An antibiotic-resistant strain of staph infection that was once largely confined to hospitals is spreading to communities, a study found.

The strain has been treated with penicillin and other common antibiotics for so long that it can now withstand them. Even vancomycin, a potent antibiotic of last resort, sometimes fails against the germ.A co-author of the study, Dr. Robert S. Daum, director of pediatric infectious diseases at the University of Chicago Children's Hospital, said the finding underscores the need to stop prescribing so many antibiotics.

"Colds and flu and stuff go away by themselves the vast majority of times, and it's very rare that it needs an antibiotic," he said.

"We should regard antibiotics as the precious resource that they are. They may not be here forever to help us, and they are for special circumstances, not to be used in everyday life or everyday diseases."

Staph bacteria are the No. 1 cause of hospital-acquired infections in the United States, blamed for 13 percent of the 2 million hospital infections annually. The 2 million infections kill 60,000 to 80,000 people.

In the study, the number of children admitted to the University of Chicago Children's Hospital with methicillin-resistant staphylococcus aureus infections that were acquired outside the hospital rose from eight in 1988 to 35 in 1995.

The study was reported in Wednesday's Journal of the American Medical Association.