A dangerous germ easily mistaken for an innocuous one has become alarmingly common around the United States, raising concern that seemingly minor boils, pimples and abscesses could increasingly become disfiguring or even life-threatening, researchers reported yesterday.
Because the microbe has become invulnerable to the most commonly used antibiotics, the discovery means doctors should now routinely test all skin infections to identify patients who need urgent treatment with one of the handful of drugs still capable of killing the aggressive pathogen, experts said.
"This should serve as a red flag to doctors whenever they are treating skin infections," said Scott K. Fridkin of the federal Centers for Disease Control and Prevention, who led the study reported in today's issue of the New England Journal of Medicine. "This is a new bug that has emerged in the community. It's a cause for concern."
The widespread emergence of the microbe is the latest manifestation of the growing threat of antibiotic resistance, a trend that has seen an increasing number of microorganisms evolve into strains that defeat many of modern medicine's most important weapons.
"This is just another sign that, unfortunately, the bugs are winning," said Loren G. Miller of the Harbor-UCLA Medical Center, the lead author of a companion paper describing 14 cases of people stricken by "flesh-eating" cases of the infection.
In the first systematic attempt to assess how common the infections have become, researchers did a comprehensive analysis of these methicillin-resistant Staphylococcus aureus (MRSA) infections in Baltimore, Atlanta and Minnesota in 2001 and 2002. They found 2,107 cases in people who had no contact with hospitals, the primary locales where such infections turned up in the past. The non-hospital cases accounted for 8 percent to 20 percent of all such infections identified in the study. Children ages 2 and younger appeared to be especially vulnerable.
"A decade ago, it would have been zero percent," Fridkin said. "We wanted to see if this had become commonplace in the community. The answer is a resounding 'yes.' It's clearly no longer limited to the hospital."
The microbe is a strain of the ubiquitous bacterium Staphylococcus aureus, which usually causes well-known "staph" infections that are easily treated with common antibiotics in the penicillin family, such as methicillin and amoxicillin.
In recent years, small outbreaks of infections with a strain that is impervious to those antibiotics have been reported among athletes, inmates, children and other groups, but otherwise resistant staph strains had been almost exclusively limited to hospitals.
"We're used to resistant staph in the hospital as a problem among patients with heart failure, liver failure, cancer or other health problems," said David N. Gilbert of the Oregon Health & Science University. "It's started attacking normal healthy people, causing serious, often fatal illness."
The germ, which is spread by casual contact, produces potent toxins that kill disease-fighting white blood cells. That rapidly turns minor rug burns, cuts and other skin infections into serious health problems, apparently including "necrotizing" abscesses that eat away tissue. Previously, such cases were thought to be caused only by strep bacteria.
In other cases, the microbe gets into the lungs, causing unusually serious cases of pneumonia, often on the heels of the flu, or spreads into the bloodstream, triggering life-threatening complications.
"This has now become a significant problem in this country," said Donald M. Poretz, an infectious-disease expert at Georgetown University who serves as president of the National Foundation for Infectious Diseases. "We see dozens of these cases in our offices."
The infections can often be treated simply by lancing and draining abscesses and quickly administering less commonly used antibiotics, such as vancomycin. The risk of becoming infected can be minimized by taking common-sense precautions, such as frequent hand-washing. But experts fear doctors, especially in areas where the microbe is not yet well known, will not recognize it.
"Some of our patients had to have very extensive surgery to remove all of the dead tissue, and many of them were quite ill and required intensive care," said Miller of UCLA. "It's an infectious-disease emergency, because without prompt surgery, treatment and antibiotics, people will die."
The resistant strain probably emerged because of the overuse of antibiotics. Public health officials have become increasingly concerned about this trend, especially because little work is underway to develop a new generation of antibiotics.
Experts are also concerned that the shrinking number of effective antibiotics may also be slowly losing their power.
"What people are concerned about is that we'll be losing these drugs one by one until we don't have any effective ones left," said Walter E. Stamm, president of the Infectious Disease Society of America.