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FEMS Microbiology Letters Jul 2020Bacterial communication system known as quorum sensing (QS) is a pivotal system for bacterial survival, adaptation and pathogenesis. Members in the multicellular...
Bacterial communication system known as quorum sensing (QS) is a pivotal system for bacterial survival, adaptation and pathogenesis. Members in the multicellular community may synthesize or acquire a signaling molecule in order to elicit downstream cellular processes. Roles of indole and derivatives, a new class of quorum-sensing signal molecules, in various bacterial physiologies and virulence have been reported recently. Indole is normally found in mammal gastrointestinal tract as a metabolite of tryptophan metabolism by microbiota. Therefore, interspecies connection via indole signaling among commensal bacteria and enteric pathogens could be anticipated. Effects of indole exposure on the virulence of Listeria monocytogenes were investigated by phenotypic and molecular approaches. Results demonstrated that synthetic indole and indole-rich conditioned medium significantly diminished biofilm formation and related virulence of L. monocytogenes including motility, cell aggregation and exopolysaccharide production. Transcript levels of virulence-associated (pssE, dltA, flaA, fliI, motB, agrA and hly) and regulatory genes (codY, sigB, prfA and gmaR) were substantially downregulated in indole-treated cells. Only mogR gene encoding for a repressor of motility genes was upregulated after indole exposure. Our findings raise the possibility that L. monocytogenes may acquire indole signaling from gut microbiota for resource-effective adaptation upon transition to new environment.
Topics: Bacterial Proteins; Biofilms; Gene Expression Regulation, Bacterial; Humans; Indoles; Listeria monocytogenes; Listeriosis; Quorum Sensing; Virulence
PubMed: 32658271
DOI: 10.1093/femsle/fnaa116 -
Food Microbiology May 2020Dry dairy powder is a commonly used ingredient for ready-to-eat foods. It has been implicated in multiple foodborne outbreaks. Listeria monocytogenes can survive in...
Dry dairy powder is a commonly used ingredient for ready-to-eat foods. It has been implicated in multiple foodborne outbreaks. Listeria monocytogenes can survive in low-moisture conditions for a long duration. However, there is no information on Listeria survival in dry milk powder during storage and thermal treatments. The objectives of this study were to examine the stability of L. monocytogenes in non-fat dry milk (NFDM) during extended storage and further analyze thermal resistance of L. monocytogenes in NFDM under different water activities (a) and its thermal stability after 1-year storage. We observed approximately 1.75 and 2.93 log CFU/g reduction of L. monocytogenes in a 0.25 NFDM over 1-year storage at 4 and 22 °C, respectively. Thermal resistance of L. monocytogenes was inversely related to a, and the inactivation kinetic curves of L. monocytogenes in NFDM at target a showed a log-linear trend under all tested conditions. For a 0.25, 0.30, and 0.45 NFDM, the ranges of D-values, were 66.2-21.3, 33.5-9.4, and 14.6-4.3 min at 70, 75 and 80 °C, respectively. The z-values for L. monocytogenes in NFDM at a 0.25-0.45 were 14.6-16.0 C°. Furthermore, the thermal stability of L. monocytogenes in a 0.25 NFDM post 6-month or 12-month storage under refrigerated or ambient temperature did not deviate much from that in NFDM prior to the storage. Data indicated that a 60-min heat treatment at 80 °C resulted in ~ 5-log reduction of L. monocytogenes in NFDM of a 0.30. This provides a promising intervention strategy to enhance bactericidal efficacy of thermal treatment while maintaining the quality of milk powder.
Topics: Animals; Cattle; Colony Count, Microbial; Food Storage; Hot Temperature; Listeria monocytogenes; Milk; Powders; Temperature; Water
PubMed: 31948617
DOI: 10.1016/j.fm.2019.103376 -
Journal of Hazardous Materials Apr 2024In the food industry, ensuring food safety during transportation and storage is vital, with temperature regulation preventing spoilage. However, airborne contamination...
In the food industry, ensuring food safety during transportation and storage is vital, with temperature regulation preventing spoilage. However, airborne contamination through foodborne pathogens remains a concern. Listeria monocytogenes, a psychrotolerant foodborne pathogen, has been linked to various foodborne outbreaks. Therefore, understanding how its airborne characteristics depend on the growth temperature is imperative. As a result, when the L. monocytogenes was floated in air for 30 and 60 min, the surviving population of 15 °C-grown L. monocytogenes that was suspended in air and attached on the surface was significantly higher than L. monocytogenes grown at 25°C and 37 °C. The fatty acid analysis revealed a significantly higher proportion of shorter chain fatty acids in L. monocytogenes grown at 15 °C compared to those grown at 37 °C. Under aerosolization, L. monocytogenes encountered osmotic and cold stresses regardless of their growth temperature. Transcriptomic analysis showed that stress response related genes, such as oxidative and cold stress response, as well as PTS system related genes were upregulated at 15 °C, resulting in the enhanced resistance to various stresses during aerosolization. These results provide insights into the different responses of aerosolized L. monocytogenes according to the different growth temperatures, highlighting a critical factor in preventing airborne cross-contamination.
Topics: Temperature; Listeria monocytogenes; Fatty Acids; Gene Expression Profiling; Food Microbiology; Colony Count, Microbial
PubMed: 38364578
DOI: 10.1016/j.jhazmat.2024.133706 -
MBio Aug 2021Pregnant women are highly susceptible to infection by the bacterial pathogen Listeria monocytogenes, leading to miscarriage, premature birth, and neonatal infection. L....
Pregnant women are highly susceptible to infection by the bacterial pathogen Listeria monocytogenes, leading to miscarriage, premature birth, and neonatal infection. L. monocytogenes is thought to breach the placental barrier by infecting trophoblasts at the maternal/fetal interface. However, the fate of L. monocytogenes within chorionic villi and how infection reaches the fetus are unsettled. Hofbauer cells (HBCs) are fetal placental macrophages and the only leukocytes residing in healthy chorionic villi, forming a last immune barrier protecting fetal blood from infection. Little is known about the HBCs' antimicrobial responses to pathogens. Here, we studied L. monocytogenes interaction with human primary HBCs. Remarkably, despite their M2 anti-inflammatory phenotype at basal state, HBCs phagocytose and kill non-pathogenic bacteria like Listeria innocua and display low susceptibility to infection by L. monocytogenes. However, L. monocytogenes can exploit HBCs to spread to surrounding placental cells. Transcriptomic analyses by RNA sequencing revealed that HBCs undergo pro-inflammatory reprogramming upon L. monocytogenes infection, similarly to macrophages stimulated by the potent M1-polarizing agents lipopolysaccharide (LPS)/interferon gamma (IFN-γ). Infected HBCs also express pro-inflammatory chemokines known to promote placental infiltration by maternal leukocytes. However, HBCs maintain the expression of a collection of tolerogenic genes and secretion of tolerogenic cytokines, consistent with their tissue homeostatic role in prevention of fetal rejection. In conclusion, we propose a previously unrecognized model in which HBCs promote the spreading of L. monocytogenes among placental cells and transition to a pro-inflammatory state likely to favor innate immune responses, while maintaining the expression of tolerogenic factors known to prevent maternal anti-fetal adaptive immunity. Infection of the placental/fetal unit by the facultative intracellular pathogen Listeria monocytogenes results in severe pregnancy complications. Hofbauer cells (HBCs) are fetal macrophages that play homeostatic anti-inflammatory functions in healthy placentas. HBCs are located in chorionic villi between the two cell barriers that protect fetal blood from infection: trophoblast cells at the maternal interface (in contact with maternal blood), and fetal endothelial cells at the fetal interface (in contact with fetal blood). As the only leukocytes residing in chorionic villi, HBCs form a critical immune barrier protecting the fetus from infection. Here, we show that although HBCs display low susceptibility to L. monocytogenes, the bacterium still replicates intracellularly and can spread to other placental and fetal cells. We propose that HBCs are permissive to L. monocytogenes transplacental propagation and can repolarize toward a pro-inflammatory phenotype upon infection. However, consistent with their placental homeostatic functions, repolarized HBCs maintain the expression of tolerogenic factors known to prevent maternal anti-fetal adaptive immunity, at least at early stages of infection.
Topics: Cells, Cultured; Chemokines; Cytokines; Female; Humans; Listeria monocytogenes; Macrophages; Placenta; Pregnancy; THP-1 Cells; Trophoblasts
PubMed: 34399615
DOI: 10.1128/mBio.01849-21 -
PloS One 2022Listeria monocytogenes is a ubiquitous opportunistic foodborne pathogen capable of survival in various adverse environmental conditions. Pathogenesis of L. monocytogenes...
Listeria monocytogenes is a ubiquitous opportunistic foodborne pathogen capable of survival in various adverse environmental conditions. Pathogenesis of L. monocytogenes is tightly controlled by a complex regulatory network of transcriptional regulators that are necessary for survival and adaptations to harsh environmental conditions both inside and outside host cells. Among these regulatory pathways are members of the DeoR-family transcriptional regulators that are known to play a regulatory role in sugar metabolism. In this study, we deciphered the role of FruR, a DeoR family protein, which is a fructose operon transcriptional repressor protein, in L. monocytogenes pathogenesis and growth. Following intravenous (IV) inoculation in mice, a mutant strain with deletion of fruR exhibited a significant reduction in bacterial burden in liver and spleen tissues compared to the parent strain. Further, the ΔfruR strain had a defect in cell-to-cell spread in L2 fibroblast monolayers. Constitutive activation of PrfA, a pleiotropic activator of L. monocytogenes virulence factors, did not restore virulence to the ΔfruR strain, suggesting that the attenuation was not a result of impaired PrfA activation. Transcriptome analysis revealed that FruR functions as a positive regulator for genes encoding enzymes involved in the pentose phosphate pathway (PPP) and as a repressor for genes encoding enzymes in the glycolysis pathway. These results suggested that FruR may function to facilitate NADPH regeneration, which is necessary for full protection from oxidative stress. Interestingly, deletion of fruR increased sensitivity of L. monocytogenes to H2O2, confirming a role for FruR in survival of L. monocytogenes during oxidative stress. Using anti-mouse neutrophil/monocyte monoclonal antibody RB6-8C5 (RB6) in an in vivo infection model, we found that FruR has a specific function in protecting L. monocytogenes from neutrophil/monocyte-mediated killing. Overall, this work clarifies the role of FruR in controlling L. monocytogenes carbon flow between glycolysis and PPP for NADPH homeostasis, which provides a new mechanism allowing metabolic adaptation of L. monocytogenes to oxidative stress.
Topics: Animals; Bacterial Proteins; Gene Expression Regulation, Bacterial; Hydrogen Peroxide; Listeria monocytogenes; Mice; Peptide Termination Factors; Regulon; Transcription Factors; Virulence
PubMed: 36054213
DOI: 10.1371/journal.pone.0274005 -
International Journal of Food... Dec 2021Listeria monocytogenes is a foodborne pathogen ubiquitously found in nature and which has been isolated from food and food processing environments. This study aimed to...
Listeria monocytogenes is a foodborne pathogen ubiquitously found in nature and which has been isolated from food and food processing environments. This study aimed to characterize L. monocytogenes strains isolated from the production and processing environments of frozen sliced mushrooms (Agaricus bisporus). An analysis was executed along the mushroom processing chain including one mushroom grower and two mushroom processing factories. A total of 153 L. monocytogenes strains were isolated, which could be grouped in three PCR serogroups, namely, serogroup 1/2a-3a (39.2%), serogroup 1/2b-3b-7 (34.0%) and serogroup 4b-4d-4e (26.8%). A selection of 44 L. monocytogenes strains isolated from the processing environment after cleaning and disinfection (C&D) and from frozen sliced mushrooms was genotyped by whole genome sequencing (WGS), because these strains pose a potential risk for product contamination after C&D and for human consumption. Multilocus sequence typing (MLST) revealed 11 clonal complexes (CCs), with strains belonging to CC1, CC4, CC37 and CC87 being detected in both processing factories. Comparative WGS analysis of the 44 strains showed the presence of Listeria pathogenicity island 1 (LIPI-1) with a disrupted version of actA in all CC1, CC4, CC5, CC59 strains, and all but one CC224 strains. Notably, both inlA and inlB were detected as full-length loci in every strain, except for inlA in a CC6 strain that harbored a three amino acid deletion. LIPI-3 was detected in all CC1, CC4, CC6 and CC224 strains, while LIPI-4 was detected in all CC4 and CC87 strains. In addition, antibiotic susceptibility tests showed susceptibility towards fourteen antibiotics tested. The bcrABC operon was found in one CC5 strain, that showed a higher tolerance towards benzalkonium chloride than any other strain tested with confluent growth till 12.5 μg/ml for the CC5 strain compared to 2.5 μg/ml for the other strains. This study highlights that the ecology of L. monocytogenes in the frozen sliced mushroom production chain is highly diverse, and shows the importance of hygienic measures to control L. monocytogenes along the frozen sliced mushroom production chain.
Topics: Agaricus; Food Microbiology; Genomics; Listeria monocytogenes; Multilocus Sequence Typing
PubMed: 34715483
DOI: 10.1016/j.ijfoodmicro.2021.109438 -
BMC Genomics Mar 2022Whole genome sequencing analyzed by core genome multi-locus sequence typing (cgMLST) is widely used in surveillance of the pathogenic bacteria Listeria monocytogenes....
BACKGROUND
Whole genome sequencing analyzed by core genome multi-locus sequence typing (cgMLST) is widely used in surveillance of the pathogenic bacteria Listeria monocytogenes. Given the heterogeneity of available bioinformatics tools to define cgMLST alleles, our aim was to identify parameters influencing the precision of cgMLST profiles.
METHODS
We used three L. monocytogenes reference genomes from different phylogenetic lineages and assessed the impact of in vitro (i.e. tested genomes, successive platings, replicates of DNA extraction and sequencing) and in silico parameters (i.e. targeted depth of coverage, depth of coverage, breadth of coverage, assembly metrics, cgMLST workflows, cgMLST completeness) on cgMLST precision made of 1748 core loci. Six cgMLST workflows were tested, comprising assembly-based (BIGSdb, INNUENDO, GENPAT, SeqSphere and BioNumerics) and assembly-free (i.e. kmer-based MentaLiST) allele callers. Principal component analyses and generalized linear models were used to identify the most impactful parameters on cgMLST precision.
RESULTS
The isolate's genetic background, cgMLST workflows, cgMLST completeness, as well as depth and breadth of coverage were the parameters that impacted most on cgMLST precision (i.e. identical alleles against reference circular genomes). All workflows performed well at ≥40X of depth of coverage, with high loci detection (> 99.54% for all, except for BioNumerics with 97.78%) and showed consistent cluster definitions using the reference cut-off of ≤7 allele differences.
CONCLUSIONS
This highlights that bioinformatics workflows dedicated to cgMLST allele calling are largely robust when paired-end reads are of high quality and when the sequencing depth is ≥40X.
Topics: Genome, Bacterial; Listeria monocytogenes; Multilocus Sequence Typing; Phylogeny; Whole Genome Sequencing
PubMed: 35346021
DOI: 10.1186/s12864-022-08437-4 -
Applied and Environmental Microbiology Jun 2020The Gram-positive pathogen can be subdivided into at least 12 different serovars, based on the differential expression of a set of somatic and flagellar antigens. Of...
The Gram-positive pathogen can be subdivided into at least 12 different serovars, based on the differential expression of a set of somatic and flagellar antigens. Of note, strains belonging to serovars 1/2a, 1/2b, and 4b cause the vast majority of foodborne listeriosis cases and outbreaks. The standard protocol for serovar determination involves an agglutination method using a set of sera containing cell surface-recognizing antibodies. However, this procedure is imperfect in both precision and practicality, due to discrepancies resulting from subjective interpretation. Furthermore, the exact antigenic epitopes remain unclear, due to the preparation of the absorbed sera and the complex nature of polyvalent antibody binding. Here, we present a novel method for quantitative somatic antigen differentiation using a set of recombinant affinity proteins (cell wall-binding domains and receptor-binding proteins) derived from a collection of bacteriophages. These proteins enable rapid, objective, and precise identification of the different teichoic acid glycopolymer structures, which represent the -antigens, and allow a near-complete differentiation. This glycotyping approach confirmed serovar designations of over 60 previously characterized strains. Using select phage receptor-binding proteins coupled to paramagnetic beads, we also demonstrate the ability to specifically isolate serovar 1/2 or 4b cells from a mixed culture. In addition, glycotyping led to the discovery that strains designated serovar 4e actually possess an intermediate 4b-4d teichoic acid glycosylation pattern, underpinning the high discerning power and precision of this novel technique. is a ubiquitous opportunistic pathogen that presents a major concern to the food industry due to its propensity to cause foodborne illness. The genus contains 15 different serovars, with most of the variance depending on the wall-associated teichoic acid glycopolymers, which confer somatic antigenicity. Strains belonging to serovars 1/2 and 4b cause the vast majority of listeriosis cases and outbreaks, meaning that regulators, as well as the food industry itself, have an interest in rapidly identifying isolates of these particular serovars in food processing environments. Current methods for phenotypic serovar differentiation are slow and lack accuracy, and the food industry could benefit from new technologies allowing serovar-specific isolation. Therefore, the novel method described here for rapid glycotype determination could present a valuable asset to detect and control this bacterium.
Topics: Bacteriophages; Listeria monocytogenes; Recombinant Proteins; Serogroup; Serotyping; Viral Proteins
PubMed: 32358009
DOI: 10.1128/AEM.00612-20 -
Food Research International (Ottawa,... Jun 2022Listeria monocytogenes is a gram-positive pathogen, that usually adheres to stainless steel (SS), and other abiotic surfaces in food processing that undergo repeated...
Listeria monocytogenes is a gram-positive pathogen, that usually adheres to stainless steel (SS), and other abiotic surfaces in food processing that undergo repeated cleaning and cause the spread of Listeria. Through the enumeration of biofilm cells, extracellular polymeric substance (EPS) component and the scanning electron microscopy (SEM) analysis of biofilms, it was found that the ratio of cells and extracellular matrix is affected by nutrition status. Regardless of the temperature, all strains exhibited a higher adhesion ability when exposed to 10-fold diluted TSB-YE (DTSB-YE, nutrition deficiency). Three hour initial adhesion was significantly positively correlated with biofilm formation (p<0.01). DTSB-YE enhances initial attachment and subsequently promotes biofilm formation. The SEM analysis also showed that in DTSB-YE the adhesion and covered area of the attached cells were higher than those in TSB-YE (rich media). The amount of both extracellular polysaccharides and proteins was significantly higher when incubated in DTSB-YE than TSB-YE. The highest biofilm formation of Lm83 was observed in DTSBYE independent of temperature. The effects of nutrition deficiency on the expression of critical biofilm-associated genes of Lm 83 planktonic and biofilm cells were measured. The gene expression levels of inlA and sigB in biofilm cells in TSB-YE and DTSB-YE were approximately 95.7% and 88.0% and 42.2% and 45.7% lower than those in planktonic cells, respectively. However, the expression of inlA in DTSB-YE was significantly higher (p<0.05) than that in TSB-YE for the same cell state. Interestingly, the gene expression of motB was considerably higher in DTSB-YE than in TSBYE, regardless of the state. These results indicate that better cell motility in nutrient deficiencies might facilitate the cell aggression to promote biofilm formation.
Topics: Biofilms; Extracellular Polymeric Substance Matrix; Food Microbiology; Gene Expression; Kinetics; Listeria monocytogenes
PubMed: 35651015
DOI: 10.1016/j.foodres.2022.111143 -
MSphere Jun 2021Laura-Isobel McCall studies the relationship between location and disease pathogenesis, with a focus on infectious diseases and neglected diseases of poverty. In this...
Laura-Isobel McCall studies the relationship between location and disease pathogenesis, with a focus on infectious diseases and neglected diseases of poverty. In this mSphere of Influence article, she reflects on how three papers, "Opposing effects of fasting metabolism on tissue tolerance in bacterial and viral inflammation" (A. Wang, S. C. Huen, H. H. Luan, S. Yu, et al., Cell 166:1512-1525.e12, 2016, https://doi.org/10.1016/j.cell.2016.07.026), "Three-dimensional microbiome and metabolome cartography of a diseased human lung" (N. Garg, M. Wang, E. Hyde, R. R. da Silva, et al., Cell Host Microbe 22:705-716.e4, 2017, https://doi.org/10.1016/j.chom.2017.10.001), and "'It's like a phantom disease': patient perspectives on access to treatment for Chagas disease in the United States" (C. J. Forsyth, S. Hernandez, C. A. Flores, M. F. Roman, et al., Am J Trop Med Hyg 98:735-741, 2018, https://doi.org/10.4269/ajtmh.17-0691), shaped her spatial approach to infectious disease pathogenesis and helped her broaden her perspective from a pathogen-centric focus to a holistic view that include diseases tolerance mechanisms and barriers to health care access.
Topics: Host-Pathogen Interactions; Humans; Listeria monocytogenes; Listeriosis; Lung; Pseudomonas; Viral Tropism
PubMed: 34160240
DOI: 10.1128/mSphere.00520-21