Isolation, Identification And Study On Durg Resistance Of Pathogenicity Estherichia Coli From Large-scale Duck Farms

272 strains of virulent E.coli were isolated from the disease 5-35 days-old ducklings from 13 large-scale dack farms in the contiguous areas of Sichuan and Chongqing since 1999 .Results of animal experiment shows that all the strains have strong pathogenicity. Among the E. coli isolates, serogroups of 213 strains were determined while 52 strains were not serogroupable. 29 kinds of O serogroups were discovered in these isolated strains and predominant types were O₇6,O₇8,O₉2,O₉3,O₁49, and O₁42,which were accounted for 41.89 percents of the total serogroups. O₅1,O₅9,and O₇9,have not been reported in China. There were a great of differences in 0 serogroups between different areas. The kind of 0 serogroups in MianYang was the most, which was up to 11.The second area is GuangHan, and its kind of 0 serogroups was 8.The drug sensitivity to 33 antibioties were performed for the 113 isolated strains. The results show that these E. coli strains existed wild-ranging drug resistance and multi-resisitance was principal. The resistance spectrum of isolations varied to 21 kinds of the drugs. The most numbers of drugs to which strains were resistant were 13, 15, 11, 7,9,12, which strains were more than 53 percent. The most sensitive drug to the E. coli strains were Cephalosporin, Amikacin, Tobramycinn, Aztreonam, Spectinomycin, Netilmicin, Imipenem and Gentamicin ,which frequencency of resistance is under 20% .But the very low sensitive drug were Ampicillin, Tetracycline, Deoxycycline, Nalidixic and Rifampicin, which frequencency of resistance is up to 80%. The frequency of resistance increased from 1999 to 2005. which was from 41. 2% to 60. 2% for NOR, 51% to 80% for PIP, 6.8% to 20% for CKM.