Evolution of In Vitro Antimicrobial Susceptibility of Equine Clinical Isolates in France between 2016 and 2019.
Authors: Léon Albertine, Castagnet Sophie, Maillard Karine, Paillot Romain, Giard Jean-Christophe
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Antimicrobial Resistance Trends in Equine Pathogens (2016–2019) Researchers in France tracked antimicrobial resistance patterns across 7,806 bacterial isolates collected from horses over four years, employing standard disk diffusion susceptibility testing to monitor how common equine pathogens responded to various antimicrobial classes. Group C Streptococci dominated the collection at 27%, followed by *Escherichia coli* (18%) and *Staphylococcus aureus* (6.2%), with nearly half of all isolates originating from genital tract infections. Concurrent implementation of national antibiotic stewardship plans coincided with encouraging decreases in resistance across Group C Streptococci, *Klebsiella pneumoniae*, and some *E. coli* populations; however, the picture darkened considerably for *S. aureus* and *Enterobacter* spp., which showed increased resistance across most antimicrobial classes tested, with multidrug-resistant *S. aureus* rising from 24.5% to 37.4% and *Enterobacter* spp. jumping from 26.3% to 51.7%. These findings underscore that whilst prudent antibiotic use delivers measurable benefits against certain pathogens, emerging resistance in staphylococci and enterobacteria demands heightened clinical vigilance—particularly in reproductive cases—and reinforces the importance of culture and susceptibility testing before initiating therapy rather than relying on historical empirical prescribing patterns.
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Practical Takeaways
- •Antimicrobial selection for equine infections should be guided by current susceptibility data, as resistance patterns are evolving; S. aureus and Enterobacter spp. now show concerning increases in multi-drug resistance requiring more careful antibiotic stewardship
- •Judicious use of antibiotics in equine practice is increasingly important—national stewardship initiatives have shown measurable success in reducing resistance for some pathogens, demonstrating that clinical practice changes do impact resistance rates
- •Culture and susceptibility testing is particularly recommended for genital tract infections (45% of isolates) and when treating S. aureus or Enterobacter infections, given rising multi-drug resistance rates in these organisms
Key Findings
- •Group C Streptococci resistance decreased against five antimicrobial classes following national antibiotic stewardship plans (ECOANTIBIO 1 and 2)
- •Staphylococcus aureus multi-drug resistant strains increased from 24.5% to 37.4% between 2016 and 2019
- •Enterobacter spp. multi-drug resistant strains increased from 26.3% to 51.7% over the study period
- •Group C Streptococci (27.0%), E. coli (18.0%), and S. aureus (6.2%) were the most frequently isolated equine pathogens, predominantly from the genital tract (45.1%)