Proximity to Livestock Raises a MRSA Risk

People living near large concentrations of farm animals are at increased risk for carrying livestock-associated methicillin-resistant Staphylococcus aureus, or LA-MRSA, even if they have had no direct contact with animals, a new study has found.

Researchers studied 27 people with nose swabs positive for LA-MRSA and 60 control subjects carrying other types of the bacterium. The study, published in the November issue of Emerging Infectious Diseases, found that 12 of those who tested positive for LA-MRSA had had no contact with animals.

By plotting the locations of cases and controls against the regional populations of livestock, the investigators found that living in an area dense with livestock is a significant risk factor for carrying LA-MRSA, regardless of contact with farm animals.

Previous research has found that LA-MRSA is not transmitted person to person, but these findings suggest that it might be. It is possible, the authors write, that the germ could be transmitted by contact with other domestic animals, by air or by farm waste.

“LA-MRSA appears to be less virulent than other strains,” said the lead author, Beth J. Feingold, a researcher at Johns Hopkins. “But some research suggests that there is a possibility that, like with any bacteria, it can evolve into something more virulent, which is why it’s important to cover our bases now.”