Abstract:

Objective To investigate the variation characteristics of rpoB gene of clinical isolates of Myco⁃ bacterium tuberculosis with different drug resistance phenotypes in Guangdong，so as to provide a research basis for the development of more accurate and rapid molecular detection technology. Methods 373 clinical isolates of Mycobacterium tuberculosis which had known their sensitivity to rifampicin（R），isoniazid（H），ethambutol（E） and streptomycin（S）were screened from the Mycobacterium collection. RpoB gene fragments including rifampin resistance determination region（RRDR）were amplified and sequenced from 373 clinical isolates by polymerase chain reaction. Results Firstly，among the 373 strains，192 strains were detected with rpoB gene variation，and a total of 225 mutations occurred in 40 types of mutation including base replacement，insertion and deletion. The mutations at 531，526，511，516，533 and 515 were the most common，accounting for 43.11%（97/225），20.89% （47/225），10.22%（23/225），8%（18/225），4.44%（10/225）and 4%（9/225）respectively. Secondly，among 192 rpoB mutants，159 had only unit point mutation and 33 had double site mutation. Among them，14 mutation types such as D516V，H526L，H526D，H526R and S531W only appeared in unit point mutation，which was unit point specific variation. 21 mutation types such as M515T，H526Q，D516G，M515V and E541A only appeared in double site mutation，which was double site specific. Five mutation types，including S531L，L511P，H526Y…etc.are single⁃ and double⁃site common mutations. There is no simultaneous variation of three loci. Thirdly，the mutation rates of the rpoB gene for the four first⁃line drug fully susceptible strains（Q），R⁃sensitive and H⁃resistant strains （RSHR ），R ⁃ resistant and H ⁃ susceptible strains（RRHS）and HR ⁃ resistant strains（MDR）were 4.67%（5/107）， 28.42%（27/95），90.62（29/32），94.24%（131/139），except that the mutation rate between RRHS and MDR strains was not statistically different（P > 0.05），Q/RSHR，Q/RRHS，Q/MDR，RSHR /RRHS，RSHR /MDR strains were significantly different in rpoB gene mutation rate（P = 0.000）. Conclusions RpoB gene mutation of Mycobacterium tuberculosis in Guangdong has diversity and regional characteristics. Different drug resistance phenotypes may have a far⁃reaching impact on rpoB gene mutation.

Key words:

Mycobacterium tuberculosis, rpoB gene, rifampicin resistance determination region, gene mutation ,