Pathogenicity of Escherichia coli O157 in commercial broiler chickens

Broiler chickens are frequently infected with Escherichia coli (E. coli), which often results in disease and high economic losses. The most affected ages to infections with E. coli are chickens from 4 to 5 weeks. Several studies show that poultry are already and persistently infected by E. coli O157. The current study aimed to determine the pathogenicity of E. coli serogroup O157 in broiler chicks, a trial of prevention and treatment using probiotic and/or antibiotic. The chicks were divided into five groups including control negative, control positive, probiotic treated group, probiotic and antibiotic treated group and finally antibiotic treated group. The clinical signs, mortality, performance parameters, postmortem examination, re-isolation and E. coli count as well as the pathological changes in liver and intestine were recorded. The probiotic group gave the best results in controlling infection by E. coli O157 followed by probiotic and antibiotic and finally antibiotic. In conclusion, the E. coli O157 serogroup was pathogenic to chicks when experimentally inoculated, so particular attention must be directed toward E. coli O157 not only as a pathogen infecting bird but also of great public health impact. Also probiotics was of great value in protection against the E. coli infection and improve the performance parameters of chicks.