Epidemiology and molecular characterization of multidrug-resistant Mycobacterium tuberculosis among patients with pulmonary symptoms in Kaduna State, Nigeria.

BACKGROUND

The emergence and spread of multidrug-resistant tuberculosis (MDR-TB) is a critical-priority global health problem that requires molecular-based surveillance to understand its extent of transmission.

MATERIALS AND METHODS

Sputa from 360 patients with pulmonary symptoms were collected and processed for culture and microscopy for Mycobacterium tuberculosis (MTB). Samples were confirmed positive for MTB by immunochromatographic test kits. The GenoType MTBDRplus was used to detect mutations in the rpoB, katG, and inhA promoters, which are responsible for rifampicin and isoniazid resistance.

RESULTS

Of the samples analyzed, 65.6% were confirmed MTB positive, while 48.9% had MDR-TB (both rifampicin and isoniazid resistant). Of the patients with MDR-TB, those aged > 60 years (54.3%), those with a tertiary education level (53.9%), and civil servants (68.4%) had the highest frequency of MDR-TB. Patients with a history of TB (68.3%), cigarette smokers (74.2%), those who consume alcohol (80.7%), diabetic mellitus (53.9%), those who had contact with TB patients (66.7%) had significantly high odds of MDR-TB (Odd Ratio range: 2.55-4.87, p < 0.05). MTBDRplus detected 144 (81.8%) of 176 culture-confirmed MDR-TB strains, of which 59.7%, 10.4%, and 9% point mutations in MUT3 (S531L), MUT2B (H526D), and MUT2A (H526Y), respectively, were found in the rpoB gene. Moreover, missing W8 (530-533), W6 (521-525), and W3 (513-517) were detected in 15.3%, 2.7% and 2.7% of rpoB gene, respectively. Furthermore, 55.6% and 33.3% mutations on the katG at MUT1 (S315T) and inhA MUT1 (C15T), conferring high-level isoniazid resistance and low-level isoniazid resistance among MDR-TB isolates.

CONCLUSION

Findings from this study revealed a high frequency and risk factors of MDR-TB mediated by multiple mutations in the rpoB gene and a relatively lesser frequency of mutations in the katG and inhA genes among the MTB isolates obtained from infected patients in the study area.