Compensatory mutations in rpoA, rpoC and rpoD genes among rifampicin-resistant Mycobacterium tuberculosis isolates from Uganda

Abstract

Background; Mycobacterium tuberculosis can acquire resistance to rifampicin through mutations in the rpoB gene. This is normally accompanied by the fitness cost which however can be mitigated by the acquired secondary mutations in the rpoA, or rpoC and rpoD. The WHO, 2018 guidelines for surveillance of drug-resistant MTB recommends incorporation of molecular technologies into surveys, either alone or with screening tool before culture-based methods. However, drug resistance-conferring mutations that are normally missed in rapid molecular methods like Xpert MTB/RIF assay, for resistance to RIF have been reported. This highlights the need to expand on the diagnostics targets although little has been done to effect this in Uganda. Given that many studies have focused on rpoB gene mutations in Rifampicin resistant MTB. This particular study aimed to determine the compensatory mutations of rpoA, rpoC and rpoD genes among rifampicin-resistant Mycobacterium tuberculosis isolates from Uganda and determine other mutations in the rifampicin-resistant isolates which lack known resistance conferring mutations. Methods; Using purposive sampling, Rifampicin resistant strains, a targeted Sanger sequencing was used to analyze mutations in rpoA, rpoC, rpoD were identified in addition to rpoB mutations found in the isolates. The sequences were analyzed using Bio edit and MEGA6.06 software. Results.; We identified four compensatory mutations namely Ala521Asp, Leu516Pro and Val483Ala which was found in two isolates. all the four mutations were harbored in isolates with rpoB Ser450Leu. No mutations were found in the rpoA and rpoD. For the isolates which had no mutations in the rpoB (RRDR), no mutations were found in the rpoA, rpoC, rpoD genes. Conclusion. In conclusion, Compensatory mutations in the rifampicin resistant isolates do occur in Ugandan isolates which have mutations in the rpoB (RRDR).