Efficacy of Commercial Sanitizers Used in Food Processing Facilities for Inactivation of Listeria monocytogenes, E. Coli O157:H7, and Salmonella Biofilms

Abstract

Bacteria entrapped in biofilms are a source of recurring problems in food processing environments. We recently developed a robust, 7-day biofilm microplate protocol for creating biofilms with strongly adherent strains of Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella serovars that could be used to examine the effectiveness of various commercial sanitizers. Listeria monocytogenes 99-38, E.coli O157:H7 F4546, and Salmonella Montevideo FSIS 051 were determined from prior studies to be good biofilm formers and could be recovered and enumerated from biofilms following treatment with trypsin. Extended biofilms were generated by cycles of growth and washing daily, for 7 days, to remove planktonic cells. We examined five different sanitizers (three used at two different concentrations) for efficacy against the three pathogenic biofilms. Quaternary ammonium chloride (QAC) and chlorine-based sanitizers were the least effective, showing partial inhibition of the various biofilms within 2 h (1–2 log reduction). The best performing sanitizer across all three pathogens was a combination of modified QAC, hydrogen peroxide, and diacetin which resulted in ~6–7 log reduction, reaching levels below our limit of detection (LOD) within 1–2.5 min. All treatments were performed in triplicate replication and analyzed by one way repeated measures analysis of variance (RM-ANOVA) to determine significant differences (p < 0.05) in the response to sanitizer treatment over time. Analysis of 7-day biofilms by scanning electron microscopy (SEM) suggests the involvement of extracellular polysaccharides with Salmonella and E. coli, which may make their biofilms more impervious to sanitizers than L. monocytogenes.

Adaptive Response of Listeria monocytogenes to the Stress Factors in the Food Processing Environment

“…An important problem is the acquisition of resistance to disinfectants by L. monocytogenes due to the residues of chemical substances in sub-lethal concentrations after disinfection. The most commonly used disinfectants for L. monocytogenes are quaternary ammonium compounds (QACs) and chlorine-based biocides ( Minarovicova et al, 2018 ; Aryal and Muriana, 2019 ). Listeria monocytogenes strains resistant to disinfectants contribute to sporadic cases as well as outbreaks of listeriosis.…”

Impact of the Resistance Responses to Stress Conditions Encountered in Food and Food Processing Environments on the Virulence and Growth Fitness of Non-Typhoidal Salmonellae

“…Disinfectants can be broadly grouped into oxidizing agents, surface active compounds, and iodophores [ 184 ]. Widely used sanitizers, such as halogen-based compounds, peracetic acid (PAA), ozone, and hydrogen peroxide, fall within the group of oxidizing agents; their impact on Salmonella virulence and growth fitness was discussed above.…”

Detecting Bacterial Biofilms Using Fluorescence Hyperspectral Imaging and Various Discriminant Analyses

“…[ 15 ]. Sessile bacteria attached to biofilms are known to withstand stress better than planktonic bacteria in stressful environments such as in the presence of antibiotics, disinfectants, high temperatures, light, and dryness [ 16 , 17 ]. Cross-contamination occurs when food passes through a surface contaminated with biofilms or when cells are separated from the biofilm structure through an aerosol derived from a contaminated food processing facility [ 1 , 11 ].…”