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Acinetobacter Infections Associated with Combat Injuries Sustained in Iraq
Abstract & Commentary
By Dean L. Winslow, MD, FACP, Chief, Division of AIDS Medicine, Santa Clara Valley Medical Center; Clinical Professor of Medicine, Stanford University School of Medicine, Section Editor, HIV, is Associate Editor for Infectious Disease Alert.
Dr. Winslow serves as a consultant to Siemens Diagnostics and is on the Speakers Bureaus of Boehringer-Ingelheim and GSK.
Synopsis: An outbreak of multidrug-resistant Acinetobacter baumannii-calcoaceticus complex (ABC) infections in U.S. service members injured in Iraq was investigated. ABC organisms were isolated from the skin of only 1 of 160 patients (0.6%) and 1 of 49 (2%) of soil samples obtained from the theater of operations but ABC organisms were recovered from treatment areas of all 7 field hospitals sampled.
Source: Scott P, et al. An outbreak of multidrug-resistant Acinetobacter baumannii-calcoaceticus complex infection in the U.S. military health care system associated with military operations in Iraq. Clin Infect Dis 2007; 44:1577-1584.
Since shortly after the return of the first U.S. casualties wounded in Iraq in early 2003 to the United States, significant numbers of infections due to often multidrug-resistant Acinetobacter species have been observed in these patients shortly after arriving back in tertiary care military hospitals in the continental U.S. (CONUS). The source (s) of these infections has been unclear.
This paper looked carefully for potential environmental sources for this organism and used pulsed field gel electrophoresis (PFGE) to identify potential clonal clusters. While environmental isolates were clearly related to clinical isolates in many cases, not surprisingly the clinical isolates generally displayed much greater degrees of antimicrobial resistance, often with only imipenem, polymyxin B, and colistin retaining in vitro activity.
The paper conclusively demonstrates that the sources of these infections are almost exclusively present in theater, although the potential for secondary nosocomial outbreaks back in CONUS military hospitals is significant and their prevention requires vigilance and aggressive infection control measures.
Having served 3 deployments to Iraq with the US military since early 2003, I have seen the system at work. Aspects of military medical operations should be highlighted for the reader. As most Americans are aware, the mechanism of injury to coalition troops has shifted from gun shot wounds (GSW) with assault rifles in early 2003 to blast injuries (generally inflicted by IED's) beginning in the fall of 2003 and continuing to the present. Despite aggressive efforts by the military to mitigate this threat, the percentage of attacks due to IEDS and their lethality has continued to increase. For soldiers not incinerated in their vehicles, and for dismounted troops, horrific blast injuries result. After airway management, hemostasis and initial fluid resuscitation are accomplished in the field, the wounded personnel are generally CASEVAC'd by a U.S. Army helicopter to the nearest Army, Navy, or Air Force combat surgical facility for initial surgery. Since bed capacity in theater is severely limited, patients are generally MEDEVAC'd by U.S. Air Force fixed wing aircraft to Landstuhl Regional Medical Center near Frankfurt, Germany, within 48 hours of being wounded. While there, more definitive surgery is performed and the patient is often transferred to one of the large CONUS military medical centers within another 48-72 hour period.
Trauma management at all of the U.S. military medical facilities in Iraq is first rate. Now that we have been there for over 4 years, many of the physical facilities have transitioned from "rabbit warren" tent complexes that we had back in 2003 to very nice "hard billets" generally of modular construction. Interestingly, the rate of Acinetobacter infections has not significantly decreased despite this transition in physical facilities.1 While not specifically addressed in the article, the reality is that even the new facilities are difficult to keep as clean as one would a hospital in the United States. Talcum powder-like dust permeates the air and is carried on the boots and uniforms of soldiers coming in to the facility from being on patrol. During the rainy season, the dust all turns to a gelatinous mud which is tracked all over the hospital despite the diligence of all of us in mopping the floors sometimes as often as 3-4 times each day. Viewed simply, the Acinetobacter infections we are seeing in our wounded soldiers appear to be a predictable consequence of horrific wounds despite being managed optimally in challenging conditions. It is of note that infection with Acinetobacter (and other gram negative rods) is not unique to the wars in Iraq and Afghanistan. Acinetobacter followed by Enterobacter species and E.coli were the most common organisms associated with infection in U.S. personnel wounded during the Vietnam War.2