Prognostic Factors for Bacterial Cultures Positive for Propionibacterium acnes and Other Organisms in a Large Series of Revision Shoulder Arthroplasties Performed for Stiffness, Pain, or Loosening JBJS
This article from our team at the University of Washington points out the very high incidence of positive cultures for Propionibacterium from tissues and explants cultured at the time of surgical revision of failed arthroplasties that have none of the usual clinical manifestations of infection. This finding has been overlooked in many past investigations because (1) cultures were not obtained due to a lack of clinical suspicion of infection, (2) cultures were not observed long enough for Propionibacterium to manifest itself, or (3) positive cultures were dismissed as contaminants.
Our clinical practice has the opportunity to evaluate and manage a large number of failed shoulder arthroplasties from the Western U.S., most of which had problems of stiffness, pain, or component loosening without redness, swelling, drainage, or abnormal lab results (CBC, sed rate, C reactive protein). Five years ago we reported that in these shoulders the positive culture rate was unexpectedly high. As a result, we intensified our efforts to seek Propionibacterium in specimens harvested from each revision arthroplasty we performed.
We found that 103 of 193 revised shoulders had positive cultures, even though they had none of the traditional clinical evidences of infection. 70% of these positive cultures grew Propionibacterium. The ability to detect this organism increased when more specimens were cultured and when the cultures were observed for longer periods of time. Using univariate and multivariate statistics, we observed that male gender, humeral osteolysis, humeral component loosening, glenoid wear, cloudy joint fluid and the formation of a membrane between the humeral component and the humeral bone each significantly increased the chances of a positive culture for Propionibacterium. These findings are helpful in that steps to eradicate Propionibacterium from a surgical site, such as prosthesis exchange and immediate implementation of specific antibiotic treatment, need to be determined at the time of revision surgery - before the results of cultures become known.
We invite the interested reader to use the "Topics" function to find previous posts on Propionibacterium. In case you are wondering why we don't refer to this organism as P. Acnes, the answer may be found here.
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