Combating multidrug-resistance in <i>S. pneumoniae</i>: a G-quadruplex binding inhibitor of efflux pump and its bio-orthogonal assembly

Abstract

Antibiotic resistance poses a significant global health threat, necessitating innovative strategies to combat multidrug-resistant bacterial infections. <i>Streptococcus pneumoniae</i>, a pathogen responsible for various infections, harbors highly conserved DNA quadruplexes in genes linked to its pathogenesis. In this study, we introduce a novel approach to counter antibiotic resistance by stabilizing G-quadruplex structures within the open reading frames of key resistance-associated genes (<i>pmrA</i>, <i>recD</i> and <i>hsdS</i>). We synthesized <b>An4</b>, a bis-anthracene derivative, using Cu(I)-catalyzed azide-alkyne cycloaddition, which exhibited remarkable binding and stabilization of the G-quadruplex in the <i>pmrA</i> gene responsible for drug efflux. <b>An4</b> effectively permeated multidrug-resistant <i>S. pneumoniae</i> strains, leading to a substantial 12.5-fold reduction in ciprofloxacin resistance. Furthermore, <b>An4</b> downregulated <i>pmrA</i> gene expression, enhancing drug retention within bacterial cells. Remarkably, the <i>pmrA</i> G-quadruplex cloned into the pET28a(+) plasmid transformed into <i>Escherichia coli</i> BL21 cells can template Cu-free bio-orthogonal synthesis of <b>An4</b> from its corresponding alkyne and azide fragments. This study presents a pioneering strategy to combat antibiotic resistance by genetically reducing drug efflux pump expression through G-quadruplex stabilization, offering promising avenues for addressing antibiotic resistance.