Antimicrobial effect of grape seed extract on planktonic cells and biofilms of Campylobacter spp.

Abstract

Campylobacter is a leading cause of bacterial gastrointestinal diseases worldwide, chicken meat representing the main source of human infections. Its ability to overcome normally lethal environments, despite its fastidious nature and oxygen-sensitivity, may be attributed among other factors to its biofilm forming capability. The utilization of polyphenolic compound-rich grape seed extracts (GSE), can be a sustainable strategy that may support the current food safety assurance systems. Major public health concern regarding food preservation, is the occurrence of sublethally injured cells, which are susceptible to recovery, developing stress adaptive responses, and responsible for serious limitations in routine microbiological surveillance methods. In this work, evidence of sublethal injury (SI) in planktonic Campylobacter cells after exposure to different GSE concentrations was assessed by the inability of injured survivors to grow on selective media, propidium iodide staining and TEM visualization. GSE efficacy against Campylobacter biofilms was also tested after determining the biofilm forming abilities of four Campylobacter strains, including clinical and food-chain isolates, on glass, stainless steel, and polystyrene surfaces. GSE inhibited planktonic growth in a dose dependent-manner, exposure times being critically reduced with increasing GSE concentrations. A mechanism of cumulative damage, triggering lethal instead of SI, is suggested from SI distribution profiles and attributed to a loss of membrane integrity. All strains formed biofilms on the multiple surfaces, especially on hydrophilic glass, and sessile cells exhibited greater GSE resistance than planktonic cells. This information is essential for the optimal design of combined hurdle technologies that efficiently combat Campylobacter colonization of foods.