Recombinational Switching of the Clostridium difficile S-Layer and a Novel Glycosylation Gene Cluster Revealed by Large-Scale Whole-Genome Sequencing
Recombinational Switching of the Clostridium difficile S-Layer and a Novel Glycosylation Gene Cluster Revealed by Large-Scale Whole-Genome Sequencing
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DOI：
10.1093/infdis/jis734
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发表时间：
2013-02-15
影响因子：
6.4
通讯作者：
Crook, Derrick W.
中科院分区：
文献类型：
--
作者：
Dingle, Kate E.;Didelot, Xavier;Crook, Derrick W.
背景。艰难梭菌是院内腹泻的主要原因，30天死亡率高达30%。细胞表面由细胞壁蛋白（cwp）基因簇内的slpA基因编码的副晶蛋白s层组成。我们的目的是了解slpA及其附近基因的多样性和进化，这些基因也编码免疫显性细胞表面抗原。对具有群体结构和不同临床表型代表性的57株艰难梭菌分离株进行了全基因组测序。对它们的基因组区域（> - 63kb）进行了系统发育分析。整个cwp集群的遗传多样性在slpA、cwp66（粘附素）和secA2（分泌转位酶）中达到峰值。这些基因形成了一个10 kb的磁带，其中发现了12个不同的变体。涉及该磁带的同源重组使其与基因型随机关联。其中一盒含有一个新的插入（长度约为24 kb），类似于s层糖基化基因簇。s层包膜的遗传交换与其他物种的多糖包膜交换相似。两者都会引起主要的抗原转移，而基因组的其余部分则保持不变。因此，艰难梭菌基因型不能预测抗原型。s层转换和免疫逃逸有助于解释艰难梭菌流行病学的时间和地理差异，并可能为基因分型和疫苗接种策略提供信息。
Background. Clostridium difficile is a major cause of nosocomial diarrhea, with 30-day mortality reaching 30%. The cell surface comprises a paracrystalline proteinaceous S-layer encoded by the slpA gene within the cell wall protein (cwp) gene cluster. Our purpose was to understand the diversity and evolution of slpA and nearby genes also encoding immunodominant cell surface antigens.Methods. Whole-genome sequences were determined for 57 C. difficile isolates representative of the population structure and different clinical phenotypes. Phylogenetic analyses were performed on their genomic region (>63 kb) spanning the cwp cluster.Results. Genetic diversity across the cwp cluster peaked within slpA, cwp66 (adhesin), and secA2 (secretory translocase). These genes formed a 10-kb cassette, of which 12 divergent variants were found. Homologous recombination involving this cassette caused it to associate randomly with genotype. One cassette contained a novel insertion (length, approximately 24 kb) that resembled S-layer glycosylation gene clusters.Conclusions. Genetic exchange of S-layer cassettes parallels polysaccharide capsular switching in other species. Both cause major antigenic shifts, while the remainder of the genome is unchanged. C. difficile genotype is therefore not predictive of antigenic type. S-layer switching and immune escape could help explain temporal and geographic variation in C. difficile epidemiology and may inform genotyping and vaccination strategies.