Abstract
The pathogenic microorganism Listeria monocytogenes is ubiquitous and responsible for listeriosis, a disease with a high mortality rate in susceptible people. It can persist in different habitats, including the farm environment, the food production environments, and in foods. This pathogen can grow under challenging conditions, such as low pH, low temperatures, and high salt concentrations. However, L. monocytogenes has a high degree of strain divergence regarding virulence potential, environmental adaption, and stress response. This review seeks to provide the reader with an up-to-date overview of clonal and serotype-specific differences among L. monocytogenes strains. Emphasis on the genes and genomic islands responsible for virulence and resistance to environmental stresses is given to explain the complex adaptation among L. monocytogenes strains. Moreover, we highlight the use of advanced diagnostic technologies, such as whole-genome sequencing, to fine-tune quantitative microbiological risk assessment for better control of listeriosis.
Highlights
Listeria monocytogenes is a Gram-positive, facultative anaerobe, non-spore-forming, and psychroand salt-tolerant organism
Differences in the ability to respond to stress among the L. monocytogenes genotypes are probably linked to differences in the expression of proteins associated with the membrane, such as the penicillin-binding proteins coded by the lmo0441, lmo0540, lmo1892 genes, and lmo2229 as mentioned earlier, as well as the gene coding for σB, all of which were reported to be more expressed in lineage II than lineage I (Gravesen et al, 2004; Begley et al, 2006; Severino et al, 2007)
The notorious foodborne pathogen L. monocytogenes is ubiquitous in nature and can be found in soil, in the farm environment, in the food production environment, and in food products (Figure 3) (Kallipolitis et al, 2020)
Summary
Listeria monocytogenes is a Gram-positive, facultative anaerobe, non-spore-forming, and psychroand salt-tolerant organism. Tolerance to sanitizers and disinfectants such as benzalkonium chloride (BC) was observed in L. monocytogenes isolates from food-processing environments This tolerance may be attributed to subinhibitory concentrations of a disinfectant, which are caused by insufficient cleaning and improper sanitation, probably contributing to biofilm formation and leading to Listeria persistence (MartínezSuárez et al, 2016). It is crucial to identify the interactions between stress response and virulence and to know how this microorganism survives, adapts to adverse conditions, and triggers genes involved in virulence or promoting persistence This would help to explain the observed inverse correlation between strains with a higher prevalence of genes involved in BC tolerance, as well as other stress-related genes, amongst hypovirulent (i.e., low virulence) lineage II strains (Quereda et al, 2021). All this knowledge may contribute to the development of new intervention strategies for better control of the level of L. monocytogenes in the food chain
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