Inhibition of Listeria monocytogenes Cocktail Culture Biofilms on Crab and Shrimp Coupons and the Expression of Biofilm-Related Genes

Abstract

Listeria monocytogenes, a bacterium that is transmitted by tainted food, causes the infection listeriosis. In this study, quercetin was tested for its antibacterial properties and effectiveness as a food additive in preventing the growth of L. monocytogenes cocktail (ATCC19117, ATCC19113, and ATCC15313) biofilms on crabs and shrimps. Quercetin showed the least bactericidal activity and no discernible microbial growth at a minimum inhibitory concentration (MIC) of 250 µg/mL. The biofilm inhibition was performed at sub-MICs (1/2, 1/4, and 1/8 MIC). There was no quercetin added to the control group. Additionally, the present work examines the expression of various genes related to biofilm formation and quorum sensing (flaA, fbp, agrA, hlyA, and prfA). The levels of target genes were all significantly down-regulated. Quercetin (0-125 µg/mL) on the surfaces of the crab and shrimp was studied; its inhibitory effects were measured as log reductions at 0.39-2.31 log CFU/cm² and 0.42-2.36 log CFU/cm², respectively (p < 0.05). Quercetin reduced the formation of biofilms by disrupting cell-to-cell connections and causing cell lysis, which led to the deformation of the cells, evidenced by FE-SEM (field-emission scanning electron microscopy). These findings emphasize the significance of using natural food agents to target bacteria throughout the entire food production process.

Keywords: Listeria monocytogenes; biofilm; crabs; food safety; quercetin; relative expression; shrimps.

Figure 1

Biofilm formation of Listeria monocytogenes cocktail culture on crabs. All results are presented as mean ± SEM. Number of replicates (n = 3). Different letters (a–c) represent significant differences (p < 0.05).

Figure 2

Biofilm formation of Listeria monocytogenes cocktail culture on shrimps. All results were presented as mean ± SEM. Number of replicates (n = 3). Different letters (a–c) represent significant differences (p < 0.05).

Figure 3

Graphical images of the inhibition of Listeria monocytogenes cocktail culture on the crabs: (A) control; (B) 1/4 MIC; (C) 1/2 MIC; and shrimps: (D) control; (E) 1/4 MIC; and (F) 1/2 MIC.

Figure 4

Suppression levels of agrA, prfA, fbp, flaA, and hylA genes in Listeria monocytogenes cocktail culture for control, 1/8, and 1/2 MIC quercetin. Number of replicates (n = 3). Different letters (a,b) represent significant differences (p < 0.05).