Abstract
BackgroundDrug resistance levels and patterns among Mycobacterium tuberculosis isolates from newly diagnosed and previously treated tuberculosis patients in Mbarara Uganda were investigated.MethodsWe enrolled, consecutively, all newly diagnosed and previously treated smear-positive TB patients aged ≥ 18 years. Isolates were tested for drug resistance against rifampicin (RIF) and isoniazid (INH) using the Genotype® MDRTBplus assay and results were compared with those obtained by the indirect proportion method on Lowenstein-Jensen media. HIV testing was performed using two rapid HIV tests.ResultsA total of 125 isolates from 167 TB suspects with a mean age 33.7 years and HIV prevalence of 67.9% (55/81) were analysed. A majority (92.8%) of the participants were newly presenting while only 7.2% were retreatment cases. Resistance mutations to either RIF or INH were detected in 6.4% of the total 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 H526 D and D516V, while one strain had a Δ1 mutation in the wild type probes. There were three strains with katG (codon 315) gene mutations while only one strain showed the inhA promoter region gene mutation.ConclusionThe TB resistance rate in Mbarara is relatively low. The GenoType® MTBDRplus assay can be used for rapid screening of MDR-TB in this setting.
Highlights
Drug resistance levels and patterns among Mycobacterium tuberculosis isolates from newly diagnosed and previously treated tuberculosis patients in Mbarara Uganda were investigated
The World Health Organization (WHO) estimates current rates of multidrug resistant TB in new and previously treated cases globally at 2.9% and 15.3% respectively, with 57% of multidrug resistant tuberculosis (MDR-TB) cases coming from three high burden countries (China, India, and the Russian Federation) [1]
The new version of the latter assay (GenoType® MTBDRplus), targeting the rpoB gene associated with the resistance to rifampicin (RIF) and both genes commonly associated with the resistance to isoniazid (INH) has been evaluated mainly on cultures and clinical specimens in various low incidence settings, demonstrating excellent specificity and good concordance with phenotypic drug susceptibility test (DST) results [7,8]
Summary
Drug resistance levels and patterns among Mycobacterium tuberculosis isolates from newly diagnosed and previously treated tuberculosis patients in Mbarara Uganda were investigated. The World Health Organization (WHO) estimates current rates of multidrug resistant TB (resistance to at least isoniazid and rifampicin) in new and previously treated cases globally at 2.9% and 15.3% respectively, with 57% of multidrug resistant tuberculosis (MDR-TB) cases coming from three high burden countries (China, India, and the Russian Federation) [1]. The new version of the latter assay (GenoType® MTBDRplus), targeting the rpoB gene associated with the resistance to rifampicin (RIF) and both genes (katG and inhA) commonly associated with the resistance to isoniazid (INH) has been evaluated mainly on cultures and clinical specimens in various low incidence settings, demonstrating excellent specificity and good concordance with phenotypic drug susceptibility test (DST) results [7,8]. A recent study demonstrated the feasibility of this assay as a screening tool when applied in a high-volume public health laboratory in a high TB and HIV, but low drug resistance, incidence area [8]
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