Pseudomonas grimontii biofilm protects food contact surfaces from Escherichia coli colonization

Escherichia coli typically colonizes food contact surfaces in the presence of other bacterial strains. The aim of this work was to evaluate the influence of a resident strain isolated from a fresh-cut salad industry (Pseudomonas grimontii 13A10) on the development of a model pathogen (E. coli) on bare stainless steel (SST) and stainless steel coated with diamond-like carbon (DLC) films, a-C:H:Si:O designated by SICON® and a-C:H:Si designated by SICAN. The bacterial composition and spatial organization of single- and dual-species biofilms were analyzed by confocal laser scanning microscopy (CLSM). Biofilms were developed for 1 and 3 days at 10 °C and it was observed that the biovolume of E. coli biofilms in the presence of P. grimontii was lower than in axenic conditions, suggesting that the isolate can protect food contact surfaces from pathogen colonization. After 3 days, the dual-species biofilms contained essentially P. grimontii cells and no preferential vertical distribution of bacterial strains was observed. The use of a-C:H:Si:O coated surfaces reduced the short-term colonization of the model pathogen in single- and dual-species biofilms, whereas decreased colonization by the non-pathogenic strain was only observed after 3 days.