Comparative\nMetabolomics Reveals Changes in the Metabolic\nPathways of Ampicillin- and Gentamicin-Resistant Staphylococcus\naureus

Antibiotic resistance is a major global challenge requiring\nnew\ntreatments and a better understanding of the bacterial resistance\nmechanisms. In this study, we compared ampicillin-resistant (R-AMP)\nand gentamicin-resistant (R-GEN) Staphylococcus aureus strains with a sensitive strain (ATCC6538) using metabolomics. We\nidentified 109 metabolites; 28 or 31 metabolites in R-AMP or R-GEN\ndiffered from those in ATCC6538. Moreover, R-AMP and R-GEN were enriched\nin five and four pathways, respectively. R-AMP showed significantly\nup-regulated amino acid metabolism and down-regulated energy metabolism,\nwhereas R-GEN exhibited an overall decrease in metabolism, including\ncarbohydrate, energy, and amino acid metabolism. Furthermore, the\nactivities of the metabolism-related enzymes pyruvate dehydrogenase\nand TCA cycle dehydrogenases were inhibited in antibiotic-resistant\nbacteria. Significant decreases in NADH and ATP levels were also observed.\nIn addition, the arginine biosynthesis pathway, which is related to\nnitric oxide (NO) production, was enriched in both antibiotic-resistant\nstrains. Enhanced NO synthase activity in S. aureus promoted NO production, which further reduced reactive oxygen species,\nmediating the development of bacterial resistance to ampicillin and\ngentamicin. This study reveals that bacterial resistance affects metabolic\nprofile, and changes in energy metabolism and arginine biosynthesis\nare important factors leading to drug resistance in S. aureus.