To investigate the in vitro inhibitory mechanism of Nymphaea candida total flavonoids(NCTF)against Staphylococcus aureus(S.aureus)and its safety in mice,this study first deter-mined the antibacterial effect of NCTF on the clinically isolated strain S.aureus-C1.Subsequently,the inhibitory mechanism of NCTF on S.aureus-C1 was explored by measuring its effects on bac-terial growth curves,microstructure,intracellular AKP and LDH levels,and biofilm formation.Safety evaluation included determination of LD50 and MDT in mice,as well as analysis of serum biochemical parameters,organ indices,and histopathological observations.Results showed that NCTF effectively inhibited S.aureus-C1 proliferation,with an inhibition zone diameter of(18.98±0.67)mm and a MIC of 6.25 g/L.A concentration of 2×MIC nearly completely suppressed bacte-rial growth.Scanning electron microscopy revealed structural damage to bacterial cells,including collapse and shrinkage.AKP and LDH assays indicated significantly increased AKP activity(P＜0.05)and decreased intracellular LDH activity(P＜0.05)in the supernatant of drug-treated groups,demonstrating NCTF-induced disruption of cell walls and membranes leading to leakage of AKP and LDH.Crystal violet staining of biofilms showed significant inhibition rates of(43.77±9.16)％and(61.71±9.82)％at 2 × MIC and 4 × MIC concentrations,respectively(P＜0.05).Safe-ty assessments indicated low toxicity of NCTF in mice,with transient effects that returned to nor-mal levels within a short period.These findings demonstrate that NCTF exhibits potent antibacte-rial activity against S.aureus-C1 by damaging bacterial cell structures,increasing cell wall/mem-brane permeability,reducing biofilm formation,and displaying low toxicity.This study provides scientific evidence for clinical drug screening against bovine mastitis and the development of Nym-phaea candida resources.

To investigate the in vitro inhibitory mechanism of Nymphaea candida total flavonoids(NCTF)against Staphylococcus aureus(S.aureus)and its safety in mice,this study first deter-mined the antibacterial effect of NCTF on the clinically isolated strain S.aureus-C1.Subsequently,the inhibitory mechanism of NCTF on S.aureus-C1 was explored by measuring its effects on bac-terial growth curves,microstructure,intracellular AKP and LDH levels,and biofilm formation.Safety evaluation included determination of LD50 and MDT in mice,as well as analysis of serum biochemical parameters,organ indices,and histopathological observations.Results showed that NCTF effectively inhibited S.aureus-C1 proliferation,with an inhibition zone diameter of(18.98±0.67)mm and a MIC of 6.25 g/L.A concentration of 2×MIC nearly completely suppressed bacte-rial growth.Scanning electron microscopy revealed structural damage to bacterial cells,including collapse and shrinkage.AKP and LDH assays indicated significantly increased AKP activity(P＜0.05)and decreased intracellular LDH activity(P＜0.05)in the supernatant of drug-treated groups,demonstrating NCTF-induced disruption of cell walls and membranes leading to leakage of AKP and LDH.Crystal violet staining of biofilms showed significant inhibition rates of(43.77±9.16)％and(61.71±9.82)％at 2 × MIC and 4 × MIC concentrations,respectively(P＜0.05).Safe-ty assessments indicated low toxicity of NCTF in mice,with transient effects that returned to nor-mal levels within a short period.These findings demonstrate that NCTF exhibits potent antibacte-rial activity against S.aureus-C1 by damaging bacterial cell structures,increasing cell wall/mem-brane permeability,reducing biofilm formation,and displaying low toxicity.This study provides scientific evidence for clinical drug screening against bovine mastitis and the development of Nym-phaea candida resources.