Unité Antibiorésistance et Virulence Bactériennes, ANSES Site de Lyon, France.
Appl Environ Microbiol. 2012 Jul;78(13):4677-82. doi: 10.1128/AEM.00351-12. Epub 2012 Apr 20.
In line with recent reports of extended-spectrum beta-lactamases (ESBLs) in Escherichia coli isolates of highly virulent serotypes, such as O104:H4, we investigated the distribution of phylogroups (A, B1, B2, D) and virulence factor (VF)-encoding genes in 204 ESBL-producing E. coli isolates from diarrheic cattle. ESBL genes, VFs, and phylogroups were identified by PCR and a commercial DNA array (Alere, France). ESBL genes belonged mostly to the CTX-M-1 (65.7%) and CTX-M-9 (27.0%) groups, whereas those of the CTX-M-2 and TEM groups were much less represented (3.9% and 3.4%, respectively). One ESBL isolate was stx(1) and eae positive and belonged to a major enterohemorrhagic E. coli (EHEC) serotype (O111:H8). Two other isolates were eae positive but stx negative; one of these had serotype O26:H11. ESBL isolates belonged mainly to phylogroup A (55.4%) and, to lesser extents, to phylogroups D (25.5%) and B1 (15.6%), whereas B2 strains were quasi-absent (1/204). The number of VFs was significantly higher in phylogroup B1 than in phylogroups A (P = 0.04) and D (P = 0.02). Almost all of the VFs detected were found in CTX-M-1 isolates, whereas only 64.3% and 33.3% of them were found in CTX-M-9 and CTX-M-2 isolates, respectively. These results indicated that the widespread dissemination of the bla(CTX-M) genes within the E. coli population from cattle still spared the subpopulation of EHEC/Shiga-toxigenic E. coli (STEC) isolates. In contrast to other reports on non-ESBL-producing isolates from domestic animals, B1 was not the main phylogroup identified. However, B1 was found to be the most virulent phylogroup, suggesting host-specific distribution of virulence determinants among phylogenetic groups.
与最近有关产超广谱β-内酰胺酶（ESBL）的高毒力血清型大肠杆菌分离株（如 O104：H4）的报道一致，我们调查了 204 株产 ESBL 的大肠杆菌分离株中肠杆菌科的 phylogroups（A、B1、B2、D）和毒力因子（VF）编码基因的分布。通过 PCR 和商业 DNA 芯片（法国 Alere）鉴定 ESBL 基因、VF 和 phylogroups。ESBL 基因主要属于 CTX-M-1（65.7%）和 CTX-M-9（27.0%）组，而 CTX-M-2 和 TEM 组的基因则少得多（分别为 3.9%和 3.4%）。一株 ESBL 分离株 stx(1) 和 eae 阳性，属于主要肠出血性大肠杆菌（EHEC）血清型（O111：H8）。另外两株分离株 eae 阳性但 stx 阴性；其中一株为 O26:H11 血清型。ESBL 分离株主要属于 phylogroup A（55.4%），其次是 phylogroup D（25.5%）和 phylogroup B1（15.6%），而 phylogroup B2 菌株几乎不存在（204 株中的 1 株）。在 phylogroup B1 中发现的 VF 数量明显高于 phylogroups A（P = 0.04）和 D（P = 0.02）。在检测到的几乎所有 VF 中均发现了 CTX-M-1 分离株，而在 CTX-M-9 和 CTX-M-2 分离株中仅分别发现了 64.3%和 33.3%。这些结果表明，bla(CTX-M) 基因在牛源大肠杆菌种群中的广泛传播仍然避开了肠出血性大肠杆菌/志贺毒素产生大肠杆菌（STEC）分离株的亚群。与其他关于家畜中非产 ESBL 分离株的报告不同，B1 不是鉴定的主要 phylogroup。然而，B1 被发现是最具毒力的 phylogroup，表明毒力决定因素在进化群之间存在宿主特异性分布。
