Drug resistance profiles of Mycobacterium tuberculosis clinical isolates by genotype MTBDRplus line probe assay in Zambia: findings and implications

Background The emergence of drug resistance is a threat to global tuberculosis (TB) elimination goals. This study investigated the drug resistance profiles of Mycobacterium tuberculosis (M. tuberculosis) using the Genotype MTBDRplus Line Probe Assay at the National Tuberculosis Reference Laboratory (NTRL) in Zambia.Methods A cross-sectional study was conducted between January 2019 and December 2020. GenoType MTBDRplus line probe assay records for patients at the NTRL were reviewed to investigate drug susceptibility profiles of M. tuberculosis isolates to rifampicin and isoniazid. Data analysis was done using Stata version 16.1.Results Of the 241 patient records reviewed, 77% were for females. Overall, 44% of patients were newly diagnosed with TB, 29% had TB relapse, 10% treatment after failure and 8.3% treatment after loss to follow-up. This study found that 65% of M. tuberculosis isolates were susceptible to rifampicin and isoniazid. Consequently, 35% of the isolates were resistant to rifampicin and/or isoniazid and 21.2% were multidrug-resistant (MDR). Treatment after failure [relative risk ratios (RRR) = 6.1, 95% CI: 1.691-22.011] and treatment after loss to follow-up (RRR = 7.115, 95% CI: 1.995-25.378) were significantly associated with MDR-TB. Unknown HIV status was significantly associated with isoniazid mono-resistance (RRR = 5.449, 95% CI: 1.054-28.184).Conclusions This study found that 65% of M. tuberculosis isolates were susceptible to rifampicin and isoniazid while 35% were resistant. Consequently, a high prevalence of MDR-TB is of public health concern. There is a need to heighten laboratory surveillance and early detection of drug-resistant TB to prevent the associated morbidity and mortality.