Emergence of carriage of CTX-M-15 in faecal Escherichia coli in horses at an equine hospital in the UK; increasing prevalence over a decade (2008-2017).
Authors: Isgren C M, Edwards T, Pinchbeck G L, Winward E, Adams E R, Norton P, Timofte D, Maddox T W, Clegg P D, Williams N J
Journal: BMC veterinary research
Summary
# Editorial Summary: Rising antimicrobial resistance in equine hospital E. coli populations Over a nine-year period at a UK equine referral hospital, researchers tracked the prevalence and resistance profiles of extended-spectrum β-lactamase (ESBL)-producing E. coli isolated from hospitalised horses' faeces, using selective culture media and real-time PCR with high resolution melt analysis to differentiate between blaCTX-M-1 and blaCTX-M-15 gene variants. ESBL-producing E. coli nearly doubled from 28.7% of samples in 2008 to 50.0% in 2017, with a dramatic shift in resistance gene profiles: the proportion of CTX-M-1 group isolates increased from 12.6% to 94.1%, and whilst blaCTX-M-1 remained relatively stable, blaCTX-M-15 emerged to represent 60.8% of 2017 isolates. Resistance to doxycycline, gentamicin and third-generation cephalosporins rose significantly over the decade, indicating multi-drug resistance patterns that may complicate clinical treatment decisions in hospitalised cases. These findings highlight a concerning epidemiological shift in bacterial populations within equine hospitals and suggest nosocomial transmission dynamics or selective pressure from antimicrobial use; clinicians should be alert to increased treatment failures with commonly used agents and consider earlier diagnostic culture and susceptibility testing in hospitalised horses with suspected bacterial infections, whilst infection control protocols warrant review to limit the spread of resistant organisms.
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Practical Takeaways
- •Antimicrobial resistance in equine hospitals is increasing dramatically—empiric use of common antibiotics like doxycycline and cephalosporins is becoming less reliable; culture and sensitivity testing should guide treatment decisions
- •Hospitalized horses are increasingly likely to be carriers of multidrug-resistant E. coli; enhanced biosecurity and hygiene protocols are essential to prevent nosocomial spread
- •Veterinarians should be aware that resistance patterns change over time within their own institutions and should monitor local resistance trends to inform rational antibiotic choices
Key Findings
- •ESBL-producing E. coli prevalence increased from 28.7% in 2008 to 50.0% in 2017 in hospitalized horses
- •CTX-M-15 emerged as dominant resistance gene, rising from 0% to 60.8% of CTX-M-1 group isolates over the decade
- •Resistance to doxycycline, gentamicin, and 3rd generation cephalosporins increased significantly from 2008 to 2017
- •Real-time PCR with high resolution melt analysis successfully distinguished blaCTX-M-1 from blaCTX-M-15 variants