Despite recent reports that point to possible dangers to human health from Methicillin-Resistant Staphylococcus Aureus (MRSA), the evidence is certainly far from conclusive that this presents a food safety issue in the United States.

In fact, Staphylococcus aureus is a common organism found in nasal passages and on the skin of people and pigs.

MRSA occurs when Staphylococcus aureus develops resistance to methicillin and some other antibiotics.

University of Minnesota veterinarian Peter Davies reported last month that he found the antibiotic-resistant organism in 7.1% of 113 swine veterinarians gathered at the American Association of Swine Veterinarians (AASV) annual meeting in March in San Diego, CA.

National Pork Board swine veterinarian Liz Wagstrom says those results are a little higher than the 2% rate found in the general public in the United States. But she says it’s unclear if the slightly higher rate in swine veterinarians is “statistically significant.” Of the 113 swine veterinarians swabbed at the meeting, a number were international AASV members.

The prevalence in swine veterinarians at the AASV meeting was similar to, or lower than, several surveys of equine veterinarians. Also, that figure is lower than the 12% level found in international veterinarians surveyed at the International Pig Veterinary Society annual meeting in Copenhagen, Denmark a few years back.

The Pork Board sponsored that voluntary survey. In another Pork Board survey, Davies will look at the level of antibiotic resistance in pork at retail.

“We are definitely looking at MRSA research and if the bacteria is in pigs at slaughter or in retail meats, but we are also looking to see if there are differences on farms in terms of production systems, the impact of different antibiotic regimes and if we can identify risk factors,” Wagstrom says.

She referred to the Centers for Disease Control (CDC), which responded late last year to an inquiry into the impact of MRSA on food-producing animals by the House Agriculture Committee. CDC Director Julie Louise Gerberding responded that more than 80% of life-threatening MRSA infections appear to result from patient-to-patient transmission in health care facilities.

In contrast to reported cases of MRSA resulting from close human-livestock contact in Europe, all U.S. outbreaks have been traced to human-to-human transmission, she says.

Wagstrom referenced another project funded by the Pork Board conducted at several universities that compared 14,000 pigs raised in conventional vs. antibiotic-free pork production systems on farms in North Carolina, Ohio and Wisconsin.

The results, just released by The Ohio State University, concluded that:

  • More than half of the pigs on antibiotic-free farms tested positive for salmonella, vs. 39% of conventionally raised pigs.
  • The Toxoplasma gondii parasite was detected in 6.8% of antibiotic-free pigs, compared to 1.1% of conventionally raised pigs.

Two naturally raised pigs out of 616 sampled tested positive for Trichinella spiralis, a parasite considered virtually eradicated from traditional U.S. hog operations.

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