Abstract: Fourty-four strains of escherichia colifrom chickens were isolated from cases that were suspected to be escherichia coli, and the pathogen's characteristics were identified. It was found that the biochemical characters of these bacteria were fundamentally identical and agreed with documents. Moreover, the serotypes of 39 isolates were identified. Thirteen types of serum O were found out, among which O₇₈,O₃₅,O₂₄,O₁,O₁₅,O₇₆ and O₈₈were main serotypes with a 84.6% of all the isolates. The dominant serotype of these isolates was O₇₈with a 38.5% of all the isolates. Antibiotic resistance of 44 strains escherichia coli to nine antimicrobial drugs (Cefazolin,Gentamicin,Amikacin,streptomycin,Ciprofloxacin,Norfloxacin,Penicillin,Tobramycin,Erythromycin) was detected and analyzed by disk diffusion susceptibility test. The results indicated that the isolates showed a greater or lesser degree resistance to nine antimicrobial drugs. Most isolates showed resistance to multiple antibiotics and displayed a highest level resistance to Penicillin and Erythromycin with a frequency of 97.7%,followed by Ciprofloxacin with a frequency of resistance of 81.8%.While most isolates displayed a higher level susceptibility to Amikacin, Tobramycin and Gentamicin,especially to Amikacin with a frequency of 90.9%.

Key words: chicken; escherichia coli; separation and appraisal; serotype; drugs susceptibility test