Seasonality of Microbiology of Combat-Related Wounds and Wound Infections in Afghanistan

Introduction: Battlefield-related wound infections are a significant source of morbidity among combat casualties. Seasonality of these infections was demonstrated in previous conflicts (e.g., Korea) but has not been described with trauma-related health care–associated infections from the war in Afghanistan. Methods: The study population included military personnel wounded in Afghanistan (2009-2014) medevac’d to Landstuhl Regional Medical Center and transitioned to participating military hospitals in the United States with clinical suspicion of wound infections and wound cultures collected ≤7 days post-injury. Analysis was limited to the first wound culture from individuals. Infecting isolates were collected from skin and soft-tissue infections, osteomyelitis, and burn soft-tissue infections. Data were analyzed by season (winter [ December 1-February 28/29], spring [March 1-May 31], summer [June 1-August 31], and fall [September 1-November 30]). Results: Among 316 patients, 297 (94.0%) sustained blast injuries with a median injury severity score and days from injury to initial culture of 33 and 3.5, respectively. Although all patients had a clinical suspicion of a wound infection, a diagnosis was confirmed in 198 (63%) patients. Gram-negative bacilli (59.5% of 316) were more commonly isolated from wound cultures in summer (68.1%) and fall (67.1%) versus winter (43.9%) and spring (45.1%; P < .001). Multidrug-resistant (MDR) Gram-negative bacilli (21.8%) were more common in summer (21.8%) and fall (30.6%) versus winter (7.3%) and spring (19.7%; P = .028). Findings were similar for infecting Gram-negative bacilli (72.7% of 198)—summer (79.5%) and fall (83.6%; P = .001)—and infecting MDR Gram-negative bacilli (27.3% of 198)—summer (25.6%) and fall (41.8%; P = .015). Infecting anaerobes were more common in winter (40%) compared to fall (11%; P = .036). Gram-positive organisms were not significantly different by season. Conclusion: Gram-negative bacilli, including infecting MDR Gram-negative bacilli, were more commonly recovered in summer/fall months from service members injured in Afghanistan. This may have implications for empiric antibiotic coverage during these months.