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Soldiers acquired drug-resistant infections in field hospitals

May 22, 2007

An outbreak of drug-resistant wound infections among soldiers in Iraq likely came from the hospitals where they were treated, not the battlefield, according to a new study in the June 15 issue of Clinical Infectious Diseases, currently available online.

The outbreak of drug-resistant Acinetobacter baumannii-calcoaceticus complex (ABC) infections among U.S. service members injured in Iraq has been of major concern to military health care workers since it was first detected in 2003. ABC bacteria are commonly found in soil and water. They sometimes also exist on the skin of healthy people. The bacteria pose little risk to healthy people. However, those with open wounds or weakened immune systems are at greater risk of ABC infection. An ABC infection can cause or contribute to death, especially if the patient is immunosuppressed.

Historically, ABC infections were treated with a wide variety of drugs. Unfortunately, in recent years, strains of Acinetobacter have been emerging that are resistant to nearly all known remedies. The ABC infections found among the U.S. service members are of this type, known as multi-drug resistant (MDR).

Between March and October 2003, researchers from the Army and the Centers for Disease Control and Prevention identified 145 inpatients at U.S. military treatment facilities infected or colonized with ABC. The researchers attempted to identify the source(s) of the outbreak. They tested for the presence of ABC on the skin of casualties treated in or evacuated from Iraq. They tested soil samples taken near field hospitals in Iraq and from locations throughout Iraq and Kuwait. And they looked at samples taken from in and around patient-treatment areas in five field hospitals in Iraq and two in Kuwait.

They found ABC in only one out of 49 soil samples and just one out of 160 samples from soldiers' skin. By contrast, ABC organisms were found in the patient treatment areas of all seven field hospitals sampled. The authors therefore concluded that environmental contamination of field hospitals and transmission within health care facilities played a major role in this outbreak.

The authors noted the possibility that the infections were acquired outside the hospital cannot be ruled out completely due to limitations in the available samples from soil, patients, and field hospitals. However, they concluded, "The most likely source of this outbreak was bacteria within deployed field hospitals," said author MAJ Clinton K. Murray, MD, of the Brooke Army Medical Center in Texas.

Field hospitals by their nature present a challenging environment for infection control. As temporary structures in desert conditions, thorough cleaning is difficult. "The frequent influxes of large numbers of casualties over short periods of time increases the risk of environmental contamination with Acinetobacter and challenges the implementation of standard infection control practices," the authors observed.

However, they wrote, "Based upon these findings, maintaining infection control throughout the military health care system is essential." They add that military hospital staffs in the United States have responded to the outbreak with renewed focus on infection control procedures: strict hand hygiene, contact isolation, grouping ABC patients together, judicious antimicrobial use, active surveillance for ABC colonization, and increased staff education. "In U.S. field hospitals in Iraq, dedicated operating rooms for patients known to be infected with ABC, intra-operative wound dressing management, cohorting of infected patients when possible, antibiotic prescribing guidelines, and continual education of staff have been implemented."

"The increased emphasis on infection control procedures within military facilities in the U.S. has greatly limited the nosocomial transmission within military hospitals in the U.S.," Dr. Murray said.

Infectious Diseases Society of America