Genomic Insight into Primary Adaptation of Mycobacterium tuberculosis to Aroylhydrazones and Nitrofuroylamides In Vitro.

Background/

Objectives

New anti-tuberculosis compounds are needed to treat patients infected with multi- or extensively drug-resistant Mycobacterium tuberculosis strains. Studies based on spontaneous in vitro mutagenesis can provide insights into the possible modes of action and resistance mechanisms of such new compounds. We evaluated the primary response of M. tuberculosis in vitro to the action of new aroylhydrazones and nitrofuroylamides.

Methods

The reference strain H37Rv was cultured on solid media with compounds at increased concentrations relative to MIC. Resistant clones were investigated using whole-genome sequencing and bioinformatics tools to assess the role and potential impact of identified mutations.

Results

Some of the mutations are significant (based on in silico analysis), located in essential genes, and therefore of particular interest. Frameshift mutations were observed in (i) Rv2702/ppgK, which is associated with starvation-induced drug tolerance and persistence in mice, and (ii) Rv3696c/glpK, which has been described as a switch on/off mutation associated with drug tolerance. Nonsynonymous substitutions were found in Rv0506/mmpS2, which belongs to the Mmp protein family involved in transport and drug efflux, and in infB, encoding the translation initiation factor IF-2.

Conclusions

The primary adaptation of M. tuberculosis to the selective pressure of the tested compounds is complex and multifaceted. It involves multiple unrelated genes and pathways linked to non-specific drug tolerance, efflux systems, or mechanisms counteracting oxidative stress.