Genetic profile of Mycobacterium tuberculosis and treatment outcomes in human pulmonary tuberculosis in Tanzania

Abstract

Information on the different spoligotype families of Mycobacterium tuberculosis in Tanzania is limited, and where available is restricted to small geographical areas.  This article describes the genetic profile of M. tuberculosis across Tanzania and suggests how spoligotype families might affect drug resistance and treatment outcomes for smear positive pulmonary tuberculosis patients in Tanzania. In this study conducted from 2006 to 2008, the M. tuberculosis isolates were obtained from samples collected under the routine drug resistance surveillance system. The isolates were from specimens collected from 2001 to 2007, and stored at the Central and Reference Tuberculosis Laboratory in Dar es Salaam. A total of 487 isolates from 23 regions in Tanzania were spoligotyped. However, clinical information for 446 isolates was available. Out of the 487 isolates spoligotyped, 195 (40.0%) belonged to the Central Asian (CAS) family, 84 (17.5%) to the Latin American Mediterranean (LAM) family, 49 (10.1%) to the East-African Indian (EAI) family, and 33 (6.8%) to the Beijing family. Other isolates included 1 (0.2%) for H37Rv, 10 (2.1%) for Haarlem, 4 (0.8%) for S family, 58 (11.9%) for T family and 52 (10.7%) for unclassified.  No spoligotype patterns were consistent with M. bovis. As regards to treatment outcomes, the cure rate was 80% with no significant variation between the spoligotype families.  The overall level of MDR-TB was 2.5% (3/121), with no significant difference between the spoligotype families. All Beijing strains (11.8%, 30/254) originated from the Eastern and Southern zones of the country, of which 80% were from Dar es Salaam.  Isolates from the CAS and T families were reported disproportionately from the Eastern-Southern zone, and EAI and LAM families from the Northern-Lake zones but the difference was not statistically significant. Five isolates were identified as Non-tuberculous Mycobacteria. In conclusion, M. tuberculosis isolates from pulmonary tuberculosis cases in Tanzania were classified mostly within the CAS, LAM, and EAI and T families.  Consistently good treatment outcomes were recorded across the spoligotype families.  The proportion of drug resistance strains was low. The findings also suggest variation of spoligotype families with varying geographical localities within the country.