Worrisome Infection in Wounded US Military

November 19, 2004 -- A bacterium named Acinetobacter baumannii is a relatively uncommon cause of infection, except among people with AIDS and other types of immune deficiency and in ICUs. Now there is a worrisome increase in the number of bloodstream infections due to this bacterium in US military hospitals where service members injured in Iraq, Kuwait, and Afghanistan are being treated.

Comments: During the Vietnam War, this bacterium was also the most common microorganism of its type (gram-negative bacteria) in traumatic wounds of the arms and legs, suggesting that environmental contamination of wounds is the likely source of the infection. This bacterium is common in both water and soil. Treatment of these infections can be difficult because the bacterium has intrinsic resistance to certain antibiotics and has acquired resistance to many others.

Everyone in Iraq and Afghanistan today faces risks not only of death and injuries but also severe life-threatening infections from this bacterium. If US military hospitals are having difficulty treating it, we cannot begin to imagine the situation for civilians injured and hospitalized in Iraq or Afghanistan. War brings with it the scourge of disease.

Barbara K. Hecht, Ph.D.
Frederick Hecht, M.D.
Medical Editors, MedicineNet.com

Acinetobacter baumannii Infections Among Patients at Military Medical Facilities Treating Injured U.S. Service Members, 2002--2004

Acinetobacter baumannii is a well known but relatively uncommon cause of health-care--associated infections. Because the organism has developed substantial antimicrobial resistance, treatment of infections attributed to A. baumannii has become increasingly difficult. This report describes an increasing number of A. baumannii bloodstream infections in patients at military medical facilities in which service members injured in the Iraq/Kuwait region during Operation Iraqi Freedom (OIF) and in Afghanistan during Operation Enduring Freedom (OEF) were treated. The number of these infections and their resistance to multiple antimicrobial agents underscore 1) the importance of infection control during treatment in combat and health-care settings and 2) the need to develop new antimicrobial drugs to treat these infections.

During January 1, 2002--August 31, 2004, military health officials identified 102 patients with blood cultures that grew A. baumannii at military medical facilities treating service members injured in Afghanistan and the Iraq/Kuwait region. All of these cases met the criteria for A. baumannii bloodstream infection on the basis of criteria established by CDC's National Nosocomial Infection Surveillance (NNIS) system. Of these 102 cases, 85 (83%) were associated with activities during OIF and OEF. Most of the infections were reported from Landstuhl Regional Medical Center (LRMC), Germany (33 patients: 32 OIF/OEF casualties, one non-OIF/OEF), and Walter Reed Army Medical Center (WRAMC), District of Columbia (45 patients: 29 OIF/OEF casualties, 16 non-OIF/OEF). In both facilities, the number of patients with A. baumannii bloodstream infections in 2003 and 2004 exceeded those reported in previous years (one case during 2000--2002 at LRMC; two cases during 2001--2002 at WRAMC).

Of the 33 patients with A. baumannii bloodstream infections at LRMC, 32 (97%) were men; the median age was 30 years (range: 19--72 years). Thirty (91%) patients sustained traumatic injuries in either the Iraq/Kuwait region (25) or in Afghanistan (five). The majority (67%) were active-duty members of the U.S. Armed Forces. Thirty-two (97%) were transferred directly to the LRMC intensive care unit (ICU) from a combat theater military medical facility. In 22 (67%) of these patients, bloodstream infections were detected from blood cultures obtained within 48 hours of ICU admission.

Of the 45 patients with A. baumannii bloodstream infections at WRAMC, 39 (87%) were males; the median age was 39 years (range: 6--86 years). Twenty-nine (64%) patients sustained traumatic injuries in the Iraq/Kuwait region. Of these, 18 (62%) had bloodstream infections detected from blood cultures obtained within 48 hours of hospital admission after transfer from a combat theater medical or other military medical facility.

Antimicrobial susceptibility testing (AST) was performed by using microdilution. Results of 33 A. baumannii isolates from LRMC and 45 isolates from WRAMC indicated widespread resistance to antimicrobial agents commonly used to treat infections with this organism. AST results, expressed as a percentage of susceptible isolates, were as follows: imipenem (LRMC: 87%; WRAMC: 82%), amikacin (LRMC: 80%; WRAMC: 48%), ampicillin/sulbactam (LRMC: 8%; WRAMC: 35%), piperacillin/tazobactam (LRMC: 0%; WRAMC: 27%), cefepime (LRMC: 0%; WRAMC: 22%), and ciprofloxacin (LRMC: 3%; WRAMC: 20%).

Among the WRAMC isolates, 13 (35%) were susceptible to imipenem only, and two (4%) were resistant to all drugs tested. One antimicrobial agent, colistin (polymyxin E), has been used to treat infections with multidrug-resistant A. baumannii; however, AST for colistin was not performed on isolates described in this report.

In addition to LRMC and WRAMC, three other military treatment facilities have identified A. baumannii bloodstream infections in service members injured in Iraq, Kuwait, and Afghanistan: U.S. Navy hospital ship (USNS) Comfort (11 patients), National Naval Medical Center (NNMC), Bethesda, Maryland (eight), and Brooke Army Medical Center (BAMC), San Antonio, Texas (five).

Source: MMWR (Morbidity and Mortality Weekly Report) from the CDC (US Centers for Disease Control and Prevention), November 19, 2004