Abstract: Two hundred and forty one strains of Escherichia coli were collected from 349 samples isolated from 292 cloacas, 29 feed and water, 28 dust and padding in recent years (107 strains from Northeast,107 from South China,12 from central China,15 from North China). The percentage of isolation is 69.1%. There are 67 types of serogroup are distributed in various areas. Each serogroup owns 1-2 strains. Some areas have preponderant groups and others do not. The drug resistance of bacteria is so serious that it shows multi-drug-resistance and varies in different areas. The strains resistant to 10-19 drugs account for the majority. The highest percentage of resistance is Nalidixic (88.1%) on the whole. The percentage of resistance of others ranked as follows: Tetracycline 85.7%, Sulfamethoxazole 81.0%, Trimethoprim-sulfamethpxazole 77.1%, Ampicillin 76.2%, Amoxilline 74.3%, Streplomycin 66.2%, Fluoroquinolones 57.1%-66.7%, Chloramphenicol 52.9%, Gentamicin 39.0%, Kanamycin 36.2%. The bacteria are sensitive to Cefalexin, Amoxilline-clavulanic acid , Amikacin and Florfenicol. The drug resistance is more severe in the chicken farm using the same drugs. This study indicates the characterization of antimicrobial-resistant Escherichia coli isolated from avian in different areas of China. It will be a basis for studying drug-resistant mechanism and restricting the use of antimicrobial in the poultry industry.

Key words: Escherichia coli, Serogroups, Antimicrobial resistance