700. A Seven Year Retrospective Review From 2005 to 2011 of Propionibacterium acnes Shoulder Infections in Ottawa, Ontario, Canada
Session: Poster Abstract Session: Skin, Soft Tissue and Joint Infections
Friday, October 21, 2011
Room: Poster Hall B1
  • P acne poster.pdf (72.4 kB)
  • Background:  P.acnes is a gram-positive anaerobic bacillus commonly found in hair follicles. The organism is implicated in prosthetic shoulder infections. Extended incubation of joint aspirates and surgically obtained tissue has been suggested to optimize the recovery of P. acnes. The objectives of this study were first to identify the proportion of septic shoulder caused by P. acnes and, secondly, to evaluate the length of incubation required for P. acnes isolation.

    Methods: The culture was performed using standard anaerobic culture method. Specimens were inoculated onto both solid agar media and Thioglycollate broth media. The plates were incubated for 4 days and the broth media for up to 7 days. The joint cultures that yielded a positive culture between January 2005 and March 2011 were analyzed. The clinical characteristics of patients with P. acnes cultured from the shoulder joint were determined.

    Results: There were 499 culture positive joint specimens, of which 54 (11%) grew P. acnes. 19 of 54 specimens positive for P. acnes were not considered infection clinically, representing contamination. For cultures considered to be significant, the cumulative  rates for isolating P. acnes from shoulder specimens were 3%, 3%, 33.3%, 93.9% and 100% at day 1 to day 5 of incubation, respectively.  For cultures considered as contamination, the cumulative rates for isolation were 0, 0, 16.7%, 100%, and 100% at day 1 to day 5 of incubation, respectively. The average length of incubation required to grow P. acnes was 3.3 days. Of the 82 patients with positive shoulder joint cultures, P. acnes was recovered from 25.6% (33 specimens from 21 patients), representing the second most common bacteria isolated from shoulder joints. P. acnes was incriminated as a pathogen in 18 of the 21 (85.7%) patients, all of whom had a prior shoulder implant. In addition to surgical revision of the prosthesis, 17 of the 18 patients received parenteral antibiotic therapy.

    Conclusion: P. acnes is one of the most common bacteria causing shoulder implant infections. Our standard practice of anaerobic culture is able to detect the P. acnes from shoulder specimens. The sensitivity and specificity of more prolonged incubation remains to be determined.

    Subject Category: D. Diagnostic microbiology

    Bing Wang, Baldwin Toye, Marc Desjardins and B Lee, MD, The Ottawa Hospital, University of Ottawa, Ottawa, ON, Canada


    B. Wang, None

    B. Toye, None

    M. Desjardins, None

    B. Lee, None

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