Abstract

Bacterial resistance to antimicrobial agents is a phenomenon problem, and the understanding of resistance acquisition and transmission can contribute to the development of new strategies to the clinical and socio-economic implication of this phenomenon, especially in ruminant animals. A total of 327 fecal samples of ruminant animals were examined for E. coli O157:H7/NM and the antibiotic susceptibility testing was determined by disc diffusion according to the Clinical Laboratory Institute. Isolates were tested for susceptibility to antimicrobial drugs by the Kirby-Bauer disc diffusion method using MÏ‹ellar-Hinton agar according to the Clinical Laboratory Standards Institute. Twenty-five (7.6%)Escherichia coli O157:H7/NH were isolated, 24(96%) were resistant to one or more antibiotic agent. Six (24%) E. coli were resistant to one antibiotic agent, 11(44%) to two agents and 28% exhibited multi drug resistance. Gentamycin resistance phenotype was the most common (56.0%), followed by ampicillin (48.0%), erythromycin (40.0%), amoxicillin (16.0%), tetracycline (12.0%), chloramphenicol (8.0%) nalidixic acid (8.0%), and streptomycin (4.0%) and all E. coli O157 isolates were susceptible to cefuroxime. Considering the clinical implication of E. coli in veterinary medicine, surveillance of the bacterial pathogens became imperative for better understanding and infection control approach.

Key words: Escherichia coli O 157, ruminant feces, antibiotic resistance, Iran.