Lactocin AL705 as quorum sensing inhibitor to control Listeria monocytogenes biofilm formation

The control of Listeria monocytogenes biofilm formation using lactocin AL705 bacteriocin at sub-minimum inhibitory concentrations (MICs) through an antiquorum sensing strategy, was preliminarily investigated.

The screening for biofilm formation of different Listeria species at 10°C allowed selecting L. monocytogenes FBUNT for its use as biofilm producer. MIC and minimum bactericidal concentration of lactocin AL705 purified extract against the pathogen was determined. Bacteriocin sub-MICs were used to evaluate biofilm reduction. Concentrations between 2·5-20 AU ml^-1 of lactocin AL705 produced significant decreases in biofilm formation without affecting the growth of the pathogen after 3 days of incubation. When bacteriocin concentrations (5-20 arbitrary units per millilitre (AU ml^-1 )) were investigated as quorum sensing (QS) inhibitors using Vibrio harveyi as reporter strain, a significant reduction in luminescence by lactocin AL705 (20 AU ml^-1 ) was observed. Even when L. monocytogenes produced AI-2 like molecules as recognized by the reporter strain, bacteriocins did not interfere with this compound.

Antilisterial lactocin AL705 used to disrupt QS through a signal molecule inactivation was able to control L. monocytogenes FBUNT biofilm formation. Other molecule(s) different from the AI-2 involved during biofilm formation could be acting as target of the bacteriocin.

The use of bacteriocins derived from food-grade micro-organisms as a QS inhibition represents an effective strategy to control pathogens as well as an environmentally friendly sanitation method to mitigate postprocessing food contamination.