Assessing In Vitro Biofilm-Forming Ability and Susceptibility to Food-Grade Sanitizers of Listeria Monocytogenes Isolates from a Delicatessen Food Industry

Assessing In Vitro Biofilm-Forming Ability and Susceptibility to Food-Grade Sanitizers of Listeria Monocytogenes Isolates from a Delicatessen Food Abstract Listeria monocytogenes is a human pathogen commonly found in food-related environments. L. monocytogenes is believed to occur in food contact surfaces in biofilms, exhibiting less susceptibility to sanitizers than their planktonic form. Food-grade sanitizers are widely used in food processing plants for contamination control purposes. The aim of this work was to investigate the susceptibility of L. monocytogenes to commercial food-grade sanitizers and to benzalkonium chloride; isolates were tested in the planktonic form and in biofilms and were further assessed using genetic subtyping. Raw materials, final products and food-contact surfaces of a delicatessen food industry were tested during a 6-year period for L. monocytogenes. confirmation and serogrouping was performed by polymerase chain reaction (PCR), revealing serogoup IIc as the most common (53%). Genetic variability of the isolates was evidenced using Pulsed-field gel electrophoresis (PFGE) and three clusters were obtained. In the biofilm-forming ability assay, isolates were classified as weak biofilm producers. L. monocytogenes strains were susceptible both in the planktonic and biofilm form to oxidizing and ethanol-based compounds and to benzalkonium chloride, but not to quaternary ammonium compound. A positive association of the biofilm-forming ability and LD 90 values was found for quaternary ammonium compound and benzalkonium chloride. Overall, these results confirm the need for conscious selection and use of sanitizers in food-related environments for Listeria monocytogenes improved control .