Genetic diversity of Mycobacterium tuberculosis in Mbarara, South Western Uganda

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 techniques