The nose is not enough: Multi-site sampling is best for MRSP detection in dogs and households

Following recovery from meticillin-resistant Staphylococcus pseudintermedius (MRSP) infection of any type, dogs may continue to carry MRSP asymptomatically on skin and mucosae, contributing to the spread of this multidrug-resistant, veterinary hospital-associated pathogen with zoonotic potential to others and into the environment.

This study determined which canine anatomic and household environmental sites are most sensitive for sampling to identify carriage and contamination.

Fifty-one dogs and 22 households, MRSP-positive on at least one tested site, were sampled on 132 and 40 occasions over time, respectively. Dogs were swabbed at six sites (mouth, nose, conjunctiva, skin, prepuce/vulva, perianal area); household environments were sampled using contact plates (mannitol salt agar [MSA] and MSA + 6 mg/L oxacillin [MS+]) on five sites. MRSP was isolated after enrichment, grown on MSA/MS+ and was confirmed by PCR. Generalized estimating equations were used for calculation of sensitivity (95% confidence interval) for each site/combination.

Each anatomical and environmental site yielded MRSP at least once. MRSP was isolated from only a single site in 27.3% of dogs, with the buccal mucosa showing the highest sensitivity (63.8%). Multi-site sampling of a minimum of four canine anatomical or four environmental sites, respectively, was needed to achieve >95% sensitivity.

The canine buccal mucosa should be included in MRSP sampling protocols, ideally in addition to at least three other anatomical sites. Likewise, environment sampling should be of multiple household sites in cases where it is used as a part of clinical case management.