Genotyping of Mycobacterium tuberculosis strains isolated from the patients in Ningbo with variable number tandem repeat method

Objective:To investigate the genotyping and distribution pattern of Mycobacterium tuberculosis clinical isolates in Ningbo with variable number tandem repeats(VNTR) analysis.Methods: 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.Results: 15 VNTR loci of 90 M.tuberculosis clinical isolates were analyzed respectively.The results showed that 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 clusterⅠincluding 10 genotypes,17.8% were clusterⅡincluding 15 genotypes,65.6% were cluster Ⅲ including 54 genotypes,5.6% were cluster Ⅳ including 5 genotypes.Conclusion: 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.