The prevalence of escherichia coli o157 in broilers and molecular typing by pulsed field gel electrophoresis (PFGE)

This study was carried out to investigate the presence of Escherichia coli (E. coli) O157 in various samples collected from broiler chickens by culture and Immunomagnetic seperation (IMS). In addition, the isolates were subjected to molecular characterization in order to determine the presence of virulence genes and were then subtyped by Pulsed Field Gel Electrophoresis (PFGE) method to reveal the genotypic relationships between the strains.For this purpose, liver and caecum samples collected from 1000 broilers and carcass samples obtained from another 1000 broilers which slaughtered at three different abattoirs located in Malatya and Elazig provinces were examined. Also, faecal samples provided from 367 humans with diarrhea, who applied to five different hospitals in the region, were examined in order to reveal genetic relationships between broiler and human E. coli O157 isolates. While all the samples collected from broilers and humans were subjected to direct cultivation, caecum and human fecal samples were also examined by the combination of Immunomagnetic separation (IMS) and culture.In the Polymerase Chain Reaction (PCR) analysis of sorbitol negative isolates, E. coli O157 was identified from 0.1% (1/1000) and 0.4% (4/1000) of the liver and caecum samples of broiler chickens, respectively. In overall, the agent was detected in 0.5% (5/1000) of internal organ samples of broilers. On the other hand, none of the carcass samples were determined to be positive for E. coli O157. The percentage of 2.7% (10/367) was obtained in the PCR examination of human faecal samples.When the results were assessed at flock base, the identification percentage of E. coli O157 was calculated as 12% (3/25). Of the positive flocks, one was located in Malatya and the other two were in Elazig. The positivity rates within these flocks were detected as 2% (1/50), 4% (2/50) and 6.7% (2/30), respectively. The difference between the flocks in terms of the positivity rates were determined to be statistically significant (p<0.001).The PCR analysis specific for virulence genes showed that none of the broiler (n=5) and human (n=10) E. coli O157 isolates possessed H7, shigatoxins 1-2, and enterohemolysin genes, whereas all the broiler isolates and one of the human isolates were positive for intimin gene.In the PFGE analysis, a total of eight different profiles (four from broiler and four from human isolates) were observed. However, there were no genetic relationships between broiler and human E. coli O157 isolates which suggest that broilers do not play significant role in the transmission of infection to humans.In conclusion, this study showed that E. coli O157 was isolated from broilers. It is therefore plausible to suggest that in addition to ruminants, avian species, especially chickens, should be considered for the better understanding of the epidemiology of E. coli O157 infection. This will help develop more effective control strategies against infections and outbreaks due to E. coli O157.