of a clinical isolate of Staphylococcus aureus, though not as strongly as Staphylococcus epidermidis. Unlike with the staphylococci, the presence of a conditioning film did not make a significant difference. SEM and LCM revealed biofilm development morphologically similar to that seen with S epidermidis. Exopolymer production was also demonstrated. Conclusions: P acnes is able to adhere to biomaterials but not so avidly as S epidermidis. The adherence is not enhanced by plasma conditioning film. However, once adhered, P acnes is capable of developing a biofilm morphologically indistinguishable from that of S epidermidis. This probably explains the role of P acnes in implant infection, and the therapeutic difficulty it often poses

Introduction. Peri-prosthetic infections due to P. acnes may present as Prosthesis dysfunction without any obvious sepsis. We present our experience of efficient management of total knee prosthesis infection secondary to P. acnes which is one of the biggest case series. Materials and methods. From 2008 to 2009, 9 patients diagnosed with P. acnes infection after knee arthroplasty were retrospectively reviewed and analysed for clinical diagnosis; laboratory data (ESR, CRP); Radiological Imaging; number of days for culture growth of P acnes; organism sensitivities; antibiotic regimen and length of treatment and surgical management. Infection was diagnosed by 2 positive cultures. Results. Group 1 had 6 patients with confirmed knee prosthetic infection. 4 patients had no P.acnes detected from knee aspiration samples. All underwent two stage revisions. Group 2 had 3 patients with prosthesis dysfunction and pain without any obvious infection. All patients underwent frozen section histology test. Depending on results 2 patients with positive result had two stage revision surgeries and 1 patient with negative result had Single stage surgery. Antibiotics were administered for variable duration (4-10 weeks). In group 1 the average initial ESR and CRP were 45 mm/h and 28 mg/dl, respectively. 1. In group 2 average ESR was 15 and CRP was 6. The average number of days for positive culture was 6. All cultures were sensitive to Penicillin G and Vancomycin. All patients were treated successfully except one patient from group 1 who needed knee arthrodesis while one patient from group 2 received long term suppressive therapy. Discussion. P. acnes can cause peri-prosthetic infection where classical signs of sepsis are absent and therefore should be suspected in patients who present with subtle, delayed symptoms following joint arthroplasty. Many laboratories discard culture samples after 5 days. In our series the average time period for positive P. acnes culture is 6 days (range 5-10 days). The cultures may not be positive for as long as 10 days. So it is very important to keep the cultures for at least two weeks before discarding

Purpose: The objectives of this study were to correlate the clinical course of all patients with positive intra-operative P. acnes cultures in revision shoulder surgery with the cultures and intraoperative findings to determine the clinical significance of the positive cultures. Method: From 2005 to 2007 all revision shoulder surgeries were managed with a standard protocol in which. antibiotics were withheld until cultures obtained,. at least four fluid and tissue cultures were submitted,. frozen sections were obtained of any tissue grossly suspicious for infection, and. the surgeons’ pre-, intra-, and post-operative suspicion for infection were recorded. Samples were observed for growth for 28 days. All cases were reviewed at a mean follow-up of 4.2 months (range, 1–12). Comparisons were made between infection cases and “clinically Insignificant” cases, with respect to: (1) risk factors, (3) symptoms/signs of infection, (2) active range-of-motion, (2) Simple Shoulder Test (SST) scores, values of (3) WBC, (4) ESR and (5) CRP, number of positive cultures for (6) P acnes and (7) other organisms and (8) subjective pre-operative, intra-operative and postoperative suspicion for occult infection. Results: P. acnes was cultivated from 20 cases in 19 patients. Five cases (25%) were considered significant infections, while fifteen cases were considered “clinically insignificant”. The mean number of cultures positive for P. acnes was 1.7 (range, 1–4) per case. The mean active forward flexion (p=0.03) and internal rotation (p=0.03) was less for infection cases than for clinically Insignificant cases. Pre-operative ESR (p=0.04) and CRP (p=0.02) values were higher for infection cases. Infection cases had a higher number of positive intra-operative cultures for other organisms (p=0.04). Conclusion: No combination of clinical parameters would reliably predict clinical infection in patients with positive intra-operative P. acnes cultures in revision shoulder surgery. In particular, positive P. acnes intra-operative cultures do not always represent true clinical infections. Pre-operative loss of range-of-motion, elevated ESR and CRP and positive intra-operative cultures for other organisms appear to correlate with true infections. The determination of a clinically significant infection needs to be based on the entirety of the clinical and laboratory information for each shoulder case

Periprosthetic joint infection (PPJI) following shoulder arthroplasty is uncommon, with an overall rate of 0.98%. However, the rates following revision arthroplasty and reverse arthroplasty are much higher. Given the rapid increase in the prevalence of shoulder arthroplasty and the increasing revision burden, the cost of PPJI to society will likely increase substantially. The most common organisms found in PPJI following shoulder arthroplasty are Staphylococcus aureus, coagulase-negative Staphylococcus, and Propionibacterium acnes (P. acnes). P. acnes is especially common in males. Traditional testing for PPJI includes aspiration, white blood cell count (WBC), erythrocyte sedimentation rate (ESR), and c-reactive protein (CRP). Aspiration often yields a dry tap and when fluid is obtained for culture, a positive result is helpful but a negative result does not rule out PPJI. Although WBC, ESR, and CRP are often positive with PPJI in the lower extremity, they are most often negative in shoulder PPJI. Although bone scans and WBC labeled scans are used, they are expensive and have low sensitivity and specificity. New testing and techniques have been reported in an attempt to improve sensitivity and specificity for PPJI. These techniques can be divided into tests on serum, synovial fluid, and tissue. Serum Interleukin-6 (IL-6) is highly specific (94%) for shoulder PPJI but has low sensitivity (14%). Synovial fluid can be tested for leukocyte esterase using a simple and cheap technique. In lower extremity PPJI it has shown to be helpful. It is not as helpful in shoulder PPJI with 30% sensitivity and 67% specificity. Alpha defensin has been reported to be more sensitive (63%) and as specific (95%) as traditional techniques but still lacks predictive value. Testing for specific cytokines (IL-2, IL-6, TNF- α) within synovial fluid is not widely used as yet but has shown promise with 80% sensitivity and 90% specificity. Obtaining tissue for culture and other testing is probably the most reliable way of confirming PPJI for the shoulder. Frozen sections taken at the time of revision can be helpful but is very pathologist dependent and institution specific. With a dedicated musculoskeletal pathologist, the finding of 10 or more WBCs per high powered field has been reported to be 72% sensitive and 100% specific for P. acnes and 63% sensitive and 100% specific for other organisms. Cultures from arthroscopic tissue biopsy have also been found to have high sensitivity (100%) and specificity (100%). Genetic testing of tissue biopsy specimens (PCR/NGS) has recently been reported and shows great promise. The significance of positive cultures and other tests, especially for P. acnes is unclear. There is a high rate of positive intra-operative cultures in primary cases of shoulder arthroplasty. In addition, intra-operative cultures taken at the time of revision, even in cases in which infection is not suspected, are frequently positive for P. acnes with weak correlation with rates of post-operative clinical infection. In conclusion, shoulder PPJI is a difficult problem to deal with. The definition of shoulder PPJI is currently unclear and further study is needed. There is no ideal test to confirm it. A reasonable approach is to aspirate for culture, and perform serum tests for WBC, ESR, and C-reactive protein. If any of these is positive in the setting of a painful arthroplasty, PPJI should be assumed until proven otherwise. Operative tissue cultures are probably the most reliable test but the clinical significance is not always obvious. Synovial fluid cytokine profiles and tissue PCR/NGS show promise for the future

Infection prevention in shoulder arthroplasty is an evolving challenge as further understanding of the pathogens becomes available. Infection rates for reverse TSA is higher than anatomic TSA. Standard decolonization protocols from our hip and knee colleagues has decreased the acute post-operative infection risk to less than 1%. By identifying at risk populations anti-MRSA precautions including intranasal antibiotics and anti-bacterial soaps for pre-surgical skin preparation have reduced the incidence of staphylococcus infections. The emerging understanding of propionibacterium acnes (P. acnes) as a primary pathogen in late shoulder periprosthetic joint infection (PJI) has led to new recommendations including pre-operative skin cleansing with 5% benzoyl peroxide to reduce infection risk. Pre-operative IV antibiotic is recommended and chlorhexidine skin prep for surgery. In the operating room, the concern is the surgeon's exposure to skin and sebaceous glands where P. acnes is prevalent. After skin incision the surgeon should use a new blade for deep incision. Application of vancomycin powder to the subcutaneous tissue may be beneficial after incision to treat potential contamination from the incision through skin. Glove change prior to handling implants and thorough irrigation before implantation is prudent. The role of antibiotic loaded bone cement for infection prevention remains unproven. Topical vancomycin powder at closure is a low cost option and has shown benefit in spine surgery but efficacy is unproven in the shoulder. Silver impregnated wound dressings may also prevent infection and are a convenient option for patient care with regards to bathing. Preventing infections in shoulder arthroplasty, particularly P. acnes, remains a challenge. A significant number of revision TSAs are found to have positive cultures for P. acnes creating a significant burden for patients and surgeons

Accurate identification of pathogens is a crucial step for successful treatment of implant-associated infections. Sonication of explanted foreign material and subsequent sonicate-fluid culture is regarded to be more sensitive than conventional tissue culture. However, the duration of incubation of cultures remains controversial. The aim of our study was to evaluate diagnostic yield of prolonged 14-days incubation compared to more classical 7-days incubation. Consecutive sonicate fluid culture results from a 2-years period (2013–2015) were retrospectively analysed. All sonicate fluids were cultured aerobically, anaerobically and using blood culture system for 14 days and inspected for growth on day 1, 2, 7 and 14 days. Terminal subcultivation was performed on day 7 from broth and blood culture system for additional 7 days aerobically and anaerobically. Time of bacterial isolation was recorded. Microbiological significance was determined based on isolate quantity and concomitant growth in conventional tissue cultures. A total of 394 sonicate fluid cultures from 304 patients (8–95 years, mean age 62), 53.9% (n=164) women, were analysed. 51.0% (n=201) were from explanted osteosynthetic material, 37.6% (n=148) from hip prosthesis and 11.4% (n=45) from knee prosthesis. Overall, 57.1% (n=225) of cultures were positive. Among them, 71.1% (n=160) were monomicrobial, 21.3% bimicrobial and 7.6% (n=17) polymicrobial. In total, 312 bacterial isolates were isolated. The most frequently isolated bacteria were coagulase-negative staphylococci (CoNS) 34.6% (n=108), Staphylococcus aureus 16.4% (n=51) and Propionibacterium acnes 11.2% (n=35). Gram-negative bacteria and anaerobes represented 18.3% (n=57) and 14.4% (n=45) of isolates, respectively. Among all sonicate fluid cultures, 92.0% (n=207) were positive after 7 days while 8.0% (n=18) were positive only after prolonged 14-days incubation with P. acnes being the predominant bacteria isolated after prolonged incubation. Among all P. acnes isolates 57.1% (n=20) were isolated within 7 days and 42.9% (n=15) within 14 days. Based on microbiologic criteria, 45.7% (n=16) of them were diagnostic; 37.1% (n=13) among early isolates and 8.6% (n=3) among late isolates, difference being statistically significant (p=0.016). Prolonged 14-days incubation of sonicate fluid culture for the diagnosis of implant-associated infections offers only minor 8.0% improvement with regard to conventional 7-days incubation. The majority of P. acnes isolated after prolonged incubation are non-diagnostic using microbiologic criteria. Caution in an interpretation of significance of P. acnes isolated after 14-days incubation is warranted. However, due to a significant impact on patient management prolonged 14-days incubation is still recommended

Massive posterosuperior cuff tears (mRCT) retracted to the glenoid are surgically challenging and often associated with high retear rates. Primary repair is a less-favourable option and other salvage procedures such as SCR and tendon transfers are used. This study presents clinical and radiological outcomes of muscle advancement technique for repair of mRCT. Sixty-one patients (mean age 57±6, 77% males and 23% females) (66 shoulders) underwent all-arthroscopic rotator cuff repair that included supraspinatus and infraspinatus subperiosteal dissection off scapular bony fossae, lateral advancement of tendon laminae, and tension-free double-layer Lasso Loop repair to footprint. Pre-and post-operative range of motion (ROM), cuff strength, VAS, Constant, ASES, and UCLA scores were assessed. Radiologic assessment included modified Patte and Goutallier classifications. All patients had MRI at 6 months to evaluate healing and integrity of repair was assessed using Sugaya classification with Sugaya 4 and 5 considered retears. Advanced fatty degeneration (Goutallier 3-4) was present in 44% and 20% of supraspinatus and infraspinatus. Tendon retraction was to the level of or medial to glenoid in 22%, and just lateral in 66%. 50.8% mRCT extended to teres minor. Subscapularis was partially torn (Lafosse 1-3) in 46% and completely torn (Lafosse 4-5) in 20%. At mean follow-up (52.4 weeks), a significant increase in ROM, Relative Cuff Strength (from 57% to 90% compared to contralateral side), VAS (from 4 ±2.5 to 1±1.7), Constant (50±17.8 to 74 ±13.0), ASES (52 ±17.5 to 87 ±14.9), and UCLA (16± 4.9 to 30 ±4.9) scores were noted. There were six retears (10%), one failure due to P. acnes infection. 93% returned to pre-injury work and 89% of cases returned to pre-injury sport. Satisfaction rate was 96%. Muscle advancement technique for mRCT is a viable option with low retear rates, restoration of ROM, strength, and excellent functional outcomes

Metal instrumentation (rods and screws) is used to stabilise the spine after trauma, malignancy or deformity. Approx 3% become infected often necessitating removal of metal. At surgery tissue samples and metal are removed for culture, but many clinical laboratories are not equipped to process metal or use simple culture methods. The causative bacteria exist as biofilms on the metal and they are often anaerobic and slow-growing, so conventional culture methods often fail to detect them. Also, they are common contaminants leading to diagnostic uncertainty. We have established a laboratory protocol to overcome these problems. Removed metalwork was sonicated and the sonicate centrifuged and the supernatant discarded. Quantitative aerobic and anaerobic culture of the resuspended pellet for 14 days and microscopy were carried out. Metalwork from 11 suspected infected cases was culture-positive (median 2857, 60–5000cfu/mL). Microscopy revealed an infection due to Candida albicans that would not have been detected otherwise. Bacteria were isolated from 8 of 10 non-infected cases (median 15, 0–35 cfu/mL). Conventionally processed samples failed to grow in 4 infected cases. (cfu/mL infected vs noninfected cases p=0.0093). Micro-organisms on spinal metalwork grow as biofilms and they require sonication to dislodge them. The causative bacteria are slow-growing and P acnes is anaerobic and requires prolonged incubation. S epidermidis and P acnes are common contaminants and quantitative culture helps to distinguish pathogens from contaminants, removing the diagnostic uncertainty that conventional methods give. Microscopy of the sonicate can reveal micro-organisms that fail to grow on culture. We recommend that sonication of metalwork, prolonged anaerobic incubation and quantitative culture be adopted to improve diagnostic clarity for spinal instrumentation infections

There continues to be significant debate on the optimum treatment of the infected shoulder arthroplasty. Infection after shoulder arthroplasty is an infrequent but devastating complication with a reported incidence from 0 to 4%. The most common organism responsible for infection following rotator cuff surgery, instability surgery, ORIF proximal humerus fractures, and shoulder arthroplasty is P. acnes. A thorough history is important because many patients have a history of difficulty with wound healing or drainage. P. acnes typically does not start to grow until day 5, therefore it is critical to keep cultures a minimum of 10 to 14 days. Diagnosis can be challenging, particularly among patients undergoing revision surgery. The majority of patients with a low grade infection do not have overt signs of infection such as erythema or sinus tracts. Pre-operative lab values as well as intra-operative pathology have been shown to be unreliable in predicting who will have positive cultures at the time of revision surgery. There are a number of options for treating a patient with a post-operative infection. Essential variables include the timing of infection, status of the host, the specific organism, status of implant fixation, and the status of the rotator cuff and deltoid. One of the most frequently employed options for treating the infected shoulder arthroplasty is two stage re-implantation. However, the rate of complications with this technique as well as residual infection remains high