Addition of Fluoroquinolones or Aminoglycosides to Post-Trauma Antibiotic Prophylaxis Does Not Decrease Risk of Early Osteomyelitis

Background:  Adding expanded gram-negative (EGN) coverage (a fluoroquinolone or aminoglycoside) to combat-related open fracture antimicrobial prophylaxis is controversial.  Prior research on care of combat casualties with open fractures showed adding EGN coverage to DoD-directed post-trauma prophylaxis (cefazolin) was common (2009-2012). Following publication of new guidelines in 2011, use of EGN prophylaxis after combat trauma declined significantly. We examined whether adding EGN coverage to DoD-directed post-trauma prophylaxis decreases extremity wound skin and soft tissue infections (SSTI) and osteomyelitis during the early post-injury period.

Methods: Injury characteristics, antibiotic prophylaxis, and infection outcomes were prospectively recorded. Casualties with extremity open fractures transported to one of three U.S. military hospitals were included in the analysis if length of hospital stay was ≥7 days. Post-trauma prophylaxis groups were classified as “narrow” if antibiotic prophylaxis complied with the DoD-guideline (primarily cefazolin) and “broad” if EGN coverage (usually a fluoroquinolone or aminoglycoside) was added to the prophylaxis regimen. Osteomyelitis and SSTIs were adjudicated based on the Trauma Infectious Disease Outcomes Study protocol.

Results:  From June 2009 through May 2014, 1043 patients with open fractures met criteria for inclusion in the study. Trauma was the result of a blast in 845 casualties (81%). Severe injuries (Injury severity score [ISS]: ≥16) were sustained in 761 (72.8%) subjects, and ISS was similar between prophylaxis groups (p=0.91). Significantly more patients received narrow prophylaxis (56% vs.44% broad, p<0.05). SSTIs were more common among patients given narrow prophylaxis (27.6% vs. 21.8% with broad, p=0.02); however, the proportion of osteomyelitis was similar (7.9% vs. 7.8%, p=0.98). The proportion of patients with multidrug-resistant organism (MDRO) colonization was also similar (31% with narrow vs. 30%; p=0.84).

Conclusion:  Adding EGN coverage to DoD-directed antimicrobial prophylaxis for combat-related open fractures may decrease the risk of SSTI, but does not confer a benefit for the prevention of early osteomyelitis or increase the risk of MDRO colonization.