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A chemical disinfectant used on some medical and dental devices can fail to kill the AIDS virus, posing a potential risk of infecting patients, a study suggests.

Researchers found that in the laboratory, the disinfectant did not kill the AIDS virus in blood lodged in lubricants commonly used in dental equipment and in medical devices called endoscopes, which are inserted into the body to allow an interior view.None of the devices has ever been shown to be the cause of HIV transmission from patient to patient, said researcher David Lewis, a microbiologist at the University of Georgia in Athens.

In the study, published by Lewis and another researcher in the September issue of the journal Nature Medicine, the AIDS virus survived after the contaminated lubricants were soaked for two hours in a powerful germ-killer called glutaraldehyde.

Lewis said the study emphasizes the need to sterilize dental equipment at extremely high temperatures, as recommended by the federal government and the American Dental Association. He also said the standards for decontaminating endoscopes should be raised.

But Dr. David Fleischer, past president of the American Society for Gastrointestinal Endoscopy, said current decontaminating procedures are "extremely effective."

And, he said, the experiment failed to mimic all the steps of the decontamination procedure used on gastrointestinal endoscopes.

More than 90 percent of American dentists use heat sterilization, said Chris Martin, a spokesman for the American Dental Association.

Lewis said it is possible that contaminated dental equipment caused the case of Florida dentist Dr. David Acer, who infected six of his patients with the AIDS virus before he died. But Lewis said that possibility still remained unlikely, and that his study does not prove how the infections happened.

There has not been a single known case of AIDS resulting from the 10 million or so uses of gastrointestinal endoscopes each year, Fleischer said.

"It doesn't appear to be a clinical problem," Fleischer said.

The rate of passing along other germs is about once in every 1.5 million procedures, Fleischer said. "So overall, the record of doing this procedure has been safe with regard to infectious diseases," he said.