Drug-resistant bacteria detected in Camden, N.J. Earlier similar cases of staph infection noted in Michigan and Japan

September 25, 1997|By knight-ridder news service

PHILADELPHIA - Laboratory tests have confirmed that a patient treated last month at Our Lady of Lourdes Medical Center in Camden, N.J., near Philadelphia, was infected by a new drug-resistant strain of a common bacteria, only the third such case documented in the world.

The man was infected with a strain of Staphylococcus aureus that had moderate resistance to vancomycin, the one drug that until now has been totally effective against the bacteria.

The first such case showed up in Japan in May 1996, and the second in a Michigan patient two months ago.

The Camden patient's infection was successfully treated with a combination of other antibiotics. The hospital took precautions to prevent the spread of the staph bacteria, according to federal, state and hospital officials.

Scientists have warned for years that vancomycin should be fTC considered an antibiotic of last resort and overuse would undermine its effectiveness. Staph aureus is already resistant to another potent antibiotic, methicillin, and another common organism, enterococcus, has become resistant to vancomycin.

Scientists feared a super-strain of resistant staph might develop by taking genetic material from resistant enterococcus. New strains of microbes are constantly evolving.

'It's very scary'

But a different mechanism appears to be at work with these new strains of resistant staph. They seem to have sprung up independently and spontaneously, without transferring genetic material, tests at the Centers for Disease Control and Prevention in Atlanta showed.

"It's very scary, and it's worse than we predicted," said Neil Fishman, director of antimicrobial management at the University Pennsylvania Health Systems. "What's actually happening is not clear yet."

Staphylococcus aureus is a pervasive organism, usually carried harmlessly on the skin or mucous membranes. But if it gets into deeper tissues or the bloodstream, it can cause pneumonia or other life-threatening infections, particularly in people who have medical problems.

The Lourdes' patient, who was not identified to protect his privacy, had a history of heart disease, arthritis and other chronic illnesses when he came into the hospital last month with a fever and other symptoms of infection, said hospital epidemiologist J. Robert Williams.

Over the previous five months, the patient had repeatedly been treated with vancomycin. That was appropriate under CDC guidelines for vancomycin use because methicillin had failed to cure his staph infections. When the man was hospitalized last month, laboratory tests revealed the vancomycin-resistant staph strain. Hospital officials notified the state and CDC, which verified the finding.

Treatment

The organism was found to be moderately resistant to vancomycin - one step away from immunity. It was quickly wiped out with a trio of older antibiotics, which the patient continued to receive after he went home.

"The patient ... shows no further signs of Staphylococcus aureus infection," said Dr. Emmanual Ashong, chairman of Lourdes' infection control committee. "Patients, staff and visitors are at no risk of contracting this organism through contact with the hospital or its workers."

The Michigan patient, who had been on long-term dialysis, also responded to a combination of antibiotics after vancomycin failed to completely wipe out his staph infection, the CDC reported. In the Japanese case, a 4-month-old infant who developed a staph infection after heart surgery was successfully treated with other drugs.

Williams called the three of cases a "wake-up call."

"We need to prescribe antibiotics judiciously. And patients need to stop demanding antibiotics when they are not needed," he said.

Surveys show a large percentage of prescriptions for vancomycin violate CDC guidelines, which say it should be reserved to treat patients who have severe allergies to other antibiotics or infections that resist other antibiotics.

At Penn, for example, Fishman said the last-resort drug was used inappropriately in 65 percent of cases until about 18 months ago, when an aggressive campaign brought the figure down to 10 percent.

Overuse of antibiotics is a worldwide problem as doctors try to protect themselves from malpractice suits and patients demand sure cures. But vancomycin is especially misused.

"It has to do with dosing convenience and with a misconception vancomycin is a better drug to cover staph infection," Fishman said. "People assumed because it covers methicillin-resistant Staph aureus, it must be a better staph drug."

CDC said it is taking steps to improve compliance with its guidelines. "I think education is a big thing," said CDC epidemiologist Michele Pearson. "We're trying now to assess the compliance and potential barriers to compliance. Certainly, sometimes [vancomycin] treatment has to be started until you know what organism you're dealing with ... but if there are alternative therapies, those should be considered."

Pharmaceutical companies are working to develop new antibiotics. The one closest to approval, according to the Food and Drug Administration, is Synercid, made by Rhone-Poulenc-Rorer in Collegeville, Pa. The drug will soon complete clinical testing and is already available on an emergency basis to treat certain drug-resistant bacteria.

In laboratory tests, Synercid has killed samples of the newly isolated staph strains obtained from the CDC, said company spokesman Doug Arbesfeld.

Pub Date: 9/25/97

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