Exploring the fate of Listeria monocytogenes in an in vitro digestion and fecal fermentation model: insights into survival during digestion and interaction with gut microbiota

Abstract

Listeria monocytogenes is a foodborne pathogen that causes listeriosis, a disease with a mortality rate of 20 ~ 30%. This bacterium enters the human body through contaminated food or ingredients and encounters primary innate defense systems, including gastric acid, bile salts, and gut microbiota. These systems play a critical role in preventing pathogen colonization and infection. However, interactions with pathogens can also alter the gut microbiota profile. This study aimed to investigate the host's defense mechanisms against L. monocytogenes and the changes in the gut microbiota profile following infection. L. monocytogenes ATCC 7644 showed the greatest reduction (7.6 log CFU), followed by ATCC 19111 (5.71 log), F2365 (5.02 log), ATCC 19113 (3.96 log), and NCCP 14714 (3.38 log), while the pooled cocktail exhibited a 3.49 log CFU reduction. Notably, the clinical isolates NCCP 14714 and F2365 exhibited greater resistance to the simulated digestive process compared to the food isolate ATCC 7644. L. monocytogenes infection induced notable shifts in specific bacterial groups, including Bacteroides, Bifidobacterium, and the Mediterraneibacter gnavus group, as well as an increase in ethanol levels. These alterations may contribute to gut barrier disruption and the upregulation of immune responses, ultimately promoting the pathogenesis of L. monocytogenes infection. The findings from this study provide valuable insights into the interaction between L. monocytogenes and the human gut microbiota, offering a comparative reference for the interpretation of future research.

Keywords: Listeria monocytogenes; fecal fermentation; gut microbiota; in vitro digestion; microbial interactions.

Figure 1

The reduction of L. monocytogenes at pH 2.0 (A) and 5.5 (B) during in vitro gastric digestion. L. monocytogenes was inoculated at a final concentration of 9 log CFU/mL. Gastric and intestinal digestions are indicated in red and green, respectively. The overall reduction is shown in blue. Significant differences (p < 0.05) are indicated by alphabets.

Figure 2

Phylogenetic tree and relative abundance of gut microbiota at the phylum level after L. monocytogenes infection during fecal fermentation, categorized by (1) volunteers, (2) in vitro infection conditions, and (3) incubation time. The phylogenetic analysis was performed using weighted distance values of gut microbiota. PF, pooled feces; SF, single feces; PI, post-infected; NI, non-infected; Contl, control.

Figure 3

Violin plots and principal coordinate analysis (PCA) comparing the alpha and beta diversity of gut microbiota during fecal fermentation based on infection status (A,B) and incubation time (C,D). The plots include the species richness as measured by the chao1 index (A,C) as well as the species evenness as measured by the Simpson diversity index (B,D). PCA is presented by weighted Bray–Curtis distances (E). Significant differences (p < 0.05) are indicated by alphabets. Contl, control; NI, non-infected; PI, post-infected.

Figure 4

Relative abundance of three phyla of interest: (A) Bacteroidota, (B) Bacillota, and (C) Pseudomonadota. The color of each bar chart represents different infection conditions: control (blue), non-infected (red), and post-infected (green). Each dot represents the value for each sample.

Figure 5

Relative abundance of eight genera belonging to Bacteroidaceae, Bifidobacteriaceae, Erysipelotrichaceae, and Lachnospiraceae: (A) Bacteroides, (B) Bifidobacterium, (C) Faecalitalea, (D) Clostridium innocuum group, (E) Lachnoclostridium, (F) Blautia, (G) Ruminococcus torques group, and (H) Mediterraneibacter gnavus group. The color of each bar chart represents different infection conditions: control (blue), non-infected (red), and post-infected (green). Each dot represents the value for each sample.

Figure 6

The concentration of short-chain fatty acids and ethanol of L. monocytogenes infected and non-infected pooled fecal samples during fermentation. The color of each bar chart represents the different incubation times: 6 h (blue), 12 h (red), and 24 h (green). NI, non-infected; PI, post-infected.