Quorum sensing (QS) regulates various types of bacterial behaviour, such as motility and adhesion to biotic and abiotic surfaces. Adhesion is the initial step in biofilm formation, which cause enormous problems in the food industry. Plant formulations have shown antibacterial activity and have also shown to be effective against QS. The effect of plant formulations on QS in C. jejuni has been poorly studied so far, so we tested the effect of 30 plant formulations on QS, motility and adhesion of these bacteria. We studied the correlation between the changes in QS, motility and adhesion. To determine the effect of plant formulations against QS in C. jejuni, we have used the bioluminiscence measurement of the reporter strain V. harveyi BB170, after addition of spent medium of C. jejuni, cultivated with or without addition of plant formulation in concentration of 1/4 MIC. Most of the plant formulations have reduced the AI-2 signal for more than 80 %, with the best effect of plant secondary metabolite tyrosol (98 %). Since plant formulations have shown excellent effect on QS, we tested their effect on bacterial motility on semisolid agar. 4 plant formulations reduced the bacterial motility with statistical significance (essential oils of juniperus (Juniperus communis), oregano (Origanum vulgare) and thyme (Thymus vulgaris), as well as γ-terpinene). We have shown statistically significant correlation between the changes in QS and motility. 14 plant formulations showed antiadhesion effects on C. jejuni on the surface of the polystyrene microtiter plate, but we have not confirmed statistically significant correlations between the changes in QS and adhesion.
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