Prevention and control of methicillin-resistant Staphylococcus aureus in equine hospitals in Sweden

Abstract: Methicillin-resistant S. aureus (MRSA) was first described in 1961 and has since caused nosocomial infections and therapeutic limitations. In Sweden, the first finding of horses infected with MRSA was in 2008. Nosocomial spread of MRSA among horses is a hazard for the patients and those in contact with the animals. Therefore, there is a need to introduce or improve routines for prevention and control of MRSA in veterinary care. MRSA spa-type t011, CC398 caused an outbreak of surgical site infections in horses. MRSA CC398 is associated with livestock and has been reported in horses in Europe. The superficial infections healed without antimicrobial treatment. Longitudinal sampling of post-infected horses showed that all tested negative by time, median 143 days. The most sensitive site to test for MRSA carriage was the nostrils, with a relative sensitivity of 0.91. Due to few sampled cases (n=9) MRSA carriage in horses needs more study. Transmission of MRSA by horses and humans to the environment was shown through environmental screening. In total, 10 of 92 samples were positive. The screening was a useful tool in the implementation of basic hygiene. Rapid response combined with multidisciplinary collaboration was key in the outbreak control. This led to an improved infection control (IC) operation. Infection control procedures used in human health care were mainly applicable, but existing differences between equine and human settings require adapted solutions. Baseline data on IC procedures in three equine hospitals was collected. Overall excellent compliance with dress regulations and personal appearance (no rings or wrist watches, short nails etc.) was shown. Compliance with hand hygiene procedures was poorer. Purchase data per patient of hygiene products were useful to indirectly monitor compliance trends over time. Barriers to compliance were such as inaccessible hygiene products, insufficient knowledge of procedures and high work load. The knowledge presented in this thesis on epidemiology and prevention and control of MRSA in equine medicine can be used in the development and implementation of IC procedures in Swedish equine hospitals. Supplementary multidisciplinary studies of MRSA carriage in horses, species-specific factors affecting IC and, implementation and compliance with IC can develop the topic further.