Cross-sectional study of antimicrobial-resistant bacteria in horses. Part 1: Prevalence of antimicrobial-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus.

This research examines the prevalence of antimicrobial-resistant bacteria, specifically methicillin-resistant Staphylococcus aureus (MRSA) and antimicrobial-resistant Escherichia coli, in horses in the UK. The article highlights the fact that a high proportion of horses carry antimicrobial-resistant E. coli, while MRSA presence is relatively rare.

Study Design

• The study was cross-sectional, recruiting horses from 65 veterinary practices across the UK.
• Both nasal swabs and faecal samples were collected from each horse. Nasal swabs were cultured for staphylococcal species, with any methicillin-resistant isolates identified as S. aureus then characterised further using SCCmec and spa gene typing.
• In a similar fashion, faecal samples were cultured to isolate E. coli and identify any antimicrobial-resistant strains.
• Multilevel logistic regression models were used to calculate prevalence with adjustments for clustering at practice and premises levels.
• The study also looked at any spatial variation in the risk of antimicrobial resistance across the UK.

Results

• Data was collected from 692 horses across 525 premises.
• The results showed that approximately 69.5% of horses carried antimicrobial-resistant E. coli, including 6.3% that carried extended-spectrum β-lactamase (ESBL)-producing E. coli.
• In contrast, only 0.6% of horses were found to be nasal carriers of MRSA.
• Additionally, the research found that there was spatial variation in the UK for the risk of carriage of resistant and multidrug-resistant E. coli.

Implications

• While carriage of MRSA appears to be rare in horses in the community, the prevalence of antimicrobial-resistant E. coli is notably higher.
• This high prevalence of antimicrobial-resistant bacteria could potentially have significant health implications for the horse population in the UK.
• Depending on the level of contact between horses and humans, this finding may also have implications for public health, especially in regard to the potential transfer of antimicrobial resistance to humans.