Drug-resistant bacteria on increase in U.S.: study

Tue Nov 24, 2009

WASHINGTON (Reuters) – Cases of a drug-resistant bacterial infection known as MRSA have risen by 90 percent since 1999, and they are increasingly being acquired outside hospitals, researchers reported on Tuesday.

They found two new strains of methicillin-resistant Staphylococcus aureus — MRSA for short — were circulating in patients and they are different from the strains normally seen in hospitals.

Ramanan Laxminarayan of Princeton University in New Jersey and colleagues studied data on lab tests from a national network of 300 microbiology laboratories in the United States for their study.

“We found during 1999-2006 that the percentage of S. aureus infections resistant to methicillin increased more than 90 percent, or 10 percent a year, in outpatients admitted to U.S. hospitals,” they wrote in a report published in the journal Emerging Infectious Diseases.

“This increase was caused almost entirely by community-acquired MRSA strains, which increased more than 33 percent annually.”

MRSA is now entrenched in U.S. hospitals. It was also known to be circulating in the community but it was not clear whether patients were carrying the infections out of hospitals, or the other way around.

Laxminarayan’s team found that many more people were being diagnosed with the community-acquired strains, and these strains were not replacing the known hospital strains. Instead, they are just adding to the overall number of MRSA cases.

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