닭 대장균의 특성에 관한 연구 II. 약제내성 양상, 전달성 R plasmid의 분포 및 비적합성군, Colicin산생 및 Col Plasmid의 전달, 혈구응집능

Studies on characterization of avian escherichia coli 2. Antimicrobial Drug Resistance Pattern, Distribution and Incompatibility Group of Transferable R plasmid, Colicin-producing Ability and Transfer of Col plasmid, and Hemagglutination Activity

Escherichia coli strains isoloated from chicken with colibacillosis were tested for minimum inhibitory concentration(MIC) of antimicrobial drugs, resistance pattern, distribution and incompatibility group of transferable R Plasmid, colicin-Producing ability and transfer of Col Plasmid, and hemagglutination activity. The ranges of MIC against 346 Escherichia coli strains were 2 to 16㎍/ml in nalidixic acid(Na), 1 or less to 256㎍/ml in gentamicin(Gm) and tetracycline(Tc), and 1 or less to more than 512㎍/ml in streptomycin(Sm), sulfadimethoxine(Su), ampicillin(Am), chloramphenicol(Cm), kanamycin(Km), colistin(CI), and rifampicin(Rf). Concentrations of drugs to inhibit 90% of strains tested(MIC90) were 2-32㎍/ml in CI, Rf, Gm, and Na, respectively, while MIC75 were 256- 512㎍/ml in the other drugs. Fifty percent of them were inhibited at the concentration of 8㎍/ml or less in Am, Cm and Km, respectively. Of 346 strains. 94.2% were resistant to one or more drugs, and 53 different resistance patterns were noted. The most frequent pattern was Ts Sm Su (13.8%). Two hundred and forty one (73.9%) of 326 resistant strains possessed transferable R plasmid, and Tc-resistance pattern (17.0%) was most frequently found among R plasmid observed. The number of strains with transferable R plasmid increased, as the number of resistant drugs increase. Transferability of Cm (88.6%) or Am (78.9%) resistance was higher than that of the other drugs (50-55.7% ) in resistant strains. Four R plasmids from 3 strains selected randomly were tested for the incompatibility group, and all of them belonged to Inc N. Of 346 strains. 50.6% produced colicin to inhibit indicator strain, and the colicin-producing ability of 30.6% out of colicin-positive 72 strains which possessed transferable R plasmid was transferred to recipient strain of E. coli ML1410. Hemagglutinating (HA) activity was found in 75.7% of the 346 stains from diseased chicken, and in only 26.2% of the 65 strains from SPF-healthy chicken, Eleven different HA patterns were noted, and among them, the most frequent HA pattern was that(62.4%) of strains agglutinated erythrocytes of chicken, guinea-pig and rabbit, simultaneously.