detection of three virulence genes in e.coli isolates from commercial broilers with colibacillosis and their antibiotic resistance profiles in tabriz area, iran

colibacillosis caused by e.coli is one of the most common illnesses in commercial chickens and induce high financial losses in the poultry industry due to morbidity, mortality and antibiotic expenses because of overuses. e.coli can mostly cause disease as a secondary or opportunistic pathogen, while certain strains with specific virulence factors even as primary pathogen can cause colibacillosis. the aim of this study was to detect the three virulence genes including irp2, papc, and tsh in e.coli bacteria isolated from diseased broilers in tabriz area using by multiplex polymerase chain reaction (pcr) method. the other purpose of this study was to do the in vitro drug sensitivity of the isolates using by disk diffusion method. 38 (53.5%), 25 (35.2%) and 35 (49.3%) isolates out of total 71 isolates, showed, irp2, papc and tsh genes respectively. in 16 isolates only irp2 gene, 8 isolates only papc gene, and in 13 isolates only tsh gene were detected and 12 isolates were without all these genes. in 39 isolates 2 or 3 gene were identified simultaneously. in this study most of the isolates were resistant against enrofloxacin, doxycycline, sultrim, erythromycin and danofloxacin and most of them were sensitive only to colistin and the percentage of sensitive isolates against fosfomycin, neomycin and florfenicol were 45.9%, 45.2% and 48.3% respectively. high resistance rate to most antibiotics and prevalence of some important virulence genes in apec (avian pathogenic escherichia coli ) isolates might be a serious hazard for both poultry industry and public health.