Molecular Epidemiological Surveillance For Early Detection Of Rifampicin Resistant Clusters In Selected Districts

Outbreaks of drug-resistant TBhave been reported in South Africa, but are usually identified late and often with an accompanied high mortality. An early warning surveillance system has been introduced where strain typing of all RR TB cases is aimed at identifying areas of high risk transmission. This is being implemented at district level, with one district targeted per province. Spoligotyping has been applied as an initial measure to understand the population structure of TB strains and an example of its use is depicted in the Figure below. The challenge in endemic settings is the occurrence of endemic strains, the identification of which requires high resolution methodologies which are costly. An alternative strategy using molecular techniques has been developed and is discussed later. Using MIRU-VNTR 24 loci as the primary high resolution tool, clusters have been identified, primarily in Eastern Cape and Mpumalanga. These provide the first insights into transmission and will be followed up with further epidemiological investigations. These early developments are expected to define the threshold for investigations to further develop and utilise methodologies for intervention in endemic settings.
Figure 1: Rifampicin resistant TB Spoligotype distribution by province (N=624)
Figure 2: Spoligotype and MIRU patterns
Figure 3: IS6110 RFLP fingerprinting