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Cutibacterium acnes: a threat to shoulder surgery or an orthopedic red herring?
Manan S Patel1, Arjun M Singh1, Pietro Gregori1
1Department of Orthopaedic Surgery, The Rothman Institute at Thomas Jefferson University, Philadelphia, PA, USA.
Abstract:
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.
Insights
Cutibacterium acnes is linked to shoulder prosthetic joint infections (PJI), but positive cultures don't always mean infection. This review explores alternative roles for C. acnes, like being a contaminant, to explain this diagnostic challenge.
Area of Science:
- Orthopedics
- Infectious Diseases
- Microbiology
Background:
- Cutibacterium acnes is a common skin bacterium colonizing pilosebaceous glands.
- C. acnes is frequently implicated in prosthetic joint infections (PJI) following shoulder arthroplasty.
- PJI caused by C. acnes often presents with subtle or absent clinical, laboratory, and imaging findings.
Purpose of the Study:
- To explore alternative explanations for the discrepancy between positive C. acnes cultures and actual shoulder PJI.
- To review the potential roles of C. acnes as a commensal, bystander, or contaminant in the context of shoulder arthroplasty.
- To discuss the diagnostic utility of cultures and alternative diagnostic methods for shoulder PJI.
Main Methods:
- Literature review examining the role of C. acnes in shoulder arthroplasty.
- Analysis of studies reporting positive cultures in revision shoulder arthroplasty.
- Discussion of C. acnes virulence, microbiome, and diagnostic challenges.
Main Results:
- Over 40% of revision shoulder arthroplasties may yield positive cultures for C. acnes.
- Infection rates following a positive culture can be as low as 5%, indicating frequent contamination or colonization.
- C. acnes exhibits variable virulence and may exist as part of the normal shoulder microbiome.
Conclusions:
- The discordance between positive C. acnes cultures and confirmed infection necessitates considering alternative roles for the bacterium.
- C. acnes can act as a commensal, bystander, or contaminant, complicating PJI diagnosis.
- Further research is required to definitively establish the pathogenic role of C. acnes in shoulder PJI and refine diagnostic strategies.
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