Studies of Virulence Factors of Avian Pathogenic Escherichia coli in Avian Colibacillosis by In vitro Method and PCR

Background: Avian colibacillosis is considered as major cause of morbidity and mortality in poultry. It is a common bacterial disease of poultry and many virulence factors of E. coli are associated with the disease. The current study was aimed to investigate the presence of some virulence factors of E. coli isolated from the cases of colibacillosis. Methods: In present study, total 150 samples (liver, heart, lungs, air sacs and feaces) of chicken exhibiting pathological conditions of colibacillosis were collected from various poultry farms (organized and backyard) situated in and around Mhow and Indore cities. E. coli was isolated and identified from the samples on the basis of cultural characteristics and biochemical test. All E. coli isolates were further subjected to evaluate the presence of virulence factors such as biofilm production, haemolysis, invasiveness and molecular detection of fimH and stx1 gene. Result: Out of these 51.33% of incidence of E. coli was recorded. E. coli O84 and O149 serotypes were found most prevalent. Out of 77 isolates, 46 (59.7%) and 45 (58.4%) were positive for biofilm formation by tube method and modified CRA method, respectively. All E. coli isolates were showing invasiveness in congo red binding assay while none of the isolates was found haemolytic. Molecular detection revealed the presence of fimH (508bp) gene in 33.3% of tested samples while stx1 gene could not be detected in any isolates.