ICAAC: Pigs Add New MRSA Woe

SAN FRANCISCO, Sept. 29 -- A porcine wrinkle has emerged in the struggle against community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) in The Netherlands.

Dutch researchers said they've found CA-MRSA among pig farmers and their families that can be traced to the animals themselves, said Christina Vandenbroucke-Grauls, M.D., of VU University Medical Center in Amsterdam.

"Since 2003, we have a totally new problem," Dr. Vandenbroucke-Grauls told a news briefing at the Interscience Conference on Antimicrobial Agents and Chemotherapy here. "Dutch pigs have MRSA and are transmitting it to the pig farmers." Normally animals with MRSA are infected by humans.

How the animals acquired the disease in the first place remains a mystery, Dr. Vandenbroucke-Grauls said, but it is possible it may be associated with antibiotics included in feed. The MRSA has been shown to be resistant to tetracycline, she said, which is commonly used in animals.

The strain found in the infected farmers is genetically distinct from most other human strains, she added.

Luckily, Dr. Vandenbroucke-Grauls said, most of the cases so far have been relatively mild. On the other hand, she said they run the gamut of MRSA infections, ranging from boils through endocarditis and osteomyelitis.

Exact numbers aren't known -- "we are still counting," she said -- but she estimated about 100 cases have been seen in the past two years in the country's southern pig-farming region.

In addition to farmers and their families, Dr. Vandenbroucke-Grauls said, slaughterhouse workers and large-animal vets have tested positive for the pig-associated MRSA.

The Netherlands strictly monitors MRSA at its hospitals, she said. Every patient is screened and those with CA-MRSA are isolated until the infection is cleared. But the advent of pig-associated MRSA has made the screening program more difficult, she said.

"It's not easy to ask every patient who comes in 'what is your job'," she said. "And there are lots of pig farms in the Netherlands, so it is a huge problem."

The pig farms in question are large industrial operations with many hundreds of pigs, Dr. Vandenbroucke-Grauls said, and such facilities are also common in the U.S. "Now that we have this problem in The Netherlands," she said, "it would be wise to screen to see if it exists in the U.S."

The pig-associated MRSA hasn't been seen yet elsewhere, said Robert Spencer, M.D., chairman of the British Hospital Infection Society. While it has been known that animals could get MRSA, it was usually in pets, he said.

"Until recently, we perceived that the problem was that it went from man to animals" Dr. Spencer said. "But now, of course, we have this unique situation in Holland where we have this association with pig farmers."

Such infections can usually be treated with incision and drainage, but a few develop overwhelming sepsis and require more drastic measures, Dr. Spencer said.

The pig MRSA came to light in 2003, Dr. Vandenbroucke-Grauls, when hospital officials detected MRSA in a young girl with no obvious risk factors for the disease. When they tested her father - a pig farmer - he too was positive. So too were the rest of the family members, the other farm workers, and eventually the trail led to the pigs.