449. Epidemiology of Combat-Related Deep Soft-Tissue Wound Infections

BACKGROUND: Deep soft-tissue infections (DSTIs) are a common complication of combat-related extremity trauma. We present an epidemiologic assessment of combat-related DSTIs among wounded military personnel. METHODS: Wounded personnel were included in the analysis if they sustained an open combat-related extremity wound (2009–2014), were admitted to a participating US military hospital, had a DSTI as the first confirmed extremity wound infection (within 30 days post-injury), started antibiotics ±3 days of DSTI diagnosis, and received ≥5 days of directed antibiotic treatment. RESULTS: Among 1961 combat casualties with open extremity wounds, 259 had a DSTI diagnosis with 173 (67%) having only 1 index DSTI and 86 (33%) having >1 index DSTI diagnosed on the same day. Nearly all patients (95%) were injured via a blast mechanism. Patients with >1 index DSTI were more severely injured (median injury severity score: 35 vs. 33; P = 0.009) and required large volume blood transfusions within 24 hours of injury (median units: 23 vs. 17; P < 0.001). Initial empiric antibiotic treatment largely involved carbapenem and vancomycin (77% and 72% of patients, respectively). For diagnosis timing, 130 (50%) patients had an early DSTI diagnosis (≤7 days post-injury), while the remaining 129 (50%) patients had a delayed diagnosis (>7 days post-injury). Patients with early DSTI diagnoses more often had >1 index DSTI (47% vs. 19% with delayed DSTI; P < 0.001). Polymicrobial DSTIs were common (73% of early DSTIs; 58% of delayed DSTIs) with Enterococcus spp. most frequently identified (56% of early DSTIs; 31% of delayed DSTIs) as well as Enterobacter spp., Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter spp. Moreover, 26% and 39% of early and delayed DSTIs had multidrug-resistant Gram-negative bacteria. Receipt of >20 units of blood within 24 hours of injury and having >1 index DSTI were independently associated with an early DSTI diagnosis (odds ratio [OR]: 3.21; 95% CI: 1.47–7.02 and OR: 2.98; 95% CI: 1.63–5.42, respectively). CONCLUSION: Multiple index DSTIs and massive blood transfusion requirement are associated with early infection onset post-injury. Awareness of wound microbiology findings relative to DSTI onset provides guidance on empiric antimicrobial therapy. DISCLOSURES: All authors: No reported disclosures.