P61
Back-to-Africa introductions of Mycobacterium tuberculosis as the only cause of tuberculosis in Dar es Salaam, Tanzania
M Zwyer(1,2) E Windels(3) L Rutaihwa(2,5) J Hella(5) F Menardo(4) M Sasamalo(5) M Reinhard(1,2) A Dötsch(1,2) T Stadler(3) S Gagneux(1,2) D Brites(1,2)
1:University of Basel; 2:Swiss TPH, Basel; 3:ETH Zürich; 4:University of Zürich; 5:Ifakara Health Institue, Bagamoyo
Dar es Salaam is a high-endemic tuberculosis (TB) setting in East Africa and has the highest TB notification rate in Tanzania. We investigated the TB epidemic in the Temeke District of Dar es Salaam by analyzing 1,082 genomes of Mycobacterium tuberculosis (Mtb) isolated from patients and their clinical data collected between 2013 and 2019. Our results revealed that four Mtb lineages circulate in Dar es Salaam, whereby L3 (47%) was the most abundant followed by L4 (31%), L1 (14%), and L2 (8%). Placing the Dar es Salaam genomes into a global collection of genomes (n = 10,733) revealed that the TB epidemic in Dar es Salaam is exclusively driven by Mtb strains that have been introduced from other parts of the world during the last 300 years. Some introductions spread more successfully than others and we found L3.1.1 to be the most prevalent sublineage resulting from a single introduction. Molecular dating analyses revealed that L3.1.1 was introduced earlier than other sublineages, however in general we did not find a correlation between the date of introduction and the number of cases generated. Investigating the transmission rates suggested L2.2.1 and L3.1.1 having increased transmission rates compared to other abundant sublineages.
In summary, we found a high diversity within Mtb strains circulating in Dar es Salaam resulting from early and late introductions and the predominance of L3.1.1 being a composite of an early introduction and enhanced transmission rate.