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Background <p>Andrographolide (AG) demonstrates good inhibitory effects against single-species infections and biofilm formation. This study aimed to investigate the inhibitory effects of AG on mixed cultures of <i>Candida albicans</i> and <i>Staphylococcus aureus</i> in both planktonic and biofilm states.</p> Methods <p>Standard strains of <i>C. albicans</i> ATCC11006 and <i>S. aureus</i> ATCC25923 were selected, and minimum inhibitory concentrations were determined using the microbroth dilution method. Time-growth curves of the mixed strains under AG treatment were plotted. Furthermore, an in vitro mixed biofilm model was constructed, and biofilm formation was assessed using crystal violet staining and inverted fluorescent microscope. Finally, biofilm-related gene expression was measured using RT-qPCR.</p> Results <p>The MIC values of AG against <i>C. albicans</i>, <i>S. aureus</i> and the mixed strains were 256&#xa0;µg/ml, 512&#xa0;µg/mL and &gt; 512&#xa0;µg/mL, respectively. Time-growth curves of the mixed strains under varying AG concentrations demonstrated a concentration-dependent growth inhibition and delayed logarithmic-phase progression in planktonic cultures. Crystal violet staining revealed 512&#xa0;µg/mL AG reduced biofilm biomass by 90.23% compared to controls. Microscopic analysis revealed that the control formed compact biofilms, whereas 512&#xa0;µg/mL AG treatment resulted in thin biofilms, with most <i>C. albicans</i> in spore form and few hyphae, and <i>S. aureus</i> was scattered around them. Additionally, 512&#xa0;µg/mL AG significantly downregulated <i>EFG1</i>, <i>HWP1</i>, <i>icaA</i> and <i>cidA</i>, while lower concentrations markedly downregulate <i>icaA</i> and <i>cidA</i>.</p> Conclusions <p>AG may suppress mixed biofilm development by preventing <i>S. aureus</i> adhesion and blocking <i>C. albicans</i> hyphal formation.</p>

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In vitro evaluation of antimicrobial activity of andrographolide against mixed biofilms of Candida albicans and Staphylococcus aureus

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年2月7日

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  • Jing Yang,
  • Xiaoya Fang,
  • Yan Ma,
  • Zhiqin Xi,
  • Wenqin Yang,
  • Wenli Feng

摘要

Background

Andrographolide (AG) demonstrates good inhibitory effects against single-species infections and biofilm formation. This study aimed to investigate the inhibitory effects of AG on mixed cultures of Candida albicans and Staphylococcus aureus in both planktonic and biofilm states.

Methods

Standard strains of C. albicans ATCC11006 and S. aureus ATCC25923 were selected, and minimum inhibitory concentrations were determined using the microbroth dilution method. Time-growth curves of the mixed strains under AG treatment were plotted. Furthermore, an in vitro mixed biofilm model was constructed, and biofilm formation was assessed using crystal violet staining and inverted fluorescent microscope. Finally, biofilm-related gene expression was measured using RT-qPCR.

Results

The MIC values of AG against C. albicans, S. aureus and the mixed strains were 256 µg/ml, 512 µg/mL and > 512 µg/mL, respectively. Time-growth curves of the mixed strains under varying AG concentrations demonstrated a concentration-dependent growth inhibition and delayed logarithmic-phase progression in planktonic cultures. Crystal violet staining revealed 512 µg/mL AG reduced biofilm biomass by 90.23% compared to controls. Microscopic analysis revealed that the control formed compact biofilms, whereas 512 µg/mL AG treatment resulted in thin biofilms, with most C. albicans in spore form and few hyphae, and S. aureus was scattered around them. Additionally, 512 µg/mL AG significantly downregulated EFG1, HWP1, icaA and cidA, while lower concentrations markedly downregulate icaA and cidA.

Conclusions

AG may suppress mixed biofilm development by preventing S. aureus adhesion and blocking C. albicans hyphal formation.