Genetic Diversity and Drug Susceptibility of Mycobacterium tuberculosis Isolates in a Remote Mountain Area of China

Objective We determined the genetic diversity of Mycobacterium tuberculosis（MTB） in a remote mountainous area of southwest China and evaluated the resolving ability of single nucleotide polymorphism（SNP） genotyping combined with variable number tandem repeat（VNTR） genotyping for Beijing family strains in association with drug resistance status.Methods Three hundred thirty-one MTB strains were isolated from patients living in mountainous regions of southwest China,and 8-loci SNP,VNTR-15 genotyping assays,and drug susceptibility testing of 9 drugs were performed.Results A total of 183 [55.29%（183/331）] strains were classified into the Beijing family.Of the 183 strains,111（60.66%） were defined as modern Beijing strains.The most predominant modern Beijing sub-lineage and ancient Beijing sub-lineage were Bmyc10 [39.34%（72/183）] and Bmyc25 [20.77%（38/183）],respectively.Of the isolates,19.64%（65/331） were resistant to at least 1 of the 9 anti-TB drugs and 17 [4.98%（17/331）] MTB isolates were multi-drug resistant tuberculosis（MDR-TB）.Two hundred sixty-one isolates showed a clustering rate of 14.18%（37/261） and a discriminatory index of 0.9990.The Beijing lineage exhibited a significantly higher prevalence of MDR-TB,as well as resistance to isoniazid（INH）,rifampin（RIF）,and para-aminosalicylic acid（PAS） when analyzed independently（P = 0.005,P = 0.017,P = 0.014,and P = 0.006 respectively）.The Beijing lineage was not associated with genetic clustering or resistance to any drug.In addition,genetic clustering was not associated with drug resistance.Conclusion MTB strains demonstrate high genetic diversity in remote mountainous areas of southwest China.Beijing strains,especially modern Beijing strains,are predominant in remote mountainous area of China.The combination of 8-loci SNPs and VNTR-15 genotyping is a useful tool to study the molecular epidemiology of MTB strains in this area.

Transmission of extensively drug-resistant and multidrug resistant Mycobacterium tuberculosis in families identified by genotyping

Background Diagnosis and appropriate treatment of multidrug-resistant tuberculosis （MDR-TB） remain major challenges. We sought to elucidate that persons who share a household with drug resistance tuberculosis patients are at high risk for primary drug resistance tuberculosis and how to prevent these outbreaks. Methods We used 12-locus mycobactedal interspersed repetitive unit and 7-locus variable-number tandem repeat to identify household transmission of extensively drug resistant and multiple drug resistant Mycobacterium tuberculosis in three families admitted in Shanghai Pulmonary Hospital affiliated with Tongji University. Drug susceptibility tests were done by the modified proportion method in the MGIT 960 system in the same time. Clinical data were also obtained from the subjects＇ medical records. Results All of the six strains were defined as Beijing genotype by the deletion-targeted multiplex PCR （DTM-PCR） identification on the genomic deletion RD105. Strains from family-1 had the same minisatellite interspersed repetitive unit （MIRU） pattern （232225172531） and the same MIRU pattern （3677235）. Strains from family-2 had the same MIRU pattern （2212261553323） and the same MIRU pattern （3685134）. Strains from family-3 did not have the same MIRU pattern and they differed at only one locus （223326173533, 223325173533）, and did not have the same VNTR pattern with two locus differed （3667233, 3677234）. Conclusions Household transmission exists in the three families. A clear chain of tuberculosis transmission within family exists. Tuberculosis susceptibility should be considered when there is more than one tuberculosis patients in a familv. Household tuberculosis transmission could be prevented with adequate treatment of source Patients.