Osteoarticular infection caused by MDR Pseudomonas aeruginosa: the benefits of combination therapy with colistin plus β-lactams

Objectives: In the era of emergence of MDR Pseudomonas aeruginosa, osteoarticular infections (OIs) add more difficulties to its treatment. The role of beta-lactams (BLs) is questioned and older drugs need to be reconsidered. The objective of this study was to describe our experience in the management of OIs caused by MDR P. aeruginosa and evaluate different therapeutic options. Methods: This was a retrospective analysis of a prospectively collected cohort (2004-13) of patients with OI caused by MDR P. aeruginosa. We created two groups: (i) Group A (more difficult to treat), prosthetic joint infections (PJIs) and osteoarthritis (OA) managed with device retention; and (ii) Group B (less difficult to treat), OA managed without device retention. Antibiotic treatment was administered according to clinician criteria: monotherapy/combined therapy; and BL used by intermittent bolus (IB)/continuous infusion. Results: Of 34 patients, 15 (44.1%) had PJI and 19 (55.9%) had OA (8 related to an orthopaedic device). Twenty-three cases (68%) were caused by XDR P. aeruginosa. The initial management included removal of an orthopaedic device in 14 cases, together with antibiotic [ alone, 19 (55.9%; 4 colistin, 14 BL-IB and 1 BL continuous infusion); and in combination, 15 (44.1%; 5 BL-IB and 10 BL continuous infusion)]. The overall cure rate was 50% (39% and 63% in Groups A and B, respectively), ranging from 31.6% with monotherapy to 73.3% with combined therapy (P = 0.016), with special interest within Group A (cure rate with combined therapy 71.4%, P = 0.049). After rescue therapy, which included removal of remaining devices, the cure rate reached 85.3%. Conclusions: We suggest that the BL/colistin combination is an optimized therapy for OI caused by MDR P. aeruginosa, together with an appropriate surgical treatment.