Bactericidal activity of ZnO nanoparticles–anti-TB drug combination towards the H37Rv strain and multidrug-resistant isolates of Mycobacterium tuberculosis via SufB splicing inhibition†

Abstract

Tuberculosis (TB) remains a significant global health threat, claiming millions of lives annually. Despite advancements in treatment, the emergence of drug-resistant strains has hindered effective TB control. The current management of TB involves prolonged treatment duration with severe side effects, leading to poor patient compliance. Metal-based nanoparticles are shown to manage drug-sensitive TB when combined with anti-TB drugs. However, the mycobactericidal potential of nanoparticles towards drug-resistant TB is not confirmed yet. This work explores the bactericidal potential of zinc oxide nanoparticles (ZnONPs, 40 nm) in managing both drug-sensitive and drug-resistant TB in combination with anti-TB drugs. It was found that ZnONPs inhibit the generation of active SufB protein via splicing inhibition, an essential event for Mycobacterium tuberculosis (Mtb) survival. While TEM and UV-visible spectroscopy identified NPs–protein interaction, SEM visualised extensive membrane damage in H37Rv and multidrug-resistant (MDR) Mtb cells. Alamar blue assay and the spread plate method detected minimum inhibitory concentration and minimum bactericidal concentration of ZnONPs towards the H37Rv strain and MDR Mtb isolates. In vitro studies identified a combination with ZnONPs that reduced effective doses for anti-TB drugs towards H37Rv and MDR Mtb isolates. A correlation to splicing inhibition was made by performing Alamar blue assay in an SufB intein-less microbe, Mycobacterium smegmatis. A similar drug combination attenuated the mycobacterial load and inflammation in the spleen and lungs and protected against Mtb induced splenomegaly in infected mice. Thus, ZnONPs can be used as a potent additive in the anti-TB regimen to manage drug-susceptible and drug-resistant TB, addressing challenges such as prolonged therapy, drug toxicity and poor patient compliance.