Presence, distribution, and molecular epidemiology of methicillin-resistant Staphylococcus aureus in a small animal teaching hospital: a year-long active surveillance targeting dogs and their environment

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) is known to be present in small animal veterinary clinical environments. However, a better understanding of the ecology and dynamics of MRSA in these environments is necessary for the development of effective infectious disease prevention and control programs. To achieve this goal, a yearlong active MRSA surveillance program was established at The Ohio State University (OSU) Veterinary Medical Center to describe the spatial and molecular epidemiology of this bacterium in the small animal hospital. Antimicrobial susceptibility testing, staphylococcal chromosomal cassette mec (SCCmec) typing, pulsed-field gel electrophoresis (PFGE) typing, and dendrogram analysis were used to characterize and analyze the 81 environmental and 37 canine-origin MRSA isolates obtained during monthly sampling events. Overall, 13.5% of surfaces were contaminated with MRSA at 1 or more sampling times throughout the year. The majority of the environmental and canine isolates were SCCmec type II (93.8% and 86.5%, respectively) and USA100 (90.1% and 86.5%, respectively). By PFGE analysis, these isolates were found to be closely related, which reflects a low diversity of MRSA strains circulating in the hospital. For 5 consecutive months, 1 unique pulsotype was the most prevalent across the medical services and was recovered from a variety of surfaces and hospital locations. Carts/gurneys, doors, and examination tables/floors were the most frequently contaminated surfaces. Some surfaces maintained the same pulsotypes for 3 consecutive months. Molecular analysis found that incoming MRSA-positive dogs were capable of introducing a new pulsotype into the hospital environment during the surveillance period. Our results suggest that once a MRSA strain is introduced into the hospital environment, it can be maintained and spread for extended periods of time. These findings can aid in the development of biosecurity and biocontainment protocols aimed at reducing environmental contamination and potential exposures to MRSA in veterinary hospital staff, clients, and patients.

FIG. 1.

Distribution of methicillin-resistant Staphylococcus aureus (MRSA) prevalence on human- and canine-contact surfaces at the Small Animal Hospital in The Ohio State University Veterinary Medical Center Section during the MRSA Active Surveillance.

FIG. 2.

Prevalence comparison between pulsotype 10 (P10) and other pulsotypes combined by month during the methicillin-resistant Staphylococcus aureus (MRSA) Active Surveillance at the Small Animal Hospital in The Ohio State University Veterinary Medical Center.

FIG. 3.

Prevalence of pulsotype 10 (P10) between human- and animal-contact surfaces by month at the Small Animal Hospital in The Ohio State University Veterinary Medical Center during the methicillin-resistant Staphylococcus aureus (MRSA) Active Surveillance.

FIG. 4.

Dendrogram based on the SmaI macrorestriction fragment profiles of 118 methicillin-resistant Staphylococcus aureus (MRSA) isolates obtained from environmental surfaces and canines admitted to the Small Animal Hospital in The Ohio State University Veterinary Medical Center. The percent similarity was calculated with Dice coefficients from the pulsed-field gel electrophoresis (PFGE) data. Band position tolerance and optimization were set at 1%.

FIG. 4.

Dendrogram based on the SmaI macrorestriction fragment profiles of 118 methicillin-resistant Staphylococcus aureus (MRSA) isolates obtained from environmental surfaces and canines admitted to the Small Animal Hospital in The Ohio State University Veterinary Medical Center. The percent similarity was calculated with Dice coefficients from the pulsed-field gel electrophoresis (PFGE) data. Band position tolerance and optimization were set at 1%.