Propionibacterium acnes: an underestimated etiology in the pathogenesis of osteoarthritis?

Topical Preparations for Reducing Cutibacterium acnes Infections in Shoulder Surgery: A Systematic Review and Network Meta-analysis of Randomized Controlled Trials

BACKGROUND

Cutibacterium acnes (C acnes) is a commensal skin bacterium, primarily found in sebaceous glands and hair follicles, with a high prevalence in the shoulder region. It is the most common pathogenic organism in prosthetic joint infections after shoulder arthroplasty. Because of its low virulence, its diagnosis remains difficult.

PURPOSE

To evaluate the relative effects of topical preparations in reducing C acnes in shoulder surgery.

STUDY DESIGN

Meta-analysis; Level of evidence, 1.

METHODS

We searched the MEDLINE, Embase, PsychINFO, and Cochrane Library databases in March 2022. Randomized controlled trials (RCTs) comparing any form of topical preparation in arthroscopic or open shoulder surgery were included. The primary outcome was a reduction in the number of positive C acnes cultures. Secondary outcomes were adverse events related to the application of topical preparations. We performed a network meta-analysis to facilitate simultaneous comparisons between multiple preparations across studies. We calculated differences between preparations using odds ratios and their 95% CIs. The risk of bias was assessed using the Cochrane risk-of-bias tool.

RESULTS

The search yielded 17 RCTs (1350 patients), of which 9 were suitable for the network meta-analysis (775 patients). Overall, 2 RCTs were deemed as having a low risk of bias, and 15 raised "some concerns" of bias. Preparations included benzoyl peroxide (BPO), BPO combined with clindamycin, chlorhexidine gluconate, hydrogen peroxide, povidone-iodine, and water with soap. Only BPO resulted in significantly lower odds of a positive C acnes culture compared with placebo or soap and water (odds ratio, 0.12 [95% CI, 0.04-0.36]). There was no statistically significant difference with all other topical preparations. The only adverse events were skin irritation from BPO and chlorhexidine gluconate in a small number of reported cases.

CONCLUSION

BPO was the most effective topical agent in reducing the prevalence of C acnes in shoulder surgery. These results were limited by a combination of indirect and direct data. Future studies should focus on establishing the optimal frequency and duration of preoperative BPO to further reduce the burden of C acnes.

REGISTRATION

CRD42022310312 (PROSPERO).

Unexpected positive culture (UPC) in adults revision spine surgery: a systematic review and meta-analysis of incidence, risk factors, and management

BACKGROUND

Without clear signs of infection, spinal implant failure is attributed to mechanical overloads and aseptic loosening. However, how low-grade infections contribute to seemingly aseptic implant failure is unclear.

PURPOSE

The systematic review examined unexpected positive cultures (UPCs) in revision spine surgery regarding prevalence, isolated pathogens, risk factors, and strategies to reduce infection among asymptomatic patients undergoing revision spine surgery.

METHODS

We followed the PRISMA guidelines and searched four main databases (PubMed, EMBASE, SCOPUS, Web of Science) comprehensively until January 2023 for articles reporting UPC after presumed aseptic adult revision spine surgery. The UPC rates were pooled, and risk factors were compared with the culture-negative control group and represented as odds ratio (OR) or mean difference (MD).

RESULTS

Fifteen studies of 1057 individuals were included in two groups: culture-positive or UPCs (n = 317) and culture-negative or control (n = 740). The overall UPC prevalence was 33.2% (317/1057, range: 0 to 53%, 95% CI = 30.2%-36.4%), and Cutibacterium acnes (43.0%, 95% CI = 37.4%-48.8%), Coagulase-negative Staphylococci (CoNS), (39.5%, 95% CI = 33.2%-46.2%), and Staphylococcus species in general (49.5%, 95%CI = 43.7%-55.4%) were reported the most common isolated microbes. 16.1% of the UPCs were polymicrobial. Risk factors associated with UPC rates were female sex (OR = 2.62, 95%CI = 1.76-3.90, P < 0.001), screw loosening (OR = 4.43, 95%CI = 1.31-15.02, P = 0.02), number of operated levels (MD = 0.77, 95%CI = 0.33-1.22, P = 0.0007), and shorter time since index surgery (MD = - 8.57 months, 95%CI = - 14.76, -2.39, P = 0.02).

CONCLUSIONS

One-third of patients undergoing spine revision surgery revealed UPC in this study. Each UPC pathogen interpretation and antibiotic use decision should be interpreted case by case.

LEVEL OF EVIDENCE

IV.

Does hydrogen peroxide application to the dermis following surgical incision affect Cutibacterium acnes cultures in total shoulder arthroplasty in male patients? A randomized controlled trial

BACKGROUND

Periprosthetic joint infections occur in 1%-4% of primary total shoulder arthroplasties (TSAs). Cutibacterium acnes is the most commonly implicated organism and has been shown to persist in the dermis despite use of preoperative antibiotics and standard skin preparations. Studies have shown decreased rates of cultures positive for C acnes with use of preoperative benzoyl peroxide or hydrogen peroxide (H2O2), but even with this positive deep cultures remain common. We sought to determine whether an additional application of H2O2 directly to the dermis following skin incision would further decrease deep culture positivity rates.

METHODS

We performed a randomized controlled trial comparing tissue culture results in primary TSA in patients who received a standard skin preparation with H2O2, ethanol, and ChloraPrep (CareFusion, Leawood, KS, USA) vs. an additional application of H2O2 to the dermis immediately after skin incision. Given the sexual dimorphism seen in the shoulder microbiome regarding C acnes colonization rates, only male patients were included. Bivariable and multivariable analyses were performed to compare rates of positive cultures based on demographic and surgical factors.

RESULTS

Dermal cultures were found to be positive for C acnes at similar rates between the experimental and control cohorts for the initial (22% vs. 28%, P = .600) and final (61% vs. 50%, P > .999) dermal swabs. On bivariable analysis, the rate of positive deep cultures for C acnes was lower in the experimental group, but this difference was not statistically significant (28% vs. 44%, P = .130). However, patients who underwent anatomic TSA were found to have a significantly greater rate of deep cultures positive for C acnes (57% vs. 28%, P = .048); when controlling for this on multivariable analysis, the experimental cohort was found to be associated with significantly lower odds of having positive deep cultures (odds ratio, 0.37 [95% confidence interval, 0.16-0.90], P = .023). There were no wound complications in either cohort.

CONCLUSIONS

An additional H2O2 application directly to the dermis following skin incision resulted in a small but statistically significant decrease in the odds of having deep cultures positive for C acnes without any obvious adverse effects on wound healing. Given its cost-effectiveness, use of a post-incisional dermal decontamination protocol may be considered as an adjuvant to preoperative use of benzoyl peroxide or H2O2 to decrease C acnes contamination.

Are Cutibacterium acnes delivered from skin to deep tissues in primary reverse shoulder arthroplasty? A prospective study

INTRODUCTION

The objective of this study is to determine whether the deep tissues are inoculated during surgery with the Cutibacterium acnes still present in the skin after the surgical preparation in reverse shoulder arthroplasties.

MATERIALS AND METHODS

Prospective study including patients undergoing surgery with reverse shoulder arthroplasty. All the patients received preoperative antibiotic prophylaxis with cefazolin (2 g IV) and the skin was prepared with 2% chlorhexidine gluconate and 70% isopropyl alcohol. From all the patients, 9 cultures were obtained after the antibiotic was administrated and the skin surgically prepared. The cultures were sent to isolate C. acnes. DNA was extracted from the C. acnes isolated colonies. Isolate nucleotide distances were calculated using the Genome-based distance matrix calculator from the Enveomics collection toolbox.

RESULTS

The study included 90 patients. C. acnes was isolated in 24 patients (26.6%) with a total of 61 positive cultures. There were 12 phylotype II, 27 IB and 22 IA. In 9 patients, C. acnes was present in both skin and deep tissues, and they constituted the sample to be studied by means of genomic analysis. In 7 out of the 9 patients, deep tissue samples clustered closer to at least one of its corresponding skin isolates when compared to the other independent bacterial ones.

CONCLUSIONS

The C. acnes present in the skin at the beginning of the surgery are the same as those found in the deep tissues at the end of the surgery. This result strengthens the possibility that the C. acnes is delivered from the skin to the deep tissues.

Functional outcomes and complications of patients contaminated with Cutibacterium acnes during primary reverse shoulder arthroplasty: study at two- and five-years of follow-up

PURPOSE

The objective of the study was to compare the functional outcomes and the complication rate of the patients with C. acnes contamination at the end of the primary reverse shoulder arthroplasty (RSA) surgery to those patients without C. acnes contamination.

METHOD

A total of 162 patients were included. In all cases, skin and deep tissue cultures were obtained. A molecular typing characterization of the C. acnes strains was performed. Functional outcomes were assessed with the Constant score at the two and five year follow-up and all complications were also recorded.

RESULTS

A total of 1380 cultures were obtained from the 162 primary RSA surgeries. Of those, 96 turned out to be positive for C. acnes. There were 25 patients with positive cultures for C. acnes. The overall postoperative Constant score was not significantly different between those patients having C. acnes-positive cultures and those with negative cultures at the two and five year follow-up (59.2 vs. 59.6 at two years, p 0.870, and 59.5 vs. 62.4 at five years, p 0.360). Patients with positive cultures presented a higher complication rate (p 0.001) with two infections, one revision surgery, and one dislocation.

CONCLUSION

Patients ending up with C. acnes-positive cultures after primary shoulder arthroplasty surgery do not have worse clinical outcomes when compared to patients having negative cultures, but a greater number of complications were found in those patients with C. acnes-positive cultures.

Phenotypic and Genotypic Characterization of Cutibacterium acnes Isolated from Shoulder Surgery Reveals Insights into Genetic Diversity

Specific virulence factors that likely influence C. acnes invasion into deep tissues remain to be elucidated. Herein, we describe the frequency of C. acnes identification in deep tissue specimens of patients undergoing clean shoulder surgery and assess its phenotypic and genetic traits associated with virulence and antibiotic resistance patterns, compared with isolates from the skin of healthy volunteers. Multiple deep tissue specimens from the bone fragments, tendons, and bursa of 84 otherwise healthy patients undergoing primary clean-open and arthroscopic shoulder surgeries were aseptically collected. The overall yield of tissue sample cultures was 21.5% (55/255), with 11.8% (30/255) identified as C. acnes in 27.3% (23/84) of patients. Antibiotic resistance rates were low, with most strains expressing susceptibility to first-line antibiotics, while a few were resistant to penicillin and rifampicin. Phylotypes IB (73.3%) and II (23.3%) were predominant in deep tissue samples. Genomic analysis demonstrated differences in the pangenome of the isolates from the same clade. Even though strains displayed a range of pathogenic markers, such as biofilm formation, patients did not evolve to infection during the 1-year follow-up. This suggests that the presence of polyclonal C. acnes in multiple deep tissue samples does not necessarily indicate infection.

Unexpected intraoperative positive culture (UIPC) in presumed aseptic revision spine surgery: a systematic review and meta-analysis

BACKGROUND CONTEXT

Unexpected intraoperative positive culture (UIPC) has recently become increasingly common in revision spine surgery, being implicated as an etiological factor in revision spine surgery indications such as implant failure or pseudoarthrosis.

PURPOSE

Utilizing the available literature, this study aimed to investigate the prevalence of UIPC, and its clinical importance in patients following presumed aseptic revision spine surgery.

STUDY DESIGN

Meta-analysis and systematic review.

METHODS

Multiple databases and reference articles were searched until May 2022. The primary outcome was the pooled rate of UIPC, and the secondary outcomes were the microbiological profile of UIPC, the risk factors of UIPC, and the clinical fate of UIPC.

RESULTS

Twelve studies were eligible for meta-analysis, with a total of 1,108 patients. The pooled rate of UIPC was 24.3% (95% CI=15.8%-35.5%) in adult patients, and 43.2% (95% CI=32.9%-54.2%) in pediatric patients. The UIPC rate was higher when both conventional wound culture and sonication were used together compared to sonication alone or conventional wound culture alone. The rates were 28.9%, 23.6%, and 15.5 %, respectively. In adult and pediatric patients, the most commonly cultured organism was Cutibacterium acnes (42.5% vs 57.7%), followed by coagulase-negative Staphylococcus (39.9% vs 30.5%). Male patients had a higher rate of UIPC (OR= 2.6, 95% CI=1.84-3.72, p<.001), as did patients with a longer fusion construct (MD=0.76, 95% CI=0.27-1.25, p<.001).

CONCLUSIONS

The pooled rate of UIPC in aseptic spine revision surgery was 24.3% and 43.2% in adult and pediatric patients respectively. The most common organisms were C. acnes and coagulase-negative Staphylococcus. The impact of UIPC on patients` clinical outcomes is not fully understood. We are not able to recommend routine culture in revision spine surgery, however, adding sonication may aid in the diagnosis of UIPC. There is not enough evidence to recommend specific treatment strategies at this time, and further studies are warranted.

Detection of Cutibacterium acnes in Tissue Samples from Clean Primary Shoulder Surgeries - Part II

Objective  Research and identification of Cutibacterium acnes ( C. acnes ) and other microorganisms in deep tissue samples collected in clean shoulder surgeries of patients who did not undergo any previous invasive joint procedure and who had no clinical history of infection. Methods  We analyzed the results of cultures of intraoperative deep tissue samples from 84 patients submitted to primary clean shoulder surgery. Tubes containing culture medium were used for storage and transport of anaerobic agents, prolonged incubation time, and mass spectrometer for diagnosis of bacterial agents. Results  Bacteria growth was evidenced in 34 patients (40.4%) of the 84 included in the study. Of these, 23 had growth of C. acnes in at least one sample of deep tissue collected, corresponding to 27.3% of the total patients. The second most common agent was Staphylococcus epidermidis , present in 7.2% of the total individuals included. We showed a higher relationship between sample positivity and males, a lower mean age, absence of diabetes mellitus, ASA I score, and antibiotic prophylaxis in anesthetic induction with cefuroxime. Conclusions  A high percentage of isolates of different bacteria was found in shoulder tissue samples of patients undergoing clean and primary surgeries, who had no history of previous infection. Identification of C. acnes was high (27.6%), and Staphylococcus epidermidis was the second most frequent agent (7.2%).

C.acnes in the joint, is it all just a false positive?

BACKGROUND

Cutibacterium Acnes (C.acnes) has been linked to several shoulder pathologies. An alternative hypothesis suggests it only occurs in the joint secondary to previous instrumentation. Our hypothesis was patients with previous instrumentation would have C.acnes in their joint if it was in skin.

MATERIALS AND METHODS

Sixty-six patients undergoing arthroscopic shoulder surgery had biopsies taken from the affected joint at the time of surgery, along with control biopsies of subdermal fat. The extended culture results were assessed and correlated to previous intervention.

RESULTS

35% tested positive for C.acnes in their joint. 78% were male. 53% had absence of C.acnes in both skin and joint and 29% had presence in both (p = 0.0001). 15% with previous surgery had C.acnes. 53% with previous injection had C.acnes. 25% of patients with virgin joints had C.acnes. There was no statistical difference in the presence of C.acnes in the joint between those with previous instrumentation and without.

CONCLUSION

The significant factors for joint C.acnes were male sex and the presence of the bacteria in the fat. Previous instrumentation was not correlated with C.acnes in the joint. This raises the question of whether the process of biopsy itself may lead to inoculation of the joint.

Minimal number of cultures needed to detect Cutibacterium acnes in primary reverse shoulder arthroplasty: a prospective study

BACKGROUND

The objective of this study was to determine the minimum number of cultures needed to detect Cutibacterium acnes in primary reverse shoulder arthroplasties (RSAs).

METHODS

It is a prospective study including 160 primary RSAs. Exclusion criteria included an active infection, an invasive shoulder treatment in the last 6 months before surgery, an Arthro-SCAN or Arthro-MRI in the last 6 months before surgery, previous shoulder surgeries and revision cases. In 90 cases, 11 cultures were obtained. Another 10 cultures were obtained in the other 70 cases (culture 10 was a sterile sponge to detect false positives). To determine the minimum number of cultures needed to detect C acnes, the prevalence of C acnes contamination of the 160 patients included was determined.

RESULTS

There were 128 females and 32 males, with a mean age of 74 years. There were 1690 cultures obtained from the 160 primary RSA surgeries, and 132 of them turned out to be positive for C acnes. There were 42 patients with positive cultures. Twenty of them were males and 22 females. When considering the skin and the deep tissue cultures altogether, the prevalence of positive cultures for C acnes was of 26.25%. If only deep tissues cultures were considered, the prevalence of positive cultures for C acnes was of 23.13%. When considering the skin and the deep tissue cultures together, the sensitivity to detect the C acnes is 19% if only 1 culture is obtained, 31% if 2 cultures are obtained, 50% if 3 cultures are obtained, 59.5% if 4 cultures are obtained, 66.7% if 5 cultures are obtained, 73.8% if 6 cultures are obtained, 85.7% if 7 cultures are obtained, and 92.9% if 8 cultures are obtained. When considering only the deep tissue cultures, if only 1 culture is obtained, the sensitivity to detect the C acnes is 24.3%, 40.5% if 2 cultures are obtained, 54.1% if 3 cultures are obtained, 73% if 4 cultures are obtained, 89.2% if 5 cultures are obtained, and 97.3% if 6 or 7 cultures are obtained.

DISCUSSION

A minimum number of 8 cultures are needed to detect C acnes in skin. Moreover, a minimum of 6 cultures are needed to detect it in deep tissues when performing an RSA.

Evaluation of the effectiveness of skin preparation methods for the reduction of Cutibacterium acnes (formerly Propionibacterium acnes) in shoulder surgery: a systematic review

Background

Cutibacterium acnes (C. acnes) is the most common pathogen responsible for post-operative shoulder infections. The purpose of this study was to evaluate the effectiveness of skin preparation methods against C. acnes in shoulder surgery.

Methods

A systematic review was conducted evaluating the effectiveness of skin preparation methods in the reduction of C. acnes in patients undergoing shoulder surgery. Outcomes were assessed based on the effectiveness of the method used; side effects and cost were also analysed.

Results

Of the 19 included studies, 9 evaluated pre-surgical home treatments: 8 assessed benzoyl peroxide (BPO) and 6 concluded it is effective in reducing C. acnes. Nine studies assessed surgical skin preparation and concluded that Chlorhexidine gluconate (CHG) was not effective; in contrast hydrogen peroxide reduced C. acnes. Finally, one study evaluated an aseptic protocol using CHG and concluded that it was not effective.

Conclusions

It was demonstrated that BPO as home treatment is effective in reducing C. acnes load on skin; it rarely causes side effects and is also cost-effective. This study highlights non-effectiveness of CHG. There was some evidence that the addition of hydrogen peroxide could have a positive effect in the reduction of C. acnes skin load; however, more studies are required.

Techniques for Decreasing Bacterial Load for Open Shoulder Surgery

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Benzoyl peroxide (BPO) 5% has been shown to reduce Cutibacterium acnes load on the skin. BPO 5% with miconazole nitrate (MN) 2% may be beneficial, whereas BPO 5% with clindamycin cream 1% to 1.2% does not seem to have additive effects when compared with BPO 5% alone. Chlorhexidine gluconate solutions reduce the total bacterial load on the skin, but do not seem to have a significant effect on C. acnes.

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ChloraPrep seems to be the best surgical skin preparation to decrease overall positive skin cultures. Preincisional hydrogen peroxide 3% application has been shown to be a cost-effective practice to inhibit growth of C. acnes. Vancomycin powder before deltopectoral interval closure has antimicrobial effects against C. acnes and is a cost-effective practice. Finally, Bactisure surgical lavage is protective against the formation of biofilms.

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IV cefazolin has been shown to be more effective for shoulder arthroplasty infection prophylaxis than antibiotic alternatives such as vancomycin. Thus, patients with a questionable history of penicillin allergy should undergo additional testing.

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For shoulder surgery infection prophylaxis, we recommend the use of BPO 5% cream for 5 days preoperatively with chlorhexidine wipes the night before and the morning of surgery. IV cefazolin should be administered perioperatively, and patients with a questionable history of penicillin allergy should be tested. Surgeons should consider preincisional application of hydrogen peroxide 3% for 5 minutes, followed by standard ChloraPrep preparation. Normal saline should be used for preclosure lavage. Finally, application of vancomycin powder deep to the deltopectoral interval closure should be considered.

An evidence-based approach to managing unexpected positive cultures in shoulder arthroplasty

BACKGROUND

Unexpected positive cultures (UPCs) are very commonly found during shoulder arthroplasty when surgeons send intraoperative cultures to rule out periprosthetic joint infection (PJI) without clinical or radiographic signs of infection. Cutibacterium acnes is thought to be the most common bacteria cultured in this setting; however, the implications of an unexpected positive result are neither well defined nor agreed upon within the literature. The current review evaluates the incidence of UPCs and C acnes in reverse total arthroplasty; the clinical significance, if any, of these cultures; and various prognostic factors that may affect UPC incidence or recovery following PJI.

METHODS

A systematic review was performed with PRISMA guidelines using PubMed, CINAHL, and Scopus databases. Inclusion criteria included studies published from January 1, 2000, to May 20, 2021, that specifically reported on UPCs, native or revision shoulder surgery, and any study that directly addressed one of our 6 proposed clinical questions. Two independent investigators initially screened 267 articles for further evaluation. Data on study design, UPC rate/speciation, UPC risk factors, and UPC outcomes were analyzed and described.

RESULTS

A total of 22 studies met the inclusion criteria for this study. There was a pooled rate of 27.5% (653/2373) deep UPC specimen positivity, and C acnes represented 76.4% (499/653) of these positive specimens. Inanimate specimen positivity was reported at a pooled rate of 20.1% (29/144) across 3 studies. Male patients were more likely to have a UPC; however, the significance of prior surgery, surgical approach, and type of surgery conflicted across multiple articles. Patient-reported outcomes and reoperation rates did not differ between positive-UPC and negative-UPC patients. The utilization of antibiotics and treatment regimen varied across studies; however, the reinfection rates following surgery did not statistically differ based on the inclusion of antibiotics.

CONCLUSION

UPCs are a frequent finding during shoulder surgery and C acnes represents the highest percentage of cultured bacteria. Various preoperative risk factors, surgical techniques, and postoperative treatment regimens did not significantly affect the incidence of UPCs as well as the clinical outcomes for UPC vs. non-UPC patients. A standardized protocol for treatment and follow-up would decrease physician uncertainty when faced with a UPC from shoulder surgery. Given the results of this review, shoulder surgeons can consider not drastically altering the postoperative clinical course in the setting of UPC with no other evidence of PJI.

What do positive and negative Cutibacterium culture results in periprosthetic shoulder infection mean? A multi-institutional control study

BACKGROUND

Deep tissue culture specimens obtained at the time of revision shoulder arthroplasty are commonly positive for Cutibacterium. Clinical interpretation of positive cultures can be difficult. This was a multi-institutional study evaluating the accuracy of cultures for Cutibacterium using positive control (PC) and negative control (NC) samples. The relationship between time to culture positivity and strength of culture positivity was also studied.

METHODS

Eleven different institutions were each sent 12 blinded samples (10 PC and 2 NC samples). The 10 PC samples included 2 sets of 5 different dilutions of a Cutibacterium isolate from a failed total shoulder arthroplasty with a probable periprosthetic infection. At each institution, the samples were handled as if they were received from the operating room. Specimen growth, time to culture positivity, and strength of culture positivity (based on semiquantitative assessment) were reported.

RESULTS

A total of 110 PC samples and 22 NC samples were tested. One hundred percent of specimens at the 4 highest dilutions were positive for Cutibacterium. At the lowest dilution, 91% of samples showed positive findings. Cutibacterium grew in 14% of NC samples. Cutibacterium grew in PC samples at an average of 4.0 ± 1.3 days, and all of these samples showed growth within 7 days. The time to positivity was significantly shorter (P < .001) and the strength of positivity was significantly higher (P < .001) in true-positive cultures compared with false-positive cultures.

CONCLUSIONS

This multi-institutional study suggests that different institutions may report highly consistent rates of culture positivity for revision shoulder arthroplasty samples with higher bacterial loads. In contrast, with lower bacterial loads, the results are somewhat less consistent. Clinicians should consider using a shorter time to positivity and a higher strength of positivity as adjuncts in determining whether a tissue culture sample is a true positive.

Short-term Clinical Outcomes of Unexpected Culture-positive Cutibacterium acnes (Formerly Propionibacterium acnes) in Open Orthopaedic Surgery

INTRODUCTION

The clinical significance and treatment recommendations for an unexpected positive Cutibacterium acnes (C acnes) culture remain unclear. The purpose of our study was to evaluate the clinical effect of a C acnes positive culture in patients undergoing open orthopaedic surgery.

METHODS

Patients with a minimum of one positive C acnes intraoperative culture were retrospectively reviewed over a 7-year period. True C acnes infection was defined as culture isolation from ≥1 specimens in the presence of clinical or laboratory indicators of infection.

RESULTS

Forty-eight patients had a positive intraoperative C acnes culture. 4.2% had a C acnes monoinfection, and 12.5% of the patients had a coinfection. The remainder was classified as indeterminate. Significant differences were identified between the indeterminate and true C acnes infection groups, specifically in patients with surgery history at the surgical site (P = 0.04), additional antibiotic therapy before surgery (P < 0 .001), and postoperative clinical signs of infection (P < 0 .001).

DISCUSSION

Suspicion for true C acnes infection should be raised in patients with surgery site history, antibiotic therapy before surgery, and clinical infectious signs. The indeterminate unexpected positive culture patients had a low risk of developing a true clinical infection that required antibiotic therapy.

Acne cream reduces the deep Cutibacterium acnes tissue load before elective open shoulder surgery: a randomized controlled pilot trial

BACKGROUND

Cutibacterium acnes is the main pathogen in periprosthetic shoulder infections. In acne vulgaris therapy, benzoyl peroxide-miconazole nitrate cream effectively reduces the superficial C acnes burden of the skin. Its additional potential in the subcutaneous and capsular layers (eg, for prevention of future periprosthetic shoulder infections) is unknown. The aim of this study was to investigate the efficacy of a topical acne vulgaris cream (benzoyl peroxide-miconazole nitrate) to reduce subcutaneous and capsular C acnes in individuals with C acnes skin colonization undergoing open shoulder surgery.

METHODS

A prospective randomized pilot trial was performed, allocating 60 adult patients (1:1) to either a 7-day preoperative application of a commercial acne cream (benzoyl peroxide-miconazole nitrate) on the preoperative skin (intervention group) or no cream (control group) from November 1, 2018, to May 31, 2020. The superficial skin of the shoulder was sampled at enrollment and before incision, and deep subcutaneous and capsular shoulder samples were taken during surgery.

RESULTS

Sixty patients (mean age, 59 years; 55% female patients) undergoing primary open shoulder surgery (17 Latarjet procedures and 43 arthroplasties) were included in the study. At baseline, both randomized groups showed the presence of C acnes on the skin at a rate of 60% (18 of 30 patients in intervention group and 19 of 30 patients in control group, P = .79). In patients with C acnes skin colonization, the intervention resulted in a significant reduction in the overall number of intraoperative samples with positive findings compared with the control group (8 of 18 patients vs. 16 of 19 patients, P = .01), especially in capsular samples (0 of 18 patients vs. 4 of 19 patients, P = .04).

CONCLUSION

The topical 7-day preoperative skin application of acne cream (benzoyl peroxide-miconazole nitrate) significantly reduced the intraoperative C acnes load in 56% of the patients in the intervention group compared with 16% of the control patients.

Detecção de Cutibacterium acnes em amostras de tecidos de cirurgias limpas primárias do ombro – Parte I

Objective  The present study aimed to identify bacterial agents in shoulder surgery specimens from patients with no history of previous shoulder infection or surgery.

Methods  Tendon, bursa, and bone specimens were collected during surgery, stored in sterile dry bottles, and sent to a hospital-associated laboratory for culture growth analysis in media for aerobic and anaerobic agents. Findings from 141 samples from 47 shoulders were analyzed.

Results  The cultures were negative in 46 cases (97.8%) and in 140 samples (99.2%). The culture was positive in a single patient, with growth of Staphylococcus hominis from one of three specimens collected.

Conclusions  The rates of bacterial growth were not consistent with the international literature, indicating the low effectiveness of laboratory methods used in Brazil.

The management of the shoulder skin microbiome (Cutibacterium acnes) in the context of shoulder surgery: a review of the current literature

BACKGROUND

This review aims to establish current knowledge of the shoulder skin microbiome and how to manage the bacteria that reside within it.

METHODS

A review was undertaken of the current literature through OvidSP. All abstracts were reviewed by three independent researchers.

RESULTS

Thirty-five studies met the inclusion criteria. With forward referencing an additional 14 were included. None commented on organisms specific to the shoulder microbiome other than Cutibacterium acnes. Therefore, this review is focussed on the current knowledge of C. acnes.

DISCUSSION

C. acnes is a skin commensal within the pilo-sebaceous glands reported to be the primary pathogen in up to 86% of shoulder joint infections. Pre-operative culture of unprepared skin can be indicative of underlying joint infection in shoulder arthroplasty revision. Intra-articular biopsies may have a high false positive due to skin contamination. Correlating the number of positive samples and certain associated signs can give a greater than 90% probability of a true infection. Standard surgical skin preparation, peri-surgical intravenous antibiotics and oral pre-operative antibiotics do not reduce bacterial load within the skin. However, topical benzoyl peroxide and clindamycin have both demonstrated significantly reduced bacteria load. Phylogenetically there are six main types. Patients may have more than one phenotype present during infection.

Does application of hydrogen peroxide to the dermis reduce incidence of Cutibacterium acnes during shoulder arthroplasty: a randomized controlled trial

INTRODUCTION

Prosthetic joint infections (PJIs) following shoulder arthroplasty are a major source of morbidity and are most commonly caused by Cutibacterium acnes, a bacteria found concentrated in the dermis. Skin preparation using hydrogen peroxide has been shown to reduce positive cultures; however, direct application to the dermis has not been investigated. The purpose of this study is to determine whether the application of hydrogen peroxide to the dermis affects the incidence of positive C acnes cultures.

METHODS

A prospective, randomized controlled trial of patients undergoing primary shoulder arthroplasty by a single fellowship-trained surgeon was performed between February and November 2020. Enrolled patients were randomized to either receive standard skin preparation and antibiotic prophylaxis with or without an additional application of hydrogen peroxide to the dermis following incision. Culture samples were taken from the skin, dermis, glenohumeral joint, and air. Laboratory personnel and patients were blinded to randomization, and all cultures were held for 14 days. Culture positivity rate along with culture site, day of culture positivity, and bacterial abundance of positive cultures were analyzed. Stratified analysis by gender and age of ≤69 years was also performed.

RESULTS

Sixty patients undergoing primary arthroplasty were randomized. The group receiving hydrogen peroxide (n =30) and the control group (n = 30) were similar in age (71.1 ± 7.1 vs. 73.4 ± 9.8; P = .30), body mass index (29.4 ± 5.7 vs. 28.5 ± 6.0; P = .57), gender (P = .64), hand dominance (P = .65), and surgery type (P = .90). The overall rate of at least 1 positive culture was 18%. All positive cultures were C acnes. The positive culture rate in the hydrogen peroxide (20%) and control group were similar (16%; P > .99). There were no positive glenohumeral joint cultures and no wound complications. There was no significance difference in the culture site, day of culture positivity, and bacterial abundance. Stratification analysis by gender and age also demonstrated similar rates of C acnes between study groups.

CONCLUSION

Standard skin preparation and antibiotic prophylaxis results in an overall low rate of skin and dermis culture positivity. The use of hydrogen peroxide after initial incision did not significantly alter the rate of positive C acnes cultures during shoulder arthroplasty and did not increase wound complications.

Recurrent Cutibacterium acnes prosthetic valve endocarditis

A 29-year-old man with a history of congenital aortic stenosis and mechanical aortic valve replacement with previous Cutibacterium acnes prosthetic valve endocarditis (PVE) presented with a 2-week history of fevers and night sweats. Transoesophageal echocardiogram revealed a 0.6 cm×0.5 cm vegetation on the mechanical aortic valve. An anaerobic blood culture became positive for C. acnes 6 days after the blood cultures were obtained. He did not have any surgical intervention. He was successfully treated with 6 weeks of ceftriaxone, followed by chronic suppression with oral doxycycline. Despite its low virulence, a growing number of C. acnes PVE cases have been reported, owing to its biofilm production. When clinical suspicion is high, extending culture incubation duration beyond the standard 5 days might be helpful. Most cases are treated with surgical repair or replacement in conjunction with antibiotics, but medical therapy alone has been documented as being successful.

Subcutaneous tissue disinfection significantly reduces Cutibacterium acnes burden in primary open shoulder surgery

BACKGROUND

Cutibacterium acnes is one of the major pathogens responsible for infection after shoulder surgery. Surgical dissection of the dermis may expose C acnes from sebum-producing hair follicles. Because of contact with the surgeon's gloves and instruments, further spread occurs throughout the surgical field. The purpose of this study was to determine whether subcutaneous tissue disinfection could reduce the C acnes culture rate in primary open shoulder surgery.

METHODS

All patients eligible for primary open shoulder surgery by a deltopectoral approach were prospectively enrolled in our 2-arm, randomized, single-blinded clinical trial. In all patients, a skin swab of the operative field was taken prior to standard surgical skin preparation. After exposure of the deltoid fascia, the disinfection group received an additional preparation of the subcutaneous layer with povidone-iodine solution. Once the proximal humerus was completely exposed, 5 swabs from different sites were taken for microbiological examination according to a strict specimen collection protocol. All cultures were incubated in aerobic and anaerobic conditions for 14 days.

RESULTS

Between February and December 2019, 108 patients were enrolled in the 2 groups: treatment (n = 70) and control (n = 38). The 2 groups did not show any significant difference in terms of sex, age, body mass index, or occurrence of diabetes. The subcutaneous disinfection protocol significantly reduced the positive culture rate of the operating field for all germs combined (P = .036) and specifically for C acnes (P = .013). The reduction of positive swabs for C acnes was significant for the surgeon's gloves (P = .041), as well as the retractors (P = .007).

CONCLUSION

Disinfection of the subcutaneous tissue significantly reduced the C acnes culture rate during primary open shoulder surgery. We highly recommend this simple step as an adjunct to the current surgical practice to limit iatrogenic contamination of the surgical field. Future studies may observe a reduction in postoperative shoulder infection owing to this practice.

Cutibacterium acnes in shoulder surgery: a scoping review of strategies for prevention, diagnosis, and treatment

BACKGROUND

Cutibacterium acnes is a commensal, gram-positive, facultatively anaerobic bacillus that resides in the dermis. Historically thought to be a contaminant when identified on cultured specimens, recent advances in diagnostic technology have now implicated it as the most common organism responsible for postoperative shoulder infections. Despite a recognition of the role of this organism and a significant research interest in recent years, there is clear lack of consensus guideline on strategies to prevent, diagnose, and treat postoperative shoulder infection.

METHOD

The electronic databases PubMed, MEDLINE, CINAHL, Scopus, and Web of Science were searched in March 2020. All experimental and nonexperimental studies that investigate C acnes in shoulder surgery were included. Inclusion was limited to articles published after 2000 and written in English; reviews, gray literature, or abstracts were excluded. A total of 70 studies were included in this review. This scoping review was performed in accordance with the Extended Preferred Reporting Items of Systematic Reviews and Meta-Analyses Statement for Scoping Reviews (PRISMA-ScR).

RESULTS

Standard surgical prophylactic regimens such as intravenous antibiotics and topical chlorhexidine are ineffective at removing C acnes from the deep layer of the dermis, and there is a shift toward using topical benzoyl peroxide with significantly improved efficacy. An improved understanding of the bacteria has demonstrated that a prolonged culture time of up to 14 days is needed, especially in cases of established infection. Advances in diagnostics such as sonication and molecular-based testing are promising. Although usually thought to be susceptible to a broad range of antibiotics, resistance is emerging to clindamycin. An improved understanding of its ability to form a biofilm highlights the difficulty in treating an established infection.

CONCLUSION

The role of C acnes causing postoperative infection following shoulder surgery is being increasingly recognized. Strategies for prevention, diagnosis, and treatment have been outlined from both an antimicrobial and surgical perspective. A number of these strategies are emerging and require further research to demonstrate efficacy before implementation into clinical guidelines.

Unexpected positive cultures after revision shoulder arthroplasty: does it affect outcome?

BACKGROUND

Several studies have confirmed a high rate of unexpected positive cultures (UPCs) after presumably aseptic revisions of shoulder arthroplasties; however, the impact on the outcome is still unclear. The purpose of this prospective study is to compare the patient-reported outcomes of standard revisions with and without the emergence of UPCs.

METHODS

During a 3-year period, we included all patients who were revised for reasons other than suspicion of infection from 2 orthopedic centers. Five biopsies were obtained from every revision, and only cultures with the same bacteria in at least 3 biopsy specimens were classified as UPCs. All patients were assessed using the Oxford Shoulder Score (OSS) and range of motion preoperatively and after at least a 2-year follow-up.

RESULTS

In this study, 124 patients were included, with a median follow-up of 29 months (range 29-32), and UPCs emerged after 27 revisions (22%), with Cutibacterium acnes accounting for 67% (18/27). At baseline, the OSS was 22 in both the culture-negative and UPC groups (P = .46). Then, at follow-up, the OSS was 37 in the culture-negative group and 35 in the UPC group (P = .91). The forward elevation increased significantly by 44° and 41°, respectively, in the 2 groups, but no statistically significant difference between the culture-negative group and the UPC group was found (P = .66). In contrast, the external rotation was unchanged after the revision, and again, no difference in the change between the culture-negative and UPC groups (P = .54) was observed. Subgroup analyses stratified by different implant designs revealed equal patterns with no statistical differences in outcome.

CONCLUSION

We did not find a difference in outcome after a presumed aseptic revision regardless of the emergence of UPCs. Similarly, we could not demonstrate that patients with UPCs presented with poorer function at baseline compared with culture-negative patients. The clinical relevance of UPCs thus requires further evaluation, especially in the case of C acnes as a potential pathogenic versus a merely colonizing microbe.

Prosthetic Shoulder Joint Infection by Cutibacterium acnes: Does Rifampin Improve Prognosis? A Retrospective, Multicenter, Observational Study

This retrospective, multicenter observational study aimed to describe the outcomes of surgical and medical treatment of C. acnes-related prosthetic joint infection (PJI) and the potential benefit of rifampin-based therapies. Patients with C. acnes-related PJI who were diagnosed and treated between January 2003 and December 2016 were included. We analyzed 44 patients with C. acnes-related PJI (median age, 67.5 years (IQR, 57.3-75.8)); 75% were men. The majority (61.4%) had late chronic infection according to the Tsukayama classification. All patients received surgical treatment, and most antibiotic regimens (43.2%) included β-lactam. Thirty-four patients (87.17%) were cured; five showed relapse. The final outcome (cure vs. relapse) showed a nonsignificant trend toward higher failure frequency among patients with previous prosthesis (OR: 6.89; 95% CI: 0.80-58.90) or prior surgery and infection (OR: 10.67; 95% IC: 1.08-105.28) in the same joint. Patients treated with clindamycin alone had a higher recurrence rate (40.0% vs. 8.8%). Rifampin treatment did not decrease recurrence in patients treated with β-lactams. Prior prosthesis, surgery, or infection in the same joint might be related to recurrence, and rifampin-based combinations do not seem to improve prognosis. Debridement and implant retention appear a safe option for surgical treatment of early PJI.

The incidence and incubation period of false-positive culture results in shoulder surgery

BACKGROUND

Postoperative shoulder infection is a significant complication requiring timely identification and treatment. Indolent infections such as those involving Cutibacterium acnes (formerly Propionibacterium acnes) provide a diagnostic dilemma as they present differently, without the acute symptoms associated with most postoperative bone and joint infections. Furthermore, Cacnes is thought to be a common contaminant isolated from intraoperative cultures. With no consensus algorithm, long-held cultures play a major role in guiding management decisions in potential postoperative shoulder infection. Our study sought to determine the incidence of positive culture results in both open and arthroscopic procedures in noninfected patients, as well as to clarify whether an increase in the incubation time frame leads to an increased rate of culture growth.

METHODS

One hundred patients were prospectively enrolled into either the open or arthroscopic procedure group. Patients with abnormal inflammatory laboratory findings, a history of shoulder surgery, or corticosteroid injection within 6 months of surgery were excluded from the study. Three cultures were obtained for each patient: superficial tissue culture, tissue culture, and "sterile" control swab. Cultures were held for 28 days and checked at regular intervals. All patients were followed up clinically for 6 months to ensure no signs of postoperative infection occurred.

RESULTS

Ultimately, 95 patients were included in the final analysis. The false-positive rate was 17.0% in those who underwent open shoulder surgery and 10.4% in those who underwent arthroscopic shoulder surgery. The incidence of positive Cacnes culture results was 6.4% in the open group, whereas Cacnes was not isolated in the arthroscopic group. All positive bacterial culture results were reported within 7 days of collection. One culture result was positive for mold at 26 days.

CONCLUSION

A relatively high false-positive culture rate occurred in both open and arthroscopic shoulder surgery. Cacnes was the most commonly identified bacterium in cultures in the open surgery group. Knowledge of one's institutional false-positive culture rate could be important in avoiding potentially inappropriate treatment. Additionally, we found that holding cultures longer than 14 days did not lead to an increased rate of false-positive culture results.

RSA, TSA and PyC hemi-prostheses: comparing indications and clinical outcomes using a second-generation modular short-stem shoulder prosthesis

INTRODUCTION

The goal of this study was to provide an insight into the clinical results after modular short-stem shoulder arthroplasty for various indications.

MATERIALS AND METHODS

A consecutive cohort study of 76 patients followed up for 23-55 (mean 31.4) months. 23 anatomical (TSA), 32 reverse (RSA) and 21 hemi-prostheses with a pyrocarbon head (PyC), using a modular short stem with proximal porous coating were implanted. Range of motion, pain and Constant score (CS) were recorded. Comparisons of pre- vs postoperative outcomes, between prosthesis types and indications, were made.

RESULTS

All prosthesis types brought about a significant improvement (p < 0.05) in all measured outcomes. TSA had a significantly higher increase in the CS than PyC and RSA (p = 0.002 and 0.003, respectively). TSA produced superior gains in all ROM compared with RSA (p < 0.02). RSA brought about significantly smaller improvements in internal rotation than TSA and PyC (p = 0.0001 and 0.008, respectively). TSA had greater pain relief than PyC (p = 0.02). TSA with Walch A glenoids seemed to improve more than type B in the CS. PyC patients with Walch B glenoids improved more than Walch A (p = 0.03). When implanted due to Osteoarthritis (OA), PyC had a comparable final outcome to TSA (p = 0.95), although the preoperatively worse TSA patients had a greater improvement in the CS (p = 0.026). The outcome of RSA did not differ between indications, but Walch A glenoids tended to improve more.

CONCLUSIONS

Using a second-generation short-stem shoulder prostheses, TSA achieves the best clinical improvements overall, especially for OA with a Walch A glenoid. Despite refixation of the subscapularis tendon in all cases, RSA has inferior internal rotation than TSA and PyC, suggesting a mechanical limitation. OA, a Walch B glenoid and arthritis caused by instability seem to be ideal indications when considering PyC.

Cutibacterium acnes is an intracellular and intra-articular commensal of the human shoulder joint

BACKGROUND

Cutibacterium acnes (C acnes) is a mysterious member of the shoulder microbiome and is associated with chronic postoperative complications and low-grade infections. Nevertheless, it is unclear whether it represents a contaminant or whether it accounts for true infections. Because it can persist intracellularly in macrophages at several body sites, it might in fact be an intra-articular commensal of the shoulder joint.

METHODS

In 23 consecutive, otherwise healthy patients (17 male, 6 female; 58 years) who had no previous injections, multiple specimens were taken from the intra-articular tissue during first-time arthroscopic and open shoulder surgery. The samples were investigated by cultivation, genetic phylotyping, and immunohistochemistry using C acnes-specific antibodies and confocal laser scanning microscopy.

RESULTS

In 10 patients (43.5%), cultures were C acnes-positive. Phylotype IA1 dominated the subcutaneous samples (71%), whereas type II dominated the deep tissue samples (57%). Sixteen of 23 patients (69.6%) were C acnes-positive by immunohistochemistry; in total, 25 of 40 samples were positive (62.5%). Overall, 56.3% of glenohumeral immunohistochemical samples, 62.5% of subacromial samples, and 75% of acromioclavicular (AC) joint samples were positive. In 62.5% of the tested patients, C acnes was detected immunohistochemically to reside intracellularly within stromal cells and macrophages.

DISCUSSION

These data indicate that C acnes is a commensal of the human shoulder joint, where it persists within macrophages and stromal cells. Compared with culture-based methods, immunohistochemical staining can increase C acnes detection. Phylotype II seems to be most prevalent in the deep shoulder tissue. The high detection rate of C acnes in osteoarthritic AC joints might link its intra-articular presence to the initiation of osteoarthritis.

Pathogenic genetic variations of C. acnes are associated with clinically relevant orthopedic shoulder infections

Many surgeons continue to face the clinical dilemma of interpreting a positive aspiration or unexpected positive Cutibacterium acnes (C. acnes) culture. There are factors that complicate the interpretation of positive cultures including variations in both frequency of false positive cultures and virulence properties. As indices of virulence, hemolytic strains, from previously confirmed clinically infected shoulders, were compared with non-hemolytic isolates determined to be contaminants, by RNA-sequencing (RNA-Seq). Six C. acnes isolates from patients who underwent revision total shoulder arthroplasty (TSA) were identified based on previously described infection criteria. Three C. acnes isolates from each group underwent RNA-Seq. Differential gene expression analysis, principal component analysis (PCA), and heatmap analysis were used to determine the gene variation and patterning between the definite infection and probable contaminant isolates. Differential gene expression analysis identified genes that were differentially expressed between the isolates classified as definite infection and isolates classified as probable contaminants. PCA using a 500 gene subset of identified genes was able to find combinations of these genes that separated out the definite infection and probable contaminants isolates. The heatmap demonstrated similar gene expression in the three Definite Infections isolates, and significantly different expression when compared with the probable contaminant isolates. Clinical significance: C. acnes revision TSA isolates classified as definite infection and probable contaminant demonstrated a similar gene expression pattern to each respective group and different gene expression pattern when compared between groups. These findings indicate distinct differences in C. acnes strains associated with clinically relevant orthopedic TSA infections.

Detection of Cutibacterium acnes in arthroscopic rotator cuff and bankart repair

BACKGROUND

We evaluated the detection rate for Cutibacterium acnes (C. acnes) in patients who underwent arthroscopic cuff repair and Bankart repair.

METHODS

Arthroscopic cuff repair was performed in 105 patients (R group) and arthroscopic Bankart repair was performed in 29 patients (B group). Skin swabs prior to antisepsis, intraoperative synovial swabs of the glenohumeral joint (immediately after incision and prior to wound closure), suture of suture anchor, and postoperative swabs from the tip of arthroscope were cultured. Evaluation criteria were compared between groups and included the presence or absence of diabetes mellitus, operation time, frequency of preoperative injections, deep infections, and detection rate of C. acnes in multiple regions of the body.

RESULTS

There were 14 patients (12.2%) in the R group and one patient in the B group (3.6%) with diabetes mellitus, and no significant difference was found between the two groups. The frequency of injections to the shoulder was significantly greater in the R group at 3.6 ± 4.2 times compared to the B group at 1.6 ± 2.0 times. There were no deep infections in either groups. The detection rate for C. acnes was significantly greater in the synovial swabs alone (skin swabs for R and B groups, 42.3% and 47.6%, respectively; synovial swabs, 10.4% and 1.8%; suture, 8.7% and 0%; tip of arthroscope, 4.3% and 0%).

CONCLUSIONS

A significantly greater number of C. acnes samples were detected from synovial swabs of cuff tears, suggesting that its presence may be due to preoperative injections to the shoulder.

Cutibacterium acnes: a threat to shoulder surgery or an orthopedic red herring?

Cutibacterium acnes is a lipophilic, anaerobic, gram-positive bacillus that mainly colonizes the pilosebaceous glands of human skin. It has been implicated as the leading cause of prosthetic joint infection (PJI) after shoulder arthroplasty. However, PJI caused by C acnes rarely manifests as overt clinical, laboratory, or imaging features. In fact, more than 40% of shoulders undergoing revision arthroplasty are likely to be culture positive. However, rates of infection following a positive culture can be as low as 5%. The purpose of this review was to put forth alternative explanations for this discordance between positive cultures and infection. We describe C acnes roles as a commensal, bystander, and/or contaminant organism; the role of cultures in diagnosis and other methods that may be more accurate; its existence in a shoulder microbiome; and the variable virulence of C acnes. C acnes is an important cause of shoulder PJI in some patients. However, there is a large body of literature that suggests other functions that need to be considered. Further research is needed to define the role of C acnes that is logically explained by all of the literature and not only some.

Efficacy of Home Prophylactic Benzoyl Peroxide and Chlorhexidine in Shoulder Surgery: A Systematic Review and Meta-Analysis

Two predominant prophylactic home skin-disinfection regimens exist in shoulder surgery, benzoyl peroxide and chlorhexidine. Of these 2 regimens, benzoyl peroxide gel is more effective than chlorhexidine in reducing the rate of positive Cutibacterium cultures on the skin surface. At present, there are no studies that assess the impact of these home prophylactic measures on clinical infection rates.

A comprehensive review of bacterial osteomyelitis with emphasis on Staphylococcus aureus

Osteomyelitis, a significant infection of bone tissue, gives rise to two main groups of infection: acute and chronic. These groups are further categorized in terms of the duration of infection. Usually, children and adults are more susceptible to acute and chronic infections, respectively. The aforementioned groups of osteomyelitis share almost 80% of the corresponding bacterial pathogens. Among all bacteria, Staphylococcus aureus (S. aureus) is a significant pathogen and is associated with a high range of osteomyelitis symptoms. S. aureus has many strategies for interacting with host cells including Small Colony Variant (SCV), biofilm formation, and toxin secretion. In addition, it induces an inflammatory response and causes host cell death by apoptosis and necrosis. However, any possible step to take in this respect is dependent on the conditions and host responses. In the absence of any immune responses and antibiotics, bacteria actively duplicate themselves; however, in the presence of phagocytic cell and harassing conditions, they turn into a SCV, remaining sustainable for a long time. SCV is characterized by notable advantages such as (a) intracellular life that mediates a dam against immune cells and (b) low ATP production that mediates resistance against antibiotics.

Cutibacterium colonization of the anterior and lateral thigh

AIMS

Of growing concern in arthroplasty is the emergence of atypical infections, particularly Cutibacterium (formerly Propionibacterium) sp. infections. Currently, the dermal colonization rate of Cutibacterium about the hip is unknown. Therefore, the aim of this study was to investigate colonization rates of Cutibacterium sp. at locations approximating anterior and posterolateral approaches to the hip joint.

METHODS

For this non-randomized non-blinded study, 101 adult patients scheduled for hip or knee surgery were recruited. For each, four 3 mm dermal punch biopsies were collected after administration of anaesthesia, but prior to antibiotics. Prebiopsy skin preparation consisted of a standardized preoperative 2% chlorhexidine skin cleansing protocol and an additional 70% isopropyl alcohol mechanical skin scrub immediately prior to biopsy collection. Two skin samples 10 cm apart were collected from a location approximating a standard direct anterior skin incision, and two samples 10 cm apart were collected from a lateral skin incision (suitable for posterior, direct-lateral, or anterolateral approaches). Samples were cultured for two weeks using a protocol optimized for Cutibacterium.

RESULTS

A total of 23 out of 404 cultures (collected from 101 patients) were positive for a microorganism, with a total of 22 patients having a positive culture (22%). Overall, 15 of the cultures in 14 patients were positive for Cutibacterium sp. (65%), of which Cutibacterium acnes comprised the majority (n = 13; 87%). Other isolated microorganisms include coagulase-negative Staphylococcus (n = 6), Clostridium (n = 1), and Corynebacterium (n = 1). Of all positive cultures, 15 were obtained from the anterior location (65%), of which seven (60%) were from the most proximal biopsy location. However, these findings were not statistically significant (anterior vs lateral, p = 0.076; proximal vs distal, p =0.238).

CONCLUSION

Approximately 14% (14/101) of the patients demonstrated a positive Cutibacterium colonization about the hip, the majority anteriorly. Given the high colonization rate of Cutibacterium, alternative skin preparations for total hip arthroplasty should be considered. Cite this article: Bone Joint J 2020;102-B(7 Supple B):52-56.

Cutibacterium acnes is less commonly identified by next-generation sequencing than culture in primary shoulder surgery

INTRODUCTION

High rates of positive Cutibacterium acnes cultures from primary shoulder surgery make positive cultures in the revision surgery setting difficult to interpret. Our goal was to determine concordance between culture and next-generation sequencing techniques for identification of C. acnes from primary shoulder surgery.

METHODS

Patients undergoing shoulder arthroscopy for rotator cuff tear or primary anatomic shoulder arthroplasty for osteoarthritis were prospectively enrolled. Specimens were sent for culture (aerobic and anaerobic) and next-generation sequencing. For next-generation sequencing, the entire microbial DNA was sequenced in order to identify pathogens within the sample.

RESULTS

Our cohort consisted of 90 patients (45 patients in the osteoarthritis group and 45 patients in the rotator cuff tear group). At least one sample was positive for C. acnes in 18 (20%) cases by culture and in 14 (15.6%) cases by next-generation sequencing (p = 0.559). Four (22.2%) of the 18 cases with positive C. acnes cultures also had C. acnes identified by next-generation sequencing (kappa = 0.238). There was no difference in C. acnes identification rates between osteoarthritis and rotator cuff tear groups.

CONCLUSIONS

There was limited concordance between culture and next-generation sequencing for C. acnes identification. Further studies are needed to determine the potential for next-generation sequencing as a diagnostic tool.

Prevention of Cutibacterium acnes infection in arthroscopic shoulder surgery: a systematic review

BACKGROUND

Cutibacterium acnes is a gram-positive anaerobe that can lead to postoperative shoulder infections. The purpose of this study was to determine the incidence of C acnes infections following shoulder arthroscopy and evaluate the efficacy of perioperative antibiotic prophylaxis in the prevention of these infections.

METHODS

A systematic review was performed by searching PubMed, the Cochrane Library, and Embase to identify studies that evaluated the prevalence and clinical indications of C acnes infections after various arthroscopic shoulder surgical procedures. Patients were assessed based on positive culture rates, the contraction of infection, and antibiotic regimens used to prevent infection.

RESULTS

A total of 9 studies (1 level I, 5 level II, 1 level III, and 2 level IV) met the inclusion criteria, including a total of 3758 patients with a mean age of 59.9 years (range, 17-87 years) at the time of surgery. The mean follow-up time was 1.6 months (range, 1.0-12.0 months). Overall, 37.3% of patients (173 of 464) had positive C acnes skin and/or joint culture results, and in 0.22% of patients (8 of 3586), a C acnes infection was diagnosed postoperatively. The application of a topical benzoyl peroxide antibiotic in the days leading up to surgery significantly reduced the positive culture rate from 41.6% to 9.6% (P < .001).

CONCLUSIONS

C acnes infections occur at a very low rate (0.22%) following shoulder arthroscopy. The application of a topical benzoyl peroxide antibiotic in the days leading up to surgery in combination with preoperative antibiotic prophylaxis significantly reduces the prevalence of C acnes in shoulder arthroscopy patients.

Is Cutibacterium acnes early surgical site infection rate related to the duration of antibiotic prophylaxis in adolescent idiopathic scoliosis surgery?

PURPOSE

Cutibacterium acnes (C. acnes) is a gram-positive anaerobic bacillus located in pilosebaceous glands, usually responsible for late postoperative surgical site infections (SSI). A recent study performed in our institution highlighted an unexpected emergence of C. acnes early SSI. One potential explanation was the change of the perioperative antibioprophylaxis (ATB) protocol, which switched from 48 h postoperative cefamandole to intraoperative only cefazoline. The aim of this study was therefore to investigate the influence of the ATB duration on the occurrence of C. acnes early SSI, by comparing the incidence rates during 3 consecutive ATB protocols.

METHODS

Between January 2007 and September 2017, all patients who underwent posterior fusion for AIS were retrospectively reviewed. Early C. acnes SSI were reported and compared between 3 periods, during which the ATB protocols were modified. January 2007-February 2012: Intraoperative Cefamandole continued 48 h (protocol 1) March 2012-August 2016: Single shot of intraoperative Cefazoline (protocol 2) September 2016-September 2017: Intraoperative Cefazoline continued 48 h (protocol 3).

RESULTS

Fifty-three early SSI (7.2%) were reported among the 732 posterior AIS fusions included. Global incidence of C. acnes infection was 2.9%. The incidence of C. acnes in early SSI increased from 0 to 4.9% between protocol 1 and 2, but was reduced to 1.7% with protocol 3.

CONCLUSIONS

Early C acnes SSI can be explained by the difficulty to eradicate this pathogen with current skin preparation procedures and some Beta-lactam antibiotics tolerance. Longer duration antibioprophylaxis is preferable to prevent from early C. acnes SSI.

Incidence of Cutibacterium acnes in arthroscopic Bankart repair for traumatic anterior shoulder instability

Background

We evaluated the detection rate of Cutibacterium acnes (C. acnes) for patients who underwent arthroscopic Bankart repair for traumatic anterior shoulder instability.

Methods

Study subjects included 36 patients who underwent arthroscopic Bankart repair. Skin swabs prior to antisepsis, intraoperative synovial swabs of the glenohumeral joint (immediately after incision and prior to wound closure), and the suture of the suture anchor were cultured. Evaluation criteria included the detection rate of C. acnes in multiple regions of the body.

Results

Using a skin swab culture test, C. acnes was detected in 63 of 108 samples (58.3%). The bacterium was detected in 2 of 36 samples (5.5%) and 4 of 36 (11.1%) in the synovial swab culture of the glenohumeral joint immediately after surgical incision and immediately before wound closure, respectively. In the suture culture of the suture used in the arthroscopic Bankart repair, C. acnes was detected in 1 of 36 samples (2.8%).

Conclusions

C. acnes was detected in patients undergoing surgeries for shoulder instability. The relationship between C. acnes and the pathological condition of shoulder instability remains unknown.

Incidence and predictors of positive intraoperative cultures in primary shoulder arthroplasty following prior ipsilateral shoulder surgery

Background

To our knowledge, the rate of positive intraoperative cultures in patients undergoing primary shoulder arthroplasty with prior ipsilateral nonarthroplasty shoulder surgery is unknown. The aim of this study was to determine the incidence and predictors of positive cultures in these patients.

Methods

We performed a retrospective review of patients with prior ipsilateral shoulder surgery with intraoperative cultures taken at the time of primary shoulder arthroplasty. We evaluated culture results, demographics, and number of prior surgeries. Regression analysis was used to determine patient-related risk factors that predict positive cultures.

Results

A total of 682 patients underwent primary shoulder arthroplasty, 83 had at least 1 prior ipsilateral shoulder surgery: 65.1% male, mean age 64.2 ± 10.9 years. For the cohort of 83 patients, an average of 3.2 ± 1.2 tissue samples were obtained for each patient, with a mean of 0.84 ± 1.14 tissue cultures being positive (range 0-5). Thirty-seven of the 83 patients (44.5%) had at least 1 positive culture, with Cutibacterium acnes the most frequent organism (31/37; 83.4%). An average of 1.9 ± 0.96 tissue cultures resulted positive (range 1-5) for the 37 patients who had positive cultures, 40.5% (15/37) had only 1 positive tissue culture (12/15 C acnes, 2/15 Staphylococcus epidermidis, and 1/15 vancomycin-resistant enterococcus). Male sex and history of prior shoulder infection were predictive of culture positivity (odds ratios: 2.5 and 20.9, respectively). Age, race, medical comorbidities, number of prior shoulder surgeries, and time from index shoulder surgery were not predictive of culture positivity.

Conclusion

About 45% of patients with no clinical signs of infection and a history of prior ipsilateral shoulder surgery undergoing primary shoulder arthroplasty grew positive intraoperative cultures. The significance of these findings remains unclear with regard to risk of periprosthetic infection and how these patients should be managed.

Ten-day culture incubation time can accurately detect bacterial infection in periprosthetic infection in shoulder arthroplasty

Background

Cutibacterium acnes is the most commonly isolated organism involved in periprosthetic shoulder infections. C acnes has traditionally been difficult to isolate, and much debate exists over appropriate culture methods. Recently, our institution initiated a 10-day culture method using a Brucella blood agar medium to enhance anaerobic growth specifically for C acnes in shoulder specimens.

Methods

A retrospective review of shoulder cultures from 2014-2017 of patients undergoing workup for possible infected shoulder arthroplasty was performed. Cultures were obtained in patients either preoperatively or intraoperatively at the time of revision. Presence of infection was determined based on at least 1 positive culture and treatment with either prolonged antibiotics, placement of an antibiotic spacer at the time of revision, or repeat surgical débridement.

Results

The records of 85 patients with 136 cultures were reviewed. Eighty-two patients had full records with at least 1-year clinical follow-up. Fifty-eight cultures were positive, with C acnes as the most commonly recovered organism (57% of positive cultures). Clinical follow-up of patients with negative cultures found no incidence of missed periprosthetic infection.

Conclusions

Use of a 10-day culture incubation method to enhance anaerobic bacterial growth is able to accurately detect periprosthetic infection in the shoulder including those related to C acnes. Our results suggest that by adopting more uniform culture methods, a shorter culture incubation time may be adequate. Ultimately, prospective studies with rigorous microbiologic methods are needed to best understand the clinical significance of unexpected positive bacterial cultures in shoulder arthroplasty.

Next-generation sequencing for diagnosis of infection: is more sensitive really better?

BACKGROUND

The utility of next-generation sequencing (NGS) in differentiating between active infection and contaminant or baseline flora remains unclear. The purpose of this study is to compare NGS with culture-based methods in primary shoulder arthroplasty.

METHODS

A prospective series of primary shoulder arthroplasty patients with no history of infection or antibiotic use within 60 days of surgery was enrolled. All patients received standard perioperative antibiotics. After skin incision, a 10 × 3-mm sample of the medial skin edge was excised. A 2 × 2-cm synovial tissue biopsy was taken from the rotator interval after subscapularis takedown. Each sample set was halved and sent for NGS and standard cultures.

RESULTS

Samples from 25 patients were analyzed. Standard aerobic/anaerobic cultures were positive in 10 skin samples (40%, 95% confidence interval [CI] 20%-60%) and 3 deep tissue samples (12%, 90% CI 1%-23%]). NGS detected ≥1 bacterial species in 17 of the skin samples (68%, 95% CI 49%-87%) and 7 deep tissue samples (28%, 95% CI 9%-47%). There was a significant difference (P < .03) in the mean number of bacterial species detected with NGS between the positive standard culture (1.6 species) and the negative standard culture groups (5.7 species).

CONCLUSION

NGS identified bacteria at higher rates in skin and deep tissue samples than standard culture did in native, uninfected patients undergoing primary procedures. Further research is needed to determine which NGS results are clinically relevant and which are false positives before NGS can be reliably used in orthopedic cases.

Incidence of Propionibacterium acnes in arthroscopic rotator cuff repair

BACKGROUND

Recently, Propionibacterium acnes was reported to be involved in postsurgical outcomes. We investigated the detection rate of P. acnes and clinical features of P. acnes infection following arthroscopic rotator cuff repair.

METHODS

Samples were collected from skin swabs before preparation, swabs of the synovium, sutures, and swabs from the arthroscope tip. We evaluated age, sex, presence of diabetes mellitus, preoperative contracture, operation time, blood test, Japanese Orthopaedic Association (JOA) scores, cuff integrity, deep infection, and positive inoculation rate.

RESULTS

We studied 90 patients (59 men and 31 women). Mean age was 60.6 years. Cultures of P. acnes showed a 65.5% positive superficial colonization rate (78.0%, male; 41.9%, female). Among the synovium swabs, P. acnes was detected in 13.6% and 0% of patients positive and negative for skin colonization with P. acnes, respectively. Positive culture was not correlated with age, sex, presence of diabetes mellitus, preoperative contracture, blood test, JOA score, cuff integrity, deep infection, operation time, and blood test date.

CONCLUSIONS

P. acnes was detected at a higher rate in the skin of male patients. Patients with P. acnes detected on the skin showed higher rates of detection in the synovium. These findings suggest that the route of infection is via contamination.

LEVEL OF EVIDENCE

Diagnostic level III; Case-control study.

Periprosthetic Infections of the Shoulder: Diagnosis and Management

The use of shoulder arthroplasty is continuing to expand. Periprosthetic joint infection of the shoulder is a devastating complication occurring in approximately 1% of cases. The most common organisms responsible for the infection are Cutibacterium acnes (formerly Propionibacterium acnes) (∼39%) and coagulase-negative Staphylococcus (∼29%). Evaluation of patients includes history and physical examination, serologic testing, imaging, possible joint aspiration, and tissue culture. Diagnosing infections caused by lower virulence organisms (eg, C acnes) poses a challenge to the surgeon because traditional diagnostic tests (erythrocyte sedimentation rate, C-reactive protein, and joint aspiration) have a low sensitivity due to the lack of an inflammatory response. Periprosthetic joint infections of the shoulder due to Staphylococcus aureus and other highly virulent organisms are often easy to diagnose and are usually treated with two-stage revisions. However, for infections with C acnes and coagulase-negative Staphylococcus, single- and two-stage revision surgeries have shown similar ability to clear the infection. Unexpected positive cultures for C acnes during revision surgery are not uncommon; the proper management is still under investigation and remains a challenge.

Propionibacterium avidum: A Virulent Pathogen Causing Hip Periprosthetic Joint Infection

Background

Propionibacteria are important members of the human skin microbiota, but are also opportunistic pathogens associated with periprosthetic joint infection (PJI). While the role of Propionibacterium acnes in PJI has been widely described, insight into the capacity of Propionibacterium avidum to cause PJI is limited.

Methods

An unusual cluster of 4 hip PJIs caused by P. avidum in one orthopedic center in 2015 prompted us to retrospectively identify and analyze clinical data related to previous P. avidum PJI cases (1997-2015). We also characterized the hemolytic and biofilm-producing capacity of our 4 clinical P. avidum strains isolated in 2015, and investigated their phylogenetic relationships by whole-genome sequencing.

Results

We retrospectively identified 13 P. avidum PJIs, with the majority being hip-related infections (n = 11). Preoperative synovial fluid cultures were P. avidum positive in 63.6% of cases. Six of 12 patients (50%) with available case histories were treated with an exchange of the prosthesis. In all but 1 of the 6 patients treated with debridement-retention of the prosthesis, treatment failed, thus requiring a 2-stage revision. The isolated P. avidum strains showed a more pronounced hemolytic activity, but a similar biofilm-forming ability when compared to P. acnes. Whole-genome sequencing identified 2 phylogenetic clusters highly related to P. avidum PJI strains isolated in Sweden.

Conclusions

We describe the largest series of P. avidum PJI predominantly located in the hip. Phylogenetic similarity of our P. avidum strains to PJI strains isolated elsewhere suggests that these invasive lineages may be common.

A review of microscopy-based evidence for the association of Propionibacterium acnes biofilms in degenerative disc disease and other diseased human tissue

PURPOSE

Recent research shows an increasing recognition that organisms not traditionally considered infectious in nature contribute to disease processes. Propionibacterium acnes (P. acnes) is a gram-positive, aerotolerant anaerobe prevalent in the sebaceous gland-rich areas of the human skin. A ubiquitous slow-growing organism with the capacity to form biofilm, P. acnes, recognized for its role in acne vulgaris and medical device-related infections, is now also linked to a number of other human diseases. While bacterial culture and molecular techniques are used to investigate the involvement of P. acnes in such diseases, definitive demonstration of P. acnes infection requires a technique (or techniques) sensitive to the presence of biofilms and insensitive to the presence of potential contamination. Fortunately, there are imaging techniques meeting these criteria, in particular, fluorescence in situ hybridization and immunofluorescence coupled with confocal laser scanning microscopy, as well as immunohistochemistry.

METHODS

Our literature review considers a range of microscopy-based studies that provides definitive evidence of P. acnes colonization within tissue from a number of human diseases (acne vulgaris, degenerative disc and prostate disease and atherosclerosis), some of which are currently not considered to have an infectious etiology.

RESULTS/CONCLUSION

We conclude that P. acnes is an opportunistic pathogen with a likely underestimated role in the development of various human diseases associated with significant morbidity and, in some cases, mortality. As such, these findings offer the potential for new studies aimed at understanding the pathological mechanisms driving the observed disease associations, as well as novel diagnostic strategies and treatment strategies, particularly for degenerative disc disease. These slides can be retrieved under Electronic Supplementary Material.

Is Implant Coating With Tyrosol- and Antibiotic-loaded Hydrogel Effective in Reducing Cutibacterium (Propionibacterium) acnes Biofilm Formation? A Preliminary In Vitro Study

BACKGROUND

Studies have suggested that Cutibacterium acnes (formerly known as Propionibacterium) is the most frequently isolated pathogen after shoulder arthroplasty. To address the burden of periprosthetic joint infections associated with this pathogen, new prevention methods are needed. Tyrosol has a promising record of effectiveness in the field of biofilm-associated infections; however, to our knowledge, it has not been tested against C. acnes thus far.

QUESTIONS/PURPOSES

In this in vitro study, we asked: (1) Is tyrosol effective in inhibiting and eradicating C. acnes planktonic growth? (2) Is there synergy between tyrosol and rifampicin? (3) Is supplementation of hydrogel with tyrosol at the minimum inhibitory and subinhibitory concentrations efficacious in reducing free-floating C. acnes growth? (4) Is implant hydrogel coating (either alone or combined with tyrosol, rifampicin, or vancomycin) beneficial in reducing C. acnes biofilm formation? (5) Is the administration of soluble tyrosol an effective measure against C. acnes biofilm formation?

METHODS

We assessed C. acnes planktonic growth and eradication by inspecting visually the results of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. We also evaluated macroscopically the presence of synergy among tyrosol and rifampicin by means of the MIC checkerboard testing. Thereafter, we addressed colorimetrically the efficacy of tyrosol-loaded Defensive Antibacterial Coating (DAC®) hydrogel against the C. acnes free-floating form by means of the XTT cell proliferation reduction assay. Then, we explored photometrically the effect of hydrogel and soluble tyrosol at reducing C. acnes biofilm formation on titanium alloy disks that simulated orthopaedic implants by using the minimum biofilm inhibition concentration assay. In particular, 16 disks were sequentially allocated to each of the following testing conditions: (1) hydrogel alone; (2) tyrosol-loaded hydrogel; (3) rifampicin-supplemented hydrogel; (4) vancomycin-loaded hydrogel; and (5) soluble tyrosol. Subsequently, implants were sonicated and cell viability was evaluated in terms of the XTT assay.

RESULTS

Tyrosol was effective in inhibiting C. acnes planktonic (free-floating) growth demonstrating MIC values of 63 mM (9 mg/mL) and MBC values of 250 mM (35 mg/mL). Concerning synergy assessment, the checkerboard testing revealed additivity among tyrosol and rifampicin with a fractional inhibitory concentration index of 0.56. In addition, a hydrogel coating with tyrosol at the MIC showed no difference in the inhibition of free-floating C. Acnes form over control (median absorbance [MA] for tyrosol-supplemented hydrogel versus control groups were 0.21 [interquartile range {IQR}, 0.19-0.24] versus 0.26 [IQR, 0.23-0.31], p = 0.066). Furthermore, loaded hydrogel with tyrosol at 597 mg/mL (1 M) was no more effective than control in reducing C. acnes biofilm formation (MAs for tyrosol versus control were 0.12 [IQR, 0.11-0.13] versus 0.14 [IQR, 0.12-0.16], respectively; p = 0.076). This was also the case when we considered hydrogel in conjunction with vancomycin and rifampicin (MAs for vancomycin at 2% and 5% and rifampicin at 1% versus biofilm control were 0.139 [IQR, 0.133-0.143] and 0.141 [IQR, 0.133-0.143] and 0.135 [IQR, 0.128-0.146] versus 0.142 [IQR, 0.136-0.144], correspondingly). In contrast, soluble tyrosol at 597 mg/mL (1 M) inhibited biofilm formation compared to control (MAs for tyrosol and control groups were 0.11 [IQR, 0.09-0.13] versus 0.13 [IQR, 0.12-0.14], p = 0.007).

CONCLUSIONS

Although the implant coating with hydrogel (either pure or supplemented with antimicrobial agents) did not diminish C. acnes biofilm development in vitro, soluble tyrosol at 597 mg/mL (1 M) exceeded the meaningful biofilm inhibition threshold of 80%.

CLINICAL RELEVANCE

The results of the current preclinical investigation did not support the use of a fast, bioresorbable hydrogel as a coating method against C. acnes biofilms. Instead, direct local administration of soluble tyrosol at high concentrations should be further tested in future animal studies.

Proceedings from the 2018 International Consensus Meeting on Orthopedic Infections: evaluation of periprosthetic shoulder infection

The Second International Consensus Meeting on Orthopedic Infections was held in Philadelphia, Pennsylvania, in July 2018. More than 800 experts from all 9 subspecialties of orthopedic surgery and allied fields of infectious disease, microbiology, and epidemiology were assembled to form the International Consensus Group. The shoulder workgroup reached consensus on 27 questions related to culture techniques, inflammatory markers, and diagnostic criteria used to evaluate patients for periprosthetic shoulder infection. This document contains the group's recommendations and rationale for each question related to evaluating periprosthetic shoulder infection.