Biofilm co-culture with Acinetobacter johnsonii triggers lipid A remodelling and benzalkonium chloride resistance in Salmonella enterica

This work highlights the importance of inter-species interactions of bacteria found within the food production environment, which can influence the efficacy of disinfectants used on food-borne pathogens. Here we show that Acinetobacter johnsonii, a bacterium commonly found in the environment and spoiled food, increases the resistance of the major human foodborne pathogen Salmonella enterica to benzalkonium chloride when they are co-cultured in a biofilm. Further investigations revealed S. enterica activates a cell envelope modification system resulting in a modified outer membrane composition, which contributes towards resistance against the disinfectant. These results expand the knowledge of mixed-species biofilms and how significant phenotypic differences can result from bacterial interactions.