Clinical outcomes and molecular characterization of drug-resistant tuberculosis in pre- and extensively drug-resistant disease based on line probe assays

Multidrug-resistant tuberculosis (MDR-TB) represents a significant impact in transmission, outcome, and health costs. The World Health Organization recommends implementation of rapid diagnostic methods for multidrug-resistance detection. This study was performed to evaluate the frequency of pre- and extensively drug resistant tuberculosis (pre-XDR-TB and XDR-TB) among MDR-TB patients, the pattern of resistance mutations for fluoroquinolones and the clinical outcome. Adult patients followed at a Brazilian regional reference center for TB, from January 2013 to June 2019 were included. Stored Mycobacterium tuberculosis (Mtb) cultures were recovered, the DNA was extracted, and the susceptibility test was performed using the line probe assay for second line antimycobacterial drugs, Genotype MTBDRsl version 2.0 (Hain Lifescience, CmbH, Germany). Among 33 MDR-TB included patients, we diagnosed XDR-TB or pre-XDR in five (15%) cases. Of these, mutations related to fluoroquinolones resistance were observed in four Mtb isolates, including one who had no phenotypic resistance profile. In two other patients with phenotypic resistance to ofloxacin, genotypic resistance was not found. Case fatality rate was 60% in pre/XDR-TB group, compared to 3.6% in the remaining of patients. This study observed few cases of pre-XDR and XDR-TB among a MDR-TB cohort. Phenotypic and genotypic assays presented good agreement. Clinical outcome was more favorable for patients with susceptibility to fluoroquinolones and injectable drugs.