Staph germs harder than ever to treat, studies say

At least 10% of infections involving staph bacteria were able to survive antibiotics commonly used to treat them, according to a Centers for Disease Control and Prevention (CDC) report presented at a joint meeting in October of the American Society for Microbiology and the Infectious Diseases Society of America.

A number of different CDC studies show that drug-resistant staph bacteria is growing more common even among healthy members of the community, according to Rachel Gorwitz, MD, director of the health care quality promotion division of the CDC. Approximately 95,000 serious infections and 20,000 deaths occur in the United States every year due to drug-resistant staph bacteria.

Bacteria found in ordinary community settings are increasingly acquiring "superbug" powers and causing far more serious illnesses than they have in the past.

"Until recently we rarely thought of it as a problem among healthy people in the community," says Gorwitz. Now, the germs causing outbreaks in schools, on sports teams, and in other social situations are posing a growing threat. A CDC study found that at least 10% of cases involving the most common community strain were able to evade the antibiotics typically used to treat them.

The germ is methicillin-resistant Staphylococcus aureus, or MRSA. People can carry it on their skin or in their noses with no symptoms and still infect others - the reason many hospitals isolate and test new patients to see if they harbor the bug.

MRSA mostly causes skin infections.

To treat them, "we've had to dust off antibiotics so old that they've lost their patent," said Robert Daum, MD, a pediatrician at the University of Chicago.

The CDC used a network of hospitals in nine cities and states to test samples of the most common community MRSA strain, USA300, over the last few years.

MRSA usually is resistant only to penicillin-type drugs. But 10% of the 824 samples checked also could evade clindamycin, tetracycline, Bactrim or other antibiotics.

"The drugs that doctors have typically used to treat staph infections are not effective against MRSA," and family doctors increasingly are seeing a problem only hospital infection specialists once did, Gorwitz said.

Even more worrisome: many of these community strains had features allowing them to easily swap genes and become even hardier.