CRISPR靶向切割毒力因子tcdB基因抑制致病艰难梭菌生长

目的应用CRISPR/Cas9系统对艰难梭菌主要毒力因子tcdB基因进行切割,达到特异性抑制致病艰难梭菌生长的效果。方法在线设计针对tcdB的sgRNA,分别将sgRNA与Cas9单独或共同作用于tcdB基因扩增产物,验证体外切割效能;分别将穿膜肽(CPP)-sgRNA或单独的sgRNA与CPP-Cas9单独或共同作用于产毒艰难梭菌,通过监测菌液A值和菌落计数,观察对细菌生长的抑制效果。同样的方法处理肠道其他细菌,验证特异性。结果sgRNA和Cas9共同作用可把tcdB扩增产物有效切割,而单独加入sgRNA或Cas9均无切割作用;单独加入CPP-sgRNA、CPP-Cas9、CPP对细菌生长没有影响;CPP-sgRNA与CPP-Cas9共同作用,无细菌生长;单独sgRNA与CPP-Cas9共同作用,细菌生长轻度受抑。用同样的方法将CPP-sgRNA+CPP-Cas9处理肠道其他细菌后,菌液A值和菌落计数与空白对照无差别。结论建立的针对tcdB的sgRNA与Cas9混合可在体外高效切割tcdB基因,抑制细菌生长;CPP可提高sgRNA转染进入细菌的效率。

Clostridium difficile Toxin B: Insights into Its Target Genes

Clostridium difficile is a grossly Gram-positive anaerobic bacterium that has been a key factor in inducing imbalances in the gut microbiota in recent years, leading to intestinal-associated inflammation. The main pathogenic toxins of Clostridium difficile are toxin A (TcdA) and toxin B (TcdB). TcdB is the main pathogenic factor of Clostridium difficile infection. This review revealed the pathogenic mechanism of Clostridium difficile toxin B, expounded the impact of Clostridium difficile on the intestinal system, and predicted the genes on which TcdB may act, thereby providing a new therapeutic target for Clostridium difficile infection, offering theoretical basis and new strategies for clinical prevention and control.

中国部分地区艰难梭菌PCR-核糖体分型及毒素基因多态性研究

目的了解中国部分地区艰难梭菌聚合酶链反应(PCR)-核糖体型别分布及其A、B毒素基因多态性,为建立适宜中国的艰难梭菌分子检测和分子分型技术提供基础数据,同时在基因水平上为艰难梭菌感染导致的复杂临床表现提供依据。方法对中国3个城市(北京、广州、济南)分离的64株艰难梭菌临床株进行PCR-核糖体分型,并对不同型别的26株代表菌株的A、B毒素基因进行扩增测序。结果 64株艰难梭菌中,毒素基因型以A+B+型(45株,70.31%)为主,A-B+型19株(29.69%)。共存在9种PCR-核糖体型别,以017型(21株,32.81%)为主要型别,其次为001型(13株,20.31%)、012型(11株,17.19%)。A-B+菌株中,14株(73.68%)是017型,1株是001型。A、B毒素基因呈现一定的多态性,其中有7种A毒素序列型别(TSTA),6种B毒素序列型别(TSTB),8种A、B毒素序列型别组合(TSTG)。结论我国部分地区的艰难梭菌可能以PCR-核糖体017型为主,A、B毒素基因在菌株间存在多态性,且核糖体型别与毒素基因多态性间存在相对应的关联。应进一步扩大菌株数量和范围,探寻适合我国的分子检测和分子分型方法,从而帮助医院更好地预防和控制艰难梭菌感染。

Occurrence of Toxigenic Clostridium difficile in Louisiana Oysters (<i>Crassostrea virginica</i>) and Environmental Waters

Clostridium difficile infection (CDI) was generally considered as a hospital-associated disease;however, recent community-acquired CDI has raised the concerns regarding the transmission of the pathogen through environmental sources. Limited data are available regarding the presence of C. difficile in food and water. In this study, oysters (Crassostrea virginica) and the harvest water collected from the commercial harvesting areas along the Louisiana Gulf Coast as well as the influent and effluent of a municipal treatment plant in New Orleans, LA were analyzed for toxigenic C. difficile. The bacterium was isolated from 47.37% (9/19) of oysters and 37.5% (3/8) of harvest water samples. Toxigenic C. difficile were also detected in all the wastewater influent and effluent samples. All the isolates harbored the gene tcdB encoding the virulence factor toxin B. Further PCR-ribotyping showed that the C. difficile isolated from the oysters and harvest water differed from the wastewater isolates. However, similar ribotypes were found in oysters and the surrounding harvest water. We found that oysters growing in contaminated water could bioaccumulate toxigenic C. difficile and pose a health risks by serving as a vehicle for the transmission of the pathogen to humans.

临床分离艰难梭菌毒素携带特征研究

目的对医院细菌室送检粪便标本中分离出的艰难梭菌,进行毒素基因以及耐药基因的初步分析。方法将细菌室收集到的112份粪便标本,经选择性厌氧培养,谷氨酸脱氢酶(GDH)以及API 20A生化条鉴定后,分离出12株艰难梭菌,分别采用PCR的方法检测tcdA和tcdB基因、二元毒素基因,克林霉素抗性基因(ermB)。结果12株艰难梭菌中8株为毒素基因阳性,其中tcdA+tcdB+为5株,占62.5%;tcdA-tcdB+为3株,占37.5%;二元毒素基因均为阴性;耐药基因ermB阳性为4株,占50%。结论艰难梭菌tcdA-tcdB+毒株所占比例增加,临床单独检测A毒素易造成漏检;艰难梭菌耐药现象值得关注。