Microbiology of Vertebral Osteomyelitis and Implications on Empiric Therapy

BACKGROUND: The management of vertebral osteomyelitis (VO) includes empiric antibiotic therapy while clinical cultures are being processed. Optimal antimicrobial therapy for VO, particularly when Gram-negative (GN) organisms are involved, is an area of ongoing debate. Narrow spectrum and oral antimicrobial therapy are preferred. The objective of this study was to identify characteristics of local pathogens and to formulate an institution-specific antibiotic protocol for empiric treatment of VO. METHODS: We conducted a retrospective case series study of adults diagnosed with VO from August 1, 2010 to August 31, 2015 at Palmetto Health Hospitals in Columbia, South Carolina. Cases identified by ICD-9 codes were included in the analysis if they met clinical, imaging and microbiology, criteria. RESULTS: Analysis is based on 150 cases of VO with a mean age of 61 years, a male predominance (91; 61%), and an average body mass index of 29kg/m(2). Comorbidities included diabetes mellitus (69; 46%), tobacco use (33; 22%), and hemodialysis (20; 13%). Thirty-seven (25%) cases had recent related injury or vertebral surgery, and 14 (9%) had prior hardware. Bone, disc, or adjacent tissue cultures were obtained in 129 (86%) of cases; 60 (40%) of these had >1 sample taken. The remaining 14% had blood cultures alone. Thirty-six cases (24%) had culture negative VO. In the remaining 114 cases, 132 organisms were isolated. A total of 111 (84%) organisms were Gram-positive cocci (GPC). Of those, the majority was Staphylococcus aureus. (66; 59%) (26/66 were methicillin-resistant), coagulase-negative staphylococci (20; 18%) and Streptococcus spp. (17; 15%). Enterobacteriaceae accounted for 13/17 Gram-negative bacilli (GNB), with only one isolate of Pseudomonas aeruginosa. Of the GNB, 11/17 were susceptible to either ceftriaxone or ciprofloxacin. CONCLUSION: There was a predominance of VO due to GPC suggesting that intravenous vancomycin monotherapy may be reasonable for empiric therapy in noncritically ill patients while awaiting Gram stain and clinical culture results. Addition of either ceftriaxone or ciprofloxacin to vancomycin would increase cumulative antimicrobial coverage from 84 to 92%. DISCLOSURES: All authors: No reported disclosures.