Multi-drug Resistant Acinetobacter Hitchhiking to U.S. Military Hospitals with Wounded Soldiers: Presented at IDSA

By Rabiya Tuma

SAN FRANCISCO, CA -- October 11, 2005 -- More than 250 cases of multi-drug resistant Acinetobacter baumannii have been identified in United States military hospitals. Patient to patient transmission has resulted in 18 infections in non-military personnel, including 5 fatalities.

The cases were reported here on October 8^th at the Infectious Disease Society of America (IDSA) meeting by Paul Scott, MD, former Chief of Epidemiology and Threat Assessment, Walter Reed Army Institution of Research, Washington, D.C.

The first infections were detected in March 2003 at Walter Reed Army Medical Center. Since then, cases have been found in numerous medical facilities in the U.S. and along the medical evacuation route.

In one study, Dr. Scott described a 2-phase study conducted to determine what was causing the infections and who was being infected.

In the first phase, the team confirmed that the rate of infection in a cohort of 70 patients was significantly higher than what has been seen in recent history at military medical facilities, and higher than has been seen in community hospitals (1%-2% of wound infections). Dr. Scott did not specify what the overall rate of infection was at Walter Reed during this time.

Nearly a third of the infections examined in this initial cohort were the result of wounds on the extremities. Airway infections were also common, accounting for approximately one-quarter of the cases.Seven percent of the infections were completely resistant to the commonly tested antibiotics, and 26% were only susceptible to imipenem.

Individuals with infections were found in combat field hospitals in Iraq and Kuwait, in military facilities in Landstuhl, Germany, where seriously injured soldiers are taken to be stabilized prior to transport to a U.S. based facility. Infections were also detected on the US Naval Ship Comfort, which is a hospital facility.

In the second phase of the study, Dr. Scott and colleagues looked at 170 bacterial isolates obtained from 148 patients in four hospitals and 37 environmental samples from six field hospitals.Using pulse-field gel analysis, the team found that one isolate from a combat field hospital in Baghdad matched 45 isolates from patients. "Among routinely tested antibiotics, only amikacin and imipenem yielded greater than 50% susceptibility for all organisms tested," Dr. Scott said.

The strains are distinct from those found in U.S. community hospitals but are "essentially equivalent in terms of their disease causing potential," said Walter Stamm, Head of Allergy and Infectious Disease, University of Washington School of Medicine, Seattle, and President of the Infectious Disease Society of America. "That is why we are being so concerned about it."

The infections do have a clinical impact on patients, according to Dr. Scott's data, with infected patients requiring significantly longer hospital stays, more days in the intensive care, more days of antibiotic therapy, and more surgeries, compared to comparably wounded soldiers who are colonized with the bacteria but not carrying active infections.

To prevent further patient-to-patient transmission, physicians at Walter Reed and other facilities try to put newly admitted soldiers into contact isolation for several days and take swabs of skin at the groin and axilla to check for bacteria.

[Presentation title: An Outbreak of Multi-Drug Resistant Acinetobacter baumannii Infections in the Military Health Care System Associated with Operation Iraqi Freedom (OIF). Abstract 327]