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. 2022 Jan 4:12:792162.
doi: 10.3389/fmicb.2021.792162. eCollection 2021.

Different Shades of Listeria monocytogenes: Strain, Serotype, and Lineage-Based Variability in Virulence and Stress Tolerance Profiles

Francis Muchaamba  1 , Athmanya K Eshwar  1 , Marc J A Stevens  1 , Roger Stephan  1 , Taurai Tasara  1
Affiliations

Different Shades of Listeria monocytogenes: Strain, Serotype, and Lineage-Based Variability in Virulence and Stress Tolerance Profiles

Francis Muchaamba et al. Front Microbiol. .

Abstract

Listeria monocytogenes is a public health and food safety challenge due to its virulence and natural stress resistance phenotypes. The variable distribution of L. monocytogenes molecular subtypes with respect to food products and processing environments and among human and animal clinical listeriosis cases is observed. Sixty-two clinical and food-associated L. monocytogenes isolates were examined through phenome and genome analysis. Virulence assessed using a zebrafish infection model revealed serotype and genotype-specific differences in pathogenicity. Strains of genetic lineage I serotype 4b and multilocus sequence type clonal complexes CC1, CC2, CC4, and CC6 grew and survived better and were more virulent than serotype 1/2a and 1/2c lineage II, CC8, and CC9 strains. Hemolysis, phospholipase activity, and lysozyme tolerance profiles were associated with the differences observed in virulence. Osmotic stress resistance evaluation revealed serotype 4b lineage I CC2 and CC4 strains as more osmotolerant, whereas serotype 1/2c lineage II CC9 strains were more osmo-sensitive than others. Variable tolerance to the widely used quaternary ammonium compound benzalkonium chloride (BC) was observed. Some outbreak and sporadic clinical case associated strains demonstrated BC tolerance, which might have contributed to their survival and transition in the food-processing environment facilitating food product contamination and ultimately outbreaks or sporadic listeriosis cases. Genome comparison uncovered various moderate differences in virulence and stress associated genes between the strains indicating that these differences in addition to gene expression regulation variations might largely be responsible for the observed virulence and stress sensitivity phenotypic differences. Overall, our study uncovered strain and genotype-dependent variation in virulence and stress resilience among clinical and food-associated L. monocytogenes isolates with potential public health risk implications. The extensive genome and phenotypic data generated provide a basis for developing improved Listeria control strategies and policies.

Keywords: Listeria monocytogenes; genome; lysozyme; stress; virulence; zebrafish.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
An overview of distribution of 62 Listeria monocytogenes strains examined in this study based on their (A) isolation source, genetic lineage, serotypes, and (B) MLST clonal complexes. (B) MLST clonal complexes with three or more strains are presented, whereas those with less are represented under others (CC3; CC5; CC7; CC18; CC20; CC29; CC70; CC131; CC217; CC226; and CC489).
FIGURE 2
FIGURE 2
Listeria monocytogenes virulence in zebrafish varies with strain, serotype, and genotype. Presented are box plots showing virulence comparison based on (A) lineage, (B) serotype, and (C) clonal complex using zebrafish embryo infection model at 24 hpi. *Indicates that the group differs significantly from other groups (P < 0.05). Results are based on three independent biological repeats. Key; red: LI strains, blue: LII strains, green: LIII strains.
FIGURE 3
FIGURE 3
Listeria monocytogenes (A) CC1 and (B) CC9 strains display intra-clonal complex differences in zebrafish embryo virulence. Presented are Kaplan–Meier survival curves of zebrafish embryo (n = 10 per strain) infected (500 CFU) with different CC1 or CC9 L. monocytogenes strains and monitored for 3 days. Results are based on three independent biological repeats.
FIGURE 4
FIGURE 4
Hemolysis and PI-PLC activity comparison. Presented are box plots showing (A–C) relative hemolysis capacity and (D–F) PI-PLC activity comparison among strains. *Significant difference between groups (P < 0.05), based on one-way analysis of variance and Tukey post hoc test pairwise comparison. Results are based on three independent biological repeats. Key; red: LI strains, blue: LII strains, green: LIII strains. Dotted line denotes a low PI-PLC activity cutoff value.
FIGURE 5
FIGURE 5
Growth and survival of L. monocytogenes strains from different genetic backgrounds within (A) zebrafish and (B) BHI at 28°C. Key; red: LI strains, blue: LII strains, green: LIII strains. *Significant difference between lineages and time points (P < 0.05). Results are based on three independent biological repeats.
FIGURE 6
FIGURE 6
Listeria monocytogenes strains display lineage-based differences in zebrafish embryo virulence. Presented are (A) survival curves of zebrafish embryo (n = 10 per strain) infected (500 CFU) with different L. monocytogenes strains representing LI, LII, and LIII. Embryos were monitored for 3 days post-infection. (B–D) Hemolysis, PI-PLC activity, and lysozyme stress tolerance profiles of injected strains are also shown. (D) Dotted line denotes lysozyme resistant strain classification cutoff value. *Significant difference between (B) LI and LIII, (D) LII and the other lineages (P < 0.05). Results are based on three independent biological repeats.
FIGURE 7
FIGURE 7
Lysozyme stress sensitivity of L. monocytogenes varies with strain and molecular subtype. Presented are box plots showing lysozyme stress sensitivity comparison based on (A) lineage, (B) serotype, and (C) clonal complex. (D) Shows distribution of strains resistant to lysozyme. Key; red: LI strains, blue: LII strains, green: LIII strains. Results are based on three independent biological repeats.
FIGURE 8
FIGURE 8
Listeria monocytogenes osmotic stress tolerance varies with strain and molecular subtype. Presented are box plots showing comparison of fold increase in lag phase duration of strains due to osmotic stress (growth in BHI plus 8% NaCl), (A) lineages, (B) serotypes, and (C) clonal complexes. *Significant difference between (A) LI and LII, (B) serotype 1/2c and other serotypes and (C) CC9 and other CCs (P < 0.05), based on one-way analysis of variance and Tukey post hoc test pairwise comparison. Results are based on three independent biological repeats. Key; red: LI strains, blue: LII strains, green: LIII strains.
FIGURE 9
FIGURE 9
Comparison of serotype 4b L. monocytogenes strains [N2306, N12-0320, and N12-0794 (CC4), LL195 (CC1), and N16-0044 (CC6)] growth profiles at low temperature with or without NaCl osmotic stress based on (A–D) area under curve and (E–H) lag phase duration extension. *Significant difference between strains and treatments (P < 0.05). Results are based on three independent biological repeats.
FIGURE 10
FIGURE 10
Distribution of strains resistant to BC stress based on (A) lineage and serotype (B) clonal complex.
FIGURE 11
FIGURE 11
Cladogram showing genetic relatedness among L. monocytogenes strains examined in this study based on average nucleotide identity. Strain distribution with respect to lineage (branch line color), CC (node color), serotypes, isolation sources (label text color), zebrafish virulence, PI-PLC activity, lysozyme, and BC resistance is shown.
FIGURE 12
FIGURE 12
Consequences of aa changing SNPs on 3D protein structure of Hpt (A–D) and PgdA (E–H). Black arrows highlight areas of most significant change. (D,H) 3D protein structure alignment. Key; for Hpt alignment (D) LI (green), LII (blue), and LIII (red). For PgdA alignment, (H) conserved chain regions are colored magenta, TM-score LI (0.9756), and LIII (0.9689) relative to LII.
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References

    1. Abdelhamed H., Ramachandran R., Narayanan L., Ozdemir O., Cooper A., Olivier A. K., et al. (2020). Contributions of a LysR transcriptional regulator to Listeria monocytogenes virulence and identification of its regulons. J. Bacteriol. 202:e00087-20. 10.1128/JB.00087-20 - DOI - PMC - PubMed
    1. Allerberger F., Wagner M. (2010). Listeriosis: a resurgent foodborne infection. Clin. Microbiol. Infect 16 16–23. 10.1111/j.1469-0691.2009.03109.x - DOI - PubMed
    1. Angelidis A. S., Smith G. M. (2003). Role of the glycine betaine and carnitine transporters in adaptation of Listeria monocytogenes to chill stress in defined medium. Appl. Environ. Microbiol. 69 7492–7498. 10.1128/AEM.69.12.7492-7498.2003 - DOI - PMC - PubMed
    1. Aubry C., Goulard C., Nahori M. A., Cayet N., Decalf J., Sachse M., et al. (2011). OatA, a peptidoglycan O-acetyltransferase involved in Listeria monocytogenes immune escape, is critical for virulence. J. Infect. Dis. 204 731–740. - PMC - PubMed
    1. Autret N., Raynaud C., Dubail I., Berche P., Charbit A. (2003). Identification of the agr locus of Listeria monocytogenes: role in bacterial virulence. Infect. Immun. 71 4463–4471. 10.1128/iai.71.8.4463-4471.2003 - DOI - PMC - PubMed

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