The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in horse infections in France surged between 2007 and 2013, researchers report.
MRSA is a bacterium responsible for several hard-to-treat infections, being resistant to several classes of antibiotics.
It was initially reported as a major cause of hospital-acquired infections in humans, but has increasingly been reported as community-acquired infections, as well as cases in animals.
Possible transmission of MRSA between humans and animals has raised concern about the role of animals as a major reservoir.
François Guérin and his colleagues, writing in the journal BMC Microbiology, said there was little documented about the incidence and distribution of MRSA in horse infections, especially in France.
The study team set out to determine the prevalence of MRSA in horse infections from samples taken between 2007 to 2013 in France and to genetically investigate the strains found.
The regional veterinary laboratory of Normandy received 226,878 horse clinical samples between 2007 to 2013, with the recovery of 17,651 different bacterial isolates.
S. aureus was the third most frequent bacterial species isolated, in 1393 instances (7.9% of the cases), behind group-C streptococcus (25.6% of cases) and Escherichia coli (19.7%).
Out of the 1393 S. aureus horse isolates, 85 (6.1%) were categorized as MRSA. The isolates had been recovered from different areas of infection: skin and soft-tissue (39 cases), the genital tract (20), respiratory tract (8), bones and joints (8) and other areas (10).
Resistance to methicillin was due to the presence of the mecA gene in 84 strains (98.8%), while one strain (1.2%) possessed the mecC gene.
Nearly all the strains (83 out of 85, or 97.6%) were resistant to at least three different classes of antibiotics. It was important, they said, to highlight the very high proportion of strains exhibiting resistant to three-to-eight antimicrobial categories.
The prevalence of MRSA strains isolated from horse infections in France before 2011 had been low, they noted, at around 2 per cent.
The evidence showed a surge, from 2007 and 2013, mainly resulting from the spread of ST398 clones.
“Although ST398 is associated with livestock, sporadic cases, and outbreaks in equine hospitals, colonization of horses and associated personnel have been reported in Europe.
“Recently, a suspected transmission of MRSA ST398 from a horse to a Dutch girl, which resulted in a foot infection, has been reported.”
The findings, they said, highlighted the importance of horses as a potential reservoir of important antimicrobial resistance genes.
Nationwide molecular epidemiology of methicillin-resistant Staphylococcus aureus responsible for horse infections in France
François Guérin, Marguerite Fines-Guyon, Pierrick Meignen, Géraldine Delente, Caroline Fondrinier, Nancy Bourdon, Vincent CattoirEmail author and Albertine Léon
BMC Microbiology 2017 17:104 DOI: 10.1186/s12866-016-0924-z