Abstract:
BACKGROUND: Studies have shown that drug-resistant tuberculosis (DR-TB) in South Africa (SA) is clonal and is
caused mostly by transmission. Identifying transmission chains is important in controlling DR-TB. This study reports
on the sentinel molecular surveillance data of Rifampicin-Resistant (RR) TB in SA, aiming to describe the RR-TB strain
population and the estimated transmission of RR-TB cases.
METHOD: RR-TB isolates collected between 2014 and 2018 from eight provinces were genotyped using
combination of spoligotyping and 24-loci mycobacterial interspersed repetitive-units-variable-number tandem
repeats (MIRU-VNTR) typing.
RESULTS: Of the 3007 isolates genotyped, 301 clusters were identified. Cluster size ranged between 2 and 270 cases.
Most of the clusters (247/301; 82.0%) were small in size (< 5 cases), 12.0% (37/301) were medium sized (5–10 cases),
3.3% (10/301) were large (11–25 cases) and 2.3% (7/301) were very large with 26–270 cases. The Beijing genotype
was responsible for majority of RR-TB cases in Western and Eastern Cape, while the East-African-Indian-Somalian
(EAI1_SOM) genotype accounted for a third of RR-TB cases in Mpumalanga. The overall proportion of RR-TB cases
estimated to be due to transmission was 42%, with the highest transmission-rate in Western Cape (64%) and the
lowest in Northern Cape (9%).
CONCLUSION: Large clusters contribute to the burden of RR-TB in specific geographic areas such as Western Cape,
Eastern Cape and Mpumalanga, highlighting the need for community-wide interventions. Most of the clusters
identified in the study were small, suggesting close contact transmission events, emphasizing the importance of
contact investigations and infection control as the primary interventions in SA.
