MRSA Bug Found In Cows And Humans Can Evade Some Tests

Jun 3, 2011

European researchers have found a strain of drug-resistant Staphylococcus aureus that appears to have a novel way of defeating the antibiotic methicillin.

Bugs that can beat that antibiotic are known as methicillin-resistant Staphylococcus aureus, or MRSA, and present real challenges for prevention and treatment.

A report just published in the medical journal The Lancet Infectious Diseases describes the discovery of the new bug found in milk in England and in samples taken from people in Denmark and the U.K. Researchers came across the bacterium while investigating udder infections in Britain.

The upshot is that this staph germ — which doesn't contain the standard genetic bit known as mecA that MRSA bugs use to thwart methicillin — may go undetected on genetic tests that are used to rapidly detect MRSA or to check on the old-fashioned and slower results that come when the bacteria are grown on agar plates. Instead, the germ has a variation on mecA that's different enough to slip by the regular MRSA gene tests.

The paper's authors say they can't prove for sure that the bug is transmitted between cattle and people, but there is a fair amount of circumstantial evidence to support that jump.

The Washington Post reports the researchers said their finding doesn't mean people could get sick from pasteurized milk. But the germ could be passed on through unpasteurized milk, one of the authors said at a media briefing.

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