幽门螺杆菌rdxA基因的DNA序列分析

The DNA sequence analysis of rdxA gene in Helicobacter pylori

目的研究(Hp)耐药菌株与敏感菌株之间rdxA基因的DNA差异。方法取胃镜活检标本,微需氧环境培养,收集Hp菌株。进行甲硝唑药敏试验,筛选出12株耐药菌株(MTZR菌株)和9株敏感菌株(MTZS菌株)。从MTZR菌株、MTZS菌株和Hp11637中扩增rdxA基因;将PCR产物进行DNA测序,测序结果采用DNA Star和NCBI Blast分析,探讨临床菌株和标准菌株的DNA序列差异。结果临床分离菌株与Hp标准菌株26695比较rdxA基因同源性,MTZR菌株为93.25%±1.93%;MTZS菌株93.79%±1.14%,P>0.05;Hp MTZR菌株的rdxA基因突变数高于MTZS菌株;Hp MTZR菌株与MTZS菌株之间点突变的形式没有显著性差异,也缺乏明确的突变规律和突变热点,MTZR菌株与MTZS菌株之间的突变形式无统计学意义。结论rdxA基因突变(改变)以点突变为主,rdxA基因点突变与Hp耐药有关,但具体的rdxA点突变形式与耐药表型的关系尚有待进一步研究。

Objective To study the difference of rdxA genes between resistance to metronidazole（MTZ） and MTZ-susceptive strains of Helicobacter pylori. Methods H. pylori strains from gastric biopsy specimens were cultured under microaerobic conditions. Disk diffu- sion test was used to determine the susceptibility of H. pylori strains to metronidazole. 12 isolates were MTZR, with 9 isolates of MTZs. The segment of rdxA was amplified from MTZs strains, MTZs strains and H. pylori 11637 by PCR. These PCR-products were sequenced, and the nucleotide sequences were analyzed by the DNA Star software package and NCBI Blaster. Results The DNA homology of rdxA in MTZR and MTZs was 93.25%±1.93% and 93.79%±1.14% respectively compared with that gene in H. pylori standard strain 26695 （P〉 0.05）. The rdxA gene mutation in MTZS-strains was more than that of MTZS-strains. There was no significant difference between MTZR-strains and MTZS-strains in mutation genetypes. Mutation rule and mutation focus were lacking. Conclusions The point mutation is the primary form of rdxA gene mutation. The point mutation of rdxA gene may be related with resistance of H. pylori to metronidazole, but it is necessary to further insight into the relationship between the specific point mutation of rdxA gene and H. pylori drug-resistant phenotype.