Abstract
BackgroundDetermination of the prevalence and drug susceptibility of the M. tuberculosis strains is important in tuberculosis control. We determined the genetic diversity and susceptibility profiles of mycobacteria isolated from tuberculosis patients in Mbarara, South Western Uganda.MethodsWe enrolled, consecutively; all newly diagnosed and previously treated smear-positive TB patients aged ≥ 18 years. The isolates were characterized using regions of difference (RD) analysis and spoligotyping. Drug resistance against rifampicin and isoniazid were tested using the Genotype® MDRTBplus assay and the indirect proportion method on Lowenstein-Jensen media. HIV-1 testing was performed using two rapid HIV tests.ResultsA total of 125 isolates from 167 TB suspects (60% males) with a mean age 33.7 years and HIV prevalence of 67.9% (55/81) were analyzed. Majority (92.8%) were new cases while only 7.2% were retreatment cases. All the 125 isolates were identified as M. tuberculosis strict sense with the majority (92.8%) of the isolates being modern strains while seven (7.2%) isolates were ancestral strains. Spoligotyping revealed 79 spoligotype patterns, with an overall diversity of 63.2%. Sixty two (49.6%) of the isolates formed 16 clusters consisting of 2-15 isolates each. A majority (59.2%) of the isolates belong to the Uganda genotype group of strains. The major shared spoligotypes in our sample were SIT 135 (T2-Uganda) with 15 isolates and SIT 128 (T2) with 3 isolates. Sixty nine (87%) of the 79 patterns had not yet been defined in the SpolDB4.0.database. Resistance mutations to either RIF or INH were detected in 6.4% of the isolates. Multidrug resistance, INH and RIF resistance was 1.6%, 3.2% and 4.8%, respectively. The rpoβ gene mutations seen in the sample were D516V, S531L, H526Y H526D and D516V, while one strain had a Δ1 mutation in the wild type probes. There were three strains with katG (codon 315) gene mutations only while one strain showed the inhA promoter gene mutation.ConclusionThe present study shows that the TB epidemic in Mbarara is caused by modern M. tuberculosis strains mainly belonging to the Uganda genotype and anti-TB drug resistance rate in the region is low.
Highlights
Determination of the prevalence and drug susceptibility of the M. tuberculosis strains is important in tuberculosis control
Some of the applications include; predicting transmission rates and identifying dominant strains associated with outbreak [9] severe disease [10] and drug resistance
Our result show differences compared with findings that were obtained in the last National anti-tuberculosis drug resistance survey in Uganda of 1996-97 that indicated a primary resistance to isoniazid of 6.7%, that to rifampicin at 0.8%, and MDR of 0.5% [47]
Summary
Determination of the prevalence and drug susceptibility of the M. tuberculosis strains is important in tuberculosis control. We determined the genetic diversity and susceptibility profiles of mycobacteria isolated from tuberculosis patients in Mbarara, South Western Uganda. The country had more than 132,000 TB cases in 2007, with an estimated incidence rate of 330 per 100,000 people with greater Mbarara contributing about 26% of all TB cases. This region has been heavily affected by the TB/ HIV epidemic. Some of the applications include; predicting transmission rates and identifying dominant strains associated with outbreak [9] severe disease [10] and drug resistance
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