| Summary: | 碩士 === 國立臺灣大學 === 獸醫學研究所 === 88 === The aims of this study were first to establish the screening procedure for the identification of Escherichia coli O157:H7 (E. coli O157:H7) from bovine feces, and then to apply the procedure for the detection of dairy herds in Taiwan. Fresh bovine fecal specimens were collected by fecal swabs. Modified trypticase soy broth was selected for sample enrichment, and then the enriched suspension was plated on cefixime-tellurite sorbitol MacConkey agar (CT-sMAC). Pale gray to colorless colonies were picked and succeeded plated on CT-sMAC again for the further confirmation of the colony. Purified bacterial strains were then identified by API and relative biochemical tests to confirm the E. coli strains. Somatic antigen O157 was tested by slide agglutination, and those positive results were identified for the production of verocytotoxin I & II, and also H7 antigen serotyping. The genome characteristics of the bacterial strains were further confirmed by polymerase chain reaction. Modified bovine fecal samples with the known amount and strains of E. coli O157 were used for the evaluation during establishing the procedure. The detection limit of the procedure was 0.850.50 CFU/g. In field sampling, three thousand and sixty-two bovine fecal samples were collected from 78 dairy herds in Hualien county and Northern part of Taiwan. The results indicated that only 2 herds (2.56 %) with 4 (0.13 %) different dairy cows were positive, and four E. coli O157 strains were isolated. Different strains from different isolated herds were noted. Thus, two different bacterial strains were found in this survey. One strain had the ability to produce verocytotoxin II with the titer of 1:32, but not for another one. Genetic mapping of the two isolated strains had 96 % similarity, and it was 88.5 % with the strain isolated from Southern part of Taiwan. Thus, geographical differences were marked. The antibiotic profiles of the two isolated strains showed no statistical difference as well as other reference strains. We concluded that no specific drug resistance performance within these new isolated E. coli O157 strains.
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