A team of researchers in Liverpool have discovered that bacteria in a horse’s intestine appear to acquire antibiotic resistancewhile a horse is hospitalised.
The researchers, from the Philip Leverhulme Equine Hospital, found a significant increase in multiple drug resistance in E. coli samples isolated from horses’ faeces after a period of hospitalisation.
The research was led by Adele Williams, who had received funding from equine charity The Horse Trust. Ms Williams carried out the research while undergoing a Horse Trust-funded clinical training programme in equine internal medicine at the University of Liverpool.
Ms Williams et al collected faecal samples from randomly selected horses at Philip Leverhulme Equine Hospital over an 18 month period between 2006 and 2008.
Faecal samples were collected when the horse was admitted, and again after the horse had been hospitalised for seven days. The selected horses included horses treated and not treated with antibiotics before and during hospitalisation.
E. coli bacteria cultured from the samples were tested for their sensitivity to eight antibiotics (neomycin, ampicillin, ceftiofur, gentamicin, chloramphenicol, ciprofloxacin, tetracycline and trimethoprim) using the Kirby-Bauer disk diffusion method. The antibiotics chloramphenicol and tetracycline are not used at the hospital.
The researchers found a significant increase in resistance during the week’s hospitalisation for seven of the eight antibiotics; no significant difference was found for neomycin. Antibiotic resistance increased even in horses not treated with antibiotics and to antibiotics that are not used in the hospital.
This increase may be due to the transfer of antibiotic resistant genes as a result of selection pressure for antibiotic resistance in the hospital environment, or it may be because the number of resistant E. coli is greatly increased due to selective pressure so that they are much easier to detect, or that resistant isolates have been acquired from the environment.
Further research is needed to understand the source of antibiotic resistance in the environment.
Ms Williams said: “Pathogenic bacteria are likely to be exposed to the same selection pressures or could receive the same resistant genes, so it is vital we improve hygiene in equine hospitals and reduce the overuse of antibiotics. People who work in equine hospitals need to pay strict attention to hygiene and should reserve antibiotics for essential cases only.”