Multispecies biofilms between Listeria monocytogenes and Listeria innocua with resident microbiota isolated from apple juice processing equipment

Abstract

When testing conditions that prevail in fruit juice industry it was found that Listeria monocytogenes ATCC 7644 and a wild strain of Listeria innocua were highly hydrophobic, expressed swimming and twitching, co-aggregated with yeast cells and produced exopolysaccharide, all characteristics that would favor the adhesive process. In mono-species biofilms, L. innocua adhered on stainless steel at significantly higher counts than L. monocytogenes achieving values of 6.64 ± 0.01 and 5.80 ± 0.21 log CFU/cm2. In dual species biofilms with resident yeasts, L. innocua cells counts increase significantly in the presence of Candida tropicalis and Candida krusei and decrease significantly in the presence of Rhodotorula mucilaginosa and Candida kefyr. When cocultured with Candida tropicalis, the cell numbers of L. monocytogenes had a significant increase. These results revealed synergic and antagonistic interactions among species. Practical applications: The study supports the plausibility that interactions between L. monocytogenes and members of resident microbiota, such as C. tropicalis, C. krusei, C. kefyr, and R. mucilaginosa, might play an important role for the survival and dissemination of L. monocytogenes. Apple juice processing conditions was used as simulation of the real condition in fruit juice processing environment and these results will alert to fruit juice industry to adopt the best cleaning and disinfecting practices against Listeria.