In order to get better data, the team used a study model that is much-employed in human epidemiology — and has often been used for MRSA — but under-employed in veterinary medicine: a case-control study matching MRSA infections against MSSA, or drug-sensitive staph. Studies matching MRSA against MSSA have been able, for instance, to show that certain (human) MRSA infections have higher death rates, keep patients in the hospital longer, and cause more healthcare expense.
The Guelph team used the same method to compare the presentation and outcome for 40 MRSA-infected dogs and 80 dogs with MSSA who were seen between 2001 and 2007 in three veterinary hospitals, in Guelph, Philadelphia and Boston. Their verdict:
MRSA is an emerging problem in dogs, and the risk factors for MRSA infections are similar to those in humans, particularly the use of IV catheters and both beta-lactam and fluoroquinolone antibiotics.
The researchers were not able to say whether MRSA in dogs causes more deaths than MSSA, because the infections that were recorded by the hospitals were mostly superficial ones in skin and ears:
Infection types for which death would be a more realistic possible outcome were limited... Comparison of mortality rates between patients with MRSA or MSSA infections would be best performed among on ly those with invasive infections and should be considered for future studies. Here, mortality rate information was obtained retrospectively and only recorded up to the time of discharge. Therefore, whether dogs died from their infections after discharge from the referral hospital, causing an underestimate of deaths, is unknown.Dr. Scott Weese, senior author of this paper and chief of the Guelph group, has an excellent blog on infections in companion animals, called Worms and Germs. (It's in the blogroll.) And if you are looking for further information on MRSA in pets, the best resource I know of is the UK-based, but international, Bella Moss Foundation, named for a dog that died of a MRSA infection.