TB in South Africa
Tuberculosis (TB) notification rates in areas around Cape Town are among the highest in the world. TB is the most common opportunistic infection, transmitted through the air, particularly through coughing. As such, transmission is suspected to be particularly high in crowded areas. Despite South Africa’s large antiretroviral treatment (ART) programme, TB remains a major cause of death among individuals with AIDS.
The DTHF is actively engaged in research at laboratory, clinical, and public health levels to increase our understanding of this epidemic and to seek solutions to this overwhelming health problem facing South Africans.
The aerobiology project
The TB aerobiology study seeks to understand the biology of the airborne transmission of Mycobacterium tuberculosis (Mtb). This is a complex but exciting area of research, as tremendous creative efforts are required to sample, investigate and understand airborne biological components.
The aerobiology project aims to investigate the potential links between mycobacterial genotypes and the production of infectious aerosols, such as the extent of genotypic differences in Mtb populations and whether genotype correlates with bacchi released by normal exhalation and/or cough.
It is hoped that procurement of a better understanding of Mtb transmission biology will enable the development of novel interventions that reduce transmission.
Whole Genome Sequencing (WGS)
This study aims to better define transmission clusters from a 10 year Masiphumelele TB retrospective database and to analyse the transmission dynamics within this community. The study is made up of two projects.
Project 1 – The first project intends to determine the amount of genetic variability amongst aerosolised bacilli. This is accomplished by sequencing the genomes of bacilli isolated from both sputum and respiratory samples.
Preliminary data have been very revealing, granting key insights into the genetic diversity between aerosol and sputum samples in a single patient and between different patients. Specifically, in establishing degrees of heterogeneity within and between patients that are far higher than initially expected.
Project 2 – The second project plans to sequence 250 samples of TB from the Masiphumelele database. Preliminary data shows a very structured phylogenetic tree, with evidence of micro-clusters within RFLP-defined strains.
Ongoing monitoring of TB notification rates in Masiphumelele (since 1996) has enabled us to describe the impact of the escalating HIV epidemic and inform the roll-out of the ART programme on TB burden of disease in this community.
Over ten years of molecular data, including DNA fingerprinting of all TB sputum strains, has provided insights into transmission patterns in the HIV infected and uninfected populations. In addition, tuberculin skin test surveys in the community schools have provided an understanding of high TB infection rates in the community.
In collaboration with the UCT Department of Engineering, we have developed an innovative approach to the study of TB transmission by monitoring individual-based CO2 environments. These results give a surrogate measurement of the risk of TB infection, determined by the amount of rebreathed air.