Antimicrobial resistance in equine faecal Escherichia coli isolates from North West England

• Main Authors: Williams Nicola J, Clegg Peter D, Ahmed Mohamed O, Baptiste Keith E, Bennett Malcolm
• Format: Article
• Language: English
• Published: BMC 2010-04-01
• Series: Annals of Clinical Microbiology and Antimicrobials
• Online Access: http://www.ann-clinmicrob.com/content/9/1/12

<p>Abstract</p> <p>Background</p> <p><it>Escherichia coli </it>isolates of equine faecal origin were investigated for antibiotic resistance, resistance genes and their ability to perform horizontal transfer.</p> <p>Methods</p> <p>In total, 264 faecal samples were collected from 138 horses in hospital and community livery premises in northwest England, yielding 296 resistant <it>E. coli </it>isolates. Isolates were tested for susceptibility to antimicrobial drugs by disc diffusion and agar dilution methods in order to determine minimum inhibitory concentrations (MIC). PCR amplification was used to detect genes conferring resistance to: ampicillin (TEM and SHV beta-lactamase), chloramphenicol (<it>catI, catII, catIII </it>and <it>cml</it>), tetracycline <it>(tetA, tetB, tetC, tetD, tet E </it>and <it>tetG</it>), and trimethoprim (<it>dfrA1, dfrA9, dfrA12, dfrA13, dfr7</it>, and <it>dfr17</it>).</p> <p>Results</p> <p>The proportion of antibiotic resistant isolates, and multidrug resistant isolates (MDR) was significantly higher in hospital samples compared to livery samples (MDR: 48% of hospital isolates; 12% of livery isolates, p < 0.001). Resistance to ciprofloxacin and florfenicol were identified mostly within the MDR phenotypes. Resistance genes included <it>dfr</it>, TEM beta-lactamase, <it>tet </it>and <it>cat</it>, conferring resistance to trimethoprim, ampicillin, tetracycline and chloramphenicol, respectively. Within each antimicrobial resistance group, these genes occurred at frequencies of 93% (260/279), 91%, 86.8% and 73.5%, respectively; with 115/296 (38.8%) found to be MDR isolates. Conjugation experiments were performed on selected isolates and MDR phenotypes were readily transferred.</p> <p>Conclusions</p> <p>Our findings demonstrate that <it>E. coli </it>of equine faecal origin are commonly resistant to antibiotics used in human and veterinary medicine. Furthermore, our results suggest that most antibiotic resistance observed in equine <it>E. coli </it>is encoded by well-known and well-characterized resistant genes common to <it>E. coli </it>from man and domestic animals. These data support the ongoing concern about antimicrobial resistance, MDR, antimicrobial use in veterinary medicine and the zoonotic risk that horses could potentially pose to public health.</p>