Investigation of the important virulence genes and antibiotic resistance of escherichia coli's isolated from broiler

Colibacillosis induced by poultry pathogenic Escherichia coli (APEC) occurs when virulence factors that are encoded by specific genes that promote adhesion and proliferation of E. coli in the host. The aim of this study was to investigate the virulence genes encoding siderophores (iucD, iroN, iutA), toxins (astA, vatA, hlyF), adhesins (papC, tsh), serum resistance (iss, ompT) and colicin (colV) APECs isolated from broiler internal organs by polymerase chain reaction (PCR) and antibiotic resistance of isolates by disc diffusion method. The isolates carrying at least five VG were clinical APEC (cAPEC), whereas those carrying less VG were potentially APEC (pAPEC) and isolates resistant to at least three or more classes of antimicrobial agents were evaluated as multiple antibiotic resistant (MDR). Chi-Square (χ2) test was used to compare the frequency of VGs between cAPEC and pAPEC, P ≤ 0.05 was considered as significant. A hundred forty (80.1%) APEC were isolated from 173 broilers. At the end of the study, 86 (61.4%) of the 140 isolates were cAPEC, 54 (38.6%) were pAPEC and these isolates had 47 virulence genotypes. iss (78.6%), iutA (75.7%), iroN (68.6%), hylF (61.4%), ompT (60.0%) genes were the highest detected genes. Other genes investigated; iucD (40.0%), tsh (27.1%), colV (25.7%), papC (21.4%), vatA (8.6%), astA (4.3%) were detected at lower frequencies. The χ2 test showed that the distribution of all virulence genes between cAPEC and pAPEC strains was important. All isolates were found to be high level resistant to amoxicillin, trimethoprim sulfamethoxazole, amoxicillin clavulanic acid and ciprofloxacin and 90.0% had MDR. It was concluded that having more than one iron transport system plays an important role on APEC survival, the examination of virulence genes by PCR method is more practical than pathogenicity test and development of VG-based diagnostic methods that characterize virulence genotypes may be useful for future vaccine studies.