A new study funded by the Pew Charitable Trust purports to show that half of retail meat samples were contaminated with Staph aureus, a bacterium that can cause illness.

The authors of the Pew study, who are consultants to the Pew campaign, largely composed of members opposed to modern livestock production practices, including antibiotic use, admitted the public health implications of their findings were unclear.

The study found Methicillin-resistant Staph aureus (MRSA) bacterium on just one sample each of beef, pork and turkey. There were just 136 samples of beef, chicken, pork and turkey purchased from grocery stores in five cities.

Elizabeth Wagstrom, DVM, and Peter Davies, DVM, with the University of Minnesota College of Veterinary Population Medicine, pointed out that the MRSA isolates identified in the study were human types, meaning the meat was likely contaminated by a person. They also determined the type of MRSA found was resistant to antibiotics not approved for use nor used in U.S. food production. The researchers clarified three points:

  • Staph aureus is a common bacterium found on the skin of people in 30% of the population and on animals. It would have been unusual for the bacterium not to have been found on meat. While Staph can cause human illness, it usually does not. It mostly affects people with compromised immune systems or open wounds, which is why most Staph infections occur in health care facilities.
  • Staph on meat would not produce a Staph infection, but a toxin produced by Staph bacterium could cause food-borne illness, which would not be treated with antibiotics.
  • The study didn’t measure the actual level of Staph found on samples. Finding low levels of Staph is no indication of the meat’s potential to cause illness.