[Analysis on the genotyping of 90 Mycobacterium tuberculosis clinical strains isolated from Ningbo with MLVA]

To investigate the genotyping and distribution pattern of the variable number tandem repeats (VNTR) of Mycobacterium tuberculosis clinical isolates in Ningbo with multiple-locus VNTR analysis (MLVA).

M. tuberculosis clinical isolates selected from Ningbo randomly were cultured with Lowenstein-Jensen medium. The bacteria from which the genome DNA was extracted were collected. The polymorphism of VNTR locus was tested in the DNA sample with PCR respectively. The clustering of genotype was analyzed with BioNumerics.

15 VNTR loci of 90 M. tuberculosis clinical isolates were analyzed respectively. There were obvious polymorphisms of VNTRs. The clustering of genotype showed that these strains could be categorized into 4 gene clusters (I, II, III, IV) and 84 genotypes. 11.1% were cluster I including 10 genotypes, 17.8% were cluster II including 15 genotypes, 65.6% were cluster III including 54 genotypes, 5.6% were cluster IV including 5 genotypes.

The results showed that there were obvious polymorphisms of VNTRs of M. tuberculosis clinical strains preliminarily. There were at least 4 clusters of VNTR genotype and cluster III was the predominant prevalent strain in Ningbo.