Genetic Diversity of the Low-Level Vancomycin Resistance Gene vanC-2/vanC-3 and Identification of a Novel vanC Subtype (vanC-4) in Enterococcus casseliflavus
Genetic Diversity of the Low-Level Vancomycin Resistance Gene vanC-2/vanC-3 and Identification of a Novel vanC Subtype (vanC-4) in Enterococcus casseliflavus
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DOI：
10.1089/mdr.2009.0856
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发表时间：
2009-03-01
影响因子：
2.6
通讯作者：
Watanabe, Naoki
中科院分区：
文献类型：
--
作者：
Watanabe, Shojiro;Kobayashi, Nobumichi;Watanabe, Naoki
粪黄肠球菌的内在低水平万古霉素耐药性（VanC表型）由vanC基因的两种亚型（即vanC-2或vanC-3）中的任一种赋予，这两种亚型在遗传上密切相关。了解大肠杆菌vanC-2/C-3基因的遗传多样性。分析了9株临床分离株和4株低水平万古霉素耐药标准菌株的casseliflavus、vanC-2/C-3和vanC基因簇中其他遗传组分（vanXYc、vanTc、vanRc和vanSc）的核苷酸序列。虽然vanC-2/C-3基因序列在所检测的菌株中显示93-100%的同一性，但通过系统发育分析区分了两个遗传组：一个与先前报道的vanC-2或vanC-3基因（vanC-2/C-3基因型）密切相关，具有98-100%的同一性，另一个与vanC-2/C-3基因型不同（93-95%的同一性）。在三个临床分离株中发现的后一组被认为是vanC的新亚型，并暂时命名为vanC-4。在具有vanC-2/C-3基因型的菌株和具有vanC-4基因型的菌株之间，vanXYc基因也以92-93%的同一性被遗传区分。对于vanTc、vanRc和vanSc观察到相似的序列多样性（88-93%同一性）。E.通过atpA基因的系统发育分析，对casseliflavus菌株进行了系统发育分析。而在E. vanC-2/C-3基因型的casseliflavus菌株的atpA序列同源性极高（98.7%或更高），与vanC-4基因型的菌株的atpA序列同源性略低（94-96%）。这两组E.还通过用任意引物PCR进行基因分型来区分casseliflavus菌株。这些结果表明，在E.在casseliflavus中，存在至少两个具有不同vanC基因的遗传谱系，即，包括先前已知的vanC-2/C-3的单一亚型和新亚型vanC-4。
An intrinsic low-level vancomycin resistance (VanC phenotype) in Enterococcus casseliflavus is conferred by either of two subtypes of vanC genes, that is, vanC-2 or vanC-3, which are genetically closely related. To know genetic diversity of vanC-2/C-3 genes among E. casseliflavus, nucleotide sequences of vanC-2/C-3 and other genetic components in vanC gene cluster (vanXYc, vanTc, vanRc, and vanSc) were analyzed for nine clinical isolates and four standard strains that showed low-level vancomycin resistance. While the vanC-2/C-3 gene sequences showed 93-100% identities among the strains examined, two genetic groups were discriminated by phylogenetic analysis: one closely related to the previously reported vanC-2 or vanC-3 genes (vanC-2/C-3 genotype) with 98-100% identity, and the other distinct from the vanC-2/C-3 genotype (93-95% identity). The latter group found in three clinical isolates was considered as a new subtype of vanC and tentatively designated as vanC-4. Between strains with the vanC-2/C-3 genotype and those with vanC-4, vanXYc genes were also genetically discriminated with 92-93% identity. Similar sequence diversity was observed for vanTc, vanRc, and vanSc (88-93% identity). Clonal relatedness among the E. casseliflavus strains was investigated by phylogenetic analysis of atpA gene. While among E. casseliflavus strains with vanC-2/C-3 genotype, extremely high sequence identities of atpA were found (98.7% or higher), these strains showed slightly lower identity to those with vanC-4 (94-96%). These two groups of E. casseliflavus strains were also discriminated by genotyping with arbitrarily primed PCR. These findings indicated that among E. casseliflavus there are at least two genetic lineages with the distinct vanC genes, that is, a single subtype including previously known vanC-2/C-3, and a novel subtype vanC-4.