Prevalence and risk factors for colonization with methicillin resistant Staphylococcus aureus and other Staphylococci species in hospitalized and farm horses in Israel.

This research investigates the prevalence and risk factors of Methicillin-resistant Staphylococcus aureus (MRSA) and other Methicillin-resistant staphylococci (MRS) species among horses in Israel. The study found that MRS was prevalent among hospitalized horses, but not in farm horses, and unveiled that antibiotic use, pure breeding, and hospitalization could increase the risk of MRS colonization.

Methodology

• The study involved sampling nasal swabs from horses at 17 different riding stables (n=206), as well as from horses admitted to a veterinary hospital (n=84).
• Molecular biological techniques were employed for species identification. This included PCR targeting the pta gene, RFLP analysis, and gene sequencing.
• The presence of mecA gene was used to indicate MRS. Genetic relatedness of MRSA isolates was established through spa typing and MLST.
• The study also determined the SCCmec-type and the presence of the pvl gene.
• Statistical analyses, both univariable and multivariable, were carried out to identify potential risk factors for Staphylococci and MRSA colonization.

Findings

• Colonization with Staphylococci was found in 3.8% of farm horses and 50.6% of hospitalized horses. This indicates a significantly higher incidence of colonization in hospitalized horses.
• While MRS isolates were not found in any of the farm horses, they were observed in a significant portion (21.6%) of horses treated at the veterinary hospital. This accounted for 42.8% of all hospital isolates.
• MRSA was detected only among hospitalized horses, at a rate of 7.2%.
• All MRSA isolates belonged to a unique multi-drug-resistant clone, ST5-SCCmec V, which was pvl-negative and had a spa-type of t535.
• Risk factors for MRS colonization were identified as being pure bred, hospitalization, and antibiotic use.

Conclusion

• This study represents the first surveillance of Staphylococci in horses in Israel and the first report on the presence of a unique MRSA strain in hospital horses.
• The findings highlight the veterinary hospital as a potential reservoir for MRSA, an antibiotic-resistant pathogen that is relevant to human health.
• The identification of risk factors like pure breeding, hospitalization, and antibiotic usage suggests a need for more stringent infection controls and monitoring, particularly in veterinary hospitals.