Molecular typing of drug-susceptible and -resistant Mycobacterium tuberculosis in Johannesburg, South Africa

SETTING Knowledge about spoligotyping families of drug-susceptible and drug-resistant Mycobacterium tuberculosis circulating in the Johannesburg area, South Africa, is lacking. OBJECTIVE To determine the genetic diversity of M. tuberculosis isolates circulating in the Johannesburg area and to compare the results with both national and international databanks. DESIGN Five hundred cultured M. tuberculosis isolates from within the greater Johannesburg metropolitan area collected from January 2009 to December 2010 were obtained from the National Health Laboratory Services (NHLS) Mycobacteriology Referral Laboratory, Johannesburg, in MGIT vials. The isolates were specimens from individuals with tuberculosis (TB) symptoms and known TB patients submitted to the NHLS for routine mycobacterial culture and drug susceptibility testing. The isolates were genotyped using spoligotyping. RESULTS Spoligotyping generated 62 shared types, with 92% (458/500) of the sample size matching pre-existing shared types. Of the 62 shared types, eight families were predominant (clustering from 16 to 132), representing 64% (340/500) of the sample. The Beijing family (135/500) predominated (P < 0.001). CONCLUSION TB incidence in Johannesburg does not appear to be due to clonality, but is rather due to diverse circulating strains, namely the Beijing family, followed by the S, Latin American-Mediterranean and T families.