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| Archive : Winter 2006 |
THE GERM LURKS IN UNEXPECTED PLACES:
The patient's TV remote // A visitor's handbag // The doctor's gown // A nurse's computer keyboard // A thousand other spots from which it could be erased but isn't —and so kills tens of thousands of Americans each year.
A Killer Called Staph [page 3]
 By Wendy Orent
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At Allegheny, patients are now swabbed nasally when they are admitted to intensive-care units to make sure they aren't harboring MRSA. "About 8% come in with MRSA," says Shannon. "We never would have known that before." As in northern Europe, infected patients, four out of five of whom have been hospitalized previously, are isolated and treated; health-care workers and visitors must wear disposable gowns, gloves and masks; and anyone walking into these patients' rooms must use a hand sanitizer. Shannon and his team rely on a long list of little things that, taken together, can be remarkably effective. "There is no magic bullet, no vaccine," he says. "This is not about technology; it's about process."
It is also about getting physicians and other hospital personnel to take responsibility for halting the spread of MRSA—and in most U.S. hospitals, that hasn't happened. Part of the problem, according to Perreiah, is that most doctors seem to think that the main culprit is overprescription of antibiotics. But if that were indeed the case, with new strains of MRSA constantly developing to evade attack by overabundant antibiotics, researchers would expect to find a great number of clones—distinct genetic lines—with diverse ancestry. Yet 70% of MRSA strains are descendants of just two clones, one of which originated in Denmark during the late 1950s.
The resistance of S. aureus to some important drugs—the so-called beta-lactams—is based on a gene called mecA, part of a cassette of DNA that S. aureus acquired from some unknown bacterial donor. The mecA gene itself probably originated in S. sciuri, a germ that lives on the skin of many animals. Though it's not known where the cassette came from or how it entered S. aureus, it may have been through conjugation—a direct exchange of bacterial DNA through physical contact between a donor cell and S. aureus—or by some other means, such as with the help of a bacterial virus.
The mecA gene is now integrated into the S. aureus chromosome, making its association with the bacterium more stable. Whatever the ultimate source of their drug resistance, these clones have proved extraordinarily effective in their ecological niche: the hospitals of the world. Their inexorable spread underscores that hospital attendants, rather than mosquitoes, fleas or other disease-carrying vectors that aren't present in hospitals, are responsible for transmitting the disease. Still, while overuse of antibiotics is not the major reason why MRSA strains constantly evolve, it does contribute to the continued replacement of antibiotic-susceptible strains by multidrug-resistant clones.
But a misconception about the cause of the MRSA plague isn't the only reason physicians and other health workers have fallen short in efforts to defeat S. aureus. While many understand that hospital-borne infections are a national crisis, they tend to think it's not their problem, says Ronda Cochran of the CDC. "In order for clinicians to be part of the change, we need to understand their perceptions. If they think antimicrobial resistance is a problem elsewhere but not in their own backyards, they are not going to take the problem as seriously. They need to be aware of the impact that their individual actions have on their patients."
Nancy White, an infection-control nurse at Grady Memorial Hospital in Atlanta, enforces that kind of awareness. "You have to be autocratic," says White, who insists that nurses and other staff wear gowns and gloves every time they visit patients with resistant infections, and use hand sanitizers every time they leave a patient's bedside. She counts herself lucky because she has three infectious-disease doctors on staff: "A lot of smaller hospitals have only one nurse on this."
But it will take more than individual nurses and physicians, no matter how engaged and well schooled in fighting S. aureus, to reduce the awful toll on hospital patients. The PRHI, like the health systems in the Netherlands, Denmark and other countries, has systematized infection control. The PRHI model, or something like it, needs to be in place in every hospital in the country.
S. aureus has haunted humanity for millennia. It isn't going anywhere: Because the germ can live happily in the environment and on our skin, it won't be eradicated, as smallpox has been. What's more, a further complication has emerged as new strains of MRSA have begun flourishing outside hospitals. That's a problem not only for those who pick up these "community associated" bugs in health-club locker rooms but also for patients in the hospitals where the victims show up. In some parts of the United States, community-associated MRSA now accounts for about a fifth of the S. aureus strains causing skin infections. Even so, MRSA infections in hospitals can be controlled, and the chain of transmission broken. "No one expects to live forever, but they don't expect to die needlessly," says Shannon. "We want to be able to say, ‘No one will come into my hospital and be harmed.'"
 Dossier
1. The Doctors' Plague: Germs, Childbed Fever, and the Strange Story of Ignác Semmelweis, by Sherwin B. Nuland [Norton, 2003]. A moving account of Semmelweis's fierce campaign to eliminate one lethal kind of hospital-acquired infection, puerperal fever, before germs were even recognized as the agents of disease.
2. Hospital Infection: From Miasmas to MRSA, by Graham A.J. Ayliffe and Mary P. English [Cambridge University Press, 2003]. An excellent introduction to both the history of hospital-acquired infections and the present problems, including the evolution of antibiotic resistance.
3. Evolution of Infectious Disease, by Paul W. Ewald [Oxford University Press, 1994]. An indispensable text for anyone who wants to understand how bacteria like S. aureus evolve to become deadly threats.
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From top: Photo by Alan Thornton/Getty Images;
Photo by Laguna Design/Photo Researchers, Inc.; Illustration by Jack Sullivan/Alamy.
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