Susceptibility of Listeria monocytogenes planktonic cultures and biofilms to sodium hypochlorite and benzalkonium chloride

Cristina Rodríguez-Melcón; Félix Riesco-Peláez; Camino García-Fernández; Carlos Alonso-Calleja; Rosa Capita

doi:10.1016/j.fm.2019.03.020

Susceptibility of Listeria monocytogenes planktonic cultures and biofilms to sodium hypochlorite and benzalkonium chloride

Food Microbiol. 2019 Sep:82:533-540. doi: 10.1016/j.fm.2019.03.020. Epub 2019 Mar 18.

Authors

Cristina Rodríguez-Melcón¹, Félix Riesco-Peláez², Camino García-Fernández¹, Carlos Alonso-Calleja¹, Rosa Capita³

Affiliations

¹ Department of Food Hygiene and Technology, Veterinary Faculty, University of León, E-24071, León, Spain; Institute of Food Science and Technology, University of León, E-24071, León, Spain.
² Department of Electrical Engineering and Systems Engineering and Automatic Control, University of León, E-24071, León, Spain.
³ Department of Food Hygiene and Technology, Veterinary Faculty, University of León, E-24071, León, Spain; Institute of Food Science and Technology, University of León, E-24071, León, Spain. Electronic address: rosa.capita@unileon.es.

PMID: 31027816
DOI: 10.1016/j.fm.2019.03.020

Abstract

The susceptibility of four L. monocytogenes isolates from pork to sodium hypochlorite (SHY) and benzalkonium chloride (BZK) was tested. Minimum inhibitory concentration (MIC) values of 3500 ppm (SHY), or between 3 ppm and 13 ppm (BZK), were found. Minimum bactericidal concentration (MBC) values ranged from 3500 ppm to 4500 ppm (SHY), and from 3 ppm to 14 ppm (BZK). The effect of SHY and BZK on the architecture and cellular viability of 24-h-old biofilms formed by such strains on polystyrene was determined through confocal laser scanning microscopy (CLSM) in conjunction with fluorescent dyes for live cells (SYTO 9) and dead cells (propidium iodide). Strains were able to form biofilm (biovolume values in the observation field of 14,161 μm² ranged between 103,928.3 ± 6730.2 μm³ and 276,030.9 ± 42,291.9 μm³). Treatment of biofilms for 10 min with SHY (1MIC or 1.5MIC) or BZK (0.5MIC, 1MIC or 1.5MIC) decreased the biovolume of live (potentially dangerous) cells. SHY reduced the cellular viability of biofilms by more than 90%. On the other hand, BZK was able to remove most biofilm mass (live and dead cells), but decreased cellular viability only to a lesser extent, this suggesting strong biofilm detachment and dissemination of live cells.

Keywords: Biocides; Biofilm; CLSM; Listeria monocytogenes; MBC; MIC.

MeSH terms

Benzalkonium Compounds / pharmacology*
Biofilms / drug effects*
Biofilms / growth & development
Disinfectants / pharmacology*
Listeria monocytogenes / drug effects*
Listeria monocytogenes / growth & development
Microbial Sensitivity Tests
Microbial Viability / drug effects
Microscopy, Confocal
Sodium Hypochlorite / pharmacology*

Substances

Benzalkonium Compounds
Disinfectants
Sodium Hypochlorite