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Clinical impact of positive Propionibacterium acnes cultures in orthopedic surgery
V Lavergne1, M Malo2, C Gaudelli3
1Service de microbiologie médicale et infectiologie, hôpital du Sacré-Cœur de Montréal, 5400, boulevard Gouin O, C-2095, Montréal, H4J 1C5 Québec, Canada; Faculté de microbiologie, infectiologie et immunologie, université de Montréal, 2900, boulevard Édouard-Montpetit, Montréal, H3T 1J4 Québec, Canada.
Background:
The clinical significance of a positive culture to Propionibacterium acnes in orthopedic specimens remains unclear, whether about its role as a contaminant or a pathogen, or its impact as a coinfectant. Therefore, we performed a retrospective study to provide a more accurate description of the clinical impact of P. acnes in an orthopedic population aiming to determine: 1) if there is a clinical difference between P. acnes infection and contamination? 2) If there is a clinical difference between P. acnes monoinfection, and coinfection.
Hypothesis:
There is a clinical difference between P. acnes infection and contamination.
Materials And Methods:
Patients were selected over a five-year period, and those with a minimum of one positive culture for P. acnes, from any intraoperative orthopedic tissue sample, were included in the study. P. acnes infection was defined as the isolation of P. acnes from≥2 specimens, or in only one specimen, in the presence of typical perioperative findings and/or local signs of infection.
Results:
A total of 68 patients had a positive P. acnes culture, 35 of which were considered to be infected. The infections affected mostly males (29/35-83%), occurred mostly in shoulders (22/35-63%), and at a site already containing an orthopedic implant (32/35-91%). Local inflammatory signs were present in half of the cases when an infection was diagnosed. Coinfection with other pathogens was present in 31% of patients (11/35). When comparing patients coinfected with P. acnes, and those who were monoinfected, the latter presented less often with local inflammatory signs. Recurrence rate was 24% (8/35) and the only risk factor for recurrence was the presence of a monoinfection.
Discussion:
This study confirms the pathogenicity of P. acnes in an orthopedic population, as it is present in multiple samples in the same patient, and because it is present in cultures from cases with clinical recurrence. Our study showed that monoinfections differ from coinfections mainly by their higher risk of recurrence.
Level Of Evidence:
Level IV retrospective case series.
Insights
Propionibacterium acnes (P. acnes) can cause orthopedic infections, differing from contamination. Monoinfections by P. acnes present a higher risk of recurrence compared to coinfections.
Area of Science:
- Orthopedic surgery
- Infectious diseases
- Microbiology
Background:
- The role of Propionibacterium acnes (P. acnes) in orthopedic infections is debated, with uncertainty regarding its pathogenicity versus contamination.
- Distinguishing between P. acnes as a pathogen, contaminant, or coinfectant is crucial for effective patient management.
Purpose of the Study:
- To investigate the clinical significance of P. acnes in orthopedic specimens.
- To differentiate between P. acnes infection and contamination.
- To compare the clinical characteristics of P. acnes monoinfection versus coinfection.
Main Methods:
- Retrospective study of patients with positive P. acnes cultures from orthopedic specimens over a five-year period.
- Infection defined by P. acnes isolation from ≥2 specimens or 1 specimen with clinical signs.
- Comparison of clinical data between monoinfection and coinfection groups.
Main Results:
- Of 68 patients with positive P. acnes cultures, 35 were classified as infected, predominantly in males and involving orthopedic implants.
- Coinfection with other pathogens occurred in 31% of infected patients.
- P. acnes monoinfections were associated with fewer local inflammatory signs but a significantly higher recurrence rate (24%) compared to coinfections.
Conclusions:
- P. acnes is confirmed as a pathogen in orthopedic infections, evidenced by its presence in multiple samples and association with clinical recurrence.
- Orthopedic P. acnes monoinfections pose a greater risk of recurrence than coinfections.
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