Remission after treatment of osteoarticular infections due to Pseudomonas aeruginosa versus Staphylococcus aureus: a case-controlled study.

PURPOSE: Osteoarticular infections due to methicillin-susceptible Staphylococcus aureus (MSSA) or its methicillin-resistant variant (MRSA) are feared due to treatment failures. According to clinical experience, Pseudomonas aeruginosa may reveal less long-term remission than S. aureus.

METHODS: A case-controlled study comparing outcomes of osteoarticular infections due to P. aeruginosa vs S. aureus was performed at Geneva University Hospitals.

RESULTS: A total of 111 S. aureus (including 37 MRSA) and 20 P. aeruginosa osteoarticular infections were analysed in 131 patients: arthroplasties (n = 38), fracture fixation devices (n = 56), native joint arthritis (n = 7) and osteomyelitis without implant (n = 30). The median active follow-up time was 4 years. The patients underwent a median number of two surgical interventions for P. aeruginosa infections compared to two for S. aureus (two for MRSA), while the median duration of antibiotic treatment was 87 days for P. aeruginosa and 46 days for S. aureus infections (58 days for MRSA) (all p > 0.05). Overall, Pseudomonas-infected patients tended towards a lower remission rate than those infected with S. aureus (12/20 vs 88/111; p = 0.06). This was similar when P. aeruginosa was compared with MRSA alone (12/20 vs 30/37; p = 0.08). In multivariate logistic regression analyses adjusting for case mix, odds ratios (OR) for remission were as follows: P. aeruginosa vs S. aureus [OR 0.4, 95% confidence interval (CI) 0.1-1.2], number of surgical interventions (OR 0.6, 95% CI 0.5-1.0) and duration of antibiotic treatment (OR 1.0, 95% CI 1.0-1.0).

CONCLUSIONS: Despite a similar number of surgical interventions and longer antibiotic treatment, osteoarticular infections due to P. aeruginosa tended towards a lower remission rate than infections due to S. aureus in general or MRSA in particular.