Amount of usage and involvement in explosions not associated with increased contamination of prehospital vehicles with multi-drug-resistant organisms

Introduction The role of explosions and patient transport vehicles as sources and vectors of Gram-negative, multidrug-resistant organisms (MDROs) that predominate infections following lengthy evacuations after disasters due to natural hazards and in current war-trauma patients is unknown. Hypothesis/Problem Damaged or heavily-used vehicles could be sources of the MDROs subsequently linked to nosocomial infections. Methods From January through May 2008 in Iraq, inside surfaces of heavily-used, tactical vehicles (Experimental Group) were sampled with sterile, pre-moistened swabs. Swabs, along with positive and negative controls, were shipped to the reference laboratory in Washington, DC, where they underwent culture, identification and susceptibility testing, and pulsed-field gel electrophoresis. Multidrug-resistant organisms were defined according to the standard Centers for Disease Control and Prevention definitions. High risk organisms (HROs) were defined as susceptible E. coli, A. baumannii, P. aeruginosa, Enterobacter spp, or Klebsiella spp. Concurrently, new counterparts (Control Group) were similarly surveyed in a storage lot in Georgia, USA. Groups were compared using the Chi-squared test. Results One hundred thirty-nine consecutive vehicles including all available ambulances were sampled, yielding 153 swabs. Nineteen were lost or damaged during shipping. Seventy-nine swabs yielded growth of one or more Gram-negative bacteria. The amount and genotype of MDROs in heavily-used vehicles, including those involved in roadside bombings, were compared to control vehicles and to strains isolated from wounds and environmental surfaces at the base hospital. Predominant organisms included P. agglomerans (34%), S. flexneri (8%), E. vulneris (6%), Pseudomonas sp. (6%), and K. pneumonia (6%). No MDROs were isolated. Thirteen vehicles (eight of 94 experimental and five of 45 control) yielded HRO. There was no difference in contamination rates (P =.63). No HROs were isolated from ambulances. No clonal association existed between vehicle and hospital strains. Conclusion Given the implications that this knowledge gap has on military and civilian prehospital reservoirs of infection, further study is warranted to confirm these findings and identify targets for preventive intervention throughout civilian disaster and military casualty evacuation chains.