Abstract: Objective To study the prevalence of different genotypes of M. tuberculosis in Chongqing and analyze the relationships between genotype and drug-resistant phenotype.  Methods One hundred and thirteen M. tuberculosis clinical isolates were collected in Chongqing from January to December in 2011, performed drug susceptibility testing by the proportion method, analyzed the genotypes by Spoligotyping and PCR method, and then made gene glustering analysis. Results One hundred and thirteen clinical strains were divided into 2 gene clusters, namely Beijing family (68.1%, 77/113) and non-Beijing family (31.9%, 36/113). Of 77 Beijing family strains, 48 (62.3%) strains were belong to modern type, 29 (37.7%) were the ancient type. Of 36 strains with non-Beijing family, 13 (36.1%) strains were T1 type, and found 9 new genotypes. The drug-resistant rate of Beijing family strains was 24.7% (19/77), and of non-Beijing family strains was 38.9% (14/36), in which there was no significant differences (χ²=2.40, P>0.05). The drug-resistant rate of modern type strains in Beijing family was 27.1% (13/48), and of the ancient type strains was 20.7% (6/29), in which there was no significant differences (χ²=0.39, P>0.05).  Conclusion There was obvious gene polymorphism in M. tuberculosis isolates in Chongqing. Beijing family was the main epidemic strains, in which the modern type was predominant. There was no significant correlation between genotype and drug resistance.

Key words: Mycobacterium tuberculosis, Genotype, Drug resistance, bacterial, Genotyping techniques, Chongqing city