Prevalence, molecular characterization and antimicrobial resistance of necrotoxigenic Escherichia coli in diarrhoeic buffalo calves

A study was carried out to investigate the prevalence, molecular characterization and antibiotic resistance pattern of Necrotoxigenic E. coli (NTEC) isolates from diarrhoeic buffalo calves in Andhra Pradesh (AP) and Telangana States (TS). A total of 375 faecal samples from diarrhoeic buffalo calves of 1 to 90 days old were collected from various districts in AP and TS, from which 302 E. coli strains (80.53%) were isolated. The cnf2 gene was detected by PCR and in vitro antimicrobial susceptibility was tested by disk diffusion methods. The prevalence of E. coli associated diarrhoea in buffalo calves was 85.04%, of which 11.26% was due to NTEC based on the presence of cnf2 gene. The NTEC pathotypes showed highest antimicrobial resistance of 55.88% to tetracycline followed by ampicillin (52.94) and aztreonam (41.18), while chloramphenicol (2.94%) and imipenem antibiotics were effective. The present study revealed that diarrhoeic buffalo calves are the important reservoirs of NTEC, which may pose a serious threat to human health in this geographic region.