292. Ceftolozane/Tazobactam for Treatment of Osteomyelitis due to Multi-Drug-Resistant Pseudomonas aeruginosa

BACKGROUND: Ceftolozane/tazobactam (C/T) has potent activity against Pseudomonas aeruginosa (PA). Clinical data describing the use of C/T for PA osteomyelitis are limited. Our purpose is to describe clinical and microbiologic outcomes of adult patients treated with C/T for multidrug-resistant (MDR-PA) osteomyelitis. METHODS: This was a retrospective study of hospitalized patients who received C/T ≥48 hours for MDR-PA osteomyelitis between June 2015 and July 2017. MDR-PA was defined as resistance to ≥1 antibiotic from ≥3 antibiotic classes. Osteomyelitis was diagnosed by imaging, presence of systemic inflammatory signs and symptoms, elevated C-reactive protein, and positive culture for MDR-PA. Combination antibiotic therapy was defined as systemic antibiotics susceptible to MDR-PA for ≥48 hours with C/T. Clinical cure was defined as complete or partial resolution of signs and symptoms of infection without need for escalation of antimicrobials during inpatient and outpatient therapy. Microbiological success is defined as eradication of MDR-PA in follow-up bone cultures. Descriptive statistics were used and presented at percent or median [Interquartile range]. RESULTS: Eighteen patients met inclusion and four patients were lost to follow-up. Demographics were male (81.2%), age 58.5 [53.5–68.5] years, 61.1% admitted to ICU, Charlson Comorbidity Index 5.5 [4–8] and APACHE II score 13.5 [11–21]. Site of osteomyelitis was pelvic in 55.6%, sacral in 22.2% and other sites in 22.2%. Surgical debridement occurred in 22.2%, and osteomyelitis was polymicrobial in 77.8%. Duration of hospitalization was 23.5 [12–37] days and all cause in-patient mortality was 16.7%. The median mean inhibitory concentration of C/T was 2 [2–4] μg/mL. Median total duration of C/T was 42 [27–42] days. Combination antibiotics were used in 27.8% (16.7% polymyxins, 11.1% aminoglycosides, 5.6% ciprofloxacin) and 2 patients on polymyxins developed renal insufficiency. No patient developed hypersensitivity, neurologic events or C. difficile infections. Overall, clinical cure was 64.3% and 4 patients had repeat cultures with 75% achieving a microbiologic cure. CONCLUSION: These preliminary data suggest C/T maybe an option for treating patients with MDR-PA osteomyelitis, but more data are needed. DISCLOSURES: A. Gerlach, Merck: Grant Investigator, Grant recipient