A study on the presence of some potential virulence genes and quinolone resistance in avian pathogenic Escherichia coli isolated from chickens in Northeast of Iran

BACKGROUND: Avian pathogenic Escherichia coli (APEC),which is the causative agent of colibacillosis, harbors severalputative virulence genes. An important trait of APECfor both poultry and public health is antibiotic resistance.OBJECTIVES: In the present study, some potential virulencegenes of APECs isolated from Northeast of Iran and their resistanceto the quinolones antibiotics were studied. METHODS:The conventional polymerase chain reaction (PCR) was used todetermine the presence of four virulence genes, including iss,cvi, iuc, and tsh, in 52 isolates of E. coli from avian colibacillosisand 11 isolates from feces of apparently healthy chicken.Disk diffusion method was used to also determine the resistanceof all the isolates against nalidixic acid, norofloxacin,ciprofloxacin, and enrofloxacin. RESULTS: The presence of issand tsh virulence genes in isolates from diseased chickens wassignificantly higher than isolates from healthy chickens. Therewas no significant difference between APEC and fecal E. coliwhen it comes to quinolone resistance. However, cvi and iucgenes were significantly higher in susceptible isolates of E. colifrom healthy chickens. CONCLUSIONS: iss and tsh genes aremore prevalent in APEC isolates than in fecal isolates. Thereis no association between lack of virulence and resistance toquinolones in E. coli isolates from diseased chickens.

Keywords:

avian pathogenic Escherichia coli (APEC) , colibacillosis , quinolone resistance , virulence genes