Diverse plant extracts and <i>trans</i>-resveratrol inhibit biofilm formation and swarming of <i>Escherichia coli</i> O157:H7

<div><p>Infection with enterohemorrhagic <i>Escherichia coli</i> O157:H7 (EHEC) is a worldwide problem. Of the 498 plant extracts screened against EHEC, 16 inhibited the formation of biofilm of EHEC by >85% without inhibiting the growth of planktonic cells, and 14 plant extracts reduced the swarming motility of EHEC. The most active extract, <i>Carex dimorpholepis,</i> decreased swimming and swarming motilities and curli formation. Transcriptional analyses showed that the extract of <i>C. dimorpholepis</i> repressed curli genes, various motility genes, and AI-2 quorum sensing genes, which was corroborated by reduction in the production of fimbria, motility, and biofilm by EHEC. <i>Trans</i>-resveratrol at 10 μg ml<sup>−1</sup> in the extract of <i>C. dimorpholepis</i> was found to be a new anti-biofilm compound against EHEC, but importantly, the extract of <i>C. dimorpholepis</i> and <i>trans</i>-resveratrol did not inhibit the fomation of biofilm in four commensal <i>E. coli</i> strains. Furthermore, the extract of <i>C. dimorpholepis</i> decreased the adhesion of EHEC cells to human epithelial cells without affecting the viability of these cells.</p></div>

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