THURSDAY, Oct. 6, 2005 (HealthDay News) -- A bacterial infection rarely seen in U.S. hospitals since the end of the Vietnam War is making a comeback -- and this time it's proving increasingly resistant to antibiotic treatment, researchers say.
Since the onset of the Iraq War in March 2003, the bacterium Acinetobacter baumannii has infected more than 250 patients -- mostly soldiers who served in the Middle East -- being treated in American military hospitals based outside the United States.
And two recent outbreaks have occurred inside the United States, in non-military hospital settings, the researchers said.
While not typically viewed as a lethal threat among otherwise healthy patients, five previously sick patients subsequently infected with Acinetobacter have died -- raising the possibility that the germ might have contributed to their death.
Although no military personnel have died from Acinetobacter infections of the blood, wound, respiratory and urinary tract, the germ has displayed significant resistance to antibiotics that have traditionally been the first line of defense.
As a result, physicians have had to turn to a limited number of alternate and effective antibiotic options, the researchers said.
"This is another example of bacteria that has become very difficult to treat, and this is a specific problem associated with the bigger problem of emerging antibiotic resistance," said study co-author Dr. Paul Scott, chief of epidemiology and threat assessment in the division of retrovirology at Walter Reed Army Institute of Research in Washington, D.C.
Scott and his colleagues reported their findings Thursday at the Infectious Diseases Society of America annual meeting, in San Francisco.
During the Vietnam War, the bacterium -- which is present in soil and water around the world -- was one of the most common sources of infection among U.S. soldiers, the researchers said. Back then, however, such infections weren't resistant to standard antibiotic treatment.
The researchers noted that in the nearly 30-year period between the Vietnam War and the Iraq War, such infections rarely turned up at either U.S. military or civilian hospitals -- although the problem had been more common in European and Israeli hospitals during that time.
Combat situations appear to be a particularly high-risk environment for infection, because the wounds of otherwise healthy young soldiers are exposed to dirt loaded with the germ.
Many subsequent infections now seem to take place within a hospital setting, the researchers noted -- especially in intensive-care units where the elderly, severely sick, and patients with compromised immune systems are vulnerable.
To better understand the transmission process, Scott and his team analyzed lab data for 148 patients who were diagnosed with Acinetobacter infections in 2002 and 2003.
The patients had been treated at military hospitals in Washington, D.C, Germany, Baghdad, and on naval ships. The majority had been wounded by land mines, mortar fire, or bombs.
Most of those infected experienced one week of fever, with an average hospital stay of 39 days. Sixty-three percent of the patients had clinically significant infections, and 47 percent were treated in an intensive-care unit.
The researchers found that in one instance, 45 patients being treated in the same field hospital had been infected with the same strain of the bacterium -- illuminating a clear case of in-hospital cross-infection. At the Washington, D.C., hospital, where five deaths occurred among previously ill patients, cross-infections were found among 18 of 96 patients.
Patients were ultimately treated with an antibiotic regimen lasting an average of 29 days. However, physicians found that only two antibiotics -- imipenem and amikacin -- were effective against Acinetobacter more than 50 percent of the time. In less than 10 percent of the cases, imipenem was the only effective antibiotic.
Scott and his colleagues noted that new drug development for this bacterial infection has been slow, raising the possibility that the current strain could eventually become resistant to all current antibiotics.
Against this backdrop, Dr. Philip Tierno, director of the department of clinical microbiology and immunology at New York University Medical Center, is warning of the potential health threats posed by the antibiotic-resistant Acinetobacter strain.
"It's a wicked bug," said Tierno, author of both The Secret Life of Germs and Protect Yourself Against Bioterrorism. "It's an environmental organism that's wherever the soldiers are -- in the water, in the trenches. It's able to survive literally anywhere -- in food, on human skin, and in the bowels and intestines of humans. And it has become highly antibiotic-resistant, with all sorts of enzymes that incapacitate antibiotics and a pumping mechanism that literally pumps out the medicine."
Despite Acinetobacter's apparent aggressiveness, both Scott and Tierno agreed that the current situation does not warrant general alarm, given the narrow scope of the bacterial threat.
"It's not something for someone in the community to be concerned about because it's strongly associated with the sickest patients in intensive-care units in hospitals," Scott said. "It's not an epidemic that would involve otherwise healthy people in the community."
Still, both doctors cautioned that the Acinetobacter example serves, in some measure, to underline the broader public health threat posed by the mounting issue of general bacterial resistance to antibiotics.
"The ability of the Acinetobacter organism to acquire its multi-resistance is not unusual," Tierno said. "The reason in hospitals for these super-bugs is because of the overuse of powerful antibiotics by physicians. Either they do so too much, or they inappropriately treat with antibiotics. There are 150 million prescriptions written each year in the U.S., of which 90 million are for antibiotics -- and about half of those are unnecessary or inappropriate."
Tierno added that, in his opinion, antibiotic overuse -- particularly in the United States -- isn't confined to the treatment of illness. He noted that while American physicians prescribe 3 million pounds of antibiotics annually, an additional 25 million pounds are used each year by the U.S. agricultural industry.
More information
To learn more about antibiotic resistance, visit the U.S. Food and Drug Administration.
