Molecular characterization of Clostridium perfringens isolates from humans with sporadic diarrhea:: Evidence for transcriptional regulation of the beta2-toxin-encoding gene
Molecular characterization of Clostridium perfringens isolates from humans with sporadic diarrhea:: Evidence for transcriptional regulation of the beta2-toxin-encoding gene
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DOI：
10.1128/aem.71.12.8362-8370.2005
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发表时间：
2005-12-01
影响因子：
4.4
通讯作者：
Sarker, MR
中科院分区：
文献类型：
--
作者：
Harrison, B;Raju, D;Sarker, MR
A型产气荚膜梭菌食物中毒是由携带染色体肠毒素基因（epe）的产气荚膜梭菌分离株引起的，而非食源性胃肠道（GI）疾病，如腹泻相关性腹泻（AAD）和散发性腹泻（SD）则是由产气荚膜梭菌质粒epe分离株引起的。最近的一项研究报告了β 2毒素（CPB 2）与人类胃肠道疾病，特别是AAD/SD的关联，通过证明大比例的AAD/SD分离株，而不是小比例的食物中毒分离株，携带β 2毒素基因（epb 2）。在本研究中，通过表征14 cpe（+）C，进一步验证了这种假定的关系。与英国最近的人SD病例相关的产气荚膜杆菌粪便分离株（以下称为SD分离株）。14株cpe（+）菌株中有12株epe基因携带在质粒上，2株携带在染色体上。有趣的是，cpb 2仅存在于12个质粒cpe分离株中; 11个分离株在不同的质粒上携带cpe和cpb 2，但在一个分离株中cpe和cpb 2位于同一质粒上。C.产气荚膜杆菌肠毒素由所有14个CPE（+）SD分离株产生。然而，12株cpe（+）/cpb 2（+）SD分离株中只有10株产生CPB 2，且数量差异显著。低至高CPB 2生产SD分离株中的cpb 2 mRNA水平差异达到一定程度（30倍），这种差异可被视为SD分离株体外CPB 2生产水平差异的主要原因。此外，在CPB 2蛋白质印迹阴性分离株5422/94中未发现沉默或非典型cpb 2，表明5422/94中CPB 2产量的缺乏是由于cpb 2 mRNA的低表达。这得到了我们的观察结果的支持，即携带5422/94 cpb 2的重组质粒，其过表达cpb 2 mRNA，恢复了F4969（一种cpb 2阴性分离株）中的CPB 2生产。总的来说，我们目前的结果表明，CPB 2值得进一步研究作为一个辅助毒素在C。产气荚膜杆菌相关SD。
Clostridium perfringens type A food poisoning is caused by C perfringens isolates carrying a chromosomal enterotoxin gene (epe), while non-food-borne gastrointestinal (GI) diseases, such as antibiotic-associated diarrhea (AAD) and sporadic diarrhea (SD), are caused by C perfringens plasmid epe isolates. A recent study reported the association of beta2 toxin (CPB2) with human GI diseases, and particularly AAD/SD, by demonstrating that a large percentage of AAD/SD isolates, in contrast to a small percentage of food poisoning isolates, carry the beta2-toxin gene (epb2). This putative relationship was further tested in the current study by characterizing 14 cpe(+) C. perfringens fecal isolates associated with recent cases of human SD in England (referred to hereafter as SD isolates). These SD isolates were all classified as cpe(+) type A, and 12 of the 14 cpe(+) isolates carry their epe gene on the plasmid and 2 carry it on the chromosome. Interestingly, cpb2 is present in only 12 plasmid cpe isolates; 11 isolates carry cpe and cpb2 on different plasmids, but cpe and cpb2 are located on the same plasmid in one isolate. C. perfringens enterotoxin is produced by all 14 cpe(+) SD isolates. However, only 10 of the 12 cpe(+)/cpb2(+) SD isolates produced CPB2, with significant variation in amounts. The levels of cpb2 mRNA in low- to high-CPB2-producing SD isolates differed to such an extent (30-fold) that this difference could be considered a major cause of the differential level of CPB2 production in vitro by SD isolates. Furthermore, no silent or atypical cpb2 was found in a CPB2 Western blot-negative isolate, 5422/94, suggesting that the lack of CPB2 production in 5422/94 was due to low expression of cpb2 mRNA. This received support from our observation that the recombinant plasmid carrying 5422/94 cpb2, which overexpressed cpb2 mRNA, restored CPB2 production in F4969 (a cpb2-negative isolate). Collectively, our present results suggest that CPB2 merits further study as an accessory toxin in C. perfringens-associated SD.