In the past, the horizontal transfer of antimicrobial resistance genes was mainly associated with conjugative plasmids or transposons, whereas transduction by bacteriophages was thought to be a rare event. In order to analyze the likelihood of transduction of antimicrobial resistance in the field of clinical veterinary medicine, we isolated phages from Escherichia coli from a surgery suite of an equine clinic. In a pilot study, the surgery suite of a horse clinic was sampled directly after surgery and subsequently sampled after cleaning and disinfection following a sampling plan based on hygiene, surgery, and anesthesia. In total, 31 surface sampling sites were defined and sampled. At 24 of these 31 surface sampling sites, coliphages were isolated. At 12 sites, coliphages were found after cleaning and disinfection. Randomly selected phages were tested for their ability of antimicrobial resistance transduction. Ten of 31 phages were detected to transfer antimicrobial resistance. These phages most often transduced resistance to streptomycin, encoded by the addA1 gene (n = 9), followed by resistance to chloramphenicol by cmlA (n = 3) and ampicillin (n = 1). This is, to the best of our knowledge, the first report on antimicrobial resistance-transferring bacteriophages that have been isolated at equine veterinary clinics.
Keywords: Escherichia coli; antimicrobial resistance; equine; phage; surgery.