Relationship between class 1 integron and resistance in EHEC

  Objective   To study the distr ibution of class 1 integron in 48 isolates(domestic 28 strains, U.S.A 20 strains) of Entero hemorrhagic E.coli(EHEC), and to explore the sort and relationship of resistance gene cassettes in integrons.Meth ods Routine method was used to isolate EHEC, serotyping; identified virulent strains by PCR; 18 kinds of antibiotics susceptibility were tested using agardilution protocol; class 1 integron was detected also by PCR assay; PCR products were sequenced and analyzed.

  Results   Of 48 EHEC strains 23 were O157:H7.The resistance status was no difference between China and U.S.A isolates except the difference in Ampicillin and Erythromycin, the former that domestic isolates(60.7%)were higherthan those of U.S.A(30%); the latter that U.S.A isolates(95%)were higher than those of China(60.7%).There were 18 isolates(U.S.A 3, China 15)resisted to at least 3 kinds of antibiotics.All EHEC strains resisted to Sulfamethoxazole timetho prim.11(U.S.A 2, China 9)of 48(22.9%)isolates carried class 1integrons; and aadA 1 gene cassette existed in 9 isolates, aa dA 2 gene cassette existed in 2 isolates.And the resistance of aminoglycoside were confered.

  Conclusion   Class 1 integron exists in the EHEC, and determines the resistance of some antibiotics.