Environmental Research Institute and Department of Microbiology, University College Cork, Cork, Ireland.
PLoS Pathog. 2012;8(6):e1002776. doi: 10.1371/journal.ppat.1002776. Epub 2012 Jun 21.
Salmonella enterica subspecies enterica is traditionally subdivided into serovars by serological and nutritional characteristics. We used Multilocus Sequence Typing (MLST) to assign 4,257 isolates from 554 serovars to 1092 sequence types (STs). The majority of the isolates and many STs were grouped into 138 genetically closely related clusters called eBurstGroups (eBGs). Many eBGs correspond to a serovar, for example most Typhimurium are in eBG1 and most Enteritidis are in eBG4, but many eBGs contained more than one serovar. Furthermore, most serovars were polyphyletic and are distributed across multiple unrelated eBGs. Thus, serovar designations confounded genetically unrelated isolates and failed to recognize natural evolutionary groupings. An inability of serotyping to correctly group isolates was most apparent for Paratyphi B and its variant Java. Most Paratyphi B were included within a sub-cluster of STs belonging to eBG5, which also encompasses a separate sub-cluster of Java STs. However, diphasic Java variants were also found in two other eBGs and monophasic Java variants were in four other eBGs or STs, one of which is in subspecies salamae and a second of which includes isolates assigned to Enteritidis, Dublin and monophasic Paratyphi B. Similarly, Choleraesuis was found in eBG6 and is closely related to Paratyphi C, which is in eBG20. However, Choleraesuis var. Decatur consists of isolates from seven other, unrelated eBGs or STs. The serological assignment of these Decatur isolates to Choleraesuis likely reflects lateral gene transfer of flagellar genes between unrelated bacteria plus purifying selection. By confounding multiple evolutionary groups, serotyping can be misleading about the disease potential of S. enterica. Unlike serotyping, MLST recognizes evolutionary groupings and we recommend that Salmonella classification by serotyping should be replaced by MLST or its equivalents.
肠沙门氏菌亚种 enterica 传统上通过血清学和营养特性细分为血清型。我们使用多位点序列分型（MLST）将来自 554 个血清型的 4257 个分离株分配到 1092 个序列型（ST）中。大多数分离株和许多 ST 被分为 138 个遗传上密切相关的聚类，称为 eBurstGroups（eBGs）。许多 eBG 对应于一个血清型，例如大多数 Typhimurium 都在 eBG1 中，大多数 Enteritidis 都在 eBG4 中，但许多 eBG 包含一个以上的血清型。此外，大多数血清型是多源的，分布在多个不相关的 eBG 中。因此，血清型命名混淆了遗传上不相关的分离株，并且未能识别自然进化分组。血清分型无法正确分组分离株的情况在副伤寒 B 及其变体 Java 中最为明显。大多数副伤寒 B 都包含在属于 eBG5 的 ST 亚群中，该亚群还包含 Java ST 的一个单独亚群。然而，双相型 Java 变体也存在于另外两个 eBG 中，单相型 Java 变体存在于另外四个 eBG 或 ST 中，其中一个在亚种 salamae 中，第二个包括分配给肠炎、都柏林和单相副伤寒 B 的分离株。同样，Choleraesuis 存在于 eBG6 中，与属于 eBG20 的副伤寒 C 密切相关。然而，Choleraesuis var.Decatur 由来自其他七个不相关的 eBG 或 ST 的分离株组成。这些 Decatur 分离株的血清学分配给 Choleraesuis 可能反映了无关细菌之间鞭毛基因的水平基因转移和纯化选择。通过混淆多个进化群体，血清分型可能会对肠沙门氏菌的疾病潜力产生误导。与血清分型不同，MLST 识别进化分组，我们建议用 MLST 或其等效方法替代血清分型对沙门氏菌进行分类。
