Ability of meat borne Lactobacillus sakei CRL1862 bacteriocins to inhibit Listeria monocytogenes biofilm on industrial abiotic surfaces

Abstract

Research on microbial biofilms has been documented in many areas, with particular emphasis in control strategies for either preventing or remediating pathogenic biofilm colonization. Listeria monocytogenes is well known for its ability to form biofilm and to establish harborages on food-processing equipment, making its eradication even more difficult, which may led to food products contamination. Many lactic acid bacteria (LAB) are known for their ability to inhibit growth of spoilage and pathogenic microorganisms by producing antimicrobial compounds in planktonic stage, but biofilm biocontrol is not well documented. In this work biofilm formation of Listeria monocytogenes FBUNT on stainless steel (SS) and polytetrafluoroethylene (PTFE) and the ability to be inhibited by Lactobacillus sakei CRL1862 bacteriocin at low temperature was investigated. Listeria biofilm formation was tested on LB broth and LB diluted (1/10) (dLB). Petri dish containing 19 mL of media (individually) and chips (2.5 cm2) of each inert materials were inoculated with 0.1 mL of L. monocytogenes and incubated at 10 °C during 6 days; fluorescence microscopy after staining with acridine orange was used to evaluate developed biofilm. Inhibitory effect of L. sakei CRL1862 bacteriocin (266.66 AU/mL) was examined at 0 and 6 h on L. monocytogenes in biofilm by counts on BHI agar. Results showed epifluorescence microcopy pictures for L. monocytogenes only few scattered cells were adhered on both, SS and PTFE surfaces after growth on LB medium. Chips incubated on dLB medium appeared homogeneously and almost entirely covering SS surface while cell clusters were observed on PTFE. When bacteriocin effect on L. monocytogenes FBUNT biofilm was evaluated, a 1-log and 3-log reduction at 0 and 6 h, respectively, was produced. From this study, the effectiveness of the bacteriocin produced by meat borne L. sakei CRL1862 to suppress Listeria biofilm developed on industrial surfaces was demonstrated. Due to pathogen biofilms resistance to antimicrobials and sanitizing agents frequently used in the industry, this study is relevant to food microbiology providing information for biocontrol strategies to destroy or avoid the building of pathogen biofilms on processing surfaces and equipment used during the manufacturing of meat and meat products.