Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2018

Molecular characterization of fluoroquinolone-resistant avian pathogenic Escherichia coli isolated from diseased chickens in Thailand (#381)

Thotsapol Thomrongsuwannakij 1 , Niwat Chansiripornchai 1
  1. Department of Veterinary Medicine, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand

Avian pathogenic Escherichia coli (APEC) is the causative agent of colbacillosis in poultry causing economical losses in this industry worldwide. Eighty-four isolates of APEC isolated from diseased chickens in Thailand were examined for their antimicrobial susceptibility. Thirty-four isolates, which were resistance to nalidixic acid or enrofloxacin, were characterized for their mechanisms of fluoroquinolone resistance. In total, isolates demonstrated resistance to tetracycline (84.52%), amoxicillin (70.24%), doxycycline (64.29%), trimethoprim-sulfamethoxazole (51.19%), nalidixic acid (40.48%), enrofloxacin (30.95%), chloramphenicol (28.57%), and gentamicin (9.52%). Twenty-nine isolates contained a mutation in gyrA of a serine at position 83 to a leucine (Ser-83-Leu), and 23 isolates contained a mutation of Asp87 to one one of three amino acids: Asn (n=18), Tyr (n=4) or Gly (n=1). No mutation was found in gyrB. Eighteen isolates contained a mutation in parC of a Ser80 to an isoleucine, and an isolate contained a mutation of Ser87 to an arginine. Furthermore, other point mutations were also found in parC such as Ala-56-Thr (n=1), and Glu-84-Gly (n=1). Six isolates contained a mutation in parE including Ser-458-Ala (n=4), Asp-475-Glu (n=1), and Ile-464-Phe (n=1). In conclusion, the high-level fluoroquinolone resistance in APEC has a correlation with high numbers of mutations in quinolone resistance-determining region (QRDR).