Laboratorio de Inmunoquímica y Biotecnología, Centro de Investigación Veterinaria de Tandil (CIVETAN), Facultad de Ciencias Veterinarias, UNCPBA, Campus Universitario, Paraje Arroyo Seco S/N, 7000 Tandil, Argentina ; CONICET, Argentina.
Biomed Res Int. 2013;2013:390354. doi: 10.1155/2013/390354. Epub 2013 Sep 5.
VNTRs regions have been successfully used for bacterial subtyping; however, the hypervariability in VNTR loci is problematic when trying to predict the relationships among isolates. Since few studies have examined the mutation rate of these markers, our aim was to estimate mutation rates of VNTRs specific for verotoxigenic E. coli O157:H7. The knowledge of VNTR mutational rates and the factors affecting them would make MLVA more effective for epidemiological or microbial forensic investigations. For this purpose, we analyzed nine loci performing parallel, serial passage experiments (PSPEs) on 9 O157:H7 strains. The combined 9 PSPE population rates for the 8 mutating loci ranged from 4.4 × 10(-05) to 1.8 × 10(-03) mutations/generation, and the combined 8-loci mutation rate was of 2.5 × 10(-03) mutations/generation. Mutations involved complete repeat units, with only one point mutation detected. A similar proportion between single and multiple repeat changes was detected. Of the 56 repeat mutations, 59% were insertions and 41% were deletions, and 72% of the mutation events corresponded to O157-10 locus. For alleles with up to 13 UR, a constant and low mutation rate was observed; meanwhile longer alleles were associated with higher and variable mutation rates. Our results are useful to interpret data from microevolution and population epidemiology studies and particularly point out that the inclusion or not of O157-10 locus or, alternatively, a differential weighting data according to the mutation rates of loci must be evaluated in relation with the objectives of the proposed study.
VNTR 区域已成功用于细菌亚型划分；然而，当试图预测分离株之间的关系时，VNTR 基因座的高度多态性是一个问题。由于很少有研究检查这些标记的突变率，我们的目的是估计产志贺毒素大肠杆菌 O157:H7 特异性 VNTR 的突变率。了解 VNTR 突变率及其影响因素将使 MLVA 更有效地用于流行病学或微生物法医调查。为此，我们分析了 9 个 O157:H7 菌株进行平行、连续传代实验（PSPE）的 9 个基因座。8 个突变基因座的 9 个 PSPE 群体的总突变率范围为 4.4×10(-05)至 1.8×10(-03)突变/generation，总突变率为 2.5×10(-03)突变/generation。突变涉及完整的重复单位，仅检测到一个点突变。检测到单重复和多重复变化之间的相似比例。在 56 个重复突变中，59%是插入，41%是缺失，72%的突变事件与 O157-10 基因座相对应。对于重复数最多为 13 的等位基因，观察到恒定且低的突变率；同时，较长的等位基因与较高且可变的突变率相关。我们的结果有助于解释微进化和群体流行病学研究中的数据，特别是指出在与拟议研究目标相关的情况下，必须根据基因座的突变率评估包括或不包括 O157-10 基因座，或者根据突变率对数据进行不同加权的问题。
