Methicillin-resistant staphylococcal colonization in clinically normal dogs and horses in the community

To evaluate the prevalence of methicillin-resistant staphylococcal (MRS) colonization in clinically normal dogs and horses in the community.

Three hundred clinically normal horses and 200 clinically normal dogs were enrolled. One nasal swab was collected from each horse. Two swabs were taken from each dog: (i) from an anterior nare, and (ii) a combination of the perineal area and 0.5 cm into the anus. Enrichment cultures were performed. Methicillin-resistant Staphylococcus aureus (MRSA) was not identified. Methicillin-resistant Staphylococcus intermedius (MRSI) was isolated from the nasal swab from three dogs. Methicillin-resistant coagulase negative staphylococci (MRCoNS) were isolated from 126/300 (42%) horses and 26/200 (13%) dogs.

At present MRSI is not considered to be a significant zoonotic concern; however, it may become an important pathogen in dogs. MRCoNS mostly cause disease in compromised human or animal hosts. However, these bacteria can serve as reservoirs of resistance determinants in the community, which could lead to the emergence of novel MRSA strains.

This is the first report of the prevalence of MRS colonization in clinically normal dogs in a community setting. Continued surveillance is indicated to determine whether MRSA will emerge in the animal population and become a concern for animal disease and zoonotic infection.