Diverse plant extracts andtrans-resveratrol inhibit biofilm formation and swarming ofEscherichia coliO157:H7

Abstract

Infection with enterohemorrhagic Escherichia coli 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, Carex dimorpholepis, decreased swimming and swarming motilities and curli formation. Transcriptional analyses showed that the extract of C. dimorpholepis 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. Trans-resveratrol at 10 μg ml(-1) in the extract of C. dimorpholepis was found to be a new anti-biofilm compound against EHEC, but importantly, the extract of C. dimorpholepis and trans-resveratrol did not inhibit the fomation of biofilm in four commensal E. coli strains. Furthermore, the extract of C. dimorpholepis decreased the adhesion of EHEC cells to human epithelial cells without affecting the viability of these cells.

Non-toxic plant metabolites regulateStaphylococcusviability and biofilm formation: a natural therapeutic strategy useful in the treatment and prevention of skin infections

“…Nevertheless, these results confirm that the activity of the molecules involved in bacterial biofilm metabolism can be modified by the presence of plant metabolites and confirm that this effect is molecule-and species-specific. Moreover, these data support the hypothesis of Lee et al (2013) that plants have developed diverse mechanisms of action to regulate biofilm formation and to control bacterial proliferation. The ability of some non-toxic plant molecules to inhibit or enhance biofilm synthesis by the pathogen S. aureus or the commensal S. epidermidis, respectively (see Figure 1), creates the possibility of developing non-aggressive and non-toxic therapeutic strategies to modulate bacterial proliferation.…”

“…Table 2 shows the respective Lee et al (2013) values obtained for the SIC and MIC. The results reflect a variable degree of antibacterial activity against S. aureus and S. epidermidis.…”

Essential Oils and Eugenols Inhibit Biofilm Formation and the Virulence of Escherichia coli O157:H7

“…EHEC strains contain a series of fimbriae such as curli fimbriae (Csg), type I fimbriae (Fim), E. coli common pilus (Ecp), F9 fimbriae (Z2200), and other fimbrial proteins29. It has been also reported that several phytochemicals, such as, 3-indolylacetonitrile30, phloretin31, resveratrol (and its dimer viniferin)3233, cinnamaldehyde18, coumarin34, and ginkgolic acids17 inhibit EHEC biofilm formation primarily by inhibiting curli fimbriae production. Hence, it appears that fimbriae-reducing ability is not rare in the plant kingdom and that the fimbriae inhibition could be viewed a practical target for suppressing EHEC biofilm formation.…”

“…Swimming motility was assayed using 0.3% agar plates containing 1% tryptone and 0.25% NaCl, and swarming motility was assayed using LB broth supplemented with 0.8% glucose and 0.5% agar, as previously described32. Essential oils, eugenol or DMSO (the control) were added to motility agar.…”

The ability of an antimicrobial agent to penetrate a biofilm is not correlated with its killing or removal efficiency

“…Currently, there is no control strategy capable of entirely eradicating biofilms (Simões et al 2010). There is a need to find new strategies to manage antimicrobial resistance (Lee et al 2013; Traba et al 2013). 2 Resistance is the ability to withstand antimicrobial treatments.…”