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目的了解肠出血性大肠杆菌、非典型致泻性大肠杆菌、志贺菌及部分肠杆菌中CDT毒素基因存在情况及其细胞毒性。方法用PCR方法检测cdt基因,并将阳性菌株培养上清与HeLa细胞共同孵育检测细胞形态的改变,初步评价CDT毒素的表达及其细胞毒性。结果在肠出血性大肠杆菌O157∶NM中,cdt基因检出率为16.28%(7/43),其中3株为cdt-III型,其他4株为cdt-I型;携带HPI毒力岛的非典型致泻性大肠杆菌中cdt基因检出率为6.25%(5/80);在志贺菌中,cdt基因检出率为2.67%(4/150),非典型致泻性大肠杆菌和志贺菌检出的cdt基因全部为cdt-I型。而在O157∶H7大肠杆菌、枸橼酸杆菌和沙门菌未检出cdt基因。所有cdt基因阳性菌株均使HeLa细胞出现典型的细胞肿胀变化,效应滴度介于1∶2到1∶16之间。结论CDT毒素只在肠出血性大肠杆菌O157∶NM、携带HPI毒力岛的非典型致泻性大肠杆菌和志贺菌中检出,且检出率均比国外同类菌株低,其存在是否与疾病严重程度相关及其细胞毒性机制尚须进一步研究予以证明。
Objective To investigate the presence and cytotoxicity of CDT toxin gene in enterohemorrhagic Escherichia coli, atypical diarrhea-causing Escherichia coli, Shigella and some Enterobacter species. Methods The cdt gene was detected by PCR. The supernatant of the positive strain was incubated with HeLa cells to detect the change of cell morphology. The expression of CDT toxin and its cytotoxicity were preliminarily evaluated. Results The positive rate of cdt gene in enterohemorrhagic Escherichia coli O157: NM was 16.28% (7/43), of which 3 were cdt-III and the other 4 were cdt-1; The detection rate of cdt gene in atypical diarrheal E. coli was 6.25% (5/80). In Shigella, the detection rate of cdt gene was 2.67% (4/150), atypical diarrhea-causing Escherichia coli All of the cdt genes detected by the bacterium were cdt-1 type. However, no cdt gene was detected in O157: H7 Escherichia coli, Citrobacter and Salmonella. All of the cdt gene-positive strains showed typical cell swelling changes in HeLa cells with titer ranging from 1: 2 to 1:16. Conclusions CDT toxins are only detected in atherogenic E. coli O157: NM, atypical diarrhea-causing Escherichia coli and Shigella isolates carrying HPI virulence islands, and their detection rates are lower than those in other foreign isolates. Whether their presence is related to diseases The relationship between severity and its cytotoxicity needs to be further studied.