The measurement of genetic diversity in mycobacterium tuberculosis using random amplified polymorphic DNA profiling

Abstract

Mycobacterium tuberculosis has caused a resurgence in pulmonary disease in both developed and developing countries in recent times, particularly amongst people infected with the human immunodeficiency virus. The disease has assumed epidemic proportions in South Africa and in the Eastern Cape Province in particular. Of further concern is the isolation of increasing numbers of multiply drug resistant strains. Knowledge of the genetic capability of this organism is essential for the successful development of novel antibiotics and vaccines in an attempt to bring the global pandemic under control. Measurement of the genetic diversity of the organism may significantly contribute to such knowledge, and is of vital importance in monitoring epidemics and in improving treatment and control of the disease. This will entail answering a number of questions related to the degree of genetic diversity amongst strains, to the difference between urban and rural strains, and between drug resistant and drug sensitive strains, and to the geographical distribution of strains. In order to establish such baseline information, RAPD profiling of a large population of isolates from the western and central regions of the Eastern Cape Province was undertaken. A smaller number of drug resistant strains from a small area of KwaZulu-Natal were also analysed, with a view to establishing the genetic difference between strains from the two provinces. Cluster analysis, analysis of molecular variance and Geographical Information Systems technology were used to analyse the RAPD profiles generated. An unexpectedly high degree of genetic diversity was detected in strains from both provinces. While no correlation was seen between genetic diversity and either urban-rural situation or geographical location, a small degree of population structure could be correlated with drug resistance in the Eastern Cape. Furthermore, a significant degree of population structure was detected between strains from the two provinces, although this was still within the parameters for conspecific populations. Future work is necessary to further characterise strains from rural areas of both provinces, as well as from the eastern region of the Eastern Cape in an attempt to pinpoint the cause of the separation of the provincial populations.