A first insight into the genetic diversity of Mycobacterium tuberculosis in Dar es Salaam, Tanzania, assessed by spoligotyping

Background: Tanzania has a high tuberculosis incidence, and genotyping studies of Mycobacterium tuberculosis in the country are necessary in order to improve our understanding of the epidemic. Spoligotyping is a potentially powerful genotyping method due to fast generation of genotyping results, high reproducibility and low operation costs. The recently constructed SpoIDB4 database and the model-based program 'Spotclust' can be used to assign isolates to families, subfamilies and variants. The results of a study can thus be analyzed in a global context. Results: One hundred forty-seven pulmonary isolates from consecutive tuberculosis patients in Dar es Salaam were spoligotyped. SpoIDB4 and 'Spotclust' were used to assign isolates to families, subfamilies and variants. The CAS (37%), LAM (22%) and EAI (17%) families were the most abundant. Despite the dominance of these three families, diversity was high due to variation within M. tuberculosis families. Of the obtained spoligopatterns, 64% were previously unrecorded. Conclusion: Spoligotyping is useful to gain an overall understanding of the local TB epidemic. This study demonstrates that the extensive TB epidemic in Dar es Salaam, Tanzania is caused by a few successful M. tuberculosis families, dominated by the CAS family. Import of strains was a minor problem.