Using conventional broth microdilution assays,the synthetic phenolic antioxidant 2,6-di-tert-butyl-4-methylphenol(butylated hydroxytoluene,BHT)was screened for synergistic antimi-crobial activity with β-lactam antibiotics.Further validation through checkerboard assays,growth curve analysis,and time-kill curve experiments confirmed the synergistic effect of BHT and β-lac-tams against methicillin-resistant Staphylococcus aureus(MRSA)(FICI≤0.5).To elucidate the underlying mechanism of synergy,this study evaluated changes in membrane permeability and pro-ton transmembrane gradients-key factors in biofilm functionality-along with critical indicators of bacterial energy metabolism,including ATP levels and the NAD+/NADH ratio.The results dem-onstrated that BHT disrupts the proton motive force(PMF),impairs membrane potential,and perturbs bacterial energy homeostasis,thereby significantly enhancing the antibacterial efficacy ofβ-lactams.Furthermore,a murine pneumonia infection model was established to assess the in vivo therapeutic efficacy of BHT combined with amoxicillin.The combination therapy alleviated pulmo-nary tissue damage,reduced bacterial loads in target organs(liver,spleen,and lungs),and decreased systemic inflammatory responses.This study elucidates the synergistic antimicrobial action and mechanistic basis of BHT combined with amoxicillin,offering a novel combinatorial therapeutic strategy to address MRSA resistance.The findings hold significant clinical potential and research value for overcoming antibiotic resistance in MRSA infections.

Using conventional broth microdilution assays,the synthetic phenolic antioxidant 2,6-di-tert-butyl-4-methylphenol(butylated hydroxytoluene,BHT)was screened for synergistic antimi-crobial activity with β-lactam antibiotics.Further validation through checkerboard assays,growth curve analysis,and time-kill curve experiments confirmed the synergistic effect of BHT and β-lac-tams against methicillin-resistant Staphylococcus aureus(MRSA)(FICI≤0.5).To elucidate the underlying mechanism of synergy,this study evaluated changes in membrane permeability and pro-ton transmembrane gradients-key factors in biofilm functionality-along with critical indicators of bacterial energy metabolism,including ATP levels and the NAD+/NADH ratio.The results dem-onstrated that BHT disrupts the proton motive force(PMF),impairs membrane potential,and perturbs bacterial energy homeostasis,thereby significantly enhancing the antibacterial efficacy ofβ-lactams.Furthermore,a murine pneumonia infection model was established to assess the in vivo therapeutic efficacy of BHT combined with amoxicillin.The combination therapy alleviated pulmo-nary tissue damage,reduced bacterial loads in target organs(liver,spleen,and lungs),and decreased systemic inflammatory responses.This study elucidates the synergistic antimicrobial action and mechanistic basis of BHT combined with amoxicillin,offering a novel combinatorial therapeutic strategy to address MRSA resistance.The findings hold significant clinical potential and research value for overcoming antibiotic resistance in MRSA infections.