Characteristics and Treatment Outcomes of Propionibacterium acnes Prosthetic Shoulder Infections in Adults

One- vs. Two-Stage Revision for Periprosthetic Shoulder Infections: A Systematic Review and Meta-Analysis

Periprosthetic shoulder infection (PSI) remains a challenging complication after shoulder arthroplasty. Therapeutic options include one- or two-stage revision, irrigation and debridement, and resection arthroplasty. With our systematic review and meta-analysis, we aimed to compare one- and two-stage revisions for periprosthetic shoulder joint infections and determine the most appropriate therapeutic procedure. We performed an extensive literature search in PubMed, Ovid Medline, Cochrane Library, Web of Science, and CINAHL and filtered out all relevant studies. The meta-analysis was performed using the random-effects model, heterogeneity was analyzed using I2, and publication bias was assessed using the Egger's test. A total of 8 studies with one-stage revisions, 36 studies with two-stage revisions, and 12 studies with both one-stage and two-stage revisions were included. According to the random-effects model, the reinfection rate for the entirety of the studies was 12.3% (95% Cl: 9.6-15.3), with a low-to-moderate heterogeneity of I2 = 47.72%. The reinfection rate of the one-stage revisions was 10.9%, which was significantly lower than the reinfection rate of the two-stage revisions, which was 12.93% (p = 0.0062). The one-stage revision rate was significantly lower with 1.16 vs. 2.25 revisions in the two-stage revision group (p < 0.0001). The postoperative functional outcome in one-stage-revised patients was comparable but not statistically significant (p = 0.1523). In one- and two-stage revisions, most infections were caused by Cutibacterium acnes. In summary, our systematic review and meta-analysis show the superiority of single-stage revision regarding reinfection and revision rates in periprosthetic shoulder joint infection.

Successful Treatment of Cutibacterium acnes Prosthetic Joint Infection With Single-Stage Exchange and Oral Antibiotics

Interest has grown in less invasive surgical treatment and early use of oral antibiotics in the treatment of Cutibacterium acnes prosthetic joint infection. We report a series of patients who were successfully treated with single-stage exchange and an all-oral course of rifampin and linezolid.

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.

Cutibacterium acnes Prosthetic Joint Infections: Is Rifampicin-Combination Therapy Beneficial?

No consensus has been reached on the optimal antibiotic regimen to treat Cutibacterium acnes PJIs (Ca-PJIs). In vitro studies showed excellent rifampicin efficacy against biofilm-associated C. acnes infections, but clinical studies did not confirm the superiority of rifampicin-combined therapy over monotherapy. This prospective cohort study was undertaken to analyze the outcomes of 70 patients who underwent exchange arthroplasty for chronic monomicrobial Ca-PJI and were treated with rifampicin or without between 2004 and 2019. The 37 patients treated from January 2004 to August 2014 were prescribed rifampicin-combination therapy and the 33 treated from September 2014 to December 2019 received monotherapy without rifampicin. The primary endpoint was the 2-year Kaplan-Meier-estimated reinfection-free probability, including relapses and new-pathogen PJIs. The 2-year reinfection-free rate was high and not different for patients who had received rifampicin or not (89.2% vs. 93.8%, respectively; p = 0.524). None of the patients relapsed and six developed new-pathogen PJIs. Our results do not support a benefit of rifampicin-combination therapy for patients who underwent exchange arthroplasty for chronic Ca-PJIs.

Diagnostic Performance of Advanced Metal Artifact Reduction MRI for Periprosthetic Shoulder Infection

BACKGROUND

The diagnosis of periprosthetic shoulder infection (PSI) in patients with a painful arthroplasty is challenging. Magnetic resonance imaging (MRI) may be helpful, but shoulder implant-induced metal artifacts degrade conventional MRI. Advanced metal artifact reduction (MARS) improves the visibility of periprosthetic bone and soft tissues. The purpose of our study was to determine the reliability, repeatability, and diagnostic performance of advanced MARS-MRI findings for diagnosing PSI.

METHODS

Between January 2015 and December 2019, we enrolled consecutive patients suspected of having PSI at our academic hospital. All 89 participants had at least 1-year clinical follow-up and underwent standardized clinical, radiographic, and laboratory evaluations and advanced MARS-MRI. Two fellowship-trained musculoskeletal radiologists retrospectively evaluated the advanced MARS-MRI studies for findings associated with PSI in a blinded and independent fashion. Both readers repeated their evaluations after a 2-month interval. Interreader reliability and intrareader repeatability were assessed with κ coefficients. The diagnostic performance of advanced MARS-MRI for PSI was quantified using sensitivity, specificity, and the area under the receiver operating characteristic curve (AUC). When applying the International Consensus Meeting (ICM) 2018 criteria, of the 89 participants, 22 (25%) were deemed as being infected and 67 (75%) were classified as being not infected (unlikely to have PSA and not requiring a surgical procedure during 1-year follow-up).

RESULTS

The interreader reliability and intrareader repeatability of advanced MARS-MRI findings, including lymphadenopathy, joint effusion, synovitis, extra-articular fluid collection, a sinus tract, rotator cuff muscle edema, and periprosthetic bone resorption, were good (κ = 0.61 to 0.80) to excellent (κ > 0.80). Lymphadenopathy, complex joint effusion, and edematous synovitis had sensitivities of >85%, specificities of >90%, odds ratios of >3.6, and AUC values of >0.90 for diagnosing PSI. The presence of all 3 findings together yielded a PSI probability of >99%, per logistic regression analysis.

CONCLUSIONS

Our study shows the clinical utility of advanced MARS-MRI for diagnosing PSI when using the ICM 2018 criteria as the reference standard. Although the reliability and diagnostic accuracy were high, these conclusions are based on our specific advanced MARS-MRI protocol interpreted by experienced musculoskeletal radiologists. Investigations with larger sample sizes are needed to confirm these results.

LEVEL OF EVIDENCE

Diagnostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Occult prosthetic aortic valve endocarditis caused by Propionibacterium acnes: a case report

We present an unusual case of occult mechanical aortic valve endocarditis caused by Propionibacterium acnes (P. acnes), which occurred five years after the initial cardiac surgical procedure. The only potential source of this infection from the patient's past medical history was a gastric band removal followed by a gastric bypass surgery, which was performed two years prior to her redo cardiac procedure. The patient's main presenting symptom was progressive dyspnoea with worsening of gradients across the mechanical aortic valve. Of note, she had no cardinal symptoms of infection. The patient underwent redo bioprosthetic aortic valve replacement with aortic root replacement. Prosthetic valve cultures grew P. acnes, while blood cultures remained negative. She was started on intravenous antibiotics for six weeks and her postoperative course was uneventful. She remained symptom-free six months postoperatively. This case opens the discussion for the importance of administering antibiotics prophylaxis for endocarditis in patients with prosthetic heart valves undergoing gastric procedures.

Risk of revision based on timing of corticosteroid injection prior to shoulder arthroplasty

AIMS

Corticosteroid injections are often used to manage glenohumeral arthritis in patients who may be candidates for future total shoulder arthroplasty (TSA) or reverse shoulder arthroplasty (rTSA). In the conservative management of these patients, corticosteroid injections are often provided for symptomatic relief. The purpose of this study was to determine if the timing of corticosteroid injections prior to TSA or rTSA is associated with changes in rates of revision and periprosthetic joint infection (PJI) following these procedures.

METHODS

Data were collected from a national insurance database from January 2006 to December 2017. Patients who underwent shoulder corticosteroid injection within one year prior to ipsilateral TSA or rTSA were identified and stratified into the following cohorts: < three months, three to six months, six to nine months, and nine to 12 months from time of corticosteroid injection to TSA or rTSA. A control cohort with no corticosteroid injection within one year prior to TSA or rTSA was used for comparison. Univariate and multivariate analyses were conducted to determine the association between specific time intervals and outcomes.

RESULTS

In total, 4,252 patients were included in this study. Among those, 1,632 patients (38.4%) received corticosteroid injection(s) within one year prior to TSA or rTSA and 2,620 patients (61.6%) did not. On multivariate analysis, patients who received corticosteroid injection < three months prior to TSA or rTSA were at significantly increased risk for revision (odds ratio (OR) 2.61 (95% confidence interval (CI) 1.77 to 3.28); p < 0.001) when compared with the control cohort. However, there was no significant increase in revision risk for all other timing interval cohorts. Notably, Charlson Comorbidity Index ≥ 3 was a significant independent risk factor for all-cause revision (OR 4.00 (95% CI 1.40 to 8.92); p = 0.036).

CONCLUSION

There is a time-dependent relationship between the preoperative timing of corticosteroid injection and the incidence of all-cause revision surgery following TSA or rTSA. This analysis suggests that an interval of at least three months should be maintained between corticosteroid injection and TSA or rTSA to minimize risks of subsequent revision surgery. Cite this article: Bone Joint J 2022;104-B(5):620-626.

Clindamycin Efficacy for Cutibacterium acnes Shoulder Device-Related Infections

Clindamycin is an antibiotic with high bioavailability and appropriate bone diffusion, often proposed as an alternative in guidelines for C. acnes prosthetic joint infections. We aimed to evaluate the efficacy of clindamycin in the treatment of C. acnes shoulder implant joint infections (SIJI). Methods: A retrospective analysis was conducted at the University Hospital of Nice (France) between 2010 and 2019. We included patients with one shoulder implant surgical procedure and at least one C. acnes positive sample. We selected the C. acnes SIJI according to French and international recommendations. The primary endpoint was favorable outcome of C. acnes SIJI treatment after at least 1-year follow-up in the clindamycin group compared to another therapeutic group. Results: Forty-eight SIJI were identified and 33 were treated with clindamycin, among which 25 were treated with monotherapy. The median duration of clindamycin antibiotherapy was 6 weeks. The average follow-up was 45 months; one patient was lost to follow-up. Twenty-seven patients out of 33 (82%) were cured with clindamycin, compared to 9/12 (75%) with other antibiotics. The rate of favorable outcomes increased to 27/31 (87%) with clindamycin and to 9/10 (90%) for other antibiotics when no septic revision strategies were excluded (P = 1.00). Conclusions: The therapeutic strategy based on one- or two-stage revision associated with 6 weeks of clindamycin seems to be effective.

Antibiotic Therapy for Prosthetic Joint Infections: An Overview

Prosthetic joint infection (PJI) is a severe complication after arthroplasty. Its management combines surgical intervention, whose type depends on the clinical situation, and prolonged high-dose antibiotics adapted to the responsible microorganism(s) and the patient. Antibiotics are only one part of the therapeutic regimen and are closely related to the surgical strategy. Their efficacy depends to a large extent on the choice and quality of the surgical procedure, and the quality of the microbiological diagnosis. Although guidelines have been published, many aspects of antibiotic therapy remain poorly established. Choosing the optimal agent(s) is one aspect, with others being optimization of drugs’ pharmacokinetic/pharmacodynamic parameters, the choice of administration route, use of monotherapy or combination regimens, therapeutic drug-monitoring and patient education to improve compliance and tolerance. Herein, we address PJI management based on recent literature data, guidelines and the experience of our referral center for complex bone-and-joint infections.

Indolent Infection After Lumbar Interbody Fusion: An Under-recognized Cause of Pseudarthrosis, Which Can Be Successfully Treated With Anterior Revision Fusion

Introduction:

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Discussion:

A Janus-Faced Bacterium: Host-Beneficial and -Detrimental Roles of Cutibacterium acnes

The bacterial species Cutibacterium acnes (formerly known as Propionibacterium acnes) is tightly associated with humans. It is the dominant bacterium in sebaceous regions of the human skin, where it preferentially colonizes the pilosebaceous unit. Multiple strains of C. acnes that belong to phylogenetically distinct types can co-exist. In this review we summarize and discuss the current knowledge of C. acnes regarding bacterial properties and traits that allow host colonization and play major roles in host-bacterium interactions and also regarding the host responses that C. acnes can trigger. These responses can have beneficial or detrimental consequences for the host. In the first part of the review, we highlight and critically review disease associations of C. acnes, in particular acne vulgaris, implant-associated infections and native infections. Here, we also analyse the current evidence for a direct or indirect role of a C. acnes-related dysbiosis in disease development or progression, i.e., reduced C. acnes strain diversity and/or the predominance of a certain phylotype. In the second part of the review, we highlight historical and recent findings demonstrating beneficial aspects of colonization by C. acnes such as colonization resistance, immune system interactions, and oxidant protection, and discuss the molecular mechanisms behind these effects. This new insight led to efforts in skin microbiota manipulation, such as the use of C. acnes strains as probiotic options to treat skin disorders.

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.

Rifampin-accompanied antibiotic regimens in the treatment of prosthetic joint infections: a frequentist and Bayesian meta-analysis of current evidence

Prosthetic joint infections cause serious morbidity and mortality among joint arthroplasty patients. Rifampin-accompanied antibiotic regimens are recommended for gram-positive infections. This study aimed to combine current evidence supporting the rifampin supplement to an effective antibiotic in the treatment of prosthetic joint infections. We conducted a random-effects meta-analysis with frequentist and Bayesian approaches. A total of 13 studies, all observational, were included in the final analysis. The predominant bacteria in eight, two, and three studies were Staphylococcus spp., Propionibacterium spp., and Streptococcus spp., respectively. We pooled data from 568 patients in the staphylococcus subset (OR, 1.18; 95% CIs, [0.76; 1.82]; I² = 23%) and data from 80 patients in the propionibacterium subset (REM OR, 1.61; 95% CIs [0.58; 4.47]; I² = 0%). Both were insignificant with little heterogeneity. We pooled data from 483 patients in the streptococcus subset; the pooled estimate in this subset favored the use of rifampin supplemented regimens (1.84; [0.90; 3.76]) with moderate to high unaccounted heterogeneity (I² = 57%). Bayesian random-effects models produced a posterior probability density indicating that future studies will not favor rifampin supplementation in Staphylococcus infections (μ, 0.074; τ, 0.570; 89% HPD, [- 0.48; 0.54]). Bayesian posterior distribution in the Streptococcus subset displayed a tendency toward rifampin supplementation. Studies had a substantial selection bias. Available evidence did not encourage rifampin-accompanied regimens for staphylococcal infections.

Calcium sulphate mixed with antibiotics does not decrease efficacy against Cutibacterium acnes (formerly Propionibacterium acnes), in vitro study

Background

This study explored the in vitro efficacy of antibiotics mixed with calcium sulfate (ACS) against Cutibacterium acnes (C. acnes).

Methods

C. acnes isolates from orthopaedic infection sites were tested for antimicrobial susceptibility with ACS. Minimal inhibitory concentrations (MIC) were determined with a gradient diffusion method (Etest® strips).

Results

When tested with Etest®, all 22 isolates were susceptible to penicillin, ceftriaxone, vancomycin, and two were resistant to clindamycin (MICs of 4 and 8 mg/L). Penicillin and rifampin had the largest inhibition zone diameters.

Conclusions

Antibiotics retained activity against C. acnes when mixed with calcium sulfate.

Cerebral empyema and abscesses due to Cutibacterium acnes

INTRODUCTION

Cutibacterium acnes is a commensal bacterium of the skin, frequently reported in prosthetic shoulder or spinal implant infections, but rarely in cranial and intracranial infections.

METHODS

We retrospectively reviewed patients with intracranial samples positive to Cutibacterium acnes managed in the neurosurgical units of our hospital of Lyon, France, between 2008-2016.

RESULTS

We included 29 patients, of whom 23 had empyema (with or without abscess), 17 had cranial osteomyelitis, and six only had abscess. Prior neurosurgery was reported in 28 patients, and the remaining patient had four spontaneous abscesses. Twelve patients had polymicrobial infections, including methicillin-susceptible Staphylococcus in 11 cases. The clinical diagnosis was difficult because of indolent and delayed symptoms: a CT scan or MRI was required. Thirteen patients (52%) had material at the infection site. All patients with bone flap implant or bones from biological banks had a bone flap-associated infection. Drainage was surgically performed in 25 cases or by CT scan-guided aspiration in four cases. All patients received an adapted antibiotic therapy (from three weeks to six months). The outcome was favorable in 28 patients. Three patients relapsed during the antibiotic therapy, requiring further surgery.

CONCLUSION

Cutibacterium acnes can be responsible for postoperative empyema and cerebral abscesses, with particular indolent forms, which make their diagnosis difficult. They are often polymicrobial and associated with bone flap osteomyelitis. Their outcome is favorable after drainage and adapted antibiotic therapy.

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.

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

The Second International Consensus Meeting on Orthopedic Infections was held in Philadelphia, Pennsylvania, in July 2018. A multidisciplinary team of international experts from all 9 subspecialties of orthopedic surgery and allied fields of infectious disease, microbiology, and epidemiology was assembled to form the International Consensus Group. The following consensus proceedings from the International Consensus Meeting involve 30 questions pertaining to the management of periprosthetic shoulder infection.

Application of dermal chlorhexidine antisepsis is ineffective at reducing Proprionibacterium acnes colonization in shoulder surgery

BACKGROUND

Chlorhexidine as a skin surface antiseptic has been shown to be ineffective with respect to reducing Proprionibacterium acnes colonization within the dermis. The purpose of the present study was to determine whether the application of aqueous chlorhexidine solution to the dermal layer decreased P. acnes colonization during open shoulder surgery.

METHODS

The present study enrolled 50 patients who were undergoing open shoulder surgery. Patients received standard antimicrobial preparation. Three dermal swabs were taken from each patient: swab 1 following skin incision; swab taken 2 minutes to 5 minutes post-application of aqueous chlorhexidine to the dermis; and swab 3 taken 60 minutes post-application.

RESULTS

Mean age was 57.5 years (22 males, 28 females). There were 21 patients (42%) with P. acnes present on any dermal swab. There were significantly more P. acnes positive cultures identified at swab 3 compared to swab 1 (p = 0.043). In nine patients with positive P. acnes at cultures swab 1, eight also isolated P. acnes after at swabs 2 or 3. Males were significantly more likely to have P. acnes on any swab (p < 0.001). Positive P. acnes cultures were significantly more common in patients ≤50 years (p < .001). None of the patients had any clinical signs of infection at a minimum of 1 year following surgery.

CONCLUSIONS

Dermal application of aqueous chlorhexidine during open shoulder surgery fails to eradicate or reduce P. acnes on deep cultures.

The role of Cutibacterium acnes in auto-inflammatory bone disorders

Chronic nonbacterial osteomyelitis (CNO) and SAPHO (synovitis, acne, pustulosis, hyperostosis and osteitis) syndrome are auto-inflammatory disorders manifesting as chronic inflammation of bones and joints, which in SAPHO is often accompanying by skin changes. The aetiology of these diseases is unknown, but includes genetic, infectious and immunological components. It has been proposed that Cutibacterium (formerly Propionibacterium) acnes plays a role in the pathogenesis. In this review, we summarise reported cases of CNO or SAPHO syndrome in which C. acnes has been isolated from bones. To identify cases, a search was done in May 2018 using the MEDLINE Ovid interface (1946 to present). We found 14 publications reporting 98 patients with auto-inflammatory bone disorders, of whom 48 (49%) had positive bone biopsies for C. acnes. This bacterium was more frequently isolated from open biopsies than percutaneous ones (43/69 (62%) vs 1/7 (14%); p = 0.04) and biopsies were more frequently positive in patients who presented with simultaneous skin manifestations (19/36 (53%) vs 4/12 (33%); p = 0.03).Conclusion: In patients with CNO or SAPHO, C. acnes can be isolated from open biopsies suggesting that in these patients, C. acnes might be a pathogen rather than a contaminant. The fact that biopsies are more frequently positive in patients who present with simultaneous skin manifestations suggests that these individuals might have a genetic predisposition for impaired clearance of C. acnes. What is known • Chronic nonbacterial osteomyelitis (CNO) and SAPHO (synovitis, acne, pustulosis, hyperostosis and osteitis) syndrome are auto-inflammatory disorders manifesting as inflammation of bones. Both diseases are an important differential diagnosis in children who present with symptoms of (multifocal) osteomyelitis. • The pathogenesis of CNO and SAPHO is multifactorial emcompassing genetic, infectious and immunological components, including interleukin (IL)-1 dysregulation. There is a controversy as to whether Cutibacterium (formerly Propionibacterium) acnes plays a role in the aetiology of CNO and SAPHO. It has been postulated that the presence of C. acnes might trigger auto-inflammatory chronic inflammation in genetically predisposed individuals. What is new • In patients with CNO or SAPHO, C. acnes can be isolated more frequently from open biopsies, than from percutaneous ones, suggesting that C. acnes might be a pathogen rather than a contaminant. • Biopsies are more frequently positive in patients who present with simultaneous skin manifestations suggesting that these individuals might have a genetic predisposition for impaired clearance of C. acnes. Impaired C. acnes clearance likely leads to increased IL-1 beta (β) production by skin cells, bone cells and phagocytes, which is one of the main cytokines underlying chronic inflammatory bone disorders.

Growth of Cutibacterium acnes is common on osteosynthesis material of the shoulder in patients without signs of infection

Background and purpose - Cutibacterium acnes, formerly known as Propionibacterium acnes, is often isolated from deep tissues of the shoulder. It is recognized as an important causative agent of foreign-material associated infections. However, the incidence and significance of its detection in tissues from patients without clinical evidence for infection is unclear. We assessed the incidence of C. acnes colonization of osteosynthesis material in asymptomatic patients, and evaluated the short-term outcome in relation to the microbiological findings. Patients and methods - We microbiologically analyzed osteosynthesis material of 34 asymptomatic patients after surgery on the clavicle. Material obtained from 19 asymptomatic patients after osteosynthesis of the fibula served as a control group. Patients were clinically followed up for 3-24 months after removal of the osteosynthesis material. Results - Bacteria were recovered from devices in 29 of 34 patients from the clavicle group. 27 of 29 positive samples grew C. acnes. Isolation of C. acnes was more common in male than in female patients. No bacterial growth was observed on foreign material from patients in the fibula group. All patients remained asymptomatic at follow-up. Interpretation - Growth of C. acnes is common on osteosynthesis material of the shoulder, especially in males. Samples were positive irrespective of clinical signs of infection. Therefore, detection of C. acnes in this clinical setting is of questionable clinical significance. The high positivity rate in asymptomatic patients discourages routine sampling of material in cases without clinical evidence for infection.

Cutibacterium (Formerly Propionibacterium) avidum: A Rare but Avid Agent of Prosthetic Hip Infection

BACKGROUND

Cutibacterium spp. (formerly Propionibacterium) are slow-growing cutaneous anaerobic commensals, rarely reported in prosthetic joint infections (PJIs). We describe epidemiological, clinical, biological, and radiological characteristics of 15 Cutibacterium avidum PJIs, their treatments, and outcomes.

METHODS

This study is an observational, monocenter study (January 2004 to April 2017), with comparison of C avidum vs Cutibacterium acnes (n = 40) PJI characteristics.

RESULTS

Among 1179 PJIs treated during the study period, 15 (1%) PJIs were due to C avidum (14 classified as late chronic and 1 as early postoperative). They involved only obese patients with hip arthroplasties (median age 65 years, body mass index 35 kg/m²). Twelve patients' PJIs developed after primary hip arthroplasty. Thirteen patients' last clean operation had used an anterior approach. Fourteen preoperative joint aspirate cultures yielded C avidum. The 14 chronic PJIs were treated with 1-stage exchange arthroplasty, the acute case with excision synovectomy. Antibiotic therapy was administered for 12 [6-13] weeks, intravenously for 4 [2-6] weeks. The most used first-line agents were intravenous clindamycin (n = 8) or cefazolin (n = 6). After median follow-up of 27 [3-136] months, 1 relapse occurred. Compared to C acnes PJI patients, those with C avidum PJIs were significantly younger, had higher body mass indices, had only hip involvement, and had more frequent anterior surgical approach. C acnes PJIs were more frequent after revision arthroplasty.

CONCLUSION

C avidum is a rare PJI agent occurring in a particular subpopulation. Joint aspiration is the key diagnostic tool. Our results suggest that PJI risk factors include obesity, primary hip arthroplasty, and anterior surgical approach. Efforts to prevent these infections in high-risk patients should be developed.

Cutibacterium (formerly Propionibacterium) acnes infections associated with implantable devices

INTRODUCTION

Cutibacterium acnes (C. acnes), a Gram-positive biofilm-forming rod implicated in acne vulgaris, is increasingly recognized for its role in implant-associated infections. The diagnosis of C. acnes implant-associated infections remains challenging. The optimal treatment is a combination of both surgical intervention and antibiotic therapy. Areas covered: In this review, we discuss the different types of implant-associated infections caused by C. acnes. We also highlight the clinical manifestations pertaining to the various sites of infection, and identify several risk factors previously reported in the literature. We then cover the diagnostic laboratory markers, such as IL-6 and AD-1, optimizing C. acnes recovery in culture, and the specific molecular techniques. Finally, we examine the various effective antibiotic regimens and identify some preventive methods against C. acnes infections. Expert commentary: Biomarkers such as IL-6 and AD-1 should be further investigated for the diagnosis of C. acnes implant-associated infections. The use of 16S rRNA gene sequencing and other molecular techniques should be further explored in this setting. Longer incubation periods should be requested whenever C. acnes infection is suspected. If the clinical suspicion is high, sonication of the excised implant should be encouraged. Research should focus on developing effective anti-biofilm agents. Finally, preventive methods such as hair removal prior to surgery should be further explored.

Role of rifampin for the treatment of bacterial infections other than mycobacteriosis

OBJECTIVES

Rifampin was initially approved for the treatment of tuberculosis. Because of its low toxicity, broad-spectrum activity, and good bioavailability, rifampin is now commonly administered as combination antimicrobial therapy for the treatment of various infections caused by organisms other than mycobacteria. This review summarizes the most recent clinical studies on the use of rifampin combinations for treating four common non-mycobacterial infections: acute bacterial meningitis, infective endocarditis and bacteraemia, pneumonia, and biofilm-related infections.

METHODS

We performed a literature search of clinical studies published in English from January 2005 to June 2016 using the PubMed database with the search terms "rifampin" with "meningitis" or "infective endocarditis and bacteraemia" or "pneumonia" or "prosthetic joint infections.

RESULTS

Current evidence to support a rifampin combination therapy as a treatment for non-mycobacterial infections was largely based on in vitro/in vivo studies and non-comparable retrospective case series. Additionally, controlled clinical trials that directly compared outcomes resulting from rifampin treatment versus treatment without rifampin were limited.

CONCLUSIONS

Rifampin combination therapy appears promising for the treatment of non-mycobacterial infections. However, further definitive clinical trials are necessary to validate its use because the risk of adverse drug-drug interactions and of the emergence of rifampin resistance during treatment may outweigh the potential benefits.

Role of Suppressive Oral Antibiotics in Orthopedic Hardware Infections for Those Not Undergoing Two-Stage Replacement Surgery

Suppressive oral antibiotics for at least three months, but not at least six months, are associated with treatment success at one year post-diagnosis of orthopedic hardware infection.

Background. The use of suppressive antibiotics in treatment of orthopedic hardware infections (OHIs), including spinal hardware infections, prosthetic joint infections, and infections of internal fixation devices, is controversial.

Methods. Over a 4-year period at 2 academic medical centers, patients with OHI who were treated with debridement and retention of hardware components, with single-stage exchange, or without surgery were studied to determine whether use of oral antibiotics for at least 6 months after diagnosis impacts successful treatment of the infection at 1 year after diagnosis.

Results. Of 89 patients in the study, 42 (47.2%) were free of clinical infection 1 year after initial diagnosis. Suppressive antibiotics used for at least 6 months after diagnosis was not associated with being free of clinical infection (adjusted odds ratio [aOR], 5.29; 95% confidence interval [CI], .74–37.80), but being on suppressive antibiotics at least 3 months after diagnosis was associated with being free of clinical infection (OR, 3.50; 95% CI, 1.30–9.43). Causative organisms impacted the likelihood of success; patients with methicillin-resistant Staphylococcus aureus as well as with Gram-negative rods were both less likely to have achieved clinical success at 1 year after surgery (aOR = 0.018, 95% CI = .0017–.19 and aOR = 0.20, 95% CI = .039–.99, respectively).

Conclusions. Oral suppressive antibiotic therapy in treatment of OHI with retention of hardware for 3 months, but not 6 months, postdiagnosis increases the likelihood of treatment success. The organisms implicated in the infection directly impact the likelihood of treatment success.