Much more on MRSA and animals

Again from the 108th General Meeting of the American Society for Microbiology: new findings on the complex interaction of MRSA in humans, pets and food animals.

• From the University of Iowa, the first finding of MRSA in US pigs, on seven farms in Iowa and Illinois. The abstract doesn't say what subtype of MRSA was found, but a new strain of MRSA was found last year in pigs in the Netherlands and both that strain and a known human strain have been found in pigs in Canada. Carriage rates among the Midwestern pigs: from 100% of very young animals to 36% among adult swine. (Poster 983, first author AL Harper)
• From Nicholls State University and two veterinary practices in southern Louisiana, results of screening tests on pets show high rates of carriage of methicillin-resistant Staph species. The pets carried both S. aureus and S. intermedius. (Poster 1017, first author T. Rachal.) For an earlier post on pets harboring MRSA, look here.
• And from the University of Georgia, an analysis of MRSA strains isolated from 50 humans and 60 companion animals (dogs, cats, horses, birds) found the same strains in both: SCCmec type II, a hospital strain, and SCCmec type IV, the main community strain. Human carriage rates: 78% type IV, 22% type II. Animal carriage rates: overall, 40% type IV and 60% type II, but with some important differences between species — all of the cats and birds harbored type II, while the dog isolates were overwhelmingly II and the horses overwhelmingly IV. Of greatest importance, the types did not have identical resistance patterns: In humans, the type IV was sensitive to vancomycin and tetracycline, but the animal IV was sensitive to vanco only, suggesting that MRSA may be evolving differently in its transient animal hosts — an especial concern if the animal-carried strains pass back to humans. (Poster 1027, first author S. Sanchez.)