Isolation of methicillin-resistant Staphylococcus aureus from the environment in a veterinary teaching hospital.

After recognition of a cluster of methicillin-resistant Staphylococcus aureus (MRSA) infection in horses and humans at the Ontario Veterinary College Veterinary Teaching Hospital, environmental contamination with MRSA was evaluated. A total of 260 environmental surfaces were sampled during periods when MRSA-infected horses were hospitalized, and MRSA was isolated from 25/260 sites (9.6%). The most commonly contaminated sites were stalls housing MRSA-positive horses, but other stalls, medical equipment, personal items, and equine restraint devices also were contaminated. The role of the environment in the transmission of MRSA infection to horses or humans is unclear. However, relatively widespread contamination of the hospital environment, as apparently occurs when infected horses are hospitalized, suggests that the environment may be an important source of MRSA infection. This possibility must be taken into consideration when designing infection control and disinfection protocols.