RPOB S450L mutation and transmission features of mdr mycobacterium tuberculosis strains in the Republic of Moldova

Abstract

Introduction. The Republic of Moldova (RM) faces a significant challenge with a high prevalence of multidrug-resistant tuberculosis (MDR-TB). Aim of study. This study aims to explore the potential impact of rpoB S450L mutations on the phylogenetic features n of MDR Mycobacterium tuberculosis strains in RM. Methods and materials. We randomly selected MTB isolates from the biobank of the National Reference Tuberculosis Laboratory in RM, covering the period 2013-2018. After extracting MTB DNA, whole-genome sequencing (WGS) was performed. On the sequencing data a phylogenetic tree for the studied strains was generated, with consequent assessment of the impact of rpoB gene mutations on tree distribution. Results. All 288 strains included in the study had at least one resistant mutation in the rpoB gene. Clustering rate in the sequenced strains was (51,7%). It was higher in lineage 4 (L4) then in lineage 2 (L2) strains (63% for L4 vs 36.3% for L2, p < 0,001). In our study, 86.4% of MDR MTB strains exhibited the S450L mutation in the rpoB gene, with a frequency of 43% in lineage L2 and 57% in L4. Strains harboring the rpoB S450L mutation had a higher clustering rate (55,8% vs 25.6%, p=0.0005). As well, among L4 strains with rpoB S450L mutations clustering rate was higher than in those without it (66% vs 31.8%, p=0.0016). However, the difference in clustering rate in L2 strains with and without rpoB S450L was statistically unsignificant (39.2% vs 17.6%, p=0.1068). Compensatory mutations were found in 93.2% of strains with mutations in rpoB S450L, of which 83.9% were in the rpoC gene and 9.2% in the rpoB gene, whereas strains without the S450L mutation had a lower rate (38,4%) of compensatory mutation, of which in the rpoC (5.1%) and rpoB gene (33.3%). Conclusion. The rpoB S450L mutation appears linked to the evolution of resistance and transmission dynamics of distinct MTB lineages in the Republic of Moldova. of multidrug-resistant tuberculosis (MDR-TB). Aim of study. This study aims to explore the potential impact of rpoB S450L mutations on the phylogenetic features n of MDR Mycobacterium tuberculosis strains in RM. Methods and materials. We randomly selected MTB isolates from the biobank of the National Reference Tuberculosis Laboratory in RM, covering the period 2013-2018. After extracting MTB DNA, whole-genome sequencing (WGS) was performed. On the sequenc ing data a phylogenetic tree for the studied strains was generated, with consequent as sessment of the impact of rpoB gene mutations on tree distribution. Results. All 288 strains included in the study had at least one resist ant mutation in the rpoB gene. Clustering rate in the sequenced strains was (51,7%). It was hi gher in lineage 4 (L4) then in lineage 2 (L2) strains (63% for L4 vs 36.3% for L2, p < 0,001). In our study, 86. 4% of MDR MTB strains exhibited the S450L mutation in the rpoB gene, with a frequenc y of 43% in lineage L2 and 57% in L4. Strains harboring the rpoB S450L mutation had a higher clustering rate (55,8% vs 25.6%, p=0.0005). As well, among L4 strains with rpoB S450L mutations clu stering rate was higher than in those without it (66% vs 31.8%, p=0.0016). However, the differ ence in clustering rate in L2 strains with and without rpoB S450L was statistically unsig nificant (39.2% vs 17.6%, p=0.1068). Compensatory mutations were found in 93.2% of strains with m utations in rpoB S450L, of which 83.9% were in the rpoC gene and 9.2% in the rpoB gene, whereas strains without the S450L mutation had a lower rate (38,4%) of compensatory mutation, of which in the rpoC (5.1%) and rpoB gene (33.3%). Conclusion. The rpoB S450L mutation appears linked to the evolution of res istance and transmission dynamics of distinct MTB lineages in the R epublic of Moldova.