Overexpression of outer membrane protein A (OmpA) increases aminoglycoside sensitivity in mycobacteria

Abstract

Abstract Background Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb) complex infection, is a leading cause of death worldwide from a single infectious agent. The emergence of drug resistance Mtb clinical strains makes the situation more serious. The role of Mtb outer membrane protein A (OmpA) in antimicrobial resistance remains unclear. This study aimed to evaluate the effect of OmpA expression on mycobacterial drug resistance. In this study, a Mycobacterium smegmatis (Ms) strain overexpressing OmpA (Ms-OmpA) and a Mycobacterium bovis (Mb) strain overexpressing OmpA (Mb-OmpA) were constructed, and their susceptibility to anti-TB drugs was determined by performing the minimal inhibitory concentrations (MICs), the plate assay and the macrophage infection assays. Results The streptomycin MIC of the overexpressing strain was 2-fold lower than those of the wide-type (Ms) and empty plasmid strains (pMV-261) as well as amikacin and gentamicin. Moreover, both the plate and the macrophage infection assays indicate that overexpression of OmpA increases streptomycin sensitivity in Mycobacteria. The other aminoglycosides like amikacin and gentamicin have the same phenotypes as streptomycin on the plates for the virulent strain Mb-OmpA. The porin inhibitor spermidine can increase streptomycin tolerance in the overexpressing strain, and overexpressing OmpA can increase the intracellular accumulation of hydrophilic ethidium bromide, which indicates that porin protein OmpA contributes to aminoglycosides sensitivity in Mycobacteria. Conclusions In this study, we have characterized the contribution of OmpA in the antimicrobial resistance phenotype of Mycobacteria, which may provide valuable insights for understanding antibiotic resistance and designing new strategies for TB treatment.

Keywords

• Mycobacterium tuberculosis complex
• Mycobacterium smegmatis
• Mycobacterium bovis
• OmpA
• Streptomycin
• Aminoglycosides