Emergence of MRSA ST612 in horses and of MSSA CC398 in cats in France.

The recent research uncovers a new prevalence of the bacterium Staphylococcus aureus (MRSA and MSSA variants) in cats, dogs, and horses in France, with a notable upsurge in MRSA in horses and MSSA in cats. This finding calls for careful observation to prevent its spreading that could cause zoonotic diseases and to decipher the mechanism of their transmission between humans and animals.

Research Methods

• The study made use of clinical Staphylococcus aureus isolates, totalling 479. These isolates were collected from 186 cats, 143 dogs, and 150 horses spanning across France from 2022 to 2023.
• Antibiograms were carried out on each of the isolated samples.
• A Whole Genome Sequencing (WGS) was performed on the identified Methicillin-resistant Staphylococcus aureus (MRSA) and the Methicillin-sensitive Staphylococcus aureus (MSSA) CC398 isolates.
• The researchers used established methodologies to analyze the phylogenetics of the isolates based on core genome MLST (multi-locus sequence typing) and single-nucleotide polymorphisms (SNPs).
• They utilized publicly accessible tools for the characterization of isolates.

Research Findings

• Out of the total isolates, 66 were identified as MRSA: 14 from cats (7.5%), 9 from dogs (6.3%), and significant 43 from horses (28.7%).
• The prevalence of MRSA in cats and dogs remained stable in comparison to a previous study conducted in 2015. The study revealed the presence of the clonal complex (CC) 398 and human-associated clones in both animals.
• In contrast, there was a noticeable increase in the prevalence of MRSA in horses, potentially due to the emergence of the ST612 clones.
• The clone CC398 MSSA, traditionally described as independent of animals, was found in 24.2% of the cat isolates.

Implications of the Research

• The research is pioneering the framework for genomic surveillance of Staphylococcus aureus within France. It brought to light the emergence of MRSA ST612 in horses and MSSA CC398 in cats.
• The findings of this study underscore the importance of close monitoring of these clones to circumvent potential zoonotic transmissions from animals to humans.
• Understanding their dynamics of transmission between humans and animals is critical to devise strategies to control the spread of infections caused by these bacterial clones.