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<p><i>Pseudomonas aeruginosa</i> remains a major concern in clinical microbiology owing to its intrinsic multidrug resistance and its elaborate regulatory networks that enable evasion of host immune responses, particularly through robust biofilm development and the secretion of diverse virulence factors. These pathogenic behaviors are tightly governed by quorum-sensing (QS) systems, prompting increasing interest in exploiting plant-derived compounds as potential anti-virulence therapeutics. In this study, leaf extracts from <i>Ricinus communis</i> and <i>Catharanthus roseus</i> were examined for their capacity to modulate biofilm formation and QS-regulated virulence gene expression in the <i>P. aeruginosa</i> PAO1 strain.</p><p>The production of key virulence factors was evaluated using multiple standardized assays, including the crystal violet binding assay (biofilm), azocasein assay (protease), chloroform-HCl extraction (pyocyanin), and the orcinol assay (rhamnolipids), while gene expression was quantified via quantitative real-time polymerase chain reaction (qPCR). The findings indicated that the extracts, rich in tannins and flavonoids, did not affect the planktonic growth of PAO1; however, both significantly (<i>P</i> &lt; 0.05) suppressed biofilm formation and attenuated the production of pyocyanin, protease, and rhamnolipids. Additionally, qPCR analysis revealed pronounced downregulation of central QS regulatory genes, <i>lasI</i>,<i> lasR</i>,<i> and rhlR</i>, highlighting the potential of these phytochemicals to disrupt quorum-sensing-mediated pathogenicity.</p> Graphical Abstract <p></p>

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Anti-biofilm and anti-virulence properties of Ricinus communis and Catharanthus roseus leaves against Pseudomonas aeruginosa PAO1

  • 期刊论文

  • 发表日期：

    2026年3月24日

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  • Eman El Gebaly,
  • Mostafa N. Taha,
  • Hossam M. Ashour,
  • Ahmed S. Khairalla

摘要

Pseudomonas aeruginosa remains a major concern in clinical microbiology owing to its intrinsic multidrug resistance and its elaborate regulatory networks that enable evasion of host immune responses, particularly through robust biofilm development and the secretion of diverse virulence factors. These pathogenic behaviors are tightly governed by quorum-sensing (QS) systems, prompting increasing interest in exploiting plant-derived compounds as potential anti-virulence therapeutics. In this study, leaf extracts from Ricinus communis and Catharanthus roseus were examined for their capacity to modulate biofilm formation and QS-regulated virulence gene expression in the P. aeruginosa PAO1 strain.

The production of key virulence factors was evaluated using multiple standardized assays, including the crystal violet binding assay (biofilm), azocasein assay (protease), chloroform-HCl extraction (pyocyanin), and the orcinol assay (rhamnolipids), while gene expression was quantified via quantitative real-time polymerase chain reaction (qPCR). The findings indicated that the extracts, rich in tannins and flavonoids, did not affect the planktonic growth of PAO1; however, both significantly (P < 0.05) suppressed biofilm formation and attenuated the production of pyocyanin, protease, and rhamnolipids. Additionally, qPCR analysis revealed pronounced downregulation of central QS regulatory genes, lasI, lasR, and rhlR, highlighting the potential of these phytochemicals to disrupt quorum-sensing-mediated pathogenicity.

Graphical Abstract