Genotyping study of 216 Mycobacterium tuberculosis strains isolated from the patients in Tibet with MLVA and Spoligotyping

Objective To evaluate the application of spacer oligonucleotide typing(Spoligotyping)and multiple loci VNTRs(variable number of tandem repeats)analysis(MINA)in molecular epidemiology study of tu- berculosis and to discuss the characteristics of M.tuberculosis strains in Tibet.Methods M.tuberculosis strains isolated from the patients in Tibet,and typed by Spoligotyping and MLVA respectively to compare the results of the both methods and access the application of both methods in epidemiological studies of tuberculosis.Results Two hundred and sixteen clinical isolates of M.tuberculosis were collected in Tibet.By means of Spoligotyping,216 clinical isolates were typed into 3 gene groups,displaying 13 genotypos.In which the biggest group was M.tuber- culosis Beijing family including 195 strains(90.28%).In Beijing family strains,there were 89 strains(45.64%) from the patients with BCG vaccine,while 106 strains(54.36%)from the patients without BCG vaccine.There was no significant difference in statistics(X~2=0.059,P0.05).With MLVA,216 clinical isolates were typed into 19 gene groups,displaying 108 genotypes,in which 80 strains(37.03%)were typed 80 genotypes respec- tively,and 136 strains(62.96%)were typed 28 genotypes which showed 28 clusters respectively.According to the results in the 20 VNTR loci,Miru31 showed the highest diversity,Its h was 0.77,while Mtub29 and Mtubl2 showed the lowest diversity,their h was less than 0.05.The Mtub02 could identify the Beijing family strains and non-Beijing family strains,of which the results completely correspond to that by Spoligotyping.Conclusion In the study it is preliminarily confirmed that there is high polymorphism of M.tuberculosis and Beijing family is the main genotype and main prevalent strain in Tibet.According to the results we could not confirm that there is a rela- tionship between Beijing family strains and BCG vaccine.The results of this study also indicated that Spoligotyping and MLVA are useful for molecular epidmiologicai studies on tuberculosis and improve the effection of epidemiologi- ca] investigation and pathological surveillance of tuberculosis.