Journal of Applied Microbiology, Vol.118, No.2, 431-442, 2015
Dual-species relations between Candida tropicalis isolated from apple juice ultrafiltration membranes, with Escherichia coli O157:H7 and Salmonella sp.
AimsThe objective of this study was to determine the interactions between common spoilage yeast, Candida tropicalis, isolated from ultrafiltration membranes, and Escherichia coli O157:H7 and Salmonella sp. on stainless steel surfaces. Methods and ResultsSingle and dual-species attachment assays were performed on stainless steel at 25 degrees C using apple juice as culture medium. The growth of Salmonella sp. rose when it was co-cultivated with C.tropicalis in dual biofilms at 16 and 24h; the same effect was observed for E.coli O157:H7 at 24h. The colonization of C.tropicalis on stainless steel surfaces was reduced when it was co-cultivated with both pathogenic bacteria, reducing C.tropicalis population by at least 10log unit. Visualization by SEM demonstrated that E.coli O157:H7 and Salmonella sp. adhere closely to hyphal elements using anchorage structures to attach to the surface and other cells. ConclusionsThese results suggest a route for potential increased survival of pathogens in juice processing environments. These support the notion that the species involved interact in mixed yeast-bacteria communities favouring the development of bacteria over yeast. Significance and Impact of the StudyThis study support the plausibility that pathogen interactions with strong biofilm forming members of spoilage microbiota, such as C.tropicalis, might play an important role for the survival and dissemination of E.coli O157:H7 and Salmonella sp. in food-processing environments.
Keywords:apple juice;Candida tropicalis;co-cultures;Escherichia coli O157:H7;Salmonella sp;stainless steel