Genetic diversity of Mycobacterium tuberculosis in Mbarara, South Western Uganda

Abstract

Background: We determined the genetic diversity of mycobacteria isolated from tuberculosis patients in Mbarara Uganda, using region of difference (RD) analysis and spacer oligonucleotide typing (spoligotyping). Methods: Sputum samples were cultured on Lowenstein Jensen media. The isolates were characterized using RD analysis and spoligotyping. Results: The majority (92.8%) of the patients were new cases, 60% were males and 44% were HIV positive with a mean age of 33.7 years. All the 125 isolates were identified as M.tuberculosis sensu stricto. Most (92.8%) of the isolates were modern strains. Spoligotyping revealed 79 spoligotype patterns, with an overall diversity of 63.2%. Sixty (48%) isolates formed 16 clusters each consisting of 2-15 isolates. Mst (59.2 %) of the isolates were Uganda genotype strains. The major shared spoligotypes in our sample were SIT 135 (T2-Uganda) with 12 isolates and SIT 128 (T2) with 5 isolates. Sixty-nine (87%) patterns had not yet been defined in the SpolDB4.0. database. Conclusion: The TB epidemic in Mbarara is caused mainly by modern M-Tuberculosis strains of the Uganda genotype. The wide diversity of strains may indicate that the majority of the TB cases are reactivation rather than re-infection. However, this needs to be ascertained with more discriminative finger printing technique