Introduction
Gram-negative, multidrug-resistant organisms (MDROs) predominate wound and nosocomial infections in current war trauma and earthquake victims.Reference Miskin, Nir-Paz, Merin, Burshtein, Schwartz and Schwaber1, Reference Petersen, Riddle, Danko, Blazes, Hayden, Tasker and Dunne2 Despite the application of molecular fingerprinting, source attribution of MDRO outbreaks and epidemics in these settings remains challenging.Reference Wortmann, Weintrob, Barber, Scott, Zoll, Eshoo, Sampath, Ecker and Massire3, Reference Scott, Deye and Srinivasan4 Recent evidence suggests that host nation patients with little or no previous health care contact were the origins of MDROs in a new, uncontaminated health care facility at the beginning of an evacuation and referral chain.Reference Ake, Scott, Wortmann, Huang, Barber, Wang, Nikolich, VanEcho, Weintrob and Lesho5
Casualties from the current wars and disasters due to natural hazards are akin because both involve heavy environmental contamination of wounds and health care equipment, similar wound flora, and requirement for transfer to distant referral centers,Reference Miskin, Nir-Paz, Merin, Burshtein, Schwartz and Schwaber1, Reference Petersen, Riddle, Danko, Blazes, Hayden, Tasker and Dunne2 with considerable time in improvised evacuation vehicles and ground and air ambulances. Additionally, roadside bombs commonly wound service members who are inside their patrol vehicles. Therefore, it was hypothesized that these damaged or heavily-used vehicles could be sources of the MDROs subsequently linked to nosocomial infections.
No studies were found addressing this possibility in MEDLINE. Contamination with MDROs of a heavily-used (including bombed) group of these vehicles were compared with an unused control group of vehicles, and then it was determined whether any of the recovered strains were genetically related to strains subsequently isolated from nosocomial infections or environmental surfaces at the hospital served by these vehicles.
Methods
Monthly, from January through May 2008, two groups of vehicles were surveyed, one extensively utilized throughout Iraq (Experimental Group) and the other consisting of new or unused counterparts in a storage lot in Savannah, Georgia USA (Control Group), for the presence of MDRO using methods described previously, including the use of positive and negative control swabs.Reference Scott, Deye and Srinivasan4, Reference Ake, Scott, Wortmann, Huang, Barber, Wang, Nikolich, VanEcho, Weintrob and Lesho5 Inside surfaces, including door handles, panels, steering wheels, electronic equipment, stretchers, and floors, were sampled. Multidrug-resistant organisms were defined as methicillin-resistant Staphlococcus aureus (MRSA), E. coli, K. pneumoniae, A. baumannii, E. cloacae, or P. aeruginosa resistant to three or more classes of antibiotics or producing an extended spectrum beta-lactamase. High-risk organisms (HROs) were defined as susceptible isolates of the same species. All MDROs and HROs underwent pulsed-field gel electrophoreses using methods previously described.Reference Scott, Deye and Srinivasan4, Reference Ake, Scott, Wortmann, Huang, Barber, Wang, Nikolich, VanEcho, Weintrob and Lesho5 Results were compared to those from patients, staff, and surfaces at the base hospital. Isolates with ≥90% similarity on Dice coefficients were considered related. The chi-squared test was used for statistical processing.
Results
A total of 139 consecutive designated and improvised ground and air ambulances were sampled. Predominant organisms included P. agglomerans (34%), S. flexneri (8%), E. vulneris (6%), Pseudomonas sp. (6%), and K. pneumoniae (6%). No Gram-negative MDROs or MRSA were isolated. Of the total number of vehicles sampled, 13 (9.3%) vehicles (eight of 94 deployed (8.5%) and five of 45 non-deployed (11.1%)) yielded HROs. There was no statistically significant difference in the amount of HROs between deployed and non-deployed vehicles (P = .63). High-risk organisms were isolated from 20% (two of 10) of the deployed vehicles involved in explosions, 7% (six of 84) of the deployed vehicles not involved in explosions (P = .63), and 11% (five of 45) of non-deployed vehicles (Table 1). The HROs recovered from these vehicles were not related to the strains of HRO or MDRO recovered from patients, staff, or trauma equipment at the base hospital.Reference Ake, Scott, Wortmann, Huang, Barber, Wang, Nikolich, VanEcho, Weintrob and Lesho5
Table 1 Vehicle Characteristics and Statistical Analysis
Discussion
The used (experimental) vehicles did not harbor more MDROs or HROs than did the Control Group maintained in a similar hot, dusty climate, which was surprising for several reasons. First, they were continuously contaminated by soil, a known reservoir of MDROs and resistance mechanisms.Reference Dancer6-Reference D'Costa, McGrann, Hughes and Wright8 Second, the pathogens sought are environmentally hardy and persistent.Reference Kramer, Schwebke and Kampt9 Third, other than periodic removal of visible blood and sweeping of dirt, there was no ability to thoroughly disinfect or clean these vehicles between usages, nor during the course of this entire observation period. Finally, others have linked environmental contamination at a remote hospital to a cluster of serious Acinetobacter infections.Reference Tien, Battad and Bryce10 Although the sample size is small, immediate access to such vehicles during actual use or in explosions is rare and restricted.
Conclusion
The lack of clonal association between vehicle and treatment facility HRO strains isolated from patients does not support a link between vehicle contamination and clinical infection at this facility. Given the relevance to the evacuation of both civilian casualties from disasters due to natural hazards and military medicine, it is hoped that these observations lead to further confirmatory studies.
Disclaimer
The views expressed in the paper are solely those of the authors and are not to be considered official or representing those of the US Department of Defense or the US Army.
Abbreviations
- HRO:
high-risk organism
- MDRO:
multidrug-resistant organism
- MRSA:
methicillin-resistant Staphlococcus aureus
