Abstract: In order to understand the drug resistance of Escherichia coli (E.coli) in sheep in Naqu city,Tibet,and to guide clinical rational drug use,92 fresh non-polluting diarrhea samples were collected from sheep in Naqu city,Tibet,and were separated by colour medium of E.coli,examined by Gram staining microscopy,biochemical identification,molecular biological identification and biochemical identification of diarrhogenic E.coli,drug sensitivity test and drug resistance gene detection.The results showed that the isolates were blue colony and pink brevibacterium on the colour medium of E.coli.26 strains of E.coli from sheep were isolated by biochemical identification and PCR detection of 23S rRNA,the isolation rate was 28.3%,25 strains of which accorded with the biochemical characteristics of diarrhogenic E.coli,and the isolation rate of diarrhogenic E.coli was 27.2%.Drug susceptibility test showed that 25 strains of sheep-derived E.coli were resistant to ampicillin with a resistance rate of 24.0%,followed by carboxybenicillin and kanamycin with a resistance rate of 8%,piperacillin,cefuroxime,gentamicin,tetracycline and minocycline with a resistance rate of 4%.Drugs such as norfloxacin,oxygen,floxacin and ciprofloxacin were very sensitive and could be used as clinical drugs.The detection rate of bla_TEM gene was 100% in 5 drug-resistant genes,which indicated that all isolates contained corresponding drug-resistant genes.The above results showed that there was resistance to many drugs in E.coli isolated from sheep in Naqu,Tibet,suggesting that rational drug use and combined drug use should be emphasized in clinical practice to slow down the emergence of drug resistance of E.coli.

Key words: sheep; E.coli; isolation and identification; drug susceptibility test; drug resistance gene