健康畜禽肠道大肠杆菌耐药性及整合子-基因盒检测

采用微量肉汤稀释法检测455株大肠杆菌对24种抗菌药物的敏感性；多重PCR检测菌株Ⅰ、Ⅱ、Ⅲ型整合酶基因；采用PCR-RFLP和PCR-测序法对整合子-基因盒进行序列分析。结果显示，455株菌除对头孢唑啉、头孢曲松、头抱噻呋和阿米卡星耐药率低于40％外，对其余药物表现出高耐药率，99．23％菌株呈多重耐药性；455株菌Ⅰ型整合子阳性率87．69％，Ⅱ型整合子1．98％，未检出Ⅲ型整合子；随机选取的204株整合子阳性菌中174株（85．29％）扩增出了基因盒可变区。基因盒主要以编码氨基糖苷腺苷基转移酶和二氢叶酸还原酶的aadA、dfrA基因为主，耐药基因排列成Ⅰ型整合子8种基因盒，Ⅱ型整合子3种基因盒。Ⅰ型整合子以dfrA1-aadA1（32．76％）基因盒为主，其次是aadA22（24．14％）和dfrA17-aadA5（24．14％）。Ⅱ型整合子以d厂rA1-sat2-aadA1（66．67％）为主，Ⅱ型整合子阳性菌含有I型整合子-基因盒；菌株含整合子-基因盒越复杂，其多重耐药性越严重。结果表明，本次分离的健康动物肠道大肠杆菌耐药非常严重，整合子-基因盒分布广泛，已成为耐药基因储库，对耐药基因扩散起重要作用。

Detection of resistance and characterization of integron-cassettes in Escherichia coli from intestinal tract of healthy food-animals,enteric strains

To detect resistance and the distribution of integron-cassettes in E. coli strains from healthy food-animals intestinal tract. Susceptibility to 24 antimicrohial agents was tested by the broth microdilution method;the incidence in 3 classes of integrons （intI I , intI II , intI HI ） were examined by multi-PCR; the characterizations of integron-cassettes were assayed by PCR-RFLP and PCR-sequencing. The results showed that 455 strains had highly resistant rates （〈40%） against 20 agents excluding cephazoline, ceftriaxone, ceftiofier and amikacin, and 99. 23% of all strains harboured multi-resistance;87.69%,1. 98% and 0% of 455 strains were positive for intI I ,intI II and intI III,respectively;Among 204 strains selected randomly,173 （85.29%） carried gene cassettes,which encoded aminoglycoside adenyltransferase （aadA） and dihydrofolate reductase （dfrA）. The 8 and 3 cassette arrays were found within intI I and intI II , respectively. The most prevalent cassette arrays were dfrAl-aadA1（32.76 % ）, aadA22 （24.1%） and dfrA17- aadA5（24.14%） in intI I , while dfrA1-sat2-aadA1（66. 67%） was main array in intI II ; the strains,which had more complicated integron-cassette systems, showed more serious resistance. The conclusions are that E. coli strains isolated from healthy fo0d-animal are seriously resistant to antimicrobial agents,and integron-cassettes are widely existed beyond expectation. It implied that the common strains had become important resistant gene pool to provide resistant genes for frequent exchange.