Molecular Characterization of Enterohemorrhagic Escherichiacoli Isolates from Cattle

[摘要] References(37)A total of 21 (4.3%)enterohemorrhagic E. coli strains were isolated by biochemical tests andidentification of the eae+stx1+stx2+genotype from 490 stool samples obtained from calves with diarrhea during 1-year periodfrom a major farm in Tehran, Iran. All of the strains showed resistance to ampicillin,ciprofloxacin, trimethoprim, streptomycin, chloramphenicol and tetracycline, while 19%showed resistance to gentamicin. Out of 21 EHEC strains, 11 (53%) harbored class 1integron. Two different amplification products, which were approximately 750 and 1,700 bpin size, were obtained from amplified variable regions(in-F/in-R primers) in 3 (14.3%) and 4 (19%) of theEHEC isolates, which corresponded to dfrA7(dihydrofolate reductase typeI) and dfrA1/aadA1(dihydrofolatereductase/aminoglycoside adenyltransferase) resistance gene cassettes, respectively, andthis was confirmed by sequencing. Genotyping analysis revealed a total of 16 pulsotypesthat corresponded to 16 isolates with the similarity indices of 62% and 30% for the mostand least similar isolates, respectively, 9 of which harbored class 1 integron. Analysisof pulsotypes showed an extensive diversity among the isolates harboring integron, whichis indicative of a lack of any significant genetic relatedness among the isolates. Noobvious relation could be deduced between integron content and special pulsotypes. Thelittle data available on the genotyping patterns of EHEC isolates from cattle and theirresistance gene contents emphasize the need to establish genotyping databases in order tomonitor and source track the source of emergence and spread of new resistant andintegron-carrying genotypes.

[学科分类] 兽医学

[关键词] enterohemorrhagic E. coli;integrin;PFGE