Inhibition of Biofilm Formation by Cranberry Extract

https://kent-islandora.s3.us-east-2.amazonaws.com/node/10091/10205-thumbnail.jpgBacteria attach to surfaces in aqueous environments and form biofilms; mixtures of cells embedded in a matrix of extracellular material. Biofilms are important to ecosystem function but have harmful effects in undesirable settings. One issue is persistence of pathogenic bacteria in biofilms, including Listeria. Listeria can survive in protected, multi-species biofilms and some strains are resistant to stress. The purpose of this study was to demonstrate antimicrobial activity of cranberry extract (CE) against Listeria innocua. To examine survivorship, L. innocua was suspended in serial dilutions of CE neutralized to pH 7.0. Samples were collected and plated on BHI agar. Subsequently, L. innocua was grown on glass beads submerged in BHI broth or 12.5% CE in BHI. L. innocua was inoculated and incubated for 48 hours. Samples were filtered, Live-Dead stained, and enumerated. In suspension, a 4 log reduction in L. innocua was observed after 18 hours in 12.5% and 25% CE. In the biofilm experiment, there was a &gt; 1 log reduction in live and dead cells in biofilms in 12.5% CE. The formation of live microcells in the presence of CE was evidence of a stress response; poorly defined dead cells and debris were apparent with the dead stain. This study demonstrated inhibition of L. innocua by CE in suspension and biofilms. It did not distinguish between physiological stress and other mechanisms of biofilm inhibition. Future studies will examine mechanisms of biofilm inhibition and impact of CE on L. innocua in multispecies biofilms.</p