Molecular Detection of Mycobacterium tuberculosis Rifampicin Drug Resistance Using rpoB Gene Sequencing in Zimbabwe

Aim: To detect Mtb rifampicin drug resistance mutations in Zimbabwe by rpoB gene sequencing.

Study Design: This was a retrospective study.

Place of Study: The study was conducted in Zimbabwe in 2015 using archived Mtb isolates previously isolated throughout Zimbabwe during a national TB Survey.

Methodology: Archived Mtb isolates at the National Microbiology Reference Laboratory were retrieved. Genomic DNA from the isolates was extracted by the boiling method. The 81 bp region of rpoB gene that contains rifampicin drug resistance mutations was amplified by polymerase chain reaction (PCR). The PCR products were sequenced and sequences analyzed to determine mutations in the rpoB protein.

Results: RpoB mutations in 30 Mtb isolates were analyzed. Out of the 30 Mtb isolates, 19 (63.3%) had at least one codon mutation in the rpoB gene that resulted in a change of amino acid. The commonest mutation was on codons 531 (S>L), with a prevalence of 20%. Other mutations were detected at codons 511 (L>P) (3.3%), 516 (D>Y) (10.0%), 516 (D>V) (3.3%), 518 (N>H) (3.3%), 526 (H>D) (10.0%), 526 (H>L) (3.3%), 526 (H>C) (3.3%), 526 (H>Y) (3.3%) and 533 (L>P) (6.6%). The other 11 Mtb isolates (36.7%) did not have any mutations in the gene coding for drug resistance.

Conclusion: Genetic mutations that code for rifampicin drug resistance are prevalent in Mtb isolates from Zimbabwe. Further studies need to be instituted to ascertain the scope and threat of the Mtb drug resistance.