Molecular characteristics of class 1 and class 2 integrons and their relationships to antibiotic resistance in clinical isolates of Shigella sonnei and Shigella flexneri
Molecular characteristics of class 1 and class 2 integrons and their relationships to antibiotic resistance in clinical isolates of Shigella sonnei and Shigella flexneri
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DOI：
10.1093/jac/dkl228
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发表时间：
2006-08-01
影响因子：
5.2
通讯作者：
Liu, Ke-Zhou
中科院分区：
文献类型：
--
作者：
Pan, Jing-Cao;Ye, Rong;Liu, Ke-Zhou
目的：分析宋内氏志贺氏菌(31株)和福氏志贺菌(33株)耐药株的基因盒，确定1类和2类整合子的作用。方法：采用聚合酶链式反应和Southern-blotting等多种分子标记技术，对杭州、中国分离的宋内氏志贺菌和福氏志贺菌的1类和2类整合子标记进行分析。通过DNA测序和/或限制性片段长度多态性鉴定整合子中的基因盒阵列。将来自福氏志贺氏菌的两个基因组DNA片段克隆到pUC19载体中，并对其进行了测序。结果：80.6%(25/31)的宋内氏葡萄球菌和87.9%(29/33)的福氏志贺氏菌存在2类整合子。所有这些整合子2阳性的菌株都含有dfrA1+SAT1+AADA1的恒定基因盒阵列，这些基因盒阵列使其对甲氧苄啶和链霉素产生耐药性。结果表明，志贺氏菌中2类整合子位于GLMS下游attTn7基因的Tn7区域。志贺菌中有9.4%(6/)存在1类整合子。分离株。84.9%(28/33)的福氏志贺氏菌中存在一种非典型的1类整合子，称为志贺氏菌非典型1类整合子(SAI)，在志贺氏菌的染色体上没有3‘-保守区。SAI含有blA(OXA30)和aadA1两个基因盒，但在大肠杆菌宿主中，SAI对氨苄西林产生抗性，而对链霉素不产生抗性。结论：志贺氏菌在进化过程中形成了多种复杂的机制，涉及1类和2类整合子中可移动的遗传元件和抗生素耐药性。
Objectives: To analyse the gene cassettes and determine the roles of class 1 and class 2 integrons in antibiotic-resistant strains of Shigella sonnei (n = 31) and Shigella flexneri (n = 33).Methods: Various molecular techniques, including PCR and Southern-blotting analysis, were used to analyse various markers of class 1 and class 2 integrons in these 64 S. sonnei and S. flexneri isolates collected in Hangzhou, China. The gene cassette arrays in integrons were identified by DNA sequencing and/or restriction fragment length polymorphism. Two genomic DNA fragments, one containing intl1 from a S. flexneri isolate that contains intl1 but lacks 3'-conserved region and another containing intl2 from a S. sonnei isolate, were cloned into pUC19 vectors and sequenced. The links between integron gene cassette arrays and antibiotic resistance were analysed.Results: Class 2 integrons were present in 80.6% (25/31) of the S. sonnei isolates and 87.9% (29/33) of the S. flexneri isolates. All of these integron 2-positive isolates contained constant gene cassette arrays of dfrA1 + sat1 + aadA 1 which confer resistance to trimethoprim and streptomycin. It was demonstrated that the class 2 integron was located in the Tn7region inside the attTn7 locus downstream of glmS in Shigella. Class 1 integrons were found in 9.4% (6/64) of Shigella spp. isolates. An atypical class 1 integron without a 3'-conserved segment on the Shigella chromosome, termed Shigella atypical class 1 integron (SAI), was present in 84.9% (28/33) of S. flexneri isolates. The SAI contained two gene cassettes, bla(OXA30) and aadA1; however, the SAI conferred resistance to ampicillin, but not to streptomycin, in Escherichla coli host. The bla(OXA30) and aadA1 cassettes of the SAI seemed to be always coordinately excised or integrated.Conclusions: Multiple and complex mechanisms involving mobile genetic elements in class 1 and class 2 integrons and antibiotic resistance have been developed in the evolution of Shigella strains.