Lepage E, Brinster S, Caron C, Ducroix-Crepy Céline, Rigottier-Gois L, Dunny G, Hennequet-Antier C, Serror P
Unité des Bactéries Lactiques et pathogènes Opportunistes, INRA, Jouy-en-Josas, France.
J Bacteriol. 2006 Oct;188(19):6858-68. doi: 10.1128/JB.00421-06.
Enterococcus faecalis, a member of the natural microbiota of animal and human intestinal tracts, is also present as a natural contaminant in a variety of fermented foods. Over the last decade, E. faecalis has emerged as a major cause of nosocomial infections. We investigated the genetic diversity in 30 clinical and food isolates, including strains V583 and MMH594, in order to determine whether clinical and food isolates could be distinguished. Data were obtained using comparative genomic hybridization and specific PCR with a total of 202 probes of E. faecalis, selected using the available V583 genome sequence and part of the MMH594 pathogenicity island. The cognate genes encoded mainly exported proteins. Hybridization data were analyzed by a two-component mixture model that estimates the probability of any given gene to be either present or absent in the strains. A total of 78 genes were found to be variable, as they were absent in at least one isolate. Most of the variable genes were clustered in regions that, in the published V583 sequence, related to prophages or mobile genetic elements. The variable genes were distributed in three main groups: (i) genes equally distributed between clinical and dairy food isolates, (ii) genes absent from dairy food-related isolates, and (iii) genes present in MMH594 and V583 strains only. Further analysis of the distribution of the last gene group in 70 other isolates confirmed that six of the probed genes were always absent in dairy food-related isolates, whereas they were detected in clinical and/or commensal isolates. Two of them corresponded to prophages that were not detected in the cognate isolates, thus possibly extending the number of genes absent from dairy food isolates. Genes specifically detected in clinical isolates may prove valuable for the development of new risk assessment markers for food safety studies and for identification of new factors that may contribute to host colonization or infection.
粪肠球菌是动物和人类肠道自然微生物群的成员，也是多种发酵食品中的天然污染物。在过去十年中，粪肠球菌已成为医院感染的主要原因。我们研究了30株临床和食品分离株的遗传多样性，包括V583和MMH594菌株，以确定临床和食品分离株是否可以区分。使用比较基因组杂交和特异性PCR获得数据，共使用了202个粪肠球菌探针，这些探针是根据可用的V583基因组序列和MMH594致病岛的一部分选择的。同源基因主要编码分泌蛋白。杂交数据通过双组分混合模型进行分析，该模型估计任何给定基因在菌株中存在或不存在的概率。共发现78个基因是可变的，因为它们在至少一个分离株中不存在。大多数可变基因聚集在已发表的V583序列中与原噬菌体或移动遗传元件相关的区域。可变基因分布在三个主要组中：（i）在临床和乳制品分离株中均匀分布的基因，（ii）与乳制品相关的分离株中不存在的基因，以及（iii）仅存在于MMH594和V583菌株中的基因。对最后一组基因在其他70个分离株中的分布进行进一步分析证实，6个被探测基因在与乳制品相关的分离株中总是不存在，而在临床和/或共生分离株中被检测到。其中两个对应于在同源分离株中未检测到的原噬菌体，因此可能扩大了乳制品分离株中不存在的基因数量。在临床分离株中特异性检测到的基因可能对开发食品安全研究的新风险评估标志物以及识别可能有助于宿主定植或感染的新因素具有重要价值。
