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a predictive model for the effect of temperature and predrying treatments in reducing listeria monocytogenes populations during drying of beef jerky.the objective of this study was to model the effect of drying temperatures (52, 57, and 63 degrees c) and predrying treatments on the inactivation of listeria monocytogenes on beef jerky. before drying, beef slices were inoculated with a 10-strain composite of l. monocytogenes and then treated with the following: (i) nothing (c), (ii) traditional marinade (m), or (iii) dipping in 5% acetic acid solution for 10 min, followed by m (am). in addition, sequential stresses (exposure to 10% nacl, follo ...200616416902
cross-contamination between processing equipment and deli meats by listeria monocytogenes.contamination of luncheon meats by listeria monocytogenes has resulted in outbreaks of listeriosis and major product recalls. listeriae can survive on processing equipment such as meat slicers which serve as a potential contamination source. this study was conducted to determine (i) the dynamics of cross-contamination of l. monocytogenes from a commercial slicer and associated equipment onto sliced meat products, (ii) the influence of sample size on the efficacy of the bax-pcr and u.s. departmen ...200616416903
molecular characterization of listeria monocytogenes from natural and urban environments.characterization of 80 listeria monocytogenes isolates from urban and natural environments differentiated 7 and 26 ecori ribotypes, respectively. whereas the majority of isolates from the natural environment represented l. monocytogenes lineage ii (12 of 13 isolates), urban isolates grouped evenly into lineages i and ii (32 and 33 isolates, respectively) and included two lineage iii isolates. multilocus sequence typing of all natural isolates and a randomly selected subset of 30 urban isolates s ...200616416906
sensitivities of foodborne pathogens to pressure changes.eight foodborne pathogens were suspended in ultrahigh-temperature whole milk and treated at pressure levels of 0.1 to 690 mpa at 21.5 degrees c for 10 min. there was no clear trend in pressure resistance between gram-negative and gram-positive organisms. the order of the single strains tested, from most to least pressure sensitive, was vibrio parahaemolyticus < yersinia enterocolitica < listeria monocytogenes < salmonella enterica serovar typhimurium < s. enterica serovar enteritidis < escherich ...200616416910
influence of antimicrobial compounds and modified atmosphere packaging on radiation sensitivity of listeria monocytogenes present in ready-to-use carrots (daucus carota).radiosensitization of listeria monocytogenes was determined in the presence of trans-cinnamaldehyde, spanish oregano, winter savory, and chinese cinnamon on peeled minicarrots packed under air or under a modified atmosphere (60% o2, 30% co2, and 10% n2). samples were inoculated with l. monocytogenes hpb 2812 serovar 1/2a (106 cfu/g) and were coated separately with each active compound (0.5%, wt/wt) before being packaged under air or the modified atmosphere and irradiated at doses from 0.07 to 2. ...200616416924
selective targeting of antitumor immune responses with engineered live-attenuated listeria monocytogenes.improved immunization and ex vivo t-cell culture strategies can generate larger numbers and more potent tumor-specific effector cells than previously possible. nonetheless, the capacity of these cells to eliminate established tumors is limited by their ability to efficiently enter tumor-bearing organs and mediate their effector function. in the current study, we show that the administration of an engineered organ-homing microbe selectively targets tumor-specific immune responses to metastases wi ...200616424046
cutting edge: a novel nonoxidative phagosomal mechanism exerted by cathepsin-d controls listeria monocytogenes intracellular growth.deciphering how listeria monocytogenes exploits the host cell machinery to invade mammalian cells is a key issue in understanding the pathogenesis of this food-borne pathogen, which can cause diseases ranging from gastroenteritis to meningitis and abortion. in this study, we show that the lysosomal aspartyl-protease cathepsin-d (ctsd) is of considerable importance for nonoxidative listericidal defense mechanisms. we observed enhanced susceptibility to l. monocytogenes infection of fibroblasts an ...200616424157
protein vaccines induce uncommitted il-2-secreting human and mouse cd4 t cells, whereas infections induce more ifn-gamma-secreting cells.mouse and human cd4 t cells primed during an immune response may differentiate into effector phenotypes such as th1 (secreting ifn-gamma) or th2 (secreting il-4) that mediate effective immunity against different classes of pathogen. however, primed cd4 t cells can also remain uncommitted, secreting il-2 and chemokines, but not ifn-gamma or il-4. we now show that human cd4 t cells primed by protein vaccines mostly secreted il-2, but not ifn-gamma, whereas in the same individuals most cd4 t cells ...200616424174
sigma b contributes to listeria monocytogenes gastrointestinal infection but not to systemic spread in the guinea pig infection model.contributions of the alternative sigma factor sigmab to listeria monocytogenes infection were investigated using strains bearing null mutations in sigb, prfa, or inla or in selected inla or prfa promoter regions. the deltap4inla strain, which has a deletion in the sigmab-dependent p4inla promoter, and the deltasigb strain had significantly reduced invasion efficiencies relative to that of the wild-type strain in the caco-2 human colorectal epithelial cell line, while the invasion efficiency of a ...200616428730
identification of novel gammadelta t-cell subsets following bacterial infection in the absence of vgamma1+ t cells: homeostatic control of gammadelta t-cell responses to pathogen infection by vgamma1+ t cells.although gammadelta t cells are a common feature of many pathogen-induced immune responses, the factors that influence, promote, or regulate the response of individual gammadelta t-cell subsets to infection is unknown. here we show that in the absence of vgamma1+ t cells, novel subsets of gammadelta t cells, expressing t-cell receptor (tcr)-vgamma chains that normally define tcrgammadelta+ dendritic epidermal t cells (detcs) (vgamma5+), intestinal intraepithelial lymphocytes (iiels) (vgamma7+), ...200616428757
intracellular gene expression profile of listeria monocytogenes.listeria monocytogenes is a gram-positive, food-borne microorganism responsible for invasive infections with a high overall mortality. l. monocytogenes is among the very few microorganisms that can induce uptake into the host cell and subsequently enter the host cell cytosol by breaching the vacuolar membrane. we infected the murine macrophage cell line p388d1 with l. monocytogenes strain egd-e and examined the gene expression profile of l. monocytogenes inside the vacuolar and cytosolic environ ...200616428782
development of a magnetic capture hybridization-pcr assay for listeria monocytogenes direct detection in milk samples.a rapid and sensitive method for listeria monocytogenes direct detection from milk was developed. it is based on a magnetic capture hybridization procedure for selective dna purification, followed by pcr identification. a comparison with two similar commercial systems from dynal (dynabeads) was carried out.200616430514
iron acquisition systems for ferric hydroxamates, haemin and haemoglobin in listeria monocytogenes.listeria monocytogenes is a gram-positive bacterium that causes severe opportunistic infections in humans and animals. we biochemically characterized, for the first time, the iron uptake processes of this facultative intracellular pathogen, and identified the genetic loci encoding two of its membrane iron transporters. strain egd-e used iron complexes of hydroxamates (ferrichrome and ferrichrome a, ferrioxamine b), catecholates (ferric enterobactin, ferric corynebactin) and eukaryotic binding pr ...200616430693
mechanism of polarization of listeria monocytogenes surface protein acta.the polar distribution of the acta protein on the surface of the gram-positive intracellular bacterial pathogen, listeria monocytogenes, is required for bacterial actin-based motility and successful infection. acta spans both the bacterial membrane and the peptidoglycan cell wall. we have directly examined the de novo acta polarization process in vitro by using an acta-rfp (red fluorescent protein) fusion. after induction of expression, acta initially appeared at distinct sites along the sides o ...200616430699
solid-phase synthesis of polyfunctionalized natural products: application to usnic acid, a bioactive lichen compound. 200616398547
bloodstream infections in organ transplant recipients receiving alemtuzumab: no evidence of occurrence of organisms typically associated with profound t cell depletion.alemtuzumab is a humanized monoclonal antibody directed against cd52, a cell surface antigen expressed on b and t lymphocytes, monocytes and nk cells. its use results in a profound decrease in cd4 positive t lymphocytes. alemtuzumab is used as induction immunosuppression and therapy for rejection in organ transplant recipients in some centers. we followed a cohort of 449 consecutive transplant recipients who received alemtuzumab to determine the occurrence of bloodstream infections, particularly ...200616403576
[neonatal infection with listeria monocytogenes: rare, but serious].between 1993 and 2003, three infants, two girls and a boy, were found to have an invasive infection with listeria monocytogenes. they received intensive care including respiratory and circulatory support, antibiotics, and treatment of the neurological complications when possible. one of the girls survived without sequelae but the other two infants died in the neonatal period. in one of these two cases there was a clear clue to the source of the infection in the dietary history of the mother: she ...200616440567
phosphorylation, ubiquitination and degradation of listeriolysin o in mammalian cells: role of the pest-like sequence.listeria monocytogenes is a bacterial pathogen that grows within the cytosol of infected host cells. entry into the cytosol is largely mediated by a secreted bacterial cytolysin, listeriolysin o (llo). in order to prevent host cell damage, the pore-forming activity of llo is restricted to the phagosome. compartmentalization of llo requires a pest-like sequence; pest sequences can direct eukaryotic proteins for proteasomal degradation. here we test the hypothesis that llo's pest-like sequence com ...200616441444
listeria monocytogenes in platelets: a case report.efforts to reduce bacterial contamination in platelets (plts) have led to implementation of tests for bacterial detection before product release. although relatively rare as a human pathogen, listeria monocytogenes often causes serious illness and has a case-fatality rate of 20 percent.200616441611
interferon-producing killer dendritic cells provide a link between innate and adaptive immunity.natural killer (nk) cells and dendritic cells (dcs) are, respectively, central components of innate and adaptive immune responses. we describe here a third dc lineage, termed interferon-producing killer dcs (ikdcs), distinct from conventional dcs and plasmacytoid dcs and with the molecular expression profile of both nk cells and dcs. they produce substantial amounts of type i interferons (ifn) and interleukin (il)-12 or ifn-gamma, depending on activation stimuli. upon stimulation with cpg oligod ...200616444266
allelic exchange and site-directed mutagenesis probe the contribution of acta amino-acid variability to phosphorylation and virulence-associated phenotypes among listeria monocytogenes strains.to test the hypothesis that acta allelic variation contributes to virulence differences among listeria monocytogenes strains, cell-to-cell spread and intracellular acta phosphorylation patterns were characterized for 14 wild-type isolates and selected isogenic mutants. our data show that (i) while acta allelic variation is not responsible for enhanced cell-to-cell spread observed in epidemic clone i strains, acta allelic variation may contribute to reduced plaque size observed in some isolates, ...200616445760
listeria monocytogenes invades the epithelial junctions at sites of cell extrusion.listeria monocytogenes causes invasive disease by crossing the intestinal epithelial barrier. this process depends on the interaction between the bacterial surface protein internalin a and the host protein e-cadherin, located below the epithelial tight junctions at the lateral cell-to-cell contacts. we used polarized mdck cells as a model epithelium to determine how l. monocytogenes breaches the tight junctions to gain access to this basolateral receptor protein. we determined that l. monocytoge ...200616446782
ladr, a new padr-related transcriptional regulator from listeria monocytogenes, negatively regulates the expression of the multidrug efflux pump mdrl.the listeria monocytogenes genome encodes putative multidrug efflux transporters but only the mdrl transporter has been partially characterized in the wild-type lo28 strain. here, we show in the lo28 strain, that the expression of mdrl is repressed at the transcriptional level, under standard growth conditions, by the product of a new gene ladr (lmo1408), and the expression of mdrl is induced in the presence of rhodamine. phylogenetic analysis in related firmicutes shows that ladr, conserved in ...200616451184
liposome-doped nanocomposites as artificial-cell-based biosensors: detection of listeriolysin o.listeriolysin o (llo) is a pore-forming hemolysin secreted by the foodborne pathogen listeria monocytogenes and is required for bacterial virulence. current detection methods for l. monocytogenes are time-consuming, labor-intensive, and expensive, which is impractical considering the limitations of food storage. to overcome these problems, we developed a liposome-doped silica nanocomposite as a simple, inexpensive, and highly stable biosensor material that mimics existing whole-cell assays for l ...200616454489
the wild-derived inbred mouse strain spret/ei is resistant to lps and defective in ifn-beta production.although activation of toll-like receptor 4 (tlr4)-positive cells is essential for eliminating gram-negative bacteria, overactivation of these cells by the tlr4 ligand lps initiates a systemic inflammatory reaction and shock. here we demonstrate that spret/ei mice, derived from mus spretus, exhibit a dominant resistance against lps-induced lethality. this resistance is mediated by bone marrow-derived cells. macrophages from these mice exhibit normal signaling and gene expression responses that d ...200616455798
production, characterisation and potential application of a novel monoclonal antibody for rapid identification of virulent listeria monocytogenes.a panel of hybridomas was produced using intact listeria monocytogenes serotype 1/2a cells as the immunogen. an igg2a monoclonal antibody (mab) 'mab2b3' was isolated that reacted with l. monocytogenes but not with a representative panel of related listeria spp. and non-listeria spp. binding activity was greatest against l. monocytogenes serotype 1/2a and was significantly enhanced when cells were prepared in listeria enrichment broth (leb). the reactive epitope was deduced, by immunoblot analysi ...200616457899
patho-biotechnology: using bad bugs to do good things.pathogenic bacteria have evolved sophisticated strategies to overcome host defences, to interact with the immune system and to interfere with essential host systems. we coin the term 'patho-biotechnology' to describe the exploitation of these valuable traits in biotechnology, medicine and food. this approach shows promise for the development of novel vaccine and drug delivery systems, as well as for the design of more technologically robust and effective probiotic cultures with improved biotechn ...200616459072
h2-m3-restricted cd8+ t cells are not required for mhc class ib-restricted immunity against listeria monocytogenes.studies using major histocompatibility complex (mhc)-ia-deficient mice have shown that mhc-ib-restricted cd8+ t cells can clear infections caused by intracellular pathogens such as listeria monocytogenes. m3-restricted cd8+ t cells, which recognize short hydrophobic n-formylated peptides, appear to comprise a substantial portion of the mhc-ib-restricted t cell response in the mouse model of l. monocytogenes infection. in this study, we isolated formyltransferase (fmt) mutant strains of l. monocy ...200616461341
reliable and rapid identification of listeria monocytogenes and listeria species by artificial neural network-based fourier transform infrared spectroscopy.differentiation of the species within the genus listeria is important for the food industry but only a few reliable methods are available so far. while a number of studies have used fourier transform infrared (ftir) spectroscopy to identify bacteria, the extraction of complex pattern information from the infrared spectra remains difficult. here, we apply artificial neural network technology (ann), which is an advanced multivariate data-processing method of pattern analysis, to identify listeria ...200616461640
biocontrol of the food-borne pathogens listeria monocytogenes and salmonella enterica serovar poona on fresh-cut apples with naturally occurring bacterial and yeast antagonists.fresh-cut apples contaminated with either listeria monocytogenes or salmonella enterica serovar poona, using strains implicated in outbreaks, were treated with one of 17 antagonists originally selected for their ability to inhibit fungal postharvest decay on fruit. while most of the antagonists increased the growth of the food-borne pathogens, four of them, including gluconobacter asaii (t1-d1), a candida sp. (t4-e4), discosphaerina fagi (st1-c9), and metschnikowia pulcherrima (t1-e2), proved ef ...200616461659
determination of essential and variable residues in pediocin pa-1 by nnk scanning.pediocin pa-1 is an antimicrobial peptide (called bacteriocin) that shows inhibitory activity against the food-borne pathogen listeria monocytogenes. to elucidate which residue(s) is responsible for this function, the antimicrobial activities of pediocin pa-1 mutants were evaluated and compared. each of the 44 native codons was replaced with the nnk triplet oligonucleotide in a technique termed nnk scanning, and 35 mutations at each position were examined for antimicrobial activities using a mod ...200616461660
two subpopulations of listeria monocytogenes occur at subinhibitory concentrations of leucocin 4010 and nisin.in situ analyses of single listeria monocytogenes cells at subinhibitory concentrations of leucocin 4010 and nisin revealed two subpopulations when measured by fluorescence ratio imaging microscopy (frim) after staining with 5(6)-carboxyfluorescein diacetate succinimidyl ester. one subpopulation consisted of cells with a dissipated ph gradient (deltaph), and the other consisted of cells that maintained deltaph. the proportion of cells belonging to each subpopulation was estimated, and the concen ...200616461719
caenorhabditis elegans is a model host for listeria monocytogenes.here we report that caenorhabditis elegans nematodes fed listeria monocytogenes die over the course of several days, as a consequence of an accumulation of bacteria in the worm intestine. mutant strains previously shown to be important for virulence in mammalian models were also found to be attenuated in their virulence in c. elegans. however, acta, which is required for actin-based intracellular motility, appears to be dispensable during infection of c. elegans, indicating that l. monocytogenes ...200616461732
13c isotopologue perturbation studies of listeria monocytogenes carbon metabolism and its modulation by the virulence regulator prfa.the carbon metabolism of listeria monocytogenes (lm) egd and the two isogenic mutant strains lmdeltaprfa and lmdeltaprfapprfa* (showing no or enhanced expression, respectively, of the virulence factor prfa) was determined by 13c isotopologue perturbation. after growth of the bacteria in a defined medium containing a mixture of [u-13c6]glucose and glucose with natural 13c abundance (1:25, wt/wt), 14 amino acids were isolated and analyzed by nmr spectroscopy. multiply 13c-labeled isotopologues wer ...200616461909
sensor molecules in intestinal innate immunity against bacterial infections.toll-like receptors (tlrs) and nucleotide-binding oligomerization domain (nod)-containing proteins are innate immune sensors for microbial signature molecules. this review highlights new insights into the functions of these sensors in intestinal physiology.200616462163
population-based incidence of infection with selected bacterial enteric pathogens in children younger than five years of age, 1996-1998.previous studies of bacterial enteric infections have suggested a disproportionate disease burden for children younger than 5 years of age.200616462289
monocyte emigration from bone marrow during bacterial infection requires signals mediated by chemokine receptor ccr2.monocytes recruited to tissues mediate defense against microbes or contribute to inflammatory diseases. regulation of the number of circulating monocytes thus has implications for disease pathogenesis. however, the mechanisms controlling monocyte emigration from the bone marrow niche where they are generated remain undefined. we demonstrate here that the chemokine receptor ccr2 was required for emigration of ly6c(hi) monocytes from bone marrow. ccr2(-/-) mice had fewer circulating ly6c(hi) monoc ...200616462739
species specificity of the listeria monocytogenes inlb protein.inla and inlb mediate l. monocytogenes entry into eukaryotic cells. inla is required for the crossing of the intestinal and placental barriers. inla uses e-cadherin as receptor in a species-specific manner. the human e-cadherin but not the mouse e-cadherin is a receptor for inla. in human cells, inlb uses met and gc1qr as receptors. by studying the role of inlb in vivo, we found that activation of met by inlb is species-specific. in mice, inlb is important for liver and spleen colonization, but ...200616469057
genomic dissection of microbial pathogenesis in cultured drosophila cells.recent rna interference screens that were performed at a genome-wide level have identified host factors that are important for the growth of listeria monocytogenes in cultured cells from the fruit fly drosophila melanogaster. the screens identified genes that are involved in phagocytosis but did not detect genes known to be involved in immune signaling pathways. these studies provide a foundation for the identification of host factors and virulence mechanisms.200616473012
listeria monocytogenes internalins are highly diverse and evolved by recombination and positive selection.to probe the evolution of internalins with confirmed or suspected roles in listeria monocytogenes virulence we sequenced the full inlb, inlc2, inlc, inld, inle, inlf, inlg, and inlh orfs from 40 l. monocytogenes isolated from human (n=10) and animal (n=10) clinical cases, foods (n=10), and the natural environment (n=10). inlb and inle were present in all isolates, representing 26 and 20 alleles, respectively. inlc was found in all lineage i and ii isolates and represented 21 alleles. inlc2 and i ...200616473049
primary and opportunistic pathogens associated with meningitis in adults in bangui, central african republic, in relation to human immunodeficiency virus serostatus.to determine the causative organisms and characteristics of patients presenting with meningitis in bangui in order to provide guidance to physicians for case management.200616473538
impaired response to listeria in h2-m3-deficient mice reveals a nonredundant role of mhc class ib-specific t cells in host defense.the major histocompatibility complex (mhc) class ib molecule h2-m3 primes the rapid expansion of cd8+ t cells by presenting n-formylated bacterial peptides. however, the significance of h2-m3-restricted t cells in host defense against bacteria is unclear. we generated h2-m3-deficient mice to investigate the role of h2-m3 in immunity against listeria monocytogenes (lm), a model intracellular bacterial pathogen. h2-m3-deficient mice are impaired in early bacterial clearance during primary infectio ...200616476767
monoclonal antibodies binding to the cell surface of listeria monocytogenes serotype 4b.serotype 4b strains of the food-borne pathogen listeria monocytogenes are responsible for a large portion of sporadic listeric infections and all major food-borne listeriosis outbreaks in humans. hybridomas were produced from three fusions with lymphocytes of nd4 mice immunized either with the insoluble antigens of l. monocytogenes serotype 4b or with formalin-killed bacterial cells and screened for monoclonal antibodies (mabs) reactive to l. monocytogenes serotype 4b. a set of 35 mabs was ident ...200616476793
occurrence of foodborne pathogenic bacteria in retail prepackaged portions of marine fish in spain.to survey the presence of indigenous and nonindigenous foodborne bacterial pathogens in displayed prepacked portions of fresh marine fish.200616478492
evidence of an antilisterial factor induced by wounding of iceberg lettuce tissues.to examine the influence of wound-associated reactions in cut iceberg lettuce (lactuca sativa l.) tissues on the fate of listeria monocytogenes.200616478519
[listeria monocytogenes meningitis complicated after operation for thoracic aortic aneurysm].the patient was a 71-year-old male. he was admitted as an emergency to our hospital because of impending rupture of thoracic aortic aneurysm with anterior chest pain and hoarseness. the aneurysm was saccular type and located in the lesser curvature of aortic arch. emergency operation was performed. entry of the aneurysm was excluded by including artificial graft on the deep hypothermic circulatory arrest. postoperative course was uneventful, but sudden depression of consciousness level and pyrex ...200616482907
characterization of the bifunctional glycosyltransferase/acyltransferase penicillin-binding protein 4 of listeria monocytogenes.multimodular penicillin-binding proteins (pbps) are essential enzymes responsible for bacterial cell wall peptidoglycan (pg) assembly. their glycosyltransferase activity catalyzes glycan chain elongation from lipid ii substrate (undecaprenyl-pyrophosphoryl-n-acetylglucosamine-n-acetylmuramic acid-pentapeptide), and their transpeptidase activity catalyzes cross-linking between peptides carried by two adjacent glycan chains. listeria monocytogenes is a food-borne pathogen which exerts its virulenc ...200616484198
mammalian peptidoglycan recognition protein tagl inhibits listeria monocytogenes invasion into epithelial cells.peptidoglycan recognition proteins are a family of evolutionary conserved proteins that play a basic role in the innate immunity of insects, but their role in the immunity of mammals remains unclear. to elucidate its functions, a mouse member of the peptidoglycan recognition proteins family, tagl, was stably expressed in colon adenocarcinoma ht29 cells, and its effect on the invasion and intracellular growth of the enteroinvasive pathogenic bacterium listeria monocytogenes was assessed. the expr ...200616487310
a combination of diagnostic tools for rapid screening of ovine listeriosis.a combined serological and pcr method for the detection of listeria monocytogenes infection in symptomatic and asymptomatic ovine flocks was evaluated. seventy-eight milk samples and 157 serum samples were analysed using a l. monocytogenes pcr detection kit and an anti-listeriolysin o igg immunoassay kit. the combined use of these commercial kits allowed a rapid and effective detection of l. monocytogenes infection in both the early stage, before seroconversion, and in a later phase, even after ...200616487553
effect of environmental parameters (temperature, ph and a(w)) on the individual cell lag phase and generation time of listeria monocytogenes.the effect of the individual environmental factors temperature (2-30 degrees c), ph (4.4-7.4) and a(w) (0.947-0.995) as well as the combinations of these factors on the individual cell lag phase and the generation time of listeria monocytogenes was investigated. individual cells were isolated using a serial dilution protocol in microtiter plates, and subsequent growth was investigated by optical density (od) measurements at 600 nm. about 100 replicates were made for each set of environmental con ...200616488043
adsorption of a biosurfactant on surfaces to enhance the disinfection of surfaces contaminated with listeria monocytogenes.the effects of sodium hypochlorite (naocl) and peracetic acid/hydrogen peroxide (pah) on the inactivation of adherent listeria monocytogenes lo28 cells were examined. the surfaces tested were stainless steel and polytetrafluoroethylene (ptfe) conditioned or not with an anionic biosurfactant produced by pseudomonas fluorescens. dilution-neutralization methods were used to assess the effectiveness of sanitizer solutions on planktonic and adherent cells. tests were performed on l. monocytogenes cul ...200616488496
a role for cortactin in listeria monocytogenes invasion of nih 3t3 cells, but not in its intracellular motility.cortactin is an f-actin binding protein that binds to the arp2/3 complex, stimulates its actin nucleation activity, and inhibits actin filament debranching. using rna interference directed against cortactin, we explored the importance of cortactin for several processes involving dynamic actin assembly. silencing cortactin expression was efficiently achieved in hela and nih 3t3 cells, with less than 5% of cortactin expression in sirna-treated cells. surprisingly, endocytosis in hela and nih 3t3 c ...200616489553
bacteriocin production, plasmid content and plasmid location of enterocin p structural gene in enterococci isolated from food sources.to characterize bacteriocin production, antimicrobial spectrum and plasmid content in bacteriocinogenic enterococci from foods.200616599984
inactivation of salmonella typhimurium and listeria monocytogenes using high-pressure treatments: destruction or sublethal stress?to investigate potential resuscitation of listeria monocytogenes and salmonella typhimurium after high hydrostatic pressure treatments.200616599988
the development of rapid fluorescence-based immunoassays, using quantum dot-labelled antibodies for the detection of listeria monocytogenes cell surface proteins.listeria monocytogenes is an important food-borne pathogen with an extremely high mortality rate (approximately 30%). therefore, a highly sensitive, reproducible and rapid assay for its detection is vital. l. monocytogenes cells employ two surface bound proteins, internalin a (inla) and internalin b (inlb) to promote invasion into host cells. recombinant forms of both proteins were previously cloned and expressed in escherichia coli. in this paper we describe how the inlb protein was sub-divided ...200616600361
pulsenet usa: a five-year update.pulsenet usa is the molecular surveillance network for foodborne infections in the united states. since its inception in 1996, it has been instrumental in detection, investigation and control of numerous outbreaks caused by shiga toxin-producing escherichia coli o157:[h7] (stec o157), salmonella enterica, listeria monocytogenes, shigella spp., and campylobacter. this paper describes the current status of the network, including the methodologies used and its future possibilities. the currently pr ...200616602975
canadian listeriosis reference service.listeria monocytogenes, a psychrotrophic organism capable of growing at refrigeration temperatures, is of major concern in extended shelf life, refrigerated foods. considering that as much as 80-90% of human listeriosis cases are linked to the ingestion of contaminated food, human cases are predominantly seen in high-risk individuals, including organ-transplant recipients, patients with aids and hiv-infected individuals, pregnant women, cancer patients, and the elderly. in 2001, the canadian lis ...200616602988
a comparison of listeria monocytogenes serovar 4b isolates of clinical and food origin in austria by automated ribotyping and pulsed-field gel electrophoresis.in this study, two typing methods, automated ribotyping and pulsed-field gel electrophoresis (pfge), were evaluated for the subtyping of listeria monocytogenes serotype 4b. the strains originated from patients and food samples collected in austria during 2001-2005 and from europe and north america in the world health organization collaborative study on the subtyping of this species. the largest group of austrian clinical isolates was of the same pfge subtype as those isolated from foodborne outb ...200616602989
virulence phenotyping and molecular characterization of a low-pathogenicity isolate of listeria monocytogenes from cow's milk.a low-pathogenicity isolate of listeria monocytogenes from cow's milk, as screened in mouse and chicken embryonated egg models, was examined for virulence-related phenotypic traits. corresponding virulence genes (iap, prfa, plca, hly, mpl, acta, plcb, inla and inlb) were compared with l. monocytogenes reference strains 10403s and egd to elucidate the possible molecular mechanisms of low virulence. although l. monocytogenes h4 exhibited similar patterns to strain 10403s in terms of hemolytic acti ...200616604266
cytosolic recognition of flagellin by mouse macrophages restricts legionella pneumophila infection.to restrict infection by legionella pneumophila, mouse macrophages require naip5, a member of the nucleotide-binding oligomerization domain leucine-rich repeat family of pattern recognition receptors, which detect cytoplasmic microbial products. we report that mouse macrophages restricted l. pneumophila replication and initiated a proinflammatory program of cell death when flagellin contaminated their cytosol. nuclear condensation, membrane permeability, and interleukin-1beta secretion were trig ...200616606669
membrane perforations inhibit lysosome fusion by altering ph and calcium in listeria monocytogenes vacuoles.listeria monocytogenes (lm) evade microbicidal defences inside macrophages by secreting a pore-forming cytolysin listeriolysin o (llo), which allows lm to escape vacuoles. llo also inhibits lm vacuole fusion with lysosomes, which indicates llo alters vacuole chemistry prior to release of lm into cytoplasm. using fluorescent probes to measure membrane permeability, calcium and ph, we identified small membrane perforations in vacuoles containing wild-type but not llo-deficient (hly-) lm. the small ...200616611227
redox polymer and probe dna tethered to gold electrodes for enzyme-amplified amperometric detection of dna hybridization.the detection of nucleic acids based upon recognition surfaces formed by co-immobilization of a redox polymer mediator and dna probe sequences on gold electrodes is described. the recognition surface consists of a redox polymer, [os(2,2'-bipyridine)2(polyvinylimidazole)(10)cl](+/2+), and a model single dna strand cross-linked and tethered to a gold electrode via an anchoring self-assembled monolayer (sam) of cysteamine. hybridization between the immobilized probe dna of the recognition surface a ...200616615783
effect of temperature on synthesis of polyphosphates in yersinia pseudotuberculosis and listeria monocytogenes under starvation conditions.it was found that at low temperature (6-8 degrees c) in the absence of nitrogen supply and at the presence of phosphate ions in the medium, yersinia pseudotuberculosis and listeria monocytogenes are able to actively synthesize reserve substances as polyphosphates. most of the bacterial polyphosphates are alkali-soluble, especially at the preliminary stage of cell growth (lag-phase). this is proved by electron microscopic studies of ultrastructure of model microorganisms. during a long starvation ...200616615864
cytoplasmic listeria monocytogenes stimulates ifn-beta synthesis without requiring the adapter protein mavs.the mitochondria-associated adapter protein mavs (also called ips-1, visa or cardif, designated mavs for reasons of simplicity in our manuscript) relays signals from cytoplasmic sensors of viral rna to the irf3 kinase complex and the interferon-beta (ifn-beta) gene. using sirna-mediated knock-down in macrophages we show that ifn-beta synthesis in response to transfected, intracellular double-stranded rna (dsrna), a pathogen-associated molecular pattern of viruses, is decreased in absence of mavs ...200616616525
the mogr transcriptional repressor regulates nonhierarchal expression of flagellar motility genes and virulence in listeria monocytogenes.flagella are surface structures critical for motility and virulence of many bacterial species. in listeria monocytogenes, mogr tightly represses expression of flagellin (flaa) during extracellular growth at 37 degrees c and during intracellular infection. mogr is also required for full virulence in a murine model of infection. using in vitro and in vivo infection models, we determined that the severe virulence defect of mogr-negative bacteria is due to overexpression of flaa. specifically, overp ...200616617375
detection of genes encoding virulence factors and bacteriocins in fecal enterococci of poultry in portugal.seventy-six enterococcus isolates (43 e. faecalis, 30 e. faecium, two e. durans, and one e. hirae) recovered from fecal samples of poultry in a slaughterhouse (one isolate per fecal sample and one fecal sample per lot of animals) were studied for bacteriocin production and for the presence of genes encoding bacteriocins and virulence factors. the presence of genes encoding virulence factors (cpd, gee, fsr, ace, agg, and esp) and bacteriocins (enta, entb, entp, entq, entas-48, entl50a/b, cyl, and ...200616617984
serine protease inhibitor 6 protects cytotoxic t cells from self-inflicted injury by ensuring the integrity of cytotoxic granules.how cytotoxic t lymphocytes (ctls) kill intracellular pathogens without killing themselves has been a recurring question ever since their discovery. by using mice deficient in serine protease inhibitor 6 (spi6), we show that by inhibiting granzyme b (grb), spi6 protects ctls from self-inflicted injury. infection with either lymphocytic choriomeningitis virus (lcmv) or listeria monocytogenes (lm) revealed increased apoptosis and diminished survival of spi6 knockout (ko) ctls, which was cell auton ...200616618603
exploring the role of the ctl epitope region of listeriolysin o in the pathogenesis of listeria monocytogenes.listeria monocytogenes is a facultative intracellular bacterial pathogen responsible for severe opportunistic infections in humans and animals. the secreted cholesterol-dependent cytolysin, listeriolysin o (llo), mediates phagosomal escape and allows bacterial growth in the cytosol of infected cells. in order to identify new llo determinants participating in bacterial pathogenesis, this study focused on a major target of llo proteolytic cleavage in vitro, the ctl epitope region (residues 91-99). ...200616622046
how the bacterial pathogen listeria monocytogenes mediates the switch from environmental dr. jekyll to pathogenic mr. hyde. 200616622185
macrophage-activation inhibitor factor from l5178y murine lymphoma and formation of hepatic abscesses in balb/c mice.normal mice are naturally resistant to hepatic abscesses produced by listeria monocytogenes. a macrophage-activation inhibitor factor (maif) isolated from the cell-free ascitic fluid of l5178y lymphoma-bearing mice inhibited the lipopolysaccharide-induced production of nitric oxide (no) by the macrophages. because macrophages are also involved in the immune response towards l. monocytogenes, the present study had the objective of investigating whether maif was also capable of allowing l. monocyt ...200616624645
enhanced bacterial clearance and sepsis resistance in caspase-12-deficient mice.caspases function in both apoptosis and inflammatory cytokine processing and thereby have a role in resistance to sepsis. here we describe a novel role for a caspase in dampening responses to bacterial infection. we show that in mice, gene-targeted deletion of caspase-12 renders animals resistant to peritonitis and septic shock. the resulting survival advantage was conferred by the ability of the caspase-12-deficient mice to clear bacterial infection more efficiently than wild-type littermates. ...200616625199
validation of a traditional italian-style salami manufacturing process for control of salmonella and listeria monocytogenes.italian-style salami batter (formulated with pork shoulder) was inoculated with ca. 7.0 log cfu/g of either salmonella or listeria monocytogenes. salami links (55-mm cellulose casings) were fermented at 30 degrees c for 24, 40, or 72 h and then dried to target moisture/protein ratios (mprs) of 1.9:1 or 1.4:1. links were sampled after fermentation (24, 40, and 72 h) and after combined fermentation-drying treatments (mprs of 1.9:1 and 1.4:1 for all fermentation periods), and microbiological and pr ...200616629021
death of salmonella, escherichia coli o157:h7, and listeria monocytogenes in shelf-stable, dairy-based, pourable salad dressings.the objectives of this study were to determine the death rates of salmonella, escherichia coli o157:h7, and listeria monocytogenes in three commercially manufactured full-fat ranch salad dressings, three reduced-fat ranch salad dressings, two full-fat blue cheese salad dressings, and two reduced-fat blue cheese salad dressings and to affirm the expectation that these dressings do not support the growth of these pathogens. the respective initial ph values of the four types of shelf-stable, dairy- ...200616629022
prevalence and typing of listeria monocytogenes in raw catfish fillets.raw channel catfish fillets collected from three processing plants during four time periods were tested for the presence of listeria species. listeria monocytogenes was the predominant listeria species found in these catfish fillets, with 25 to 47% prevalence. other listeria species, such as l. welshimeri, l. innocua, l. ivanovii, l. grayi, and l. seeligeri, were also found. l. monocytogenes isolates were further fingerprinted by a repetitive element pcr. forty distinctive electrophoretic types ...200616629023
growth of listeria monocytogenes in fresh-cut coconut as affected by storage conditions and inoculum size.in this study, the effects of packaging atmosphere (air and modified atmosphere, 65% n2, 30% co2, and 5% o2), temperature (2, 4, 8, and 12 degrees c) and inoculum size (low inoculum, 102 cfu/g; high inoculum, 5 x 10(5) cfu/g) on the growth of listeria monocytogenes in minimally processed coconut were investigated. growth data were fitted to the gompertz equation, and the sanitary risk time (the time, in days, necessary to observe an increase of 2 log cfu/g in the level of the pathogen) was also ...200616629024
formation of biofilm at different nutrient levels by various genotypes of listeria monocytogenes.strains of listeria monocytogenes differ in their ability to form biofilms. the objectives of this study were to determine whether genetically related strains have similar biofilm-forming capacities and what effect nutrient concentration has on the ability of different strains to produce biofilms. biofilms of 30 strains of l. monocytogenes, obtained from a variety of sources were grown on stainless steel in tryptic soy broth (tsb) or in a 1:10 dilution of tsb (dtsb) for 24 h at 32 degrees c. the ...200616629025
molecular typing to trace listeria monocytogenes isolated from cold-smoked fish to a contamination source in a processing plant.in this study, listeria monocytogenes contamination in a cold-smoked fish processing plant in osaka, japan, was examined from 2002 to 2004. a total of 430 samples were collected and divided into five categories: raw fish, materials during processing, processing equipment, environment, and finished products. a total of 59 finished products were examined throughout this study. l. monocytogenes was isolated from four of these samples during summer and autumn but was not found during winter or sprin ...200616629026
comparison of listeria monocytogenes virulence in a mouse model.listeriosis results from exposure to the foodborne pathogen listeria monocytogenes. although many different strains of l. monocytogenes are isolated from food, no definitive tests currently predict which isolates are most virulent. the objectives of this study were to address two major data gaps for risk assessors, variability among l. monocytogenes strains in pathogenicity and virulence. strains used in our monkey clinical trial or additional food isolates were evaluated for their virulence and ...200616629027
prevalence and concentration of listeria monocytogenes in sliced ready-to-eat meat products in the hellenic retail market.the aim of this work was to estimate the prevalence and concentration of listeria monocytogenes in packaged precut (slices or cubes) ready-to-eat (rte) meat products available in the hellenic retail market. samples of these rte meat products (n = 209) were taken from local supermarkets during a 3-month period and analyzed for the presence of l. monocytogenes with an automated enzymatic qualitative immunoassay followed by biochemical confirmation of positive results. the concentration of the path ...200616629044
interactions of nisin with glutathione in a model protein system and meat.loss of nisin activity in meat has been ascribed, in part, to the formation of a nisin-glutathione adduct. activity is lost more quickly in raw meat than in cooked meat, and this has been taken as evidence that the reaction is enzyme mediated. formation of the nisin-glutathione adduct has been confirmed but is shown not to be enzyme mediated. retention of activity in cooked meat is shown to be due to the loss of free sulfhydryl groups during cooking as a result of the reaction of glutathione wit ...200616629047
effect of environmental stresses on antibody-based detection of escherichia coli o157:h7, salmonella enterica serotype enteritidis and listeria monocytogenes.to study the reaction patterns of selected antibodies to escherichia coli o157:h7, salmonella enterica serotype enteritidis and listeria monocytogenes cells exposed to various environmental stresses.200616630002
optimization of the components concentrations of the lactoperoxidase system by rsm.the aim of this work was to use response surface methodology (rsm) approach, a statistical mathematical tool, to model effects and interactions of glucose oxidase (god), glucose, lactoperoxidase (lpo) and ph-values on the thiocyanate (scn-) peroxidation, to determine the best concentrations of lactoperoxidase system (lp-s) components in order to obtain maximal scn- peroxidation and so to enhance the lp-s antibacterial effects.200616630004
coexpression of virulence and fosfomycin susceptibility in listeria: molecular basis of an antimicrobial in vitro-in vivo paradox.discrepancies between resistance in vitro and therapeutic efficacy in vivo are generally attributed to failure of laboratory susceptibility tests to reflect an antibiotic's pharmacokinetic or pharmacodynamic properties. we show here that this phenomenon can result from differential in vitro-in vivo expression of bacterial determinants of antibiotic susceptibility. we found that an in vivo-induced virulence factor, hpt, also mediates uptake of fosfomycin in listeria monocytogenes. these bacteria ...200616633349
quantitative and simultaneous detection of four foodborne bacterial pathogens with a multi-channel spr sensor.we report the quantitative and simultaneous detection of four species of bacteria, escherichia coli o157:h7, salmonella choleraesuis serotype typhimurium, listeria monocytogenes, and campylobacter jejuni, using an eight-channel surface plasmon resonance (spr) sensor based on wavelength division multiplexing. detection curves showing spr response versus analyte concentration were established for each species of bacteria in buffer at ph 7.4, apple juice at native ph 3.7, and apple juice at an adju ...200616635568
unidirectional development of cd8+ central memory t cells into protective listeria-specific effector memory t cells.three distinct subsets of antigen-experienced cd8(+) t cells have been identified so far: short-living effector t cells (t(ec)) and two long-living subsets, described as central (t(cm)) and effector memory (t(em)) t cells. the lineage relationships of these subpopulations as well as their involvement in protection have not yet been conclusively determined. we recently described a novel marker combination (cd127 and cd62l) to identify all three major cd8(+) t cell subsets in mice infected with li ...200616637009
roche/biotecon diagnostics lightcycler foodproof l. monocytogenes detection kit in combination with shortprep foodproof ii kit. performance-tested method 070401.a method was developed for the detection of l. monocytogenes in food based on real-time polymerase chain reaction (pcr). this advanced pcr method was designed to reduce the time needed to achieve results from pcr reactions and to enable the user to monitor the amplification of the pcr product simultaneously, in real-time. after dna isolation using the roche/biotecon diagnostics shortprep foodproof ii kit (formerly called listeria shortprep kit) designed for the rapid preparation of l. monocytoge ...200616640287
leucocins 4010 from leuconostoc carnosum cause a matrix related decrease in intracellular ph of listeria monocytogenes.a mixed culture of single cells of listeria monocytogenes and the bacteriocin producing leuconostoc carnosum 4010 showed growth inhibition of l. monocytogenes, although the intracellular ph (phi) of l. monocytogenes followed by fluorescence ratio imaging microscopy was not affected. furthermore, l. monocytogenes was exposed to the bacteriocins leucocins 4010 and nisin either in a liquid filled chamber or on the surface of an agar containing bacteriocins. both bacteriocins caused dissipation of t ...200616640575
cellular accumulation and activity of quinolones in ciprofloxacin-resistant j774 macrophages.ciprofloxacin is the substrate for a multidrug resistance-related protein (mrp)-like multidrug transporter in j774 mouse macrophages, which also modestly affects levofloxacin but only marginally affects garenoxacin and moxifloxacin (j.-m. michot et al., antimicrob. agents chemother. 49:2429-2437, 2005). two clones of ciprofloxacin-resistant cells were obtained by a stepwise increase in drug concentration (from 34 to 51 to 68 mg/liter) in the culture fluid. compared to wild-type cells, ciprofloxa ...200616641436
bacterial entry into cells: a role for the endocytic machinery.increasing evidence indicates that pathogens have evolved highly efficient strategies to induce their internalization within host cells. viruses and bacteria express and expose on their surface, molecules that mimic endogenous ligands to cell receptors, thereby inducing specific intracellular signalling cascades. more recently it has become clear that, as most viruses, bacteria can enter cells via the clathrin-mediated pathway, indicating a key role for endocytosis in pathogens entry into cells. ...200616650411
elemental analysis of the mycobacterium avium phagosome in balb/c mouse macrophages.using a hard x-ray microprobe, we showed recently that in unstimulated peritoneal macrophages from c57bl/6 mice, the phagosome of pathogenic mycobacteria (mycobacterium tuberculosis and mycobacterium avium) can accumulate iron. we expanded our studies to the m. avium infection of peritoneal macrophages of balb/c mice that show a similar degree of m. tuberculosis and m. avium-related chronic disease, but a higher susceptibility towards other intracellular pathogens such as listeria monocytogenes, ...200616650826
cytokine modulation of the innate immune response in feline immunodeficiency virus-infected cats.in vitro data suggest that innate immune function in human immunodeficiency virus type 1-infected patients is compromised; however, in vivo studies are lacking. feline immunodeficiency virus (fiv) infection in cats provides an excellent model to explore innate immune function in vivo. the innate response against listeria monocytogenes is well understood, making it a useful immune probe.200616652280
listeriosis due to infection with a catalase-negative strain of listeria monocytogenes.a strain of listeria monocytogenes recovered from blood and cerebrospinal fluid had no detectable catalase activity, a characteristic used for primary identification. the sporadic occurrence of pathogenic catalase-negative strains highlights the need for a reconsideration of diagnostic criteria and questions the role of catalase in the pathogenesis of listeria infection.200616672441
control of listeria spp. by competitive-exclusion bacteria in floor drains of a poultry processing plant.in previous studies workers determined that two lactic acid bacterium isolates, lactococcus lactis subsp. lactis c-1-92 and enterococcus durans 152 (competitive-exclusion bacteria [ce]), which were originally obtained from biofilms in floor drains, are bactericidal to listeria monocytogenes or inhibit the growth of l. monocytogenes both in vitro and in biofilms at 4 to 37 degrees c. we evaluated the efficacy of these isolates for reducing listeria spp. contamination of floor drains of a plant in ...200616672472
role of efflux pumps in adaptation and resistance of listeria monocytogenes to benzalkonium chloride.in this study, potential mechanisms underlying resistance and adaptation to benzalkonium chloride (bc) in listeria monocytogenes were investigated. two groups of strains were studied. the first group consisted of strains naturally sensitive to bc which could be adapted to bc. the second group consisted of naturally resistant strains. for all adapted isolates, there was a correlation between the resistance to bc and ethidium bromide, but this was not the case for the naturally resistant isolates. ...200616672496
listeric meningoencephalomyelitis in a cougar (felis concolor): characterization by histopathologic, immunohistochemical, and molecular methods.listeria monocytogenes has been recognized as an important food-borne pathogen in animals. records of the disease caused by this bacterium in large felids are, however, rare. the nervous form of listeriosis was diagnosed in a 12-year-old male cougar (felis concolor) with a several-day history of neurologic disease characterized by excess salivation, head pressing, and circling that progressed to recumbency and death. microscopically, the main alteration in the brain and spinal cord was a variabl ...200616672590
the bacterial quality of red meat and offal in casablanca (morocco).the present study aimed to evaluate the bacteriological quality of beef (n = 52), lamb (n = 52) and beef offal (n = 52) marketed in casablanca, morocco. meat and offal samples (n = 156), were collected randomly from butcheries, supermarkets, and slaughterhouses. two sampling periods were considered, one during the hot season and the second one during the cold season. the samples were analyzed for the presence of the following bacteria: escherichia coli, coagulase-positive staphylococcus, clostri ...200616676376
bactericidal effects of cao (scallop-shell powder) on foodborne pathogenic bacteria.this study was investigated the bactericidal effects of calcium oxide (cao) on three common foodborne pathogenic bacteria: escherichia coli, listeria monocytogenes, and salmonella typhimurium. each bacteria level was determined in a cao solution (0.01, 0.03, 0.05, 0.10, 0.15, and 0.20% [w/v]) exposed for either 15 sec, 30 sec, 1 min, 2 min, 3 min, 5 min, 10 min, or 30 min. all three bacteria were not greatly affected by cao solutions at concentrations of 0.01 and 0.03%, however, the decline of e ...200616681035
identification of small hfq-binding rnas in listeria monocytogenes.the rna-binding protein hfq plays important roles in bacterial physiology and is required for the activity of many small regulatory rnas in prokaryotes. we have previously shown that hfq contributes to stress tolerance and virulence in the gram-positive human pathogen listeria monocytogenes. in the present study, we performed coimmunoprecipitations followed by enzymatic rna sequencing to identify hfq-binding rna molecules in l. monocytogenes. the approach resulted in the discovery of three small ...200616682563
identification, subtyping and virulence determination of listeria monocytogenes, an important foodborne pathogen.listeria monocytogenes is an opportunistic intracellular pathogen that has become an important cause of human foodborne infections worldwide. given its close relationship to other listeria species and its tendency to produce non-specific clinical symptoms, the availability of rapid, sensitive and specific diagnostic tests for the differentiation of l. monocytogenes from other listeria species is helpful for selecting appropriate treatment regimens. in addition, with l. monocytogenes comprising a ...200616687581
escherichia coli interactions with acanthamoeba: a symbiosis with environmental and clinical implications.the ability of acanthamoeba to feed on gram-negative bacteria, as well as to harbour potential pathogens, such as legionella pneumophila, coxiella burnetii, pseudomonas aeruginosa, vibrio cholerae, helicobacter pylori, listeria monocytogenes and mycobacterium avium, suggest that both amoebae and bacteria are involved in complex interactions, which may play important roles in the environment and in human health. in this study, acanthamoeba castellanii (a keratitis isolate belonging to the t4 geno ...200616687585
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