Detection and genetic characterisation of vanA-containing Enterococcus strains in healthy Lusitano horses.
Authors: Moura I, Radhouani H, Torres C, Poeta P, Igrejas G
Journal: Equine veterinary journal
Summary
# Editorial Summary: Vancomycin-Resistant Enterococci in Lusitano Horses Researchers screened healthy Lusitano horses for vancomycin-resistant enterococci (VRE) harbouring the vanA resistance gene, which confers high-level resistance to critical last-resort antibiotics used in human medicine. Faecal samples were cultured and isolated enterococci were characterised for antibiotic susceptibility and genetic resistance mechanisms. All vanA-positive isolates demonstrated extremely high vancomycin resistance (MIC ≥128 mg/l) alongside resistance to teicoplanin, ciprofloxacin, erythromycin and tetracycline; crucially, the tet(L) and erm(B) resistance genes were present in every isolate, indicating stable genetic elements rather than sporadic resistance. The findings establish that healthy horses can asymptomatically harbour multidrug-resistant VRE in their gastrointestinal tract, raising significant concerns about equine operations as a potential reservoir for transferring these resistance genes to human pathogens through environmental contamination, manure handling and indirect contact. Equine professionals should be aware that routine antimicrobial therapy—particularly with fluoroquinolones, macrolides or tetracyclines—may select for these resistant populations, and biosecurity measures around manure disposal and hand hygiene warrant closer attention in yards managing multiple horses.
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Practical Takeaways
- •Healthy horses can harbour multidrug-resistant enterococci without clinical signs, posing a zoonotic and cross-contamination risk in equine facilities
- •Vancomycin-resistant enterococci in horse populations may complicate treatment options for serious infections in both horses and humans
- •Biosecurity and hygiene protocols in stables should consider antimicrobial-resistant pathogens as a potential hidden health risk
Key Findings
- •vanA-containing Enterococcus strains were detected in healthy Lusitano horses with high-level vancomycin (MIC ≥128 mg/l) and teicoplanin resistance (MIC 64 mg/l)
- •All vanA isolates carried tet(L) and erm(B) resistance genes conferring tetracycline and erythromycin resistance respectively
- •Lusitano horse intestinal tracts represent a potential reservoir for vanA-containing enterococci