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

One hundred forty-seven pulmonary isolates from consecutive tuberculosis patients in Dar es Salaam were spoligotyped. SpolDB4 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.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.In Tanzania, the tuberculosis (TB) incidence doubled between 1990 and 2004 [1]. The rate of all forms of the disease is estimated at 524/100,000 and the rate of new sputum smear positive disease is approximately 157/100,000 [1] with Dar es Salaam contributing about 26% of all TB cases [2]. The World Health Organization estimates that Tanzania has the 14th highest TB burden in the world [1]. Points of concern include the proportion of patients lost to follow-up, currently at 9%, an average diagnostic delay of 6 months, decreasing case detection rate (from 55% in 1997 to 45% in 2004) and the continuing high prevalence of HIV [3]. The high case rate in many African countries has contributed to a rise of the global TB incidence, despite stable or declining rates in the rest of the world [1]. Tanzania with its 37 million inhabitants, has 701 district laboratories diagnosing TB, three laboratories culturing M. tuberculosis and one National reference laboratory that perform drug susceptibility testing of M. tuberculosis isolates. Measures are undertaken to establish molecular genotyping methods such as spoligotyping [4], but currently no laboratory in Tanzania offers this service. Previous studies have described the molecular epidemiolog