BEC, a Novel Enterotoxin of Clostridium perfringens Found in Human Clinical Isolates from Acute Gastroenteritis Outbreaks
BEC, a Novel Enterotoxin of Clostridium perfringens Found in Human Clinical Isolates from Acute Gastroenteritis Outbreaks
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DOI：
10.1128/iai.01759-14
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发表时间：
2014-06-01
影响因子：
3.1
通讯作者：
Iida, Tetsuya
中科院分区：
文献类型：
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作者：
Yonogi, Shinya;Matsuda, Shigeaki;Iida, Tetsuya
产气荚膜梭菌是食源性胃肠炎的病原体，其中C。产气荚膜杆菌肠毒素（CPE）被认为是一个重要因素。最近，我们经历了两次食源性胃肠炎的爆发，其中非CPE生产者的C。强烈怀疑产气荚膜杆菌是病因。本文报道了一种新的由C.产气荚膜梭菌分离株、BEC（C.产气荚膜杆菌）。C.产气荚膜杆菌菌株在兔回肠袢和乳鼠试验中显示出液体积累活性。对培养上清中的肠毒物质进行纯化和基因组DNA的高通量测序，发现BEC由BECa和BECb组成。BECa和BECb与其他二元毒素家族成员如C.产气荚膜杆菌i毒素。将becAB基因定位于54.5-kb pCP 13样质粒上。重组BECb（rBECb）单独在乳鼠试验中具有液体蓄积活性。虽然rBECa单独没有表现出肠毒性活性，rBECa增强rBECb的肠毒性时，同时给予乳鼠。与亲本菌株相比，其中becB基因被破坏的突变体的肠毒性显著降低。rBECa对纯化的肌动蛋白具有ADP核糖基化活性。虽然我们没有直接评估BECb是否将BECa递送到细胞中，但是仅当用rBECa和rBECb两者处理细胞时才发生Vero细胞的变圆。这些结果表明BEC是一种新的C.产BEC的C.产气荚膜杆菌菌株可以是人类急性胃肠炎的病原体。此外，在不同的C.产气荚膜杆菌分离株表明在毒素基因的获得中涉及水平基因转移。
Clostridium perfringens is a causative agent of food-borne gastroenteritis for which C. perfringens enterotoxin (CPE) has been considered an essential factor. Recently, we experienced two outbreaks of food-borne gastroenteritis in which non-CPE producers of C. perfringens were strongly suspected to be the cause. Here, we report a novel enterotoxin produced by C. perfringens isolates, BEC (binary enterotoxin of C. perfringens). Culture supernatants of the C. perfringens strains showed fluid-accumulating activity in rabbit ileal loop and suckling mouse assays. Purification of the enterotoxic substance in the supernatants and high-throughput sequencing of genomic DNA of the strains revealed BEC, composed of BECa and BECb. BECa and BECb displayed limited amino acid sequence similarity to other binary toxin family members, such as the C. perfringens iota toxin. The becAB genes were located on 54.5-kb pCP13-like plasmids. Recombinant BECb (rBECb) alone had fluid-accumulating activity in the suckling mouse assay. Although rBECa alone did not show enterotoxic activity, rBECa enhanced the enterotoxicity of rBECb when simultaneously administered in suckling mice. The entertoxicity of the mutant in which the becB gene was disrupted was dramatically decreased compared to that of the parental strain. rBECa showed an ADP-ribosylating activity on purified actin. Although we have not directly evaluated whether BECb delivers BECa into cells, rounding of Vero cells occurred only when cells were treated with both rBECa and rBECb. These results suggest that BEC is a novel enterotoxin of C. perfringens distinct from CPE, and that BEC-producing C. perfringens strains can be causative agents of acute gastroenteritis in humans. Additionally, the presence of becAB on nearly identical plasmids in distinct lineages of C. perfringens isolates suggests the involvement of horizontal gene transfer in the acquisition of the toxin genes.