Study On The Genotyping And Drug-resistance Epidemiology Of Mycobacterium Tuberculosis In Beijing

Objective To find out the distribution of M.tb genotyping,leading epidemic type of679clinial isolates of TB in Beijing to compare the similarities and differences of two genotyping methods-Spoligotyping and MIRU-VNTR. Also to analyze the correlation between different genotypes and drug resistance. So as to explore the molecular-epidemiology of Mycobacterium tuberculosis in Beijing and analyze the two genotyping methods. Methods679M.tuberculosis strains were collected from20TB dispensaries or hospitals in Beijing in2008. The465clinical isolates were genotyped by mycobacterial interspersed repetitive units-variable number of tandem repeats (MIRU-VNTR) and Spoligotyping methods respectively and the results of two genotypes were compared. The data of the tests were dealt with cluster analysis by means of the NatureEdge and the main epidemic strains and genotype were obtained. The genotyping results analyzed and combined with DST (appropriate concentrations)as well as epidemiological data. Chi-square was used to compare the difference between different groups. Results The Spoligotyping results demonstrated that82.6%(561/679) of the strains belonged to the Beijing genotype which is the domain genotype in Beijing in2008.Of the patients who had received BCG-vaccination,81.7%(384/470) infectied with strains of Beijing genotype and83.5%(240/269) of the patients were not BCG-vaccinated.However,the difference was not statistically significant.In the study,drug resistance rates to Km, RFB, Pto, RFT, INH, S, LFX, PAS, Cm, EMB were61.76%,54.65%,44.16%,39.71%,23.37%,22.22%,18.87%,8.70%,6.52%,4.71%.Drug resistant rate from those strains of Beijing genotype was86.11%(186/216), lower than that of non-Beijing genotype93.93%(437/465).The Spoligotyping showed93.93%(437/465) were strains of cluster and73genotypes,while22.37%(104/465) that of MIRU-VNTR and398genotypes. HGI of MIRU-VNTR465isolates and Beijing genotype isolates are0.9576which is higher than that of Spoligotyping (0.9547).DNA fingerprint of MIRU -VNTR presented polymorphism to different strain or different locus, there was different allelic diversity at each MIRU-VNTR locus,the QUB-1lblocus had the highest diversity and the QUB-4156c locus has the lowest diversity.And this is the same results to Beijing genotype. Conclusions The Beijing genotype of M.tuberculosis were found to be the dominant strains in Beijing in2008.The association between Beijing genotype of M.tuberculosis were vaccination or drug-resistant were not found.Results from cluster analysis suggested that some cases might belong to the newly developed cases. MIRU-VNTR has more diversified results and its HGI is higher than that of Spoligotyping.HGI difference between all isolates and Beijing genotype isolates is very slight by MIRU-VNTR, whereas high by Spoligotyping.