What's in Your Practice? S. aureus and MRSA in a Veterinary Academic Community

During ID Week 2016, researchers from The Ohio State University’s Veterinary Public Health Program and Department of Veterinary Preventive Medicine presented results on the prevalence and risk factors of Staphylococcus aureus (SA) and methicillin-resistant S. aureus (MRSA) carriage within a large veterinary academic community.

MRSA is an opportunistic pathogen. Yearlong active MRSA surveillance studies have reported the presence of MRSA in small animal and equine teaching hospitals. At a small animal teaching hospital, MRSA surveillance identified several surfaces (gurneys/carts, doors, examination tables and floors, doors) that were frequently contaminated with MRSA; several MRSA isolates had circulated throughout the hospital for as long as nine months’ time. Using molecular epidemiology, researchers observed an introduction of MRSA into the hospital environment by incoming MRSA-positive canine patients. Interestingly, there was little genetic diversity between environmental and canine-derived MRSA isolates.

At an equine teaching hospital, researchers identified MRSA on approximately 9% of surfaces and in 6% of equine patients. Computers, feed and water buckets, and surgery tables and mats were the most commonly MRSA-contaminated surfaces. Molecular epidemiological analysis demonstrated a constant introduction and/or reintroduction of various MRSA strains into the hospital environment. Notably, MRSA contamination was significantly higher in the fall (October to December) than the summer.

Although MRSA poses a serious health concern, researchers noted in the conference abstract that “occupational safety among high risk populations, specifically veterinary personnel, has been poorly researched and requires further understanding to improve safety and health protection in the workplace.”

Researchers conducted a cross-sectional study at an academic veterinary teaching hospital and its associated veterinary school. They collected samples from hospital and veterinary school personnel, canine patients, and the hospital environment. After sample collection, researchers analyzed the SA and MRSA isolates using antimicrobial susceptibility testing, staphylococcal cassette chromosome mec (SCCmec) testing, pulsed-field gel electrophoresis, and molecular epidemiology. SCCmec is a mobile genetic sequence in staphylococci that contains the mecA gene, which codes for methicillin resistance.

Nearly 26% of the veterinary community demonstrated nasal SA colonization; 2% of the community had nasal colonization with MRSA. When comparing hospital personnel (HP) with veterinary school personnel, HP were about 1.5 times more likely to have nasal MRSA colonization. Among HP, residents and fourth-year veterinary students demonstrated the highest prevalence of nasal colonization. Compared with third-year veterinary students, fourth-year veterinary students had a three-fold greater likelihood of nasal SA colonization.

Genetic analysis revealed similarities between personnel and environmental strains of SA and MRSA. Among strains found in the personnel, 10% of SA strains and 33% of MRSA strains demonstrated either clonal or close relation to hospital environment strains. Notably, researchers observed environmental and personnel MRSA strains circulating within the veterinary community.

Researchers identified three risk factors for SA carriage: not washing hands between patients, not using gloves while handling patients, and not covering visible hand lesions. Compared with HP who washed their hands between patients, those who did not were about 4 times more likely to have nasal SA colonization. Approximately 90% of HP reported washing their hands between patients.

Given the study’s findings, researchers emphasized the “importance of personal hygiene and compliance with infectious controls measurements for the prevention of SA/MRSA colonization among personnel with high occupational exposure.”

Dr. JoAnna Pendergrass received her doctorate in veterinary medicine from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, LLC.