Reduced redox-dependent mechanism and glucose-mediated reversal in gentamicin-resistant Vibrio alginolyticus

Strategy of managing antibiotic-resistant Vibrio alginolyticus, a bacterial pathogen that threatens human health and animal farming, is not available due to the lack of knowledge about the underlying mechanism of antibiotic resistance. Here, we showed that gentamicin-resistant V. alginolyticus (VA-R-GEN) has four mutations on metabolism and one mutation on a two-component system by whole-genome and PCR-based sequencing, indicating the metabolic shift in VA-R-GEN. Thus, metabolic profile was investigated by GC-MS based metabolomics. Glucose was identified as a crucial biomarker, whose abundance was decreased in VA-R-GEN. Further analysis with iPath, and gene expression and enzyme activity of the pyruvate cycle (the P cycle) demonstrated a global depressed metabolic pathway network in VA-R-GEN. Consistently, NADH, sodium-pumping NADH:ubiquinone oxidoreductase (Na(+)-NQR) system, membrane potential and intracellular gentamicin were decreased in VA-R-GEN. These findings indicate that the reduced redox state contributes to antibiotic resistance. Interestingly, exogenous glucose potentiated gentamicin to efficiently kill VA-R-GEN through the promotion of the P cycle, NADH, membrane potential and intracellular gentamicin. The potentiation was further confirmed in a zebrafish model. These results indicate that the gentamicin resistance reduces the P cycle and Na(+)-NQR system and thereby decreases redox state, membrane potential and gentamicin uptake, which can be reversed by exogenous glucose.