Use of the GenoType ® MTBDRplus assay to assess anti-TB drug resistance levels and patterns among Mycobacterium tuberculosis isolates from TB patients in rural Uganda

Background: Drug resistance levels and patterns among Mycobacterium tuberculosis isolates from newly diagnosed and previously treated tuberculosis patients in Mbarara Uganda were investigated. Methods: We enrolled, consecutively; all newly diagnosed and previously treated smearpositive TB patients aged ≥ 18 years. Isolates were tested for drug resistance against rifampicin and isoniazid using the Genotype® MDRTBplus assay. HIV-1 testing was performed using two rapid HIV tests. Results: A total of 125 isolates from 167 TB suspects 60% males with a mean age 33.7 years and HIV prevalence of 67.9% were analysed. 92.8% were new cases and 17.2% were retreatment cases. Resistance mutations to either RIF or INH were detected in 6.4% of the isolates. MDR, INH and RIF monoresistance was 3.2%, 4% and 5.6%, respectively. rpoB gene mutations were D516V, S531L, H526Y and H526D together with D516V, while one strain had a ∆1 mutation in the wild type probes. There were three strains with katG (codon 315) gene mutations only and one strain with inhA gene mutation. Conclusion. TB resistance rate in Mbarara is relatively low with a substantial proportion of INH monoresistance. GenoType® MTBDRplus assay can be used for rapid screening of MDR-TB in this setting. Introduction Despite the availability of drugs to treat tuberculosis (TB), it remains the world’s leading cause of death from a single infectious disease and the global rates continue to rise as do the rates of drug-resistance. 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 MDR-TB cases coming from three high burden countries (China, India, and the Russian Federation)[1]. Uganda is currently ranked 16 th among the highest TB burdened countries in the world [2]. The prevalence of MDR-TB in new cases in this setting has previously been reported to be low at less than 2% [3]. However, there are recent reports that 12.7% of retreatment cases attending the National Tuberculosis and Leprosy Program (NTLP) clinic in Kampala, the capital city of Uganda, had MDR-TB [4] and that in one peri-urban population of Kampala the prevalence of MDR-TB was 4.4% in new cases [5]. Although drug susceptibility testing is not routinely undertaken in Uganda it would be advantageous to know the drug susceptibility status especially of re-treatment patients to facilitate appropriate patient management. Several competing technologies have been proposed for rapid detection of drug resistant tuberculosis. Some commercial assays are currently available, including INNO-LiPA Rif.TB (Innogenetics N.V, Ghent, Belgium) and GenoType® MTBDR (HAIN Lifesciences GmbH, Nehren, Germany) [6]. 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 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]. This study aimed at determining the levels and patterns of anti-TB drug resistance to the two key drugs (rifampin and isoniazid) in Mycobacterium tuberculosis strains isolated from TB patients from the rural setting of Mbarara, South-Western Uganda, using the commercially available GenoType® MTBDRplus assay.