Molecular detection of multidrug-resistant tuberculosis among smear-positive pulmonary tuberculosis patients in Jigjiga town, Ethiopia

Abstract

BackgroundMolecular methods that target drug resistance mutations are suitable approaches for rapid drug susceptibility testing to detect multidrug-resistant tuberculosis (MDR-TB). The aim of the study was to determine MDR-TB cases and to analyze the frequency of gene mutations associated with rifampicin (RIF) and/or isoniazid (INH) resistance of Mycobacterium tuberculosis among smear-positive pulmonary tuberculosis patients.MethodsInstitution-based cross-sectional study design was employed. Sputum specimens were collected, and using a pretested questionnaire, data for associated risk factors for drug resistance were collected from 105 consecutive smear-positive pulmonary tuberculosis patients in Karamara General Hospital. Specimens were transported to Harar Health Research and Regional Laboratory, Harar, where molecular drug susceptibility testing was performed using GenoType® MTBDRplus assay.ResultsOf the total 105 sputum specimens, 98 (93.3%) gave interpretable results, in which 67 (68.4%) were new cases and 31 (31.6%) were previously treated cases. Of these, 80 (81.6%) were sensitive to both drugs and 18 (18.4%) were resistant to RIF and/or INH. The prevalences of MDR-TB in total cases, new, and previously treated cases were 10 (10.2%), 3 (4.5%), and 7 (22.6%), respectively. Among the ten total RIF-resistant specimens, eight (80%) had resulted because of absence of rpoB WT8 and presence of MUT3 and in all specimens, the amino acids changed were Ser531Lue. Of the 18 total INH-resistant specimens, 15 (83.3%) had mutations in the katG gene (katG MUT1, Ser315Thr1), indicating high-level resistance, while 3 (14.7%) had mutations in the inhA promoter gene (Cys15Thr), indicating low-level resistance.ConclusionAmong the mutations associated with resistance to RIF and INH, the majority were in codon 531 of the rpoB gene and codon 315 of the katG gene. Relatively high prevalence of MDR-TB was observed in the study.

Phenotypic and genotypic drug sensitivity of <em>Mycobacterium tuberculosis</em> complex isolated from South Omo Zone, Southern Ethiopia

“…42 , 43 Molecular detection of RIF resistance is used as a surrogate marker for MDR-TB. 11 , 13 , 28 Hence, the identification of RIF-resistant and MDR isolates in the present study indicated the existence of MDR-TB in the study area, which highlights the need for strengthening of the TB control program in the study area.…”

“… 47 Such type of mutation with an amino acid change of H526D was previously reported in Ethiopia in the proportion of 0%–22%. 28 , 48 , 51 , 53 The other RIF mono-resistant isolate missed rpoB WT8 and had no known mutation, which may not indicate real resistance but rather it could be due to a silent mutation in rpoB gene. 54 Similarly, such resistance was reported in previous studies of Ethiopia with various proportions including 11.8% 53 and 44.4%.…”

“…Majority of the isolates were recovered from the economically productive age group, and this observation is similar with observation made by the previous studies. 28 – 31 The reason could be due to the mobility of this age group for economy and social reasons. Similarly, relatively large number of isolates were recovered from males than females which is in agreement with the WHO report.…”

“… 50 The amino acid change of S315T2 (AGC→ACA) in this isolate was not previously reported from Ethiopia but the most common reported amino acid change in Ethiopia has been S315T1, which is in the range of 83%–100%. 28 , 48 , 51 – 53 …”

“… 51 But most RIF-resistant isolates missing rpoB WT8 are accompanied by an S531L amino acid change. 28 , 48 , 53 , 55 RIF mono-resistant isolates were identified from the new TB cases, which could be acquired from TB patients who had RIF-resistant TB or the patients could previously be treated with RIF for other bacterial infection. 42 , 43 Molecular detection of RIF resistance is used as a surrogate marker for MDR-TB.…”