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Trends in Microbiology Sep 2021Listeria monocytogenes is a foodborne pathogen responsible for listeriosis, an infection that can manifest in humans as bacteremia, meningoencephalitis in... (Review)
Review
Listeria monocytogenes is a foodborne pathogen responsible for listeriosis, an infection that can manifest in humans as bacteremia, meningoencephalitis in immunocompromised patients and the elderly, and fetal-placental infection in pregnant women. Reference strains from this facultative intracellular bacterium have been instrumental in the investigation of basic mechanisms in microbiology, immunology, and cell biology. The integration of bacterial population genomics with environmental, epidemiological, and clinical data allowed the uncovering of new factors involved in the virulence of L. monocytogenes and its adaptation to different environments. This review illustrates how these investigations have led to a better understanding of the bacterium's virulence and the driving forces that shaped it.
Topics: Adaptation, Physiological; Animals; Biodiversity; Humans; Listeria monocytogenes; Listeriosis; Virulence
PubMed: 33583696
DOI: 10.1016/j.tim.2021.01.008 -
Microbiological Reviews Sep 1991The gram-positive bacterium Listeria monocytogenes is an ubiquitous, intracellular pathogen which has been implicated within the past decade as the causative organism in... (Review)
Review
The gram-positive bacterium Listeria monocytogenes is an ubiquitous, intracellular pathogen which has been implicated within the past decade as the causative organism in several outbreaks of foodborne disease. Listeriosis, with a mortality rate of about 24%, is found mainly among pregnant women, their fetuses, and immunocompromised persons, with symptoms of abortion, neonatal death, septicemia, and meningitis. Epidemiological investigations can make use of strain-typing procedures such as DNA restriction enzyme analysis or electrophoretic enzyme typing. The organism has a multifactorial virulence system, with the thiol-activated hemolysin, listeriolysin O, being identified as playing a crucial role in the organism's ability to multiply within host phagocytic cells and to spread from cell to cell. The organism occurs widely in food, with the highest incidences being found in meat, poultry, and seafood products. Improved methods for detecting and enumerating the organism in foodstuffs are now available, including those based on the use of monoclonal antibodies, DNA probes, or the polymerase chain reaction. As knowledge of the molecular and applied biology of L. monocytogenes increases, progress can be made in the prevention and control of human infection.
Topics: Animals; Food Microbiology; Humans; Listeria monocytogenes; Listeriosis; Virulence
PubMed: 1943998
DOI: 10.1128/mr.55.3.476-511.1991 -
Journal of Applied Microbiology Oct 2018Listeria monocytogenes is an intracellular human pathogen which enters the body through contaminated food stuffs and is known to contaminate fresh leafy produce such as... (Review)
Review
Listeria monocytogenes is an intracellular human pathogen which enters the body through contaminated food stuffs and is known to contaminate fresh leafy produce such as spinach, lettuce and rocket. Routinely, fresh leafy produce is grown and processed on a large scale before reaching the consumer through various products such as sandwiches and prepared salads. From farm to fork, the fresh leafy produce supply chain (FLPSC) is complex and contains a diverse range of environments where L. monocytogenes is sporadically detected during routine sampling of produce and processing areas. This review describes sources of the bacteria in the FLPSC and outlines the physiological and molecular mechanisms behind its survival in the different environments associated with growing and processing fresh produce. Finally, current methods of source tracking the bacteria in the context of the food supply chain are discussed with emphasis on how these methods can provide additional, valuable information on the risk that L. monocytogenes isolates pose to the consumer.
Topics: Colony Count, Microbial; Food Contamination; Food Handling; Humans; Listeria monocytogenes; Plant Leaves; Vegetables
PubMed: 30039586
DOI: 10.1111/jam.14025 -
Cellular Microbiology Oct 2017Listeria monocytogenes, the causative agent of listeriosis, is an intracellular pathogen that is exquisitely evolved to survive and replicate in the cytosol of... (Review)
Review
Listeria monocytogenes, the causative agent of listeriosis, is an intracellular pathogen that is exquisitely evolved to survive and replicate in the cytosol of eukaryotic cells. Eukaryotic cells typically restrict bacteria from colonising the cytosol, likely through a combination of cell autonomous defences, nutritional immunity, and innate immune responses including induction of programmed cell death. This suggests that L. monocytogenes and other professional cytosolic pathogens possess unique metabolic adaptations, not only to support replication but also to facilitate resistance to host-derived stresses/defences and avoidance of innate immune activation. In this review, we outline our current understanding of L. monocytogenes metabolism in the host cytosol and highlight major metabolic processes which promote intracellular replication and survival.
Topics: Cytosol; Immunity, Innate; Listeria monocytogenes; Virulence
PubMed: 28656691
DOI: 10.1111/cmi.12762 -
Microbiology Spectrum Jul 2019Whereas obligate human and animal bacterial pathogens may be able to depend upon the warmth and relative stability of their chosen replication niche, environmental... (Review)
Review
Whereas obligate human and animal bacterial pathogens may be able to depend upon the warmth and relative stability of their chosen replication niche, environmental bacteria such as that harbor the ability to replicate both within animal cells and in the outside environment must maintain the capability to manage life under a variety of disparate conditions. Bacterial life in the outside environment requires adaptation to wide ranges of temperature, available nutrients, and physical stresses such as changes in pH and osmolarity as well as desiccation. Following ingestion by a susceptible animal host, the bacterium must adapt to similar changes during transit through the gastrointestinal tract and overcome a variety of barriers associated with host innate immune responses. Rapid alteration of patterns of gene expression and protein synthesis represent one strategy for quickly adapting to a dynamic host landscape. Here, we provide an overview of the impressive variety of strategies employed by the soil-dwelling, foodborne, mammalian pathogen to straddle diverse environments and optimize bacterial fitness both inside and outside host cells.
Topics: Animals; Bacterial Proteins; Gene Expression Regulation, Bacterial; Humans; Immunity, Innate; Listeria monocytogenes; Listeriosis; Osmolar Concentration; Virulence
PubMed: 31441398
DOI: 10.1128/microbiolspec.GPP3-0064-2019 -
Current Opinion in Microbiology Feb 2019Listeria monocytogenes (Lm) is a Gram-positive bacterium that thrives in nature as a saprophyte and in the mammalian host as an intracellular pathogen. Both environments... (Review)
Review
Listeria monocytogenes (Lm) is a Gram-positive bacterium that thrives in nature as a saprophyte and in the mammalian host as an intracellular pathogen. Both environments pose potential danger in the form of redox stress. In addition, endogenous reactive oxygen species (ROS) are continuously generated as by-products of aerobic metabolism. Redox stress from ROS can damage proteins, lipids, and DNA, making it highly advantageous for bacteria to evolve mechanisms to sense and detoxify ROS. This review focuses on the five redox-responsive regulators in Lm: OhrR (to sense organic hydroperoxides), PerR (peroxides), Rex (NAD/NADH homeostasis), SpxA1/2 (disulfide stress), and PrfA (redox stress during infection).
Topics: Gene Expression Regulation, Bacterial; Listeria monocytogenes; Metabolic Networks and Pathways; Oxidation-Reduction; Reactive Oxygen Species
PubMed: 30412828
DOI: 10.1016/j.mib.2018.10.006 -
Food Microbiology Sep 2021Food business operators are responsible for food safety and assessment of shelf lives for their ready-to-eat products. For assisting them, a customized software based on...
Food business operators are responsible for food safety and assessment of shelf lives for their ready-to-eat products. For assisting them, a customized software based on predictive models, ListWare, is being developed. The aim of this study was to develop and validate a predictive model for the growth of Listeria monocytogenes in sliced roast beef. A challenge study was performed comprising 51 different combinations of variables. The growth curves followed the Baranyi and Roberts model with no clear lag phase and specific growth rates in the range <0.005-0.110 hr. A linear regression model was developed based on 528 observations and had an adjusted R-square of 0.80. The significant predictors were storage temperature, sodium lactate, interactions between sodium acetate and temperature, and MAP packaging and temperature. The model was validated in four laboratories in three countries. For conditions where the model predicted up to + log 2 cfu/g Listeria concentration, the observed concentrations were true or below the predicted concentration in 90% of the cases. For the remaining 10%, the roast beef was coated with spices and therefore different from the others. The model will be implemented in ListWare web-application for calculation of "Listeria shelf life".
Topics: Animals; Cattle; Fast Foods; Food Contamination; Food Safety; Food Storage; Kinetics; Listeria monocytogenes; Meat Products; Models, Biological; Regression Analysis; Temperature
PubMed: 33875206
DOI: 10.1016/j.fm.2021.103770 -
Trends in Microbiology Aug 2008Listeria monocytogenes can respond rapidly to changing environmental conditions, as illustrated by its ability to transition from a saprophyte to an orally transmitted... (Review)
Review
Listeria monocytogenes can respond rapidly to changing environmental conditions, as illustrated by its ability to transition from a saprophyte to an orally transmitted facultative intracellular pathogen. Differential associations between various alternative sigma factors and a core RNA polymerase provide a transcriptional mechanism for regulating bacterial gene expression that is crucial for survival in rapidly changing conditions. Alternative sigma factors are key components of complex L. monocytogenes regulatory networks that include multiple transcriptional regulators of stress-response and virulence genes, regulation of genes encoding other regulators, and regulation of small RNAs. In this article, the contributions of various sigma factors to L. monocytogenes stress response and virulence are described.
Topics: Bacterial Proteins; Gene Expression Regulation, Bacterial; Listeria monocytogenes; Sigma Factor; Virulence; Virulence Factors
PubMed: 18619843
DOI: 10.1016/j.tim.2008.05.006 -
International Journal of Food... Jun 2021Listeria monocytogenes is a foodborne human pathogen that causes systemic infection, fetal-placental infection in pregnant women causing abortion and stillbirth and...
Listeria monocytogenes is a foodborne human pathogen that causes systemic infection, fetal-placental infection in pregnant women causing abortion and stillbirth and meningoencephalitis in elderly and immunocompromised individuals. This study aimed to analyse L. monocytogenes from different sources from New Zealand (NZ) and to compare them with international strains. We used pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and whole-genome single nucleotide polymorphisms (SNP) to study the population structure of the NZ L. monocytogenes isolates and their relationship with the international strains. The NZ isolates formed unique clusters in PFGE, MLST and whole-genome SNP comparisons compared to the international isolates for which data were available. PFGE identified 31 AscI and 29 ApaI PFGE patterns with indistinguishable pulsotypes being present in seafood, horticultural products and environmental samples. Apart from the Asc0002:Apa0002 pulsotype which was distributed across different sources, other pulsotypes were site or factory associated. Whole-genome analysis of 200 randomly selected L. monocytogenes isolates revealed that lineage II dominated the NZ L. monocytogenes populations. MLST comparison of international and NZ isolates with lineage II accounted for 89% (177 of 200) of the total L. monocytogenes population, while the international representation was 45.3% (1674 of 3473). Rarefaction analysis showed that sequence type richness was greater in NZ isolates compared to international trend, however, it should be noted that NZ isolates predominantly came from seafood, horticulture and their respective processing environments or factories, unlike international isolates where there was a good mixture of clinical, food and environmental isolates.
Topics: Environmental Microbiology; Food Handling; Food Microbiology; Genetic Variation; Genome, Bacterial; Horticulture; Humans; Listeria monocytogenes; New Zealand; Seafood
PubMed: 33838478
DOI: 10.1016/j.ijfoodmicro.2021.109166 -
Journal of Food Protection Nov 2002Several virulence factors of Listeria monocytogenes have been identified and extensively characterized at the molecular and cell biologic levels, including the hemolysin... (Review)
Review
Several virulence factors of Listeria monocytogenes have been identified and extensively characterized at the molecular and cell biologic levels, including the hemolysin (listeriolysin O), two distinct phospholipases, a protein (ActA), several internalins, and others. Their study has yielded an impressive amount of information on the mechanisms employed by this facultative intracellular pathogen to interact with mammalian host cells, escape the host cell's killing mechanisms, and spread from one infected cell to others. In addition, several molecular subtyping tools have been developed to facilitate the detection of different strain types and lineages of the pathogen, including those implicated in common-source outbreaks of the disease. Despite these spectacular gains in knowledge, the virulence of L. monocytogenes as a foodborne pathogen remains poorly understood. The available pathogenesis and subtyping data generally fail to provide adequate insight about the virulence of field isolates and the likelihood that a given strain will cause illness. Possible mechanisms for the apparent prevalence of three serotypes (1/2a, 1/2b, and 4b) in human foodborne illness remain unidentified. The propensity of certain strain lineages (epidemic clones) to be implicated in common-source outbreaks and the prevalence of serotype 4b among epidemic-associated stains also remain poorly understood. This review first discusses current progress in understanding the general features of virulence and pathogenesis of L. monocytogenes. Emphasis is then placed on areas of special relevance to the organism's involvement in human foodborne illness, including (i) the relative prevalence of different serotypes and serotype-specific features and genetic markers; (ii) the ability of the organism to respond to environmental stresses of relevance to the food industry (cold, salt, iron depletion, and acid); (iii) the specific features of the major known epidemic-associated lineages; and (iv) the possible reservoirs of the organism in animals and the environment and the pronounced impact of environmental contamination in the food processing facilities. Finally, a discussion is provided on the perceived areas of special need for future research of relevance to food safety, including (i) theoretical modeling studies of niche complexity and contamination in the food processing facilities; (ii) strain databases for comprehensive molecular typing; and (iii) contributions from genomic and proteomic tools, including DNA microarrays for genotyping and expression signatures. Virulence-related genomic and proteomic signatures are expected to emerge from analysis of the genomes at the global level, with the support of adequate epidemiologic data and access to relevant strains.
Topics: Consumer Product Safety; Disease Outbreaks; Foodborne Diseases; Genes, Bacterial; Hemolysin Proteins; Humans; Listeria monocytogenes; Prevalence; Serotyping; Virulence
PubMed: 12430709
DOI: 10.4315/0362-028x-65.11.1811