Presence of Fluoroquinolone mono-resistance among drug-sensitive Mycobacterium tuberculosis isolates: An alarming trend and implications

Abstract

Background: The phenomenon of Drug Resistant Tuberculosis (DRTB) has been evolving aggressively and is posing great threat to tuberculosis control programs worldwide. But what really is fueling drug resistance in high disease burden countries apart from other well known risk factors, with this intent in mind the present study was developed and carried out to. The aim was to capture the presence of Fluoroquinolone (FQ) mono-resistance among drug-sensitive TB cases. Methods: A total of 1280 sputum smear-positive patients were enrolled in the study and were subjected for Drug Susceptibility Testing (DST) using First-Line Drugs (FLD's; Rifampicin, Streptomycin, Isoniazid and Ethambutol) using liquid culture DST and Line Probe Assay. These samples were further subjected to second-line drugs DST (ofloxacin and kanamycin) and DNA sequencing to confirm FQ mono-resistance. Results: The occurrence of FQ mono-resistance among FLD sensitive cases was found to be 3.2% (35/1099). Xpert MTB/RIF assay and rpoB gene sequencing were showed 100% concordance with FLD DST. A total of 35 FQ mono-resistant isolates were further sequenced for gyrA, gyrB and rrs genes. The gene sequencing was found to be in agreement with the DST results for 34 (3.1%) isolates with gyrA and gyrB genes. Conclusion: Presence of FQ resistance among drug sensitive TB cases is a red flag sign. The findings of the present study suggest that, second-line DST should be routinely performed not only for drug-resistant cases but also for drug-sensitive cases so as to capture prevailing true drug resistance at an initial stage.