Listeria monocytogenes: A species of gram-positive, rod-shaped bacteria widely distributed in nature. It has been isolated from sewage, soil, silage, and from feces of healthy animals and man. Infection with this bacterium leads to encephalitis, meningitis, endocarditis, and abortion.Listeriosis: Infections with bacteria of the genus LISTERIA.Listeria: A genus of bacteria which may be found in the feces of animals and man, on vegetation, and in silage. Its species are parasitic on cold-blooded and warm-blooded animals, including man.Meningitis, Listeria: Inflammation of the meninges caused by LISTERIA MONOCYTOGENES infection, usually occurring in individuals under the age of 3 years or over the age of 50 years. It may occur at any age in individuals with IMMUNOLOGIC DEFICIENCY SYNDROMES. Clinical manifestations include FEVER, altered mentation, HEADACHE, meningeal signs, focal neurologic signs, and SEIZURES. (From Medicine 1998 Sep;77(5):313-36)Food Microbiology: The presence of bacteria, viruses, and fungi in food and food products. This term is not restricted to pathogenic organisms: the presence of various non-pathogenic bacteria and fungi in cheeses and wines, for example, is included in this concept.Hemolysin Proteins: Proteins from BACTERIA and FUNGI that are soluble enough to be secreted to target ERYTHROCYTES and insert into the membrane to form beta-barrel pores. Biosynthesis may be regulated by HEMOLYSIN FACTORS.Bacterial Proteins: Proteins found in any species of bacterium.Virulence: The degree of pathogenicity within a group or species of microorganisms or viruses as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenic capacity of an organism is determined by its VIRULENCE FACTORS.Peptide Termination Factors: Proteins that are involved in the peptide chain termination reaction (PEPTIDE CHAIN TERMINATION, TRANSLATIONAL) on RIBOSOMES. They include codon-specific class-I release factors, which recognize stop signals (TERMINATOR CODON) in the MESSENGER RNA; and codon-nonspecific class-II release factors.Cheese: A nutritious food consisting primarily of the curd or the semisolid substance formed when milk coagulates.Heat-Shock Proteins: Proteins which are synthesized in eukaryotic organisms and bacteria in response to hyperthermia and other environmental stresses. They increase thermal tolerance and perform functions essential to cell survival under these conditions.Bacterial Toxins: Toxic substances formed in or elaborated by bacteria; they are usually proteins with high molecular weight and antigenicity; some are used as antibiotics and some to skin test for the presence of or susceptibility to certain diseases.Colony Count, Microbial: Enumeration by direct count of viable, isolated bacterial, archaeal, or fungal CELLS or SPORES capable of growth on solid CULTURE MEDIA. The method is used routinely by environmental microbiologists for quantifying organisms in AIR; FOOD; and WATER; by clinicians for measuring patients' microbial load; and in antimicrobial drug testing.Nisin: A 34-amino acid polypeptide antibiotic produced by Streptococcus lactis. It has been used as a food preservative in canned fruits and vegetables, and cheese.Meat Products: Articles of food which are derived by a process of manufacture from any portion of carcasses of any animal used for food (e.g., head cheese, sausage, scrapple).Food-Processing Industry: The productive enterprises concerned with food processing.Macrophages: The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood MONOCYTES. Main types are PERITONEAL MACROPHAGES; ALVEOLAR MACROPHAGES; HISTIOCYTES; KUPFFER CELLS of the liver; and OSTEOCLASTS. They may further differentiate within chronic inflammatory lesions to EPITHELIOID CELLS or may fuse to form FOREIGN BODY GIANT CELLS or LANGHANS GIANT CELLS. (from The Dictionary of Cell Biology, Lackie and Dow, 3rd ed.)Spleen: An encapsulated lymphatic organ through which venous blood filters.Bacteriocins: Substances elaborated by specific strains of bacteria that are lethal against other strains of the same or related species. They are protein or lipopolysaccharide-protein complexes used in taxonomy studies of bacteria.Gene Expression Regulation, Bacterial: Any of the processes by which cytoplasmic or intercellular factors influence the differential control of gene action in bacteria.Food Preservation: Procedures or techniques used to keep food from spoiling.Food Contamination: The presence in food of harmful, unpalatable, or otherwise objectionable foreign substances, e.g. chemicals, microorganisms or diluents, before, during, or after processing or storage.Foodborne Diseases: Acute illnesses, usually affecting the GASTROINTESTINAL TRACT, brought on by consuming contaminated food or beverages. Most of these diseases are infectious, caused by a variety of bacteria, viruses, or parasites that can be foodborne. Sometimes the diseases are caused by harmful toxins from the microbes or other chemicals present in the food. Especially in the latter case, the condition is often called food poisoning.DNA, Bacterial: Deoxyribonucleic acid that makes up the genetic material of bacteria.Mice, Inbred C57BLMolecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Mice, Inbred BALB CFood Preservatives: Substances capable of inhibiting, retarding or arresting the process of fermentation, acidification or other deterioration of foods.Microbial Viability: Ability of a microbe to survive under given conditions. This can also be related to a colony's ability to replicate.Immunity, Innate: The capacity of a normal organism to remain unaffected by microorganisms and their toxins. It results from the presence of naturally occurring ANTI-INFECTIVE AGENTS, constitutional factors such as BODY TEMPERATURE and immediate acting immune cells such as NATURAL KILLER CELLS.Virulence Factors: Those components of an organism that determine its capacity to cause disease but are not required for its viability per se. Two classes have been characterized: TOXINS, BIOLOGICAL and surface adhesion molecules that effect the ability of the microorganism to invade and colonize a host. (From Davis et al., Microbiology, 4th ed. p486)Culture Media: Any liquid or solid preparation made specifically for the growth, storage, or transport of microorganisms or other types of cells. The variety of media that exist allow for the culturing of specific microorganisms and cell types, such as differential media, selective media, test media, and defined media. Solid media consist of liquid media that have been solidified with an agent such as AGAR or GELATIN.Serotyping: Process of determining and distinguishing species of bacteria or viruses based on antigens they share.Food Handling: Any aspect of the operations in the preparation, processing, transport, storage, packaging, wrapping, exposure for sale, service, or delivery of food.Milk: The white liquid secreted by the mammary glands. It contains proteins, sugar, lipids, vitamins, and minerals.Phagosomes: Membrane-bound cytoplasmic vesicles formed by invagination of phagocytized material. They fuse with lysosomes to form phagolysosomes in which the hydrolytic enzymes of the lysosome digest the phagocytized material.Genes, Bacterial: The functional hereditary units of BACTERIA.Immunity, Cellular: Manifestations of the immune response which are mediated by antigen-sensitized T-lymphocytes via lymphokines or direct cytotoxicity. This takes place in the absence of circulating antibody or where antibody plays a subordinate role.Lethal Dose 50: The dose amount of poisonous or toxic substance or dose of ionizing radiation required to kill 50% of the tested population.Caco-2 Cells: Human colonic ADENOCARCINOMA cells that are able to express differentiation features characteristic of mature intestinal cells, such as ENTEROCYTES. These cells are valuable in vitro tools for studies related to intestinal cell function and differentiation.Phagocytosis: The engulfing and degradation of microorganisms; other cells that are dead, dying, or pathogenic; and foreign particles by phagocytic cells (PHAGOCYTES).Bacterial Adhesion: Physicochemical property of fimbriated (FIMBRIAE, BACTERIAL) and non-fimbriated bacteria of attaching to cells, tissue, and nonbiological surfaces. It is a factor in bacterial colonization and pathogenicity.Benzalkonium Compounds: A mixture of alkylbenzyldimethylammonium compounds. It is a bactericidal quaternary ammonium detergent used topically in medicaments, deodorants, mouthwashes, as a surgical antiseptic, and as a as preservative and emulsifier in drugs and cosmetics.Interferon-gamma: The major interferon produced by mitogenically or antigenically stimulated LYMPHOCYTES. It is structurally different from TYPE I INTERFERON and its major activity is immunoregulation. It has been implicated in the expression of CLASS II HISTOCOMPATIBILITY ANTIGENS in cells that do not normally produce them, leading to AUTOIMMUNE DISEASES.Antigens, Bacterial: Substances elaborated by bacteria that have antigenic activity.Environmental Microbiology: The study of microorganisms living in a variety of environments (air, soil, water, etc.) and their pathogenic relationship to other organisms including man.Anti-Bacterial Agents: Substances that reduce the growth or reproduction of BACTERIA.CD8-Positive T-Lymphocytes: A critical subpopulation of regulatory T-lymphocytes involved in MHC Class I-restricted interactions. They include both cytotoxic T-lymphocytes (T-LYMPHOCYTES, CYTOTOXIC) and CD8+ suppressor T-lymphocytes.Sigma Factor: A protein which is a subunit of RNA polymerase. It effects initiation of specific RNA chains from DNA.Bacterial Vaccines: Suspensions of attenuated or killed bacteria administered for the prevention or treatment of infectious bacterial disease.Immunity, Active: Resistance to a disease agent resulting from the production of specific antibodies by the host, either after exposure to the disease or after vaccination.Macrophage Activation: The process of altering the morphology and functional activity of macrophages so that they become avidly phagocytic. It is initiated by lymphokines, such as the macrophage activation factor (MAF) and the macrophage migration-inhibitory factor (MMIF), immune complexes, C3b, and various peptides, polysaccharides, and immunologic adjuvants.Betaine: A naturally occurring compound that has been of interest for its role in osmoregulation. As a drug, betaine hydrochloride has been used as a source of hydrochloric acid in the treatment of hypochlorhydria. Betaine has also been used in the treatment of liver disorders, for hyperkalemia, for homocystinuria, and for gastrointestinal disturbances. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1341)Liver: A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.Hemolysin Factors: Plasmids controlling the synthesis of hemolysin by bacteria.Ampicillin: Semi-synthetic derivative of penicillin that functions as an orally active broad-spectrum antibiotic.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Hypersensitivity, Delayed: An increased reactivity to specific antigens mediated not by antibodies but by cells.Pediococcus: A genus of gram-positive, facultatively anaerobic bacteria whose growth is dependent on the presence of a fermentable carbohydrate. No endospores are produced. Its organisms are found in fermenting plant products and are nonpathogenic to plants and animals, including humans.Phosphoinositide Phospholipase C: A type C phospholipase with specificity towards PHOSPHATIDYLINOSITOLS that contain INOSITOL 1,4,5-TRISPHOSPHATE. Many of the enzymes listed under this classification are involved in intracellular signaling.Membrane Proteins: Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.Bacterial Typing Techniques: Procedures for identifying types and strains of bacteria. The most frequently employed typing systems are BACTERIOPHAGE TYPING and SEROTYPING as well as bacteriocin typing and biotyping.Gene Deletion: A genetic rearrangement through loss of segments of DNA or RNA, bringing sequences which are normally separated into close proximity. This deletion may be detected using cytogenetic techniques and can also be inferred from the phenotype, indicating a deletion at one specific locus.Hot Temperature: Presence of warmth or heat or a temperature notably higher than an accustomed norm.Refrigeration: The mechanical process of cooling.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Bacterial Load: Measurable quantity of bacteria in an object, organism, or organism compartment.Cold Temperature: An absence of warmth or heat or a temperature notably below an accustomed norm.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.Stainless Steel: Stainless steel. A steel containing Ni, Cr, or both. It does not tarnish on exposure and is used in corrosive environments. (Grant & Hack's Chemical Dictionary, 5th ed)Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Hemolysis: The destruction of ERYTHROCYTES by many different causal agents such as antibodies, bacteria, chemicals, temperature, and changes in tonicity.Temperature: The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.Immunologic Memory: The altered state of immunologic responsiveness resulting from initial contact with antigen, which enables the individual to produce antibodies more rapidly and in greater quantity in response to secondary antigenic stimulus.Alanine Racemase: A pyridoxal-phosphate protein that reversibly catalyzes the conversion of L-alanine to D-alanine. EC Chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. (Grant & Hackh's Chemical Dictionary, 5th ed)Meat: The edible portions of any animal used for food including domestic mammals (the major ones being cattle, swine, and sheep) along with poultry, fish, shellfish, and game.Species Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Ribotyping: RESTRICTION FRAGMENT LENGTH POLYMORPHISM analysis of rRNA genes that is used for differentiating between species or strains.Immunization, Passive: Transfer of immunity from immunized to non-immune host by administration of serum antibodies, or transplantation of lymphocytes (ADOPTIVE TRANSFER).Cell Wall: The outermost layer of a cell in most PLANTS; BACTERIA; FUNGI; and ALGAE. The cell wall is usually a rigid structure that lies external to the CELL MEMBRANE, and provides a protective barrier against physical or chemical agents.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Peritoneal Cavity: The space enclosed by the peritoneum. It is divided into two portions, the greater sac and the lesser sac or omental bursa, which lies behind the STOMACH. The two sacs are connected by the foramen of Winslow, or epiploic foramen.Electrophoresis, Gel, Pulsed-Field: Gel electrophoresis in which the direction of the electric field is changed periodically. This technique is similar to other electrophoretic methods normally used to separate double-stranded DNA molecules ranging in size up to tens of thousands of base-pairs. However, by alternating the electric field direction one is able to separate DNA molecules up to several million base-pairs in length.Hydrogen-Ion Concentration: The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH = log 1/2[1/(H+)], where (H+) is the hydrogen ion concentration in gram equivalents per liter of solution. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)

Phenotype of mice and macrophages deficient in both phagocyte oxidase and inducible nitric oxide synthase. (1/3136)

The two genetically established antimicrobial mechanisms of macrophages are production of reactive oxygen intermediates by phagocyte oxidase (phox) and reactive nitrogen intermediates by inducible nitric oxide synthase (NOS2). Mice doubly deficient in both enzymes (gp91(phox-/-)/NOS2(-/-)) formed massive abscesses containing commensal organisms, mostly enteric bacteria, even when reared under specific pathogen-free conditions with antibiotics. Neither parental strain showed such infections. Thus, phox and NOS2 appear to compensate for each other's deficiency in providing resistance to indigenous bacteria, and no other pathway does so fully. Macrophages from gp91(phox-/-)/NOS2(-/-) mice could not kill virulent Listeria. Their killing of S. typhimurium, E. coli, and attenuated Listeria was markedly diminished but demonstrable, establishing the existence of a mechanism of macrophage antibacterial activity independent of phox and NOS2.  (+info)

Role of Listeria monocytogenes exotoxins listeriolysin and phosphatidylinositol-specific phospholipase C in activation of human neutrophils. (2/3136)

Polymorphonuclear leukocytes (PMN) are essential for resolution of infections with Listeria monocytogenes. The present study investigated the role of the listerial exotoxins listeriolysin (LLO) and phosphatidylinositol-specific phospholipase C (PlcA) in human neutrophil activation. Different Listeria strains, mutated in individual virulence genes, as well as purified LLO were used. Coincubation of human neutrophils with wild-type L. monocytogenes provoked PMN activation, occurring independently of phagocytosis events, with concomitant elastase secretion, leukotriene generation, platelet-activating factor (PAF) synthesis, respiratory burst, and enhanced phosphoinositide hydrolysis. Degranulation and leukotriene formation were noted to be solely dependent on LLO expression, as these features were absent when the LLO-defective mutant EGD- and the avirulent strain L. innocua were used. These effects were fully reproduced by a recombinant L. innocua strain expressing LLO (INN+) and by the purified LLO molecule. LLO secretion was also required for PAF synthesis. However, wild-type L. monocytogenes was more potent in eliciting PAF formation than mutants expressing LLO, suggesting the involvement of additional virulence factors. This was even more obvious for phosphoinositide hydrolysis and respiratory burst: these events were provoked not only by INN+ but also by the LLO-defective mutant EGD- and by a recombinant L. innocua strain producing listerial PlcA. We conclude that human neutrophils react to extracellularly provided listerial exotoxins by rapid cell activation. Listeriolysin is centrally involved in triggering degranulation and lipid mediator generation, and further virulence factors such as PlcA apparently contribute to trigger neutrophil phosphoinositide hydrolysis and respiratory burst. In this way, listerial exotoxins may influence the host defense against infections with L. monocytogenes.  (+info)

Noncompetitive expansion of cytotoxic T lymphocytes specific for different antigens during bacterial infection. (3/3136)

Listeria monocytogenes is an intracellular bacterium that elicits complex cytotoxic T-lymphocyte (CTL) responses in infected mice. The responses of CTL populations that differ in antigen specificity range in magnitude from large, dominant responses to small, subdominant responses. To test the hypothesis that dominant T-cell responses inhibit subdominant responses, we eliminated the two dominant epitopes of L. monocytogenes by anchor residue mutagenesis and measured the T-cell responses to the remaining subdominant epitopes. Surprisingly, the loss of dominant T-cell responses did not enhance subdominant responses. While mice immunized with bacteria lacking dominant epitopes developed L. monocytogenes-specific immunity, their ability to respond to dominant epitopes upon rechallenge with wild-type bacteria was markedly diminished. Recall responses in mice immunized with wild-type or epitope-deficient L. monocytogenes showed that antigen presentation during recall infection is sufficient for activating memory cells yet insufficient for optimal priming of naive T lymphocytes. Our findings suggest that T-cell priming to different epitopes during L. monocytogenes infection is not competitive. Rather, T-cell populations specific for different antigens but the same pathogen expand independently.  (+info)

Dopamine beta-hydroxylase deficiency impairs cellular immunity. (4/3136)

Norepinephrine, released from sympathetic neurons, and epinephrine, released from the adrenal medulla, participate in a number of physiological processes including those that facilitate adaptation to stressful conditions. The thymus, spleen, and lymph nodes are richly innervated by the sympathetic nervous system, and catecholamines are thought to modulate the immune response. However, the importance of this modulatory role in vivo remains uncertain. We addressed this question genetically by using mice that lack dopamine beta-hydroxylase (dbh-/- mice). dbh-/- mice cannot produce norepinephrine or epinephrine, but produce dopamine instead. When housed in specific pathogen-free conditions, dbh-/- mice had normal numbers of blood leukocytes, and normal T and B cell development and in vitro function. However, when challenged in vivo by infection with the intracellular pathogens Listeria monocytogenes or Mycobacterium tuberculosis, dbh-/- mice were more susceptible to infection, exhibited extreme thymic involution, and had impaired T cell function, including Th1 cytokine production. When immunized with trinitrophenyl-keyhole limpet hemocyanin, dbh-/- mice produced less Th1 cytokine-dependent-IgG2a antitrinitrophenyl antibody. These results indicate that physiological catecholamine production is not required for normal development of the immune system, but plays an important role in the modulation of T cell-mediated immunity to infection and immunization.  (+info)

Infrarenal endoluminal bifurcated stent graft infected with Listeria monocytogenes. (5/3136)

Prosthetic graft infection as a result of Listeria monocytogenes is an extremely rare event that recently occurred in a 77-year-old man who underwent endoluminal stent grafting for infrarenal abdominal aortic aneurysm. The infected aortic endoluminal prosthesis was removed by means of en bloc resection of the aneurysm and contained endograft with in situ aortoiliac reconstruction. At the 10-month follow-up examination, the patient was well and had no signs of infection.  (+info)

Evaluation of accuracy and repeatability of identification of food-borne pathogens by automated bacterial identification systems. (6/3136)

The performances of five automated microbial identification systems, relative to that of a reference identification system, for their ability to accurately and repeatedly identify six common food-borne pathogens were assessed. The systems assessed were the MicroLog system (Biolog Inc., Hayward, Calif.), the Microbial Identification System (MIS; MIDI Inc., Newark, Del.), the VITEK system (bioMerieux Vitek, Hazelwood, Mo.), the MicroScan WalkAway 40 system (Dade-MicroScan International, West Sacramento, Calif.), and the Replianalyzer system (Oxoid Inc., Nepean, Ontario, Canada). The sensitivities and specificities of these systems for the identification of food-borne isolates of Bacillus cereus, Campylobacter jejuni, Listeria monocytogenes, Staphylococcus aureus, Salmonella spp., and verotoxigenic Escherichia coli were determined with 40 reference positive isolates and 40 reference negative isolates for each pathogen. The sensitivities of these systems for the identification of these pathogens ranged from 42.5 to 100%, and the specificities of these systems for the identification of these pathogens ranged from 32.5 to 100%. Some of the systems had difficulty correctly identifying the reference isolates when the results were compared to those from the reference identification tests. The sensitivity of MIS for the identification of S. aureus, B. cereus, E. coli, and C. jejuni, for example, ranged from 47.5 to 72. 5%. The sensitivity of the Microlog system for the identification of E. coli was 72.5%, and the sensitivity of the VITEK system for the identification of B. cereus was 42.5%. The specificities of four of the five systems for the identification of all of the species tested with the available databases were greater than or equal to 97.5%; the exception was MIS for the identification of C. jejuni, which displayed a specificity of 32.5% when it was tested with reference negative isolates including Campylobacter coli and other Campylobacter species. All systems had >80% sensitivities for the identification of Salmonella species and Listeria species at the genus level. The repeatability of these systems for the identification of test isolates ranged from 30 to 100%. Not all systems included all six pathogens in their databases; thus, some species could not be tested with all systems. The choice of automated microbial identification system for the identification of a food-borne pathogen would depend on the availability of identification libraries within the systems and the performance of the systems for the identification of the pathogen.  (+info)

The isoflavone genistein inhibits internalization of enteric bacteria by cultured Caco-2 and HT-29 enterocytes. (7/3136)

The dietary isoflavone genistein is the focus of much research involving its role as a potential therapeutic agent in a variety of diseases, including cancer and heart disease. However, there is recent evidence that dietary genistein may also have an inhibitory effect on extraintestinal invasion of enteric bacteria. To study the effects of genistein on bacterial adherence and internalization by confluent enterocytes, Caco-2 and HT-29 enterocytes (cultivated for 15-18 d and 21-24 d, respectively) were pretreated for 1 h with 0, 30, 100, or 300 micromol/L genistein, followed by 1-h incubation with pure cultures of Listeria monocytogenes, Salmonella typhimurium, Proteus mirabilis, or Escherichia coli. Pretreatment of Caco-2 and HT-29 enterocytes with genistein inhibited bacterial internalization in a dose-dependent manner (r = 0.60-0.79). Compared to untreated enterocytes, 1-h pretreatment with 300 micromol/L genistein was generally associated with decreased bacterial internalization (P < 0. 05) without a corresponding decrease in bacterial adherence. Using Caco-2 cell cultures, decreased bacterial internalization was associated with increased integrity of enterocyte tight junctions [measured by increased transepithelial electrical resistance (TEER)], with alterations in the distribution of enterocyte perijunctional actin filaments (visualized by fluorescein-labeled phalloidin), and with abrogation of the decreased TEER associated with S. typhimurium and E. coli incubation with the enterocytes (P < 0.01). Thus, genistein was associated with inhibition of enterocyte internalization of enteric bacteria by a mechanism that might be related to the integrity of the enterocyte tight junctions, suggesting that genistein might function as a barrier-sustaining agent, inhibiting extraintestinal invasion of enteric bacteria.  (+info)

Listeria monocytogenes phospholipase C-dependent calcium signaling modulates bacterial entry into J774 macrophage-like cells. (8/3136)

Listeria monocytogenes secretes several proteins that have been shown to contribute to virulence. Among these is listeriolysin O (LLO), a pore-forming hemolysin that is absolutely required for virulence. Two other virulence factors are phospholipases: a phosphatidylinositol-specific phospholipase C (PI-PLC [plcA]) and a broad-range PLC (plcB). Although mutations in plcA or plcB resulted in small increases in mouse 50% lethal dose (LD50), deletions in both genes resulted in a 500-fold increase in LD50. We have examined the role of these secreted proteins in host intracellular signaling in the J774 macrophage-like cell line. Measurements of cytosolic free calcium ([Ca2+]i) have revealed a rapid spike upon exposure of these cells to wild-type L. monocytogenes. This is followed by a second peak at 5 min and a third prolonged peak with a maximal [Ca2+]i of 800 to 1,000 nM. The pattern of calcium changes was greatly altered by deletion of any of the three virulence factors. An LLO mutant produced none of these elevations in [Ca2+]i; however, a transient elevation was observed whenever these bacteria entered the cell. A PI-PLC mutant produced a diminished single elevation in [Ca2+]i at 15 to 30 min. A broad-range PLC mutant produced only the first calcium spike. Studies with inhibitors suggested that the first elevation arises from influx of calcium from the extracellular medium through plasma membrane channels and that the second and third elevations come from release of Ca2+ from intracellular stores. We observed that internalization of wild-type bacteria and the broad-range PLC mutant was delayed for 5 to 10 min, but the LLO and PI-PLC mutants were internalized rapidly upon infection. Inhibitors that affected calcium signaling changed the kinetics of association of wild-type bacteria with J774 cells, the kinetics of entry, and the efficiency of escape from the primary phagosome.  (+info)

  • WASHINGTON, September 25, 2014- Foster Farms, a Farmerville, La., establishment, is recalling approximately 39,747 pounds of frozen pre-cooked chicken products due to possible contamination with Listeria monocytogenes , the U.S. Department of Agriculture's Food Safety and Inspection Service (FSIS) announced today. (
  • The present study aimed to assess bacteriological contamination with Escherichia coli and Listeria monocytogenes in the raw milk samples of the dairy farms in Golestan province, Iran. (
  • E. coli and L. monocytogenes contamination was significantly higher in traditional dairy farms than industrial dairy farms (P ˂ 0.05). (
  • Survival and recovery of Listeria monocytogenes in the ready-to-eat (RTE) meat processing environment were studied, from environmental contamination to intervention. (
  • It is the investigators intention to investigate whether a specially designed vaccine, based on a genetically modified strain of the bacterium Listeria monocytogenes and called ADXS11-001 is safe to use and is able to boost the immune system of patients presenting with Human Papilloma Virus (HPV) associated oropharyngeal cancer (OPSCC). (
  • The majority of Listeria monocytogenes that have been isolated from food product or human cases are of the serotypes ½ a, ½ b and 4b. (
  • We observed PMSCs in 35% of L. monocytogenes isolates (n = 54) recovered from the British Columbia food supply, including serotypes 1/2a (30%), 1/2c (100%), and 3a (100%), and a 3-codon deletion (amino acid positions 738 to 740) seen in 57% of 4b isolates from fish-processing facilities. (
  • The PS-binding receptor TIM-4 (encoded by the Timd4 gene) contributes to efficient cell-to-cell spread by L. monocytogenes in macrophages in vitro and growth of these bacteria is impaired in Timd4 −/− mice. (
  • Our results indicate that PS-targeted therapeutics may be useful in the fight against infections by L. monocytogenes and other bacteria that use similar strategies of cell-to-cell spread during infection. (
  • Irreversible loss of membrane-binding activity of Listeria -derived cytolysins in non-acidic conditions: a distinct difference from allied cytolysins produced by other Gram-positive bacteria. (
  • SIRT2 is recruiter to the transcription star sites of genes repressed during inection leading to H3K18 deacetylation and transcriptional repression.finnaly, my results demonstrate that SIRT2 is hijacked by L monocytogenes and promotes an increase in intracellular bacteria. (
  • Due to the recent outbreaks, recalls and deaths associated with Listeria monocytogenes in ready-to-eat meat products, the United States Department of Agriculture (USDA), Food Safety and Inspection Service (FSIS) on October 2, 2003 issued a directive for the control of Listeria monocytogenes on ready-to-eat products. (
  • This study was conducted to determine the prevalence of VA SNPs in inlA among L. monocytogenes from environments associated with RTE food production and handling. (
  • This alternative sigma factor contributes to the ability of organisms such as Listeria monocytogenes , Bacillus subtilis , and Staphylococcus aureus to survive under environmental and energy stress conditions ( 4 , 10 , 18 , 19 , 65 ).σ B also contributes to biofilm formation in S. aureus and Staphylococcus epidermidis ( 37 , 55 ). (
  • U jednom od 30 uzoraka je utvrđena prisutnost bakterije Listeria monocytogenes, a u tri uzorka je utvrđena prisutnost Listeria innocua. (
  • Alberti-Segui, C., Goeden, K. R. & Higgins, D. E. Differential function of Listeria monocytogenes listeriolysin O and phospholipases C in vacuolar dissolution following cell-to-cell spread. (
  • 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. (
  • Listeriolysin O (LLO) is a major virulence factor secreted by the pathogenic Listeria monocytogenes and acts as pore-forming cytolysin. (
  • Immunoassay method in samples of fresh cow cheese, and from the obtained positive samples with Horizontal method for the detection and enumeration of cells and biochemical prove the presence of species Listeria monocytogenes. (
  • The survival of Listeria monocytogenes at freezer temperatures on a variety of ready-to-eat meat products was also assessed. (
  • Our study has been successful in understanding the survival of Listeria monocytogenes at freezer temperatures on the surface of ready-to-eat meat products under vacuum and non-vacuum package storage conditions. (
  • Desiccated cells of L. monocytogenes were not observed to go into viable but non-culturable (VBNC) state well indicating that current methods of using nonselective media, tryptic soy agar with 0.6% yeast extract, is adequate in recovering the majority of the viable cells. (
  • The human, food and environmental isolates were of the same serotype and were indistinguishable by molecular typing.This is the first community outbreak of L monocytogenes reported in Scotland since the current outbreak surveillance was established in 1996. (