Desiccation Survival of Listeria monocytogenes in Mixed Biofilms with Pseudomonas fluorescens, Serratia liquefaciens and Shewanella putrefaciens

Abstract

Listeria monocytogenes has been found to withstand harsh environmental conditions including desiccation. The pathogen is also known to form biofilm when in co-culture with other bacteria found in food products. This study investigated the desiccation survival of L. monocytogenes in mixed biofilms with Pseudomonas fluorescens, Serratia liquefaciens and Shewanella putrefaciens. To this end, mono- or binary species biofilms were formed and desiccated (43% relative humidity, 21 days at 15°C) on stainless steel coupons and the double Weibull model was fitted to the resulting survivor curves. The presence of the competitor Gram-negative food spoilage bacteria with the exception of Sh. putrefaciens suppressed (p<0.05) L. monocytogenes during biofilm formation (100% relative humidity, 15°C and 48 h) and subsequently decreased (P<0.05) the desiccation survival in L. monocytogenes without affecting the resistance of individual cells. Microscopic approaches revealed different biofilm forming capabilities in the mono- and binary bacterial combinations.