Exogenous methionine contributes to reversing the resistance of to macrolides.

() has been increasingly recognized as a porcine zoonotic pathogen that threatens the health of both pigs and humans. Multidrug-resistant is becoming increasingly prevalent, and novel strategies to treat bacterial infections caused by these organisms are desperately needed. In the present study, an untargeted metabolomics analysis showed that the significant decrease in methionine content and the methionine biosynthetic pathway were significantly affected by the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis in drug-resistant . The addition of L-methionine restored the bactericidal activity of macrolides, doxycycline, and ciprofloxacin on and . Further studies showed that the exogenous addition of methionine affects methionine metabolism by reducing S-adenosylmethionine synthetase activity and the contents of S-adenosylmethionine, S-adenosyl homocysteine, and S-ribose homocysteine. Methionine can decrease the total methylation level and methylesterase activity in multidrug resistant . The drug transport proteins and efflux pump genes were significantly downregulated in by exogenous L-methionine. Moreover, the exogenous addition of methionine can reduce the survival of by affecting oxidative stress and metal starvation in bacteria. Thus, L-methionine may influence the development of resistance in through methyl metabolism and metal starvation. This study provides a new perspective on the mitigation of drug resistance in .IMPORTANCEBacterial antibiotic resistance has become a severe threat to human and animal health. Increasing the efficacy of existing antibiotics is a promising strategy against antibiotic resistance. Here, we report that L-methionine enhances the efficacy of macrolides, doxycycline, and ciprofloxacin antibiotics in killing , including multidrug-resistant pathogens. We investigated the mechanism of action of exogenous methionine supplementation in restoring macrolides in and the role of the methionine cycle pathway on methylation levels, efflux pump genes, oxidative stress, and metal starvation in . It provides a theoretical basis for the rational use of macrolides in clinical practice and also identifies a possible target for restoring drug resistance in .