The disease often spreads through football teams because players not only contact one another but suffer abrasions from the sport. Five cases were recently reported among football players at Harriton High School, in Lower Merion School District.

Attempts to sterilize rooms or buildings could lead to a false sense of security, Fishman said.

"It's impossible to sterilize the environment; it will constantly become recolonized with a variety of organisms [including MRSA]," he said. "The critical factors of transmission are related to personal hygiene."

The cleanup at Indian Lane Elementary School, where classes were canceled, was initiated by the district's superintendent, Denise Kerr.

"I knew once we told parents we had a MRSA case at the elementary level we would have a tremendous amount of concern, and the best way would be take extra time to clean the building," she said. "The feedback from parents was very positive."

Fishman said the newer strain, sometimes called the community-associated, or CA, strain, is actually curable with a wider range of antibiotics than the older, hospital-associated variety, but it tends to cause more invasive skin infections.

What's interesting about the CA strain is that it appears to be the first antibiotic-resistant bacterium to have originated outside of hospitals, said Stuart Levy, professor of medicine and microbiology at Tufts University Medical School.

Today both strains are intermingled, he said, so you can get the community-associated bug in a hospital or the hospital-associated bug somewhere else.

Experts worry that the overuse of antibiotics has led to an environment that could breed still more dangerous infectious agents. Antibiotics leach into the environment not only through medicine but through their use in cattle and chicken feed.

And scientists are turning up things far scarier than MRSA.

"We're starting to see more infections with organisms that aren't susceptible to any antibiotics," Fishman said. One, called acinetobacter, is infecting troops wounded in Iraq.

"I do think we are facing a national crisis of antibiotic resistance," he said. "But MRSA represents just the tip of the iceberg."

The Facts on a Staph Infection

Researchers determined this week that the most serious infections from

a specific, drug-resistant staph bacterium known as MRSA were more common than had been thought.

Answer: Staphylococcus aureus is a group of generally harmless bacteria. They typically are present in at least 25 percent of