In vitro and in vivo antibacterial activity of compound L007-0069 against Staphylococcus epidermidis and its antibacterial mechanism

YANG Wen-yi; TU Xi-chen; HOU Zheng-li

doi:10.20251/j.cnki.1003-3734.2026.05.011

Abstract：Objective:The drug resistance of Staphylococcus epidermidis(S.epidermidis)and its biofilm have become a thorny problem in clinical work.The exploration of novel antibacterial drugs could provide a breakthrough for the treatment of related infectious diseases in clinical practice.In this study,the antibacterial activity of the novel small molecule compound L007-0069 against S.epidermidis was investigated and its mechanism of action was further elucidated.Methods:The antibacterial susceptibility of L007-0069 against S.epidermidis was evaluated in vitro using disk diffusion and broth microdilution assays.Time-kill curves were used to study the bactericidal activity of L007-0069 against S.epidermidis and its persister cells.A checkerboard dilution assay was used to assess the combined efficacy of L007-0069 when used with gentamicin;an XTT assay was used to detect the antibacterial activity of L007-0069 against S.epidermidis biofilms;SYTO9/PIdual fluorescence staining was used to observe the disruptive effect of L007-0069 on the structural integrity of S.epidermidis biofilms;the disruption of the cell membrane integrity of S.epidermidis by L007-0069 was detected using DiSC3(5)and SYTOX Green fluorescent probes;finally,the in vivo antibacterial effect of L007-0069 on S.epidermidis was studied using a mouse skin abscess model.Results:L007-0069 exhibited a minimum inhibitory concentration(MIC)and minimum bactericidal concentration of 4 μg·mL-1 against S.epidermidis strains RP62A and ATCC 12228,and also showed significant antimicrobial activity against clinical isolates.L007-0069 demonstrated time-and concentration-dependent bactericidal activity.Disk diffusion assays indicated that 80 μg of L007-0069 produced a significant inhibition zone compared to the untreated group[(0.000±0.000)vs(9.267±1.201)mm;q=16.631,P<0.0001],and the diameter of the inhibition zone increased with higher concentrations of L007-0069.When combined with gentamicin,L007-0069 exhibited synergistic antibacterial activity against S.epidermidis with the fractional inhibitory concentration index of 0.5.At a concentration of 4 μg·mL-1,L007-0069 significantly inhibited S.epidermidis biofilm formation,reducing the absorbance at 570 nm(A570)from(0.896±0.167)to(0.049±0.019)(q=5.551,P=0.0004).At 4 μg·mL-1,L007-0069 also be effectively destroyed formed biofilms,reducing A570nm from(1.367±0.198)to(0.237±0.072)(q=10.03,P<0.0001).Confocal laser scanning microscopy revealed that L007-0069 significantly disrupted the three-dimensional structure of the biofilm and significantly reduced the total biofilm.DiSC3(5)assays showed a significant increase in bacterial membrane potential.Similarly,SYTOX Green assays showed that 1/2×MIC of L007-0069 significantly increased SYTOX Green fluorescence intensity in a concentration-dependent manner,further confirming its membrane-disruptive activity.The in vivo animal model indicates that L007-0069 significantly reduced the viable bacterial load in the abscess tissue and decreased the infiltration of inflammatory cells.Conclusion:L007-0069 exerts antibacterial effects both in vitro and in vivo by damaging the cell membranes of S.epidermidis.It is expected to become a potential alternative therapeutic drug for infections related to S.epidermidis biofilm.