College of Public Health Spotlights
This little piggy went to market, this little piggy stayed home, and this little piggy has MRSA, an antibiotic-resistant infection. Not exactly how the age-old nursery rhyme goes, but a research finding that documented MRSA--methicillin-resistant Staphylococcus aureus--in some pigs and their caretakers has epidemiologists changing their tune when it comes to MRSA research and prevention.
“Iowa ranks first in the nation in swine production,” said Tara Smith, assistant professor of epidemiology. “Transmission of MRSA on swine farms or in veterinary facilities could complicate efforts to reduce MRSA transmission statewide and beyond.”
Staphylococcus aureus, often called “staph,” are bacteria commonly carried on the skin or in the nose of healthy people. MRSA is a type of staph that is resistant to the broad-spectrum antibiotics generally used to treat it, and it can be fatal. The best-known strain is found in hospitals.
Prompted by research in the Netherlands and Canada that documented a strain of MRSA called ST398 in hogs, cattle, and horses, Smith and colleagues in the UI Center for Emerging Infectious Diseases (CEID) launched research focused on two swine operations in Iowa and Illinois.
Investigators analyzed nasal swabs of 299 swine and 20 swine workers from two different production systems and found colonized MRSA in pigs and their caretakers at one of the operations, which included a number of individual locations. Within that production system, the overall prevalence of MRSA was 70 percent in swine and 64 percent in workers.
“Because ST398 was found in both animals and humans, it suggests transmission between the two. Our findings also suggest that once MRSA is introduced, it may spread broadly among both swine and their caretakers,” said Smith. “Agricultural animals could become an important reservoir for this bacterium.”
This is the first known study to investigate carriage of MRSA among swine in the United States. The studies were small and many questions remain, Smith said.
“We are looking more generally at MRSA in rural Iowa and in the farm environment,” Smith said. “We will be recruiting additional farms, including both confinement operations and free range antibiotic‐free farms, in order to better examine the role of antibiotics in the spread of MRSA. And beginning this summer, we are hoping to get some samples from other types of animals – cattle, chickens – to look for MRSA carriage there.”