A study of the genetic diversity of Mycobacterium tuberculosis isolated from patients in the eastern province of South Africa using random amplified polymorphic DNA profiling.

Abstract

This population genetics study was done to determine the degree of genetic diversity amongst clinical isolates of Mycobacterium tuberculosis in one of the largest provinces of South Africa. Three hundred and fifty-nine individual cultures were obtained from single patients over a nine-month period. Bacterial DNA was extracted and amplified with two arbitrary ten-mer primers, using the random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) technique. RAPD markers were separated by agarose gel electrophoresis, visualised with ethidium bromide, and then analysed for similarity using the GelCompar programme. The isolates were seen to fall into two major population groups. A high degree of genetic diversity was seen, with a total of 350 unique strains occurring amongst the 359 isolates. The majority of drug-resistant isolates grouped together in the smaller population group. The genetic data were also correlated with geographical locality. It was found that a slight preponderance of isolates that grouped together closely, vis. that were either genetically identical or very similar (similarity index of approximately 97%), were from areas that were considered to be geographically distant. Antibiotic resistance patterns were also examined, revealing a total of 16 different resistance profiles among the 68 drug-resistant isolates. RAPD-PCR has proved to be a cost- and time-effective technique, suitable for such a large-scale population genetics study. It has provided useful information on the genetic diversity of an organism which is responsible for an increasing amount of morbidity and mortality in South Africa's second-largest province.