Tuberculosis drug resistance (DR) is a global problem that is not fully elucidated. Previously, overexpression of esxG and esxH genes was reported in a multidrug-resistant (MDR) Mycobacterium tuberculosis isolate compared with a reference H37Rv strain. To evaluate the roles of esxG and esxH in DR, analysis of their regulatory and coding sequences in sensitive and resistant strains was performed, and the expression levels of their transcriptional regulators IdeR, Zur, and MntR were evaluated. esxG and esxH were expressed heterologously using mycobacterial constructs, and the orthologs Msmeg_0620 and Msmeg_0621 were attenuated in Mycobacterium smegmatis by antisense knockdown. We found no differences in the regulatory and coding sequences of esxG and esxH between the sensitive strain and the MDR isolate. Expression analysis of transcriptional regulators showed that ideR was upregulated in isoniazid (INH)-resistant isolates; in addition, growth inhibition of the M. smegmatis strain was observed in the presence of rifampicin (RIF) and INH when esxG and esxH were expressed heterologously, while faster growth in the presence of RIF was observed when the orthologs were attenuated. In conclusion, the expression of esxG and esxH altered the growth of Mycobacterium in the presence of INH and RIF, suggesting a potential association with DR.
Keywords: M. smegmatis; Mycobacterium; drug resistance; esxG-esxH.