264. PROPIONIBACTERIUM ACNES IN BONE AND JOINT SURGEY: SIMPLE CONTAMINANT OR TRUE PATHOGEN?

Abstract

Purpose of the study: Propionibacterium acnes (PBA) is an anaerobic Gram-positive commensal bacillus of human skin which can cause bone and joint infections (Lutz 2005, Zeller 200, Levy 2008). The purpose of this work was to evaluate over a given period the frequency of PBA infections and the reality of its role as a pathogenic organism.

Material and methods: A retrospective survey of activity from 2006 to 2008 using bacteriology laboratory data identified 34 patients (22 male and 12 female) with at least one sample collected during an orthopaedic or traumatology surgical procedure that was positive for PBA. The mean number of positive samples was 3.6; 17 from the thoracic limb, 17 from the pelvic limb, involving 16 arthroplasties (4 hips, 6 knees, 5 shoulders, 1 elbow), 13 osteosynthesis procedures, 3 cuff repairs and 1 acromioclavicular procedure. Six of 20 histology samples showed a septic granuloma.

Results: The PBA was the only germ isolated in 18 cases; it was associated with other bacteria in 16 cases. Other blood tests were abnormal (WBC 6800 leukocytes, CRP 25mg/L en average). According to the Lutz classification, three groups of infection could be identified: certain infection with clinical signs and at least two positive samples (n=12), possible with clinical signs but only one positive sample (n=5), and probable without clinical signs and one or more positive samples (n=17). Of the 12 patients in the first group, eight had material (three shoulder prostheses, three hips, one knee and one femoral nail), which had to be removed for six with use of a cemented spacer in four. Mean duration of antibiotics was five weeks. Four patients in this group have not yet achieved cure. In the second group, all samples were taken from a thoracic limb and had another germ in four cases; all patients have achieved cure. In the third group, the samples were systematic (two shoulder arthroplasties, two repeated cuff repairs, five revision prostheses, four nonunions and four material removal); only one sample was positive in ten cases and only five patients were given antibiotics; all achieve cure.

Discussion: This series is in agreement with the literature: frequent localization on a thoracic limb, association with another germ, questionable attribution to PBA. Patients meeting the criteria of the first group should be treated. If a PBA infection is suspected, samples should be repeated, with prolonged culture; this attitude should be validated prospectively.