Determination of invasiveness and antibiotic resistance pattern of avian pathogenic Escherichia coli isolated from broilers

Abstract

Diseases of poultry caused by Escherichia coli are of economic importance in the poultry industry. The organism is responsible for 30–40% mortality in broiler industry and the losses due to weight loss and poor carcass quality do not taken into consideration when the birds are infected with avian pathogenic E. coli (APEC). In this investigation Escherichia coli was isolated from moribund birds with different pathological conditions, characterized and studied the antibiotic resistance pattern of different serotypes and in-vitro pathogenicity. Serotyping of these isolates revealed 36 ‘O’ serotypes, 15 un-typable strains and 1 rough isolate. The most frequently occurring serotypes were O2, O157, O17, O89, O153, and O132. The in-vitro pathogenicity was also conducted using Congo red binding assay and hemolytic tests. The results showed that 86% of the isolates were Congo red positive while none of isolate was found haemolysin positive. In vitro antibiotic activities of 15 antibiotic substances against the isolates were determined by disc diffusion test. Multiple resistances to antibiotics were observed in all the isolates. Antibiogram profiles indicated maximum resistance to erythromycin (90%) followed by neomycin (80%) enrofloxacin (76%) oxytetracycline (75%), cotrimoxazole (75%) and cephalexin (74%). Highly sensitive was found towards chloramphenicol (89%), ciprofloxacin (85%) and norfloxacin (76%). All strains were susceptible to ampicillin. It is concluded that the CR binding assay could be used as a phenotypic marker to distinguish between invasive and non invasive isolates.