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Bacteria Have New Resistance Genes That Make Them Far More Virulent
By LAURA LANDRO
A couple of months ago, seven-year-old Zacharias Nunley was admitted to Hermann Children's Hospital in Houston complaining of severe pain in his leg, with a fever of nearly 103. Doctors performed hip surgery and discovered a virulent drug-resistant staph infection that was causing a blood clot in the leg that could have killed him.
No one could figure out how, where, or when the child got the infection. "It came out of nowhere," says his mother, Charla Rigsby.
Until recently, drug-resistant infections have mostly plagued hospitals, which, given the number of very sick people residing in them, tend to be enclosed swamps of bacteria. But drug-resistant infections are suddenly emerging beyond hospital walls -- spreading among families, toddlers in day-care centers and school sports teams.
The problem has "probably been smoldering for years, but recently it's almost like a switch got triggered," says Stuart H. Cohen, a medical professor at the University of California, Davis.
According to several new studies being released Thursday at a meeting of the Infectious Diseases Society of America (www.idsociety.org1) in San Diego, healthy people, particularly children, are in growing danger from so-called community-acquired staph infections. The MRSA strain (for methicillin-resistant staphylococcus aureus), which is what Zacharias Nunley had, is of particular concern. It can't be treated with the penicillin-related antibiotics that have been used to treat staph for decades. And though often mild, it can progress to life-threatening blood or bone infections.
Researchers at the University of Texas say that of the children with staph infections admitted to Hermann and other hospitals affiliated with its medical school in June 2000 to July 2001, nearly 45% had the MRSA type that didn't respond to first-line antibiotics -- compared with virtually none before 1995. In a new study now under way, the Texas researchers say, the percentage has leapt to nearly 70%.
"Not only are they resistant to drugs, but it seems to us that the bacteria are becoming more virulent," says Gloria P. Heresi, associate professor of pediatric infectious diseases at the University of Texas. "We really aren't sure how we're going to deal with this."
Doctors and scientists say overuse of antibiotics is a culprit in all drug-resistant infections. But they are unsure why the community-acquired infections are suddenly so sharply on the rise. Though the bugs probably started migrating from hospitals a few years ago, researchers now believe the bacteria in the community have acquired new resistance genes that make them far more virulent.
The federal Centers for Disease Control and Prevention, which says three stains of MRSA are causing the community infections, last month awarded $3 million in new grants to four medical schools to study issues such as bacteria's genetic characteristics, and how patients acquire and spread the infections. In particular, the CDC has been keeping a close eye on outbreaks among school sports teams, where children can become infected merely by touching objects such as towels, sheets, wound dressings, or sports equipment contaminated by someone else's infected skin.
In community-acquired strains, it is sometimes hard to pinpoint the exact source of the infection. In only half of pediatric cases, for example, can researchers pinpoint a risk factor, such as day-care attendance, previous heavy antibiotic use, or exposure to an adult who had been hospitalized. In a study of adults with community-acquired MRSA infections at the University of California at Davis, one in five patients had no identifiable risk factors such as diabetes or a history of intravenous drug use.
Part of the problem is that bacteria are literally everywhere; at any time about a third of us are already "colonized," meaning we have the bacteria living on our bodies, usually in our nose or on our skin. But if the bacteria enter the skin or bloodstream through a cut or boil, or a person's immune system is weakened by, say, flu or medications, a staph infection can set in, then spread quickly to other people who come in even slight contact. Signs of infection include pus or fluid draining from a wound, or redness or swelling near it.
Despite repeated warnings that antibiotics aren't necessary for common ailments like colds and the flu, patients continue to demand them -- and doctors keep prescribing them, especially for kids. The federal CDC last month launched a national public service campaign to warn parents against using antibiotics when they aren't warranted, such as to treat a cold or flu.
It's likely to get worse: Antibiotic resistance is developing quickly, while investment by pharmaceutical companies in more powerful drugs to counter infections is on the decline. A study reported this week in the journal Pediatrics found that in 16 Massachusetts communities, 25% of children are carriers of the S. pneumoniae bacteria -- and of those, one-third have a strain that is resistant to common antibiotics.
Some studies have shown that as many as one in four children is resistant to all three antibiotics used to treat the bug -- penicillin, erythromycin and cotrimoxazole -- which causes meningitis, bloodstream infections and pneumonia. Fortunately, a new vaccine for S. pneumoniae, recommended for all children under two years old, is reducing the strains that can cause significant infection, according to the Pediatrics study. Researchers are investigating possible staph vaccines.
"Antibiotic resistance is increasing too quickly and in too many organisms," says Jonathan Finkelstein, the pediatric infectious disease specialist who helped carry out the Massachusetts study.
There are drugs other than common antibiotics that can combat these infections, though they are far more expensive and often have tough side effects. Zacharias Nunley, for example, is out of the hospital and taking the antibiotic clindamycin, along with blood thinner, until March. But his mother must take him to the doctor for weekly blood tests to make sure the antibiotic isn't damaging to his kidneys. A new antibiotic called linezolid can be given via pill or IV but it costs about $100 a day, compared with a few dollars for other antibiotics. The drug vancomycin still works in most cases but must be administered intravenously. And, says Dr. Heresi, "we're very worried that if we use it a lot we'll start seeing resistance to it."
The CDC Web site has a list of frequently asked questions about MRSA, including practical advice about preventing infection on sports teams by informing coaches of any skin lesions and diligently cleaning sports equipment after use. But while families need to use common sense, John F Mohr III, a co-author of the University of Texas study, says they shouldn't go overboard: "We wouldn't tell anyone not to play sports because of fear of MRSA."
E-mail me at informedpatient@wsj.com