Effect of different conditions on listeria monocytogenes biofilm formation and removal

Listeria monocytogenes poses a major risk for the safety of food products due to the ability to persist in food products and process line surfaces as biofilm. In this work, we investigated the L. monocytogenes biofilms in relation to development factors and possible control under different conditions. In particular, the ability of six strains of L. monocytogenes from vegetable and animal sources to form biofilms was evaluated on glass or polystyrene substrates under different temperatures (15, 30 and 37°C) and availability of nutrients, by using rich (BHI) or poor (HTM) growth media. Moreover, the effectiveness of three commonly used sanitizers (benzalkonium chloride, sodium hypochlorite and hydrogen peroxide) was compared to eradicate established biofilms. Our results showed that starved conditions, hydrophilic surfaces, and high temperatures increased the L. monocytogenes ability to produce biofilms. In general, benzalkonium chloride was the most effective chemical to remove established biofilms.