High diversity of Mycobacterium tuberculosis genotypes in South Africa and preponderance of mixed infections among ST53 isolates.

The reemergence of tuberculosis (TB) has become a major health problem worldwide, especially in Asia and Africa. Failure to combat this disease due to nonadherence or inappropriate drug regimens has selected for the emergence of multiple-drug-resistant (MDR) TB. The development of new molecular genotyping techniques has revealed the presence of mixed Mycobacterium tuberculosis infections, which may accelerate the emergence of drug-resistant strains. There are some studies describing the local distribution of circulating strains in South Africa, but to date, reports describing the frequency and distribution of M. tuberculosis genotypes, and specifically MDR genotypes, across the different provinces are limited. Thus, 252 isolates (of which 109 were MDR) from eight of the nine provinces of South Africa were analyzed by spoligotyping. Spoligotyping showed 10 different lineages, and ST53 (11.1%) and ST1 (10.3%) were the most frequent genotypes. Of the 75 different spoligopatterns observed, 20 (7.9%) were previously unreported. Analysis of the mycobacterial interspersed repetitive units of variable-number tandem repeats of the ST53 and ST1 isolates revealed that approximately 54% of the ST53 isolates were of mixed M. tuberculosis subpopulations. Drug resistance (defined as resistance to at least isoniazid and/or rifampin) could only be linked to a history of previous anti-TB treatment (adjusted odds ratio, 4.0; 95% confidence interval, 2.27 to 7.10; P = <0.0001). This study describes a high diversity of circulating genotypes in South Africa in addition to a high frequency of mixed M. tuberculosis subpopulations among the ST53 isolates. MDR TB in South Africa could not be attributed to the spread of any single lineage.