Departamento de Sanidad Animal y Medicina Preventiva, Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Tandil, Buenos Aires, Argentina.
Appl Environ Microbiol. 2011 Jan;77(1):73-9. doi: 10.1128/AEM.01445-10. Epub 2010 Oct 29.
In this study, we determined vt subtypes and evaluated verotoxicity in basal as well as induced conditions of verotoxin-producing Escherichia coli (VTEC) strains isolated from cattle and meat products. Most (87%) of the 186 isolates carried a vt(2) gene. Moreover, the vt(2) subtype, which is associated with serious disease, was present in 42% of our VTEC collection. The other vt subtypes detected were vt(1), vt(1d), vt(2vha), vt(2vhb), vt(2O118), vt(2d) (mucus activatable), and vt(2g). A total of 41 (22%) of the isolates possessed more than one vt subtype in its genome, and among them the most frequent combination was vt(1)/vt(2), but we also observed multiple combinations among vt(2) subtypes. Differences in verotoxicity titers were found among a selection of 54 isolates. Among isolates with a single vt(2) variant, those carrying the vt(2) subtype had high titers under both uninduced and induced conditions. However, the highest increase in cytotoxicity under mitomycin C treatment was detected among the strains carrying vt(2vha) or vt(2hb) variants. Notably, the isolates carrying the vt(1) subtype showed a lesser increase than that of most of the vt(2)-positive VTEC strains. Furthermore, the presence of more than one vt gene variant in the same isolate was not reflected in higher titers, and generally the titers were lower than those for strains with only one gene variant. The main observation was that both basal and induced cytotoxic effects seemed to be associated with the type and number of vt variants more than with the serotype or origin of the isolate.
在这项研究中，我们确定了产肠毒素大肠杆菌（VTEC）菌株的 vt 亚型，并评估了基础条件和诱导条件下的 verotoxicity。在 186 个分离株中，大多数（87%）携带 vt(2)基因。此外，与严重疾病相关的 vt(2)亚型存在于我们 VTEC 分离株的 42%中。检测到的其他 vt 亚型有 vt(1)、vt(1d)、vt(2vha)、vt(2vhb)、vt(2O118)、vt(2d)（粘液激活）和 vt(2g)。在其基因组中共有 41 个（22%）分离株携带不止一种 vt 亚型，其中最常见的组合是 vt(1)/vt(2)，但我们也观察到 vt(2)亚型之间的多种组合。在选择的 54 个分离株中，发现了 verotoxicity 滴度的差异。在携带单一 vt(2)变体的分离株中，在未诱导和诱导条件下，携带 vt(2)亚型的分离株具有高滴度。然而，在用丝裂霉素 C 处理时，携带 vt(2vha)或 vt(2hb)变体的菌株的细胞毒性增加最高。值得注意的是，携带 vt(1)亚型的分离株的增加幅度小于大多数 vt(2)阳性 VTEC 菌株。此外，同一分离株中存在不止一个 vt 基因变体并不反映在更高的滴度上，通常比具有单个基因变体的菌株的滴度低。主要观察结果是，基础和诱导的细胞毒性效应似乎与 vt 变体的类型和数量更相关，而不是与分离株的血清型或来源相关。
