Abstract & Commentary

MDR-Gram-Negative Bacteria in a U.S. Hospital in Afghanistan

By Dean L. Winslow, MD, FACP, FIDSA, Chief, Division of AIDS Medicine, Santa Clara Valley, Medical Center; Clinical Professor, Stanford University School of Medicine, is Associate Editor for Infectious Disease Alert.

Dr. Winslow is a speaker for Cubist Pharmaceuticals and GSK, and is a consultant for Siemens Diagnostic.

Synopsis: Cultures obtained from US and Afghan patients at a US military hospital in Afghanistan in 2007-2008 were reviewed. 211 of 411 (51%) bacterial isolates were multidrug-resistant (MDR). Afghan patients were commonly infected and/or colonized with gram-negative rods and of these 70% were MDR.

Source: Sutter DE, et al. High incidence of multidrug-resistant gram-negative bacteria recovered from Afghan patients at a deployed US military hospital. Infect Contrl Hosp Epi 2011;32:854-860.

US and Afghan patients with positive bacterial culture results from Sept 2007 through August 2008 were reviewed. 266 patients had 411 isolates identified during the study period. MDR organisms as defined in this study included vancomycin-resistant enterococcus (VRE), methicillin-resistant Staphylococcus aureus (MRSA), and gram-negative rods displaying resistance to 3 or more classes of antimicrobials (penicillins, cephalosporins, aminoglycosides, fluoroquinolones, and carbapenems) and/or presumed production of extended-spectrum beta lactamases (ESBL) by Enterobacteriaceae. 211 (51%) of isolates were MDR. 241 gram-negative rods were isolated from Afghan patients and of these 70% were classified as MDR. Of these gram-negative rods isolated from Afghan patients, 53% of E.coli, 63% of Klebsiella, and 90% of Acinetobacter were MDR. Approximately half of the MDR isolates were felt to be community acquired. 100 environmental swab samples were obtained, 18 of these yielded MDR bacteria including 10 Acinetobacter species, but no ESBL-producing Enterobacteriaceae.

Commentary

Acquisition of highly resistant gram-negative rods by US military personnel wounded in Iraq or Afghanistan has recently received significant attention. The isolation of MDR Acinetobacter (including in many cases carbapenem-resistant organisms) has received particular emphasis. This study examines the prevalence of bacterial pathogens over a one year period in the largest US military hospital in Afghanistan (presumably the Craig Joint Theater Hospital at Bagram Air Field in Parwan province). The study was performed retrospectively but gives a good sense of the problem of MDR bacterial infection in the Afghanistan theater of operations.

While this study was conducted during 2007-2008 in Afghanistan, it is consistent with my experience while deployed to Iraq in 2006 and 2008 and in Afghanistan in 2011. A closer look at the patients studied shows that only 15 US adult inpatients were included and majority of patients were Afghan adult inpatients (108) and Afghan pediatric inpatients (30). Only 1 US adult was a trauma patient whereas 93 Afghan adults and 21 Afghan children were trauma patients with the majority of Afghan patients having sustained blast injuries from improvised explosive devices (IED's) and a smaller number having been injured by gunshot wounds (GSW's) or motor vehicle accidents (MVA's).

The preponderance of Afghan over US patients included in this study is due to the fact that Coalition troops wounded in Afghanistan are stabilized in theater, then evacuated to Landstuhl Regional Medical Center (LRMC) in Germany generally within 24 hours then on to tertiary care military medical centers in the continental US (CONUS) within 48 hours. Therefore infections with MDR organisms acquired in theater generally do not present until the patient is either at LRMC or back in one of the CONUS military medical centers. It is primarily Afghan adults (including Afghan National Army soldiers and police) and children who remain hospitalized for days to weeks at the coalition military hospitals in Afghanistan because in many cases they require a level of care which cannot be delivered by the Afghan civilian or military hospitals.

When I was deployed most recently to Bagram Air Field as a USAF flight surgeon in 2011 I volunteered to do Infectious Diseases clinical consultations at Craig Joint Theater Hospital (CJTH) in addition to my primary duties supporting combat operations. The Chief of Clinical Services asked me to review the antibiograms of bacterial isolates obtained from patients treated at all the US military medical facilities in theater and make some empiric antibiotic treatment recommendations.

The isolates obtained last year in Afghanistan were very consistent with the ones reported in this study. Since I had access to the in vitro antimicrobial susceptibility data on individual isolates, I was similarly struck by the number of MDR organisms. In addition to the E.coli, Klebsiella and Acinetobacer isolates which predominated in this study, I also noted quite a number of Pseudomonas and Enterobacter species. My anecdotal assessment was that many of Pseudomonas, Enterobacter and Acinetobacter isolates likely possessed AmpC beta lactamases due to frequent expression of resistance to beta lactam/beta lactamase inhibitor combinations as well as to cephalosporins. Empiric therapy of these organisms prior to the availability of susceptibility test results would logically include use of a carbapenem. However, the increasing prevalence of carbapenem resistance in Southwest Asia may soon limit the use of this class of agents as well.