Area de Bioquímica y Biología Molecular, Universidad de La Rioja, Logroño, Spain.
Vet Microbiol. 2010 Aug 26;144(3-4):493-7. doi: 10.1016/j.vetmic.2010.01.026. Epub 2010 Feb 4.
To study the frequency and diversity of class 1 integrons lacking the 3'-conserved segment (CS) in intI1-positive Escherichia coli isolates of different origins.
The presence of intI1 was previously detected in 84 E. coli isolates of food (21 isolates), animal (32) and healthy-human volunteer (31) origins. The qacEDelta1-sul1 genes were analyzed by PCR and those isolates that lacked these genes were included in this work. The genetic structure of class 1 integrons was determined, using the PCR and sequencing primer-walking strategy. Isolates and plasmids were typed.
Class 1 integrons lacking the 3'-CS were found in 13 of the 84 intI1-positive E. coli isolates (15.5%) of food, animal, and human origins. All 13 isolates showed unrelated patterns by REP-PCR. The following gene cassette arrangements were identified inside the class 1 integrons of these 13 strains: dfrA1; dfrA5; dfrA12-orfF-aadA2-cmlA1-aadA1-qacH-IS440-sul3; dfrA12-orfF-aadA2-cmlA1-aadA1-IS440-sul3; estX-psp-aadA2-cmlA1-aadA1-qacH-IS440-sul3; and a new arrangement estX-psp-aadA2-cmlA1Delta-IS1294-DeltacmlA1-aadA1-qacH-IS440-sul3 that contain the IS1294 into the cmlA1 gene (included in GenBank, number EU704128). Complete or truncated mef(B) gene was detected upstream of sul3 gene in this type of integrons. Plasmids were identified in four of the studied strains by PCR-replicon-typing, detecting different combinations of IncY, I1, FIC, FII, FIB plasmids. Non-classic integrons were located into plasmids of 100-150 kb in four studied strains.
Occurrence and diversity of class 1 integrons lacking 3'-CS among the studied intI1-positive E. coli isolates of different origins were relatively high. The sul3 gene was detected in most of class 1 integrons lacking 3'-CS.
研究不同来源的 intI1 阳性大肠杆菌分离株中缺乏 3'-保守片段（CS）的 1 类整合子的频率和多样性。
先前已在 84 株食源（21 株）、动物源（32 株）和健康人类志愿者源（31 株）的大肠杆菌分离株中检测到 intI1。通过 PCR 分析 qacEDelta1-sul1 基因，将缺乏这些基因的分离株纳入本研究。使用 PCR 和测序引物行走策略确定 1 类整合子的遗传结构。对分离株和质粒进行分型。
在 84 株 intI1 阳性大肠杆菌分离株中，有 13 株（15.5%）来自食品、动物和人类来源，它们缺乏 3'-CS 的 1 类整合子。所有 13 株分离株的 REP-PCR 图谱均不相关。在这 13 株菌的 1 类整合子内，鉴定出以下基因盒排列：dfrA1；dfrA5；dfrA12-orfF-aadA2-cmlA1-aadA1-qacH-IS440-sul3；dfrA12-orfF-aadA2-cmlA1-aadA1-IS440-sul3；estX-psp-aadA2-cmlA1-aadA1-qacH-IS440-sul3；以及一种新的排列方式 estX-psp-aadA2-cmlA1Delta-IS1294-DeltacmlA1-aadA1-qacH-IS440-sul3，其中包含 IS1294 到 cmlA1 基因（包含在 GenBank 中，编号为 EU704128）。在这种类型的整合子中，sul3 基因上游检测到完整或截短的 mef(B)基因。通过 PCR-复制子分型，在 4 株研究菌株中鉴定出不同组合的 IncY、I1、FIC、FII、FIB 质粒。非经典整合子位于 4 株研究菌株的 100-150kb 质粒中。
不同来源的 intI1 阳性大肠杆菌分离株中缺乏 3'-CS 的 1 类整合子的发生率和多样性相对较高。在大多数缺乏 3'-CS 的 1 类整合子中检测到 sul3 基因。
