INSERM, UMR-S 722, Paris, F-75018, France.
Environ Microbiol. 2011 Sep;13(9):2468-77. doi: 10.1111/j.1462-2920.2011.02519.x. Epub 2011 Jun 8.
Strains phenotypically indistinguishable from Escherichia coli and belonging to at least five distinct cryptic lineages, named Escherichia clades I to V, that are genetically divergent from E. coli yet members of the genus have been recently found using multi-locus sequence typing (MLST). Very few epidemiological data are available on these strains as their detection by MLST is not suitable for large-scale studies. In this work, we developed a rapid PCR method based on aes and chuA allele-specific amplifications that assigns a strain a cryptic lineage membership. By screening more than 3500 strains with this approach, we show that the cryptic lineages of Escherichia are unlikely to be detected in human faecal samples (2-3% frequency) and even less likely to be isolated from extra-intestinal body sites (< 1% frequency). They are more abundant in animal faeces ranging from 3-8% in non-human mammals to 8-28% in birds. Overall, the strains from the clade V are the most abundant and from the clade II very rare. These results suggest that members of the cryptic clades are unlikely to be of significance to human and health but may influence the use of 'E. coli' as an indicator of water quality.
与大肠埃希氏菌表型上无法区分的菌株，属于至少五个不同的隐秘谱系，分别命名为大肠埃希氏菌 clade I 到 V，它们在遗传上与大肠埃希氏菌有很大差异，但最近使用多位点序列分型 (MLST) 发现它们是该属的成员。由于 MLST 对这些菌株的检测不适合大规模研究，因此有关这些菌株的流行病学数据非常有限。在这项工作中，我们开发了一种基于 aes 和 chuA 等位基因特异性扩增的快速 PCR 方法，该方法可将菌株分配到隐秘谱系中。通过使用这种方法筛选了 3500 多个菌株，我们表明，隐秘谱系的大肠埃希氏菌不太可能在人类粪便样本中被检测到（频率为 2-3%），甚至更不可能从肠道外身体部位分离到（频率<1%）。它们在动物粪便中更为丰富，从非人类哺乳动物的 3-8%到鸟类的 8-28%不等。总体而言，clade V 的菌株最为丰富，而 clade II 的菌株则非常罕见。这些结果表明，隐秘谱系的成员不太可能对人类和健康产生重大影响，但可能会影响将“大肠埃希氏菌”用作水质指标。
