Publications

TitleAbstractYear(sorted descending)
Filter
PMID
Filter
influence of gastric acid on susceptibility to infection with ingested bacterial pathogens.despite the widely held belief that gastric acid serves as a barrier to bacterial pathogens, there are almost no experimental data to support this hypothesis. we have developed a mouse model to quantify the effectiveness of gastric acid in mediating resistance to infection with ingested bacteria. mice that were constitutively hypochlorhydric due to a mutation in a gastric h(+)/k(+)-atpase (proton pump) gene were infected with yersinia enterocolitica, salmonella enterica serovar typhimurium, citr ...200818025100
salmonellae interplay with host cells.salmonellae are important causes of enteric diseases in all vertebrates. characterization of the molecular mechanisms that underpin the interactions of salmonellae with their animal hosts has advanced greatly over the past decade, mainly through the study of salmonella enterica serovar typhimurium in tissue culture and animal models of infection. knowledge of these bacterial processes and host responses has painted a dynamic and complex picture of the interaction between salmonellae and animal c ...200818026123
in vitro effect of subinhibitory concentrations of antibiotics on biofilm formation by clinical strains of salmonella enterica serovar typhimurium isolated in slovakia.in this study, we examined the biofilm formation of 75 salmonella enterica serovar typhimurium (salm. typhimurium) human clinical isolates and the effect of subinhibitory concentrations (sub-mics) of gentamicin, ciprofloxacin and cefotaxime on biofilm formation and exopolysaccharides (eps) production.200818028358
during infection of epithelial cells salmonella enterica serovar typhimurium undergoes a time-dependent transcriptional adaptation that results in simultaneous expression of three type 3 secretion systems.the biogenesis of the salmonella-containing vacuole within mammalian cells has been intensively studied over recent years. however, the ability of salmonella to sense and adapt to the intracellular environment of different types of host cells has received much less attention. to address this issue, we report the transcriptome of salmonella enterica serovar typhimurium sl1344 within epithelial cells and show comparisons with salmonella gene expression inside macrophages. we report that s. typhimu ...200818031307
the vi-capsule prevents toll-like receptor 4 recognition of salmonella.the viab locus enables salmonella enterica serotype typhi to reduce toll-like receptor (tlr) dependent cytokine production in tissue culture models. this dna region contains genes involved in the regulation (tvia), biosynthesis (tvibcde) and export (vexabcde) of the vi capsule. expression of the vi capsule in s. typhimurium, but not expression of the tvia regulatory protein, reduced tumour necrosis factor-alpha (tnf-alpha) and il-6 production by murine bone-marrow derived macrophages. production ...200818034866
modulation of horizontally acquired genes by the hha-ydgt proteins in salmonella enterica serovar typhimurium.we describe a transcriptomic study of the effect of hha and ydgt mutations in salmonella enterica serovar typhimurium. a large number of genes showing altered expression are located in at-rich horizontally acquired dna sequences. many of these genes have also been reported to be targets for h-ns. as hha and ydgt interact with h-ns, our findings strongly suggest that hha and/or ydgt must form complexes with h-ns when they silence these dna regions.200818039769
in vitro activity of cefpodoxime, an expanded-spectrum cephalosporin, against salmonella enterica serotype typhi. 200818039924
innate immunity to intraphagosomal pathogens is mediated by interferon regulatory factor 8 (irf-8) that stimulates the expression of macrophage-specific nramp1 through antagonizing repression by c-myc.macrophages are a central arm of innate immune defense against intracellular pathogens. they internalize microbes into phagosomes where the invaders are being killed by oxygen and nitrogen reactive species. despite this battery of antimicrobial molecules, some are able to thrive within the phagosome thus termed intraphagosomal pathogens among which are salmonella, leishmania, and mycobacteria. in mice, a single dominant gene termed nramp1/slc11a1 controls innate resistance to such pathogens. thi ...200818045875
antimicrobial resistance in salmonella enterica serovar typhimurium from human and animal sources in italy.salmonella typhimurium strains isolated in italy in the period 2002-2004 from human and animal sources were examined for their antimicrobial susceptibility. resistance to tetracycline (t, 73.6%), sulfonamides (su, 73.3%), ampicillin (a, 67.6%), streptomycin (s, 65.4%) and chloramphenicol (c, 32.3%) were frequently observed. resistance to ciprofloxacin was only observed in a swine strain, but most human strains resistant to nalidixic acid showed reduced susceptibility to that drug (mic > or = 0.1 ...200818054179
identification of novel plasmid-mediated extended-spectrum beta-lactamase ctx-m-57 in salmonella enterica serovar typhimurium. 200818054206
donor-strand exchange in chaperone-assisted pilus assembly revealed in atomic detail by molecular dynamics.adhesive multi-subunit fibres are assembled on the surface of many pathogenic bacteria via the chaperone-usher pathway. in the periplasm, a chaperone donates a beta-strand to a pilus subunit to complement its incomplete immunoglobulin-like fold. at the outer membrane, this is replaced with a beta-strand formed from the n-terminal extension (nte) of an incoming pilus subunit by a donor-strand exchange (dse) mechanism. this reaction has previously been shown to proceed via a concerted mechanism, i ...200818054959
regulation of the yjjq-bglj operon, encoding luxr-type transcription factors, and the divergent yjjp gene by h-ns and leuo.the yjjq and bglj genes encode luxr-type transcription factors conserved in several enterobacterial species. yjjq is a potential virulence factor in avian pathogenic escherichia coli. bglj counteracts the silencing of the bgl (beta-glucoside) operon by h-ns in e. coli k-12. here we show that yjjq and bglj form an operon carried by e. coli k-12, whose expression is repressed by the histone-like nucleoid structuring (h-ns) protein. the lysr-type transcription factor leuo counteracts this repressio ...200818055596
growth and genetic responses of salmonella typhimurium to ph-shifts in an anaerobic continuous culture.salmonella infection of chickens that leads to potential human foodborne salmonellosis continues to be a concern. changes in the ph of poultry gastrointestinal tract could influence salmonella growth and virulence response. in the current study, growth responses of a chicken isolate salmonella enterica serovar typhimurium (st) to three incremental ph-shifts (6.17-7.35) in continuous cultures (cc) were evaluated. the expression of rpos and hila was determined by real time-polymerase chain reactio ...200818061487
extended spectrum beta-lactamase shv-12-producing salmonella from poultry.salmonella strains isolated from poultry and poultry products over the period 2005-2006 have been investigated in order to ascertain the presence of extended spectrum cephalosporins (esc) resistance. twelve (esc)-resistant isolates (n=1 s. enteritidis, n=1 s. braenderup and n=10 s. livingstone) were characterized as shv-12-positive. the multi-drug resistant s. livingstone shv-12-producing isolates, untypeable by pulsed-field gel electrophoresis (pfge), showed a clonal relationship by random ampl ...200818063489
reactive oxygen species are the major antibacterials against salmonella typhimurium purine auxotrophs in the phagosome of raw 264.7 cells.intramacrophage survival appears to be a pathogenic trait common to salmonellae and definition of the metabolic requirements of salmonella within macrophages might provide opportunities for novel therapeutic interventions. we show that loss of purg function in salmonella enterica serovar typhimurium sl1344 leads to death of the bacterium in raw264.7 cells, which was due to unavailability of purine nucleotides but not thiamine in the phagosome of raw264.7 cells. phagosomal escape of purg mutant r ...200818067606
translating innate response into long-lasting antibody response by the intrinsic antigen-adjuvant properties of papaya mosaic virus.identifying the properties of a molecule involved in the efficient activation of the innate and adaptive immune responses that lead to long-lasting immunity is crucial for vaccine and adjuvant development. here we show that the papaya mosaic virus (papmv) is recognized by the immune system as a pathogen-associated molecular pattern (pamp) and as an antigen in mice (pamptigen). a single immunization of papmv without added adjuvant efficiently induced both cellular and specific long-lasting antibo ...200818070030
survival and growth of salmonella enteritidis pt 30 in almond orchard soils.to evaluate factors potentially contributing to the long-term persistence of salmonella enterica serovar enteritidis phage type (pt) 30 in an almond orchard.200818070039
broad-spectrum in vitro antibacterial activities of clay minerals against antibiotic-susceptible and antibiotic-resistant bacterial pathogens.the capacity to properly address the worldwide incidence of infectious diseases lies in the ability to detect, prevent and effectively treat these infections. therefore, identifying and analysing inhibitory agents are worthwhile endeavours in an era when few new classes of effective antimicrobials have been developed. the use of geological nanomaterials to heal skin infections has been evident since the earliest recorded history, and specific clay minerals may prove valuable in the treatment of ...200818070832
foodborne zoonoses due to meat: a quantitative approach for a comparative risk assessment applied to pig slaughtering in europe.foodborne zoonoses have a major health impact in industrialised countries. new european food safety regulations were issued to apply risk analysis to the food chain. the severity of foodborne zoonoses and the exposure of humans to biological hazards transmitted by food must be assessed. for meat, inspection at the slaughterhouse is historically the main means of control to protect consumers. however, the levels of detection of biological hazards during meat inspection have not been established i ...200818073088
prevalence and characterization of multidrug-resistant (type acssut) salmonella enterica serovar typhimurium strains in isolates from four gosling farms and a hatchery farm.salmonella enterica serovar typhimurium strains of phage types dt104 and u302 are often resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline (the acssut resistance type) and are major zoonotic pathogens. increased consumption of goose meat may enhance the risk of transferring s. enterica serovar typhimurium and other enteric pathogens from geese to human due to the consumption of meats from infected geese or improper preparation of meats. therefore, we character ...200818077649
structure of the receptor-binding protein of bacteriophage det7: a podoviral tail spike in a myovirus.a new salmonella enterica phage, det7, was isolated from sewage and shown by electron microscopy to belong to the myoviridae morphogroup of bacteriophages. det7 contains a 75-kda protein with 50% overall sequence identity to the tail spike endorhamnosidase of podovirus p22. adsorption of myoviruses to their bacterial hosts is normally mediated by long and short tail fibers attached to a contractile tail, whereas podoviruses do not contain fibers but attach to host cells through stubby tail spike ...200818077713
pseudo-b12 joins the cofactor family. 200818083805
phenotypic and proteomic characterization of multiply antibiotic-resistant variants of salmonella enterica serovar typhimurium selected following exposure to disinfectants.in previous work, salmonella enterica serovar typhimurium strain sl1344 was exposed to sublethal concentrations of three widely used farm disinfectants in daily serial passages for 7 days in an attempt to investigate possible links between the use of disinfectants and antimicrobial resistance. stable variants oxcr1, qacfgr2, and topr2 were obtained following treatment with an oxidizing compound blend, a quaternary ammonium disinfectant containing formaldehyde and glutaraldehyde, and a tar acid-b ...200818083849
cancer immunotherapy based on recombinant salmonella enterica serovar typhimurium aroa strains secreting prostate-specific antigen and cholera toxin subunit b.prostate cancer is the most common malignant tumor in men and is normally associated with increased serum levels of prostate-specific antigen (psa). therefore, psa is one potential target for a prostate cancer vaccine. in this study we analyzed the functionality of new bacterial psa vaccines, expressed and secreted via the hemolysin (hlya) secretion system of escherichia coli, the prototype of type i secretion systems (t1ss) using an attenuated salmonella enterica serovar typhimurium aroa strain ...200818084243
structural basis for the catalytic mechanism of phosphothreonine lyase.salmonella spvc belongs to a new enzyme family designated phosphothreonine lyases that irreversibly inactivate mitogen-activated protein kinases. the crystal structure of spvc reported here reveals that the two phosphorylated residues in the substrate peptide predominantly mediate its recognition by spvc. substrate-induced conformational changes in spvc sequester the phosphothreonine in a completely solvent-free environment, preventing the hydrolysis of the phosphate group and facilitating the e ...200818084305
a salmonella enterica serovar typhimurium succinate dehydrogenase/fumarate reductase double mutant is avirulent and immunogenic in balb/c mice.previously we showed that the tricarboxylic acid (tca) cycle operates as a full cycle during salmonella enterica serovar typhimurium sr-11 peroral infection of balb/c mice (m. tchawa yimga et al., infect. immun. 74:1130-1140, 2006). the evidence was that a deltasuccd mutant (succinyl coenzyme a [succinyl-coa] synthetase), which prevents the conversion of succinyl-coa to succinate, and a deltasdhcda mutant (succinate dehydrogenase), which blocks the conversion of succinate to fumarate, were both ...200818086808
isolation and purification of enterocin e-760 with broad antimicrobial activity against gram-positive and gram-negative bacteria.strain nrrl b-30745, isolated from chicken ceca and identified as enterococcus durans, enterococcus faecium, or enterococcus hirae, was initially identified as antagonistic to campylobacter jejuni. the isolate produced a 5,362-da bacteriocin (enterocin) that inhibits the growth of salmonella enterica serovar enteritidis, s. enterica serovar choleraesuis, s. enterica serovar typhimurium, s. enterica serovar gallinarum, escherichia coli o157:h7, yersinia enterocolitica, citrobacter freundii, klebs ...200818086839
kinetic and structural analysis of bisubstrate inhibition of the salmonella enterica aminoglycoside 6'-n-acetyltransferase.aminoglycosides are antibacterial compounds that act by binding to the a site of the small 30s bacterial ribosomal subunit and inhibiting protein translation. clinical resistance to aminoglycosides is generally the result of the expression of enzymes that covalently modify the antibiotic, including phosphorylation, adenylylation, and acetylation. bisubstrate analogs for the aminoglycoside n-acetyltransferases are nanomolar inhibitors of enterococcus faecium aac(6')-ii. however, in the case of th ...200818095712
expression of in vivo-inducible salmonella enterica promoters during infection of caenorhabditis elegans.in vitro mimicking of the stimuli controlling in vivo-inducible bacterial promoters during infection of the host can be complex. therefore, the use of the nematode caenorhabditis elegans was evaluated, as a surrogate host to examine the expression of salmonella enterica promoters. green fluorescent protein (gfp+) was put under the control of the promoters of the pagc, mgtb, ssea, pgte and fur genes of s. enterica. after infection of c. elegans with an s. enterica serovar typhimurium vaccine stra ...200818096019
multiple-locus variable-number tandem-repeats analysis of listeria monocytogenes using multicolour capillary electrophoresis and comparison with pulsed-field gel electrophoresis typing.the multiple-locus variable-number tandem-repeats analysis (mlva) method for genotyping has proven to be a fast and reliable typing tool in several bacterial species. mlva is in our laboratory the routine typing method for salmonella enterica subsp. enterica serovar typhimurium and escherichia coli o157. the gram-positive bacteria listeria monocytogenes, while not isolated as frequent as s. typhimurium and e. coli, causes severe illness with an overall mortality rate of 30%. thus, it is importan ...200818096258
the lysr-type transcriptional regulator leuo controls expression of several genes in salmonella enterica serovar typhi.leuo is a lysr-type transcriptional regulator that has been implicated in the bacterial stringent response and in the virulence of salmonella. a genomic analysis with salmonella enterica serovar typhi revealed that leuo is a positive regulator of omps1, omps2, asst, and sty3070. in contrast, leuo down-regulated the expression of ompx, tpx, and sty1978. transcriptional fusions supported the positive and negative leuo regulation. expression of omps1, asst, and sty3070 was induced in an hns mutant, ...200818156266
[pediatric salmonellosis at the tokoin's teaching hospital, lomé (togo)].the authors had for aim to describe the epidemiological, clinical, and bacteriological aspects and outcome of pediatric salmonella enterica, salmonella septicemia, over the last 10 years.200818160240
enteric salmonellosis disrupts the microbial ecology of the murine gastrointestinal tract.the commensal microbiota protects the murine host from enteric pathogens. nevertheless, specific pathogens are able to colonize the intestinal tract and invade, despite the presence of an intact biota. possibly, effective pathogens disrupt the indigenous microbiota, either directly through pathogen-commensal interaction, indirectly via the host mucosal immune response to the pathogen, or by a combination of these factors. this study investigates the effect of peroral salmonella enterica serovar ...200818160481
coordinate regulation of salmonella pathogenicity island 1 (spi1) and spi4 in salmonella enterica serovar typhimurium.salmonella enterica serovar typhimurium harbors five pathogenicity islands (spi) required for infection in vertebrate hosts. although the role of spi1 in promoting epithelial invasion and proinflammatory cell death has been amply documented, spi4 has only more recently been implicated in salmonella virulence. spi4 is a 24-kb pathogenicity island containing six open reading frames, siia to siif. secretion of the 595-kda siie protein requires a type i secretory system encoded by siic, siid, and si ...200818160484
card6 is interferon inducible but not involved in nucleotide-binding oligomerization domain protein signaling leading to nf-kappab activation.we have previously reported the cloning and characterization of card6, a caspase recruitment domain (card)-containing protein that is structurally related to the interferon (ifn)-inducible gtpases. card6 associates with microtubules and with receptor-interacting protein 2 (rip2). rip2 mediates nf-kappab activation induced by the intracellular nucleotide-binding oligomerization domain (nod) receptors that sense bacterial peptidoglycan. here we report that the expression of card6 and rip2 in bone ...200818160713
proteomics analysis of the causative agent of typhoid fever.typhoid fever is a potentially fatal disease caused by the bacterial pathogen salmonella enterica serotype typhi ( s. typhi). s. typhi infection is a complex process that involves numerous bacterially encoded virulence determinants, and these are thought to confer both stringent human host specificity and a high mortality rate. in the present study, we used a liquid chromatography-mass spectrometry (lc-ms)-based proteomics strategy to investigate the proteome of logarithmic, stationary phase, an ...200818166006
periplasmic cu,zn superoxide dismutase and cytoplasmic dps concur in protecting salmonella enterica serovar typhimurium from extracellular reactive oxygen species.several bacteria possess periplasmic cu,zn superoxide dismutases which can confer protection from extracellular reactive oxygen species. thus, deletion of the sodc1 gene reduces salmonella enterica serovar typhimurium ability to colonize the spleens of wild type mice, but enhances virulence in p47phox mutant mice. to look into the role of periplamic cu,zn superoxide dismutase and into possible additive effects of the ferritin-like dps protein involved in hydrogen peroxide detoxification, we have ...200818166161
powdered infant formula as a source of salmonella infection in infants.powdered infant formula is not sterile and may be intrinsically contaminated with pathogens, such as salmonella enterica, that can cause serious illness in infants. in recent years, at least 6 outbreaks of salmonella infection in infants that have been linked to the consumption of powdered infant formula have been reported. many of these outbreaks were identified because the salmonella strains were unique in some way (e.g., a rare serotype) and a well-established salmonella surveillance network, ...200818171262
aminoglycosides affect intracellular salmonella enterica serovars typhimurium and virchow.the high antibacterial activity and selectivity of aminoglycosides and their low activity against intracellular bacteria associated with eukaryotic cells make them the antibiotics of choice for the elimination of extracellular bacteria during intracellular studies. given the evidence that aminoglycosides can penetrate the eukaryotic cell membrane, the goal of this study was to examine the influence of aminoglycosides on macrophage-associated salmonella. herein, we show that gentamicin, kanamycin ...200818172002
n-terminal residues of sipb are required for its surface localization on salmonella enterica serovar typhimurium.sipb, one of the invasion proteins encoded in salmonella pathogenicity island 1 (spi-1), is known to be secreted outside the cell, where it functions as a translocon by assembling into a host-cell plasma membrane-integral structure. here, we confirmed that wild-type sipb could be localized to the bacterial outer membrane, and further showed that its localization was dependent on extracellular secretion, and was independent of the presence of the sipd protein. proteinase k susceptibility and immu ...200818174139
reactive nitrogen species contribute to innate host defense against campylobacter jejuni.campylobacter jejuni, a gram-negative, invasive organism, is a common cause of food-borne bacterial diarrheal disease. however, the relationship between c. jejuni and the innate immune system is not well described. to better characterize host defense against c. jejuni, we investigated the ability of nitric oxide/reactive nitrogen species to kill two strains of c. jejuni. c. jejuni viability was measured after exposure to reactive nitrogen species produced biochemically as acidified nitrite and b ...200818174337
decreased potency of the vibrio cholerae sheathed flagellum to trigger host innate immunity.vibrio cholerae is a monoflagellated gram-negative bacterium that causes the severe diarrheal disease cholera. in contrast to salmonella enterica serovar typhimurium infection, which is accompanied by both acute diarrhea and high-level inflammation, v. cholerae infection is largely noninflammatory in human hosts. bacterial flagella are composed of flagellin, a highly conserved protein that is also a target of the innate immune response. because the v. cholerae flagellum is covered by a sheath, w ...200818174340
nalidixic acid-resistant salmonella enterica serotype typhi infection presenting with sub-intestinal obstruction and mesenteric adenitis.nalidixic acid-resistant salmonella typhi narst infections increase minimal inhibitory concentrations of fluoroquinolones, due to chromosomal mutations in the gene encoding dna gyrase, and can lead to a delayed treatment response. this in turn alters the course of the disease allowing for a protracted period of illness and the occurrence of complications. in this case report, we present a patient from the indian sub-continent, who was diagnosed with narst complicated by sub-intestinal obstructio ...200818176688
genetic detoxification of an aroa salmonella enterica serovar typhimurium vaccine strain does not compromise protection against virulent salmonella and enhances the immune responses towards a protective malarial antigen.live salmonella vaccines are limited in use by the inherent toxicity of the lipopolysaccharide. the waan gene encodes a myristyl transferase required for the secondary acylation of lipid a in lipopolysaccharide. a waan mutant exhibits reduced induction of the inflammatory cytokines associated with lipopolysaccharide toxicity. here the characteristics of a salmonella enterica serovar typhimurium aroa waan mutant (sk100) in vitro and in vivo compared with its parent aroa strain (sl3261) were descr ...200818177343
use of episcopic differential interference contrast microscopy to identify bacterial biofilms on salad leaves and track colonization by salmonella thompson.zoonotic pathogens such as salmonella can cause gastrointestinal illness if they are ingested with food. foods such as salads pose a greater risk because they are consumed raw and have been the source of major outbreaks of disease from fresh produce. the novel light microscopy methods used in this study allow detailed, high resolution imaging of the leaf surface environment (the phyllosphere) and allow pathogen tracking. episcopic differential interference contrast microscopy coupled with epiflu ...200818177375
conjugal transfer of the salmonella enterica virulence plasmid in the mouse intestine.balb/c mice were infected with two salmonella enterica serovar typhimurium strains, one of which lacked the virulence plasmid. transconjugants were found at high frequencies in the mouse feces and at low frequencies in the liver and the spleen, suggesting that mating occurred in the gut. laboratory conditions that mimic those of the small intestine (microaerophilic growth in the presence of 0.3 m nacl) increased the frequency of virulence plasmid transfer. sodium deoxycholate, which is found at ...200818178735
epa worst case water microcosms for testing phage biocontrol of salmonella.a microplate method was developed as a tool to test phages for their ability to control salmonella in aqueous environments. the method used epa (u.s. environmental protection agency) worst case water (wcw) in 96-well plates. the wcw provided a consistent and relatively simple defined turbid aqueous matrix, high in total organic carbon (toc) and total dissolved salts (tds), to simulate swine lagoon effluent, without the inconvenience of malodor and confounding effects from other biological factor ...200818178900
characterization of multiple-antimicrobial-resistant salmonella enterica subsp. enterica isolated from indigenous vegetables and poultry in malaysia.the aims of this communication were to study characterization of serogroups among salmonella isolates and the relationship of antimicrobial resistance to serogroups. multiple antimicrobial resistance (mar) was performed on 189 salmonella enterica isolates associated with 38 different serovars that were recovered from poultry and four types of indigenous vegetables.200818179445
induction of the carrier state in pigeons infected with salmonella enterica subspecies enterica serovar typhimurium pt99 by treatment with florfenicol: a matter of pharmacokinetics.paratyphoid caused by salmonella enterica subsp. enterica serovar typhimurium is the main bacterial disease in pigeons. the ability of salmonella serovar typhimurium to persist intracellularly inside pigeon macrophages results in the development of chronic carriers, which maintain the infection in the flock. in this study, the effect of drinking-water medication with florfenicol on salmonella infection in pigeons was examined. the pharmacokinetics of florfenicol in pigeons revealed a relatively ...200818180355
transduction of bla(cmy-2), tet(a), and tet(b) from salmonella enterica subspecies enterica serovar heidelberg to s. typhimurium.antimicrobial resistance of salmonella spp., especially resistance mediated by extended spectrum beta-lactamases (esbl), is a growing public health concern. understanding the mechanisms through which salmomella spp. acquire the resistance genes can lead to the development of intervention and mitigation strategies. thirty-one salmonella isolates of bovine origin were analyzed by serotyping, antimicrobial susceptibility testing, phage induction and bacterial host range determination, and phage tra ...200818187273
diseases and reproductive success in a wild mammal: example in the alpine chamois.density-dependent and climatic factors affect reproduction and dynamics of wild ungulates. parasites can also decrease reproductive success through either a direct abortive effect or a negative impact on host growth and body condition. however, few studies have investigated the effect of parasitism on fecundity of ungulates in natural conditions. we studied three bacterial infections caused by salmonella enterica serovar abortusovis, chlamydophila abortus and coxiella burnetii. these bacteria ar ...200818189146
molecular characterization of the salmonella enterica serovar typhi vi-typing bacteriophage e1.some bacteriophages target potentially pathogenic bacteria by exploiting surface-associated virulence factors as receptors. for example, phage have been identified that exhibit specificity for vi capsule producing salmonella enterica serovar typhi. here we have characterized the vi-associated e1-typing bacteriophage using a number of molecular approaches. the absolute requirement for vi capsule expression for infectivity was demonstrated using different vi-negative s. enterica derivatives. the p ...200818192390
biosynthesis and iroc-dependent export of the siderophore salmochelin are essential for virulence of salmonella enterica serovar typhimurium.in response to iron deprivation, salmonella enterica serovar typhimurium secretes two catecholate-type siderophores, enterobactin and its glucosylated derivative salmochelin. although the systems responsible for enterobactin synthesis and acquisition are well characterized, the mechanisms of salmochelin secretion and acquisition, as well as its role in salmonella virulence, are incompletely understood. herein we show by liquid chromatography-mass spectrometry analysis of culture supernatants fro ...200818194158
aggregation via the red, dry, and rough morphotype is not a virulence adaptation in salmonella enterica serovar typhimurium.the salmonella rdar (red, dry, and rough) morphotype is an aggregative and resistant physiology that has been linked to survival in nutrient-limited environments. growth of salmonella enterica serovar typhimurium was analyzed in a variety of nutrient-limiting conditions to determine whether aggregation would occur at low cell densities and whether the rdar morphotype was involved in this process. the resulting cultures consisted of two populations of cells, aggregated and nonaggregated, with the ...200818195033
toll-like receptor 5-deficient mice have dysregulated intestinal gene expression and nonspecific resistance to salmonella-induced typhoid-like disease.the recognition of flagellin by toll-like receptor 5 (tlr5) is the dominant means by which model intestinal epithelia activate proinflammatory gene expression in response to salmonella enterica. the role of the flagellin-tlr5 interaction in vivo has been addressed primarily via studies that use flagellar mutants. such studies suggest that host recognition of flagellin promotes rapid neutrophil recruitment that protects the host from this pathogen. however, these works do not directly address the ...200818195036
the mcdonald-kreitman test and slightly deleterious mutations.it is possible to estimate the proportion of substitutions that are due to adaptive evolution using the numbers of silent and nonsilent polymorphisms and substitutions in a mcdonald and kreitman-type analysis. unfortunately, this estimate of adaptive evolution is biased downward by the segregation of slightly deleterious mutations. it has been suggested that 1 way to cope with the effects of these slightly deleterious mutations is to remove low-frequency polymorphisms from the analysis. we inves ...200818195052
peptide-assisted degradation of the salmonella mgtc virulence factor.mgtc is a virulence factor common to several intracellular pathogens that is required for intramacrophage survival and growth in magnesium-depleted medium. in salmonella enterica, mgtc is coexpressed with the mgtb magnesium transporter and transcription of the mgtcb operon is induced by magnesium deprivation. despite the high level of mgtcb transcriptional induction in magnesium-depleted medium, the mgtc protein is hardly detected in a wild-type salmonella strain. here, we show that downregulati ...200818200043
flagellin is required for salmonella-induced expression of heat shock protein hsp25 in intestinal epithelium.flagellin is a bacterial protein responsible for activation of toll-like receptor 5 (tlr5), which we hypothesize is involved in salmonella's induction of cytoprotective heat shock proteins in intestinal epithelial cells. flagellin induces the cytoprotective heat shock protein hsp25 in different intestinal epithelial cell lines and in mouse intestine. flagellin induces hsp25 expression in a time-dependent manner in vitro. this effect is transcriptional, as confirmed by luciferase reporter assays ...200818202113
role of mitogen-activated protein kinases in the inos production and cytokine secretion by salmonella enterica serovar typhimurium porins.the expression of inducible nitric oxide synthase (inos) is a critical factor in both physiological and pathological functions. the present study examined the role of mitogen-activated protein kinases (mapks) in the regulation of inos and proinflammatory cytokine production in raw 264.7 cells in response to salmonella enterica serovar typhimurium porins. by use of western blotting for inos detection and enzyme-linked immunosorbent assay (elisa) for quantization of cytokine secretion, selective p ...200818206384
inactivation kinetics of inoculated escherichia coli o157:h7 and salmonella enterica on lettuce by chlorine dioxide gas.the purpose of this investigation was to study inactivation kinetics of inoculated escherichia coli o157:h7 and salmonella enterica on lettuce leaves by clo(2) gas at different concentrations (0.5, 1.0, 1.5, 3.0, and 5.0 mg l(-1)) for 10 min and to determine the effect of clo(2) gas on the quality and shelf life of lettuce during storage at 4 degrees c for 7 days. one hundred microliters of each targeted organism was separately spot-inoculated onto the surface (5 cm(2)) of lettuce (approximately ...200818206766
survival of enteric microorganisms on grass surfaces irrigated with treated effluent.treated effluent can be reused for the irrigation of parks and sports grounds but there is an associated potential public health risks from microbial pathogens present on the grass surface, particularly when used for contact sports. the main aim of this study was to investigate the survival of pathogenic and indicator microorganisms on the grass surface of a sports ground irrigated with treated effluent under differing climatic conditions. results showed that salmonella enterica serotype typhimu ...200818209287
enzyme-assisted processing increases antimicrobial and antioxidant activity of bilberry.the effects of nine cell wall-degrading enzymes on the antimicrobial and antioxidant activities of bilberry were studied. antimicrobial activity was measured using the human pathogens salmonella enterica sv. typhimurium and staphylococcus aureus as test strains. enzyme treatments liberated phenolics from the cell wall matrix, which clearly increased the antimicrobial activity of berry juices, press cakes, and berry mashes on the basis of plate counts. antibacterial effects were stronger against ...200818211029
binding specificity of salmonella plasmid-encoded fimbriae assessed by glycomics.the salmonella enterica serotype typhimurium (s. typhimurium) genome encodes 12 intestinal colonization factors of the chaperone/usher fimbrial assembly class; however, the binding specificity is known for only one of these adhesins, known as type 1 fimbriae. here we explored the utility of glycomics to determine the carbohydrate binding specificity of plasmid-encoded fimbriae from s. typhimurium. a cosmid carrying the pef operon was introduced into escherichia coli and expression of fimbrial fi ...200818211897
clinical response and outcome of infection with salmonella enterica serotype typhi with decreased susceptibility to fluoroquinolones: a united states foodnet multicenter retrospective cohort study.patients with typhoid fever due to salmonella enterica serotype typhi strains for which fluoroquinolones mics are elevated yet that are classified as susceptible by the current interpretive criteria of the clinical and laboratory standards institute may not respond adequately to fluoroquinolone therapy. patients from seven u.s. states with invasive salmonella serotype typhi infection between 1999 and 2002 were enrolled in a multicenter retrospective cohort study. patients infected with salmonell ...200818212096
distinct roles of the flii atpase and proton motive force in bacterial flagellar protein export.translocation of many soluble proteins across cell membranes occurs in an atpase-driven manner. for construction of the bacterial flagellum responsible for motility, most of the components are exported by the flagellar protein export apparatus. the flii atpase is required for this export, and its atpase activity is regulated by flih; however, it is unclear how the chemical energy derived from atp hydrolysis is used for the export process. here we report that flagellar proteins of salmonella ente ...200818216858
energy source of flagellar type iii secretion.bacterial flagella contain a specialized secretion apparatus that functions to deliver the protein subunits that form the filament and other structures to outside the membrane. this apparatus is related to the injectisome used by many gram-negative pathogens and symbionts to transfer effector proteins into host cells; in both systems this export mechanism is termed 'type iii' secretion. the flagellar secretion apparatus comprises a membrane-embedded complex of about five proteins, and soluble fa ...200818216859
plasmid-mediated quinolone resistance in salmonella enterica, united kingdom. 200818258138
evaluation of the premi test salmonella, a commercial low-density dna microarray system intended for routine identification and typing of salmonella enterica.a new commercial system based on genetic profiling and aimed at identifying salmonella enterica serovars was evaluated by comparing its performance with classical serotyping on 443 strains. within 62 serovars represented, 60 gave unique genetic profiles while 2 were undistinguishable. results were obtained within 8 h, were reproducible and clear-cut. the system allowed single-tube processing of the samples and required no peculiar technical skill. it showed interesting potential for routine labo ...200818258323
architectural adaptation and protein expression patterns of salmonella enterica serovar enteritidis biofilms under laminar flow conditions.salmonella enterica serovar enteritidis is a significant biofilm-forming pathogen. the influence of a 10-fold difference in nutrient laminar flow velocity on the dynamics of salmonella enteritidis biofilm formation and protein expression profiles were compared in order to ascertain how flow velocity influenced biofilm structure and function. low-flow (0.007 cm s(-1)) biofilms consisted of diffusely-arranged microcolonies which grew until merging by approximately 72 h. high-flow (0.07 cm s(-1)) b ...200818261816
the capacity of salmonella to survive inside dendritic cells and prevent antigen presentation to t cells is host specific.infection with salmonella enterica serovar typhimurium (s. typhimurium) causes a severe and lethal systemic disease in mice, characterized by poor activation of the adaptive immune response against salmonella-derived antigens. recently, we and others have reported that this feature relies on the ability of s. typhimurium to survive within murine dendritic cells (dcs) and avoid the presentation of bacteria-derived antigens to t cells. in contrast, here we show that infection of murine dcs with ei ...200818266715
subcutaneous vaccination with attenuated salmonella enterica serovar choleraesuis c500 expressing recombinant filamentous hemagglutinin and pertactin antigens protects mice against fatal infections with both s. enterica serovar choleraesuis and bordetella bronchiseptica.salmonella enterica serovar choleraesuis strain c500 is a live, attenuated vaccine that has been used in china for over 40 years to prevent piglet paratyphoid. we compared the protective efficacies of subcutaneous (s.c.) and oral vaccination of balb/c mice with c500 expressing the recombinant filamentous hemagglutinin type i domain and pertactin region 2 domain antigen (rf1p2) of bordetella bronchiseptica. protective efficacy against both s. enterica serovar choleraesuis infection in an oral fat ...200818268026
overcoming h-ns-mediated transcriptional silencing of horizontally acquired genes by the phop and slya proteins in salmonella enterica.the acquisition of new traits through horizontal gene transfer depends on the ability of the recipient organism to express the incorporated genes. however, foreign dna appears to be silenced by the histone-like nucleoid-structuring protein (h-ns) in several enteric pathogens, raising the question of how this silencing is overcome and the acquired genes are expressed at the right time and place. to address this question, we investigated transcription of the horizontally acquired ugtl and pagc gen ...200818270203
tolc, but not acrb, is involved in the invasiveness of multidrug-resistant salmonella enterica serovar typhimurium by increasing type iii secretion system-1 expression.the acrab-tolc efflux system is involved in multidrug and bile salt resistances. in addition, this pump has recently been suggested to increase the invasion of salmonella enterica serovar typhimurium (s. typhimurium) into host cells in vitro and could therefore have an important clinical relevance for multidrug-resistant strains. the aim of this study was to investigate the role of the tolc outer membrane channel and the acrb transporter in the interaction of multidrug-resistant s. typhimurium s ...200818272427
salmonella enterica serovar senftenberg human clinical isolates lacking spi-1.nontyphoidal salmonella species cause gastrointestinal disease worldwide. the prevailing theory of salmonella enteropathogenesis is that bacterial invasion of the intestinal epithelium is essential for virulence and that this requires the virulence-associated genomic region salmonella pathogenicity island 1 (spi-1). recent studies of salmonella enterica infection models have demonstrated that enterocolitis and diarrhea in mice and cows can occur independently of spi-1. in this study, we sought t ...200818272702
simple, rapid, and affordable point-of-care test for the serodiagnosis of typhoid fever.we developed a point-of-care test for the serodiagnosis of typhoid fever in the format of an immunochromatographic lateral flow assay. the flow assay for typhoid fever is based on the detection of salmonella enterica serotype typhi lipopolysaccharide-specific immunoglobulin m (igm) antibodies. the assay was evaluated on serum samples collected in a hospital in south sulawesi, indonesia, where typhoid fever is endemic, and the results were compared with culture and widal test. the sensitivity of ...200818276100
parallel evolution of multidrug-resistance in salmonella enterica isolated from swine.the increase in frequency of salmonella enterica resistant to antibiotics in food-producing animals is of great concern to public health. determining the rate at which different resistance phenotypes are generated and maintained in the environment is thus of great importance. the distribution and evolution of antibiotic resistance and multidrug-resistance in 362 salmonella stains as part of a cross-sectional study of the canadian swine industry were investigated. the susceptibility of all isolat ...200818279339
emergence of highly fluoroquinolone-resistant salmonella enterica serovar typhi in a community-based fever surveillance from kolkata, india. 200818280709
influence of housing system, grain type, and particle size on salmonella colonization and shedding of broilers fed triticale or corn-soybean meal diets.salmonella colonization in poultry may be influenced by grain type and particle size. broilers reared either in nonlitter cage-based housing or in a conventionally floored litter house from 0 to 42 d were assigned to 1 of 4 dietary treatments: 1) ground corn-soybean meal (c, 560 microm), 2) coarsely ground corn-soybean meal (cc, >1,700 microm), 3) ground triticale-soybean meal (t, 560 microm), or 4) whole triticale-soybean meal (wt). a 4-strain cocktail of salmonella enterica was orally gavaged ...200818281566
salmonella species in free-living spur-thighed tortoises (testudo graeca) in central western morocco. 200818281632
nucleotide biosynthesis is critical for growth of bacteria in human blood.proliferation of bacterial pathogens in blood represents one of the most dangerous stages of infection. growth in blood serum depends on the ability of a pathogen to adjust metabolism to match the availability of nutrients. although certain nutrients are scarce in blood and need to be de novo synthesized by proliferating bacteria, it is unclear which metabolic pathways are critical for bacterial growth in blood. in this study, we identified metabolic functions that are essential specifically for ...200818282099
growth control in the salmonella-containing vacuole.salmonella enterica is an intracellular bacterial pathogen that inhabits membrane-bound vacuoles of eukaryotic cells. coined as the 'salmonella-containing vacuole' (scv), this compartment has been studied for two decades as a replicative niche. recent findings reveal, however, marked differences in the lifestyle of bacteria enclosed in the scv of varied host cell types. in fibroblasts, the emerging view supports a model of bacteria facing in the scv a 'to grow' or 'not to grow' dilemma, which is ...200818282735
spvc is a salmonella effector with phosphothreonine lyase activity on host mitogen-activated protein kinases.spvc is encoded by the salmonella virulence plasmid. we have investigated the biochemical function of spvc and the mechanism by which it is secreted by bacteria and translocated into infected macrophages. we constructed a strain carrying a deletion in spvc and showed that the strain is attenuated for systemic virulence in mice. spvc can be secreted in vitro by either the spi-1 or spi-2 type iii secretion systems. cell biological and genetic experiments showed that translocation of the protein in ...200818284579
flil is essential for swarming: motor rotation in absence of flil fractures the flagellar rod in swarmer cells of salmonella enterica.flil is the first gene in a flagellar operon that specifies members of the switch complex and type iii export system in salmonella enterica and escherichia coli, but no function has been ascribed to this gene thus far. here we report that a flil mutant is slightly impaired for swimming but completely defective in swarming in both organisms, and have studied this phenotype further in s. enterica. we have found that on swarm agar, mutant cells release or 'eject' their flagellar filaments. the rele ...200818284590
nitric oxide homeostasis in salmonella typhimurium: roles of respiratory nitrate reductase and flavohemoglobin.nitric oxide (no) is generated in biological systems primarily via the activity of no synthases and nitrate and nitrite reductases. here we show that salmonella enterica serovar typhimurium (s. typhimurium) grown anaerobically with nitrate is capable of generating polarographically detectable no after nitrite (no(2)(-)) addition. no accumulation is sensitive to the no scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide. neither an fnr mutant nor an fnr hmp double mutant p ...200818285340
infection of epithelial cells with salmonella enterica.salmonella enterica serovars cause a variety of diseases ranging from self-limiting gastroenteritis to severe systemic infections. virulence of these facultative intracellular pathogens is dependent on their ability to invade and replicate within non-phagocytic cells, and cultured epithelial cell systems have been used extensively to dissect the molecular mechanisms involved. for efficient invasion in vitro, the bacterial cell growth conditions as critical since the invasion associated type iii ...200818287758
terpenoid compositions, and antioxidant and antimicrobial properties of the rhizome essential oils of different hedychium species.a phytochemical study of the rhizome essential oils of four different hedychium species was performed by means of gc and gc/ms analyses. h. ellipticum mainly contained 1,8-cineole, sabinene, and terpin-4-ol, while h. aurantiacum possessed terpin-4-ol, para-cymene, and bornyl acetate as the major entities. similarly, trans-meta-mentha-2,8-diene and linalool were noticed in h. coronarium. three different collections (i-iii) of h. spicatum showed amazing differences in the relative contents of thei ...200818293443
construction and use of new cloning vectors for the rapid isolation of recombinant proteins from escherichia coli.we describe the construction and use of two sets of vectors for the over-expression and purification of protein from escherichia coli. the set of ptev plasmids (ptev3, 4, 5) directs the synthesis of a recombinant protein with a n-terminal hexahistidine (his(6)) tag that is removable by the tobacco etch virus (tev) protease. the set of pkld plasmids (pkld66, 116) directs the synthesis of a recombinant protein that contains a n-terminal his(6) and maltose-binding protein tag in tandem, which can a ...200818295882
yjgf is required for isoleucine biosynthesis when salmonella enterica is grown on pyruvate medium.the yjgf/yer057c/uk114 family of proteins is conserved across the three domains of life, yet no biochemical function has been clearly defined for any member of this family. in salmonella enterica, a deletion of yjgf results in a requirement for isoleucine when the mutant strain is grown in glucose-serine or pyruvate medium. feedback inhibition of ilva is required for the curative effect of isoleucine on glucose-serine medium. on pyruvate medium, yjgf mutants are unable to synthesize enough isole ...200818296521
microcompartments for b12-dependent 1,2-propanediol degradation provide protection from dna and cellular damage by a reactive metabolic intermediate.salmonella enterica grows on 1,2-propanediol (1,2-pd) in a coenzyme b(12)-dependent fashion. prior studies showed that a bacterial microcompartment (mcp) is involved in this process and that an mcp-minus mutant undergoes a 20-h period of growth arrest during 1,2-pd degradation. it was previously proposed that growth arrest resulted from propionaldehyde toxicity, but no direct evidence was presented. here, high-pressure liquid chromatography analyses of culture medium were used to show that the m ...200818296526
viability of zoonotic pathogens escherichia coli and salmonella in swine manure slurries with and without a urease inhibitor and thymol.to determine the effects of urine, a urease inhibitor and/or an odour-reducing antimicrobial compound, on zoonotic pathogens in swine manure slurries.200818298450
display of heterologous proteins on the surface of lactococcus lactis using the h and w domain of prtb from lactobacillus delburueckii subsp. bulgaricus as an anchoring matrix.the aim of this study was to develop a cell-surface display system for foreign antigens on the surface of a lactococcus lactis strain using an h and w domain of prtb from lactobacillus delburueckii subsp. bulgaricus as an anchoring matrix.200818298534
caspase-3-dependent phagocyte death during systemic salmonella enterica serovar typhimurium infection of mice.growth of salmonella enterica in mammalian tissues results from continuous spread of bacteria to new host cells. our previous work indicated that infective s. enterica are liberated from host cells via stochastic necrotic burst independently of intracellular bacterial numbers. here we report that liver phagocytes can undergo apoptotic caspase-3-mediated cell death in vivo, with apoptosis being a rare event, more prevalent in heavily infected cells. the density-dependent apoptotic cell death is l ...200818298550
inactivation of salmonella enterica ser. enteritidis in tomato juice by combining of high-intensity pulsed electric fields with natural antimicrobials.the effect of high-intensity pulsed electric field (hipef) treatment (35kv/cm, 4 mus pulse length in bipolar mode without exceeding 38 degrees c) as influenced by treatment time (200, 600, and 1000 micros) and pulse frequency (100, 150, and 200 hz) for inactivating salmonella enterica ser. enteritidis inoculated in tomato juice was evaluated. similarly, the effect of combining hipef treatment with citric acid (0.5%, 1.0%, 1.5%, and 2.0%[wt/vol]) or cinnamon bark oil (0.05%, 0.10%, 0.2%, and 0.3% ...200818298735
detection of sublethal thermal injury in salmonella enterica serotype typhimurium and listeria monocytogenes using fourier transform infrared (ft-ir) spectroscopy (4000 to 600 cm(-1)).fourier transform infrared (ft-ir) spectroscopy (4000 to 600 cm(-1)) was utilized to detect sublethally heat-injured microorganisms: salmonella enterica serotype typhimurium atcc 14028, a gram-negative bacterium, and listeria monocytogenes atcc 19113, a gram-positive bacterium. a range of heat treatments (n= 2) at 60 degrees c were evaluated: 0d (control), 2d, 4d, 6d, and 8d using a d(60 degrees c) (s. enterica serotype typhimurium atcc 14028 = 0.30 min, l. monocytogenes atcc 19113 = 0.43 min). ...200818298736
role of soil, crop debris, and a plant pathogen in salmonella enterica contamination of tomato plants.in the u.s., tomatoes have become the most implicated vehicle for produce-associated salmonellosis with 12 outbreaks since 1998. although unconfirmed, trace backs suggest pre-harvest contamination with salmonella enterica. routes of tomato crop contamination by s. enterica in the absence of direct artificial inoculation have not been investigated.200818301739
the salmonella-containing vacuole: moving with the times.salmonella pathogenesis is dependent on its ability to invade and replicate within host cells. following invasion the bacteria remain within a modified phagosome known as the salmonella-containing vacuole (scv), within which they will survive and replicate. invasion and scv biogenesis are dependent on two type iii secretion systems, t3ss1 and t3ss2, which are used to translocate distinct cohorts of bacterial effector proteins into the host cell. elucidating the roles of individual effector prote ...200818304858
the pdux enzyme of salmonella enterica is an l-threonine kinase used for coenzyme b12 synthesis.here, the pdux enzyme of salmonella enterica is shown to be an l-threonine kinase used for the de novo synthesis of coenzyme b(12) and the assimilation of cobyric acid (cby). pdux with a c-terminal his tag (pdux-his(6)) was produced at high levels in escherichia coli, purified by nickel affinity chromatography, and partially characterized. (31)p nmr spectroscopy established that purified pdux-his(6) catalyzed the conversion of l-threonine and atp to l-threonine-o-3-phosphate and adp. enzyme assa ...200818308727
small outer-membrane lipoprotein, smpa, is regulated by sigmae and has a role in cell envelope integrity and virulence of salmonella enterica serovar typhimurium.smpa is a small outer-membrane lipoprotein that is a component of the essential yaet outer-membrane protein assembly complex. in salmonella enterica serovar typhimurium (s. typhimurium), expression of the smpa gene was shown to be directed by two promoters, smpap1 and smpap2. the more distal promoter, smpap1, is dependent upon the extracytoplasmic stress response sigma factor sigma(e). an smpa null mutant was constructed in s. typhimurium sl1344 and was shown to be more sensitive than its wild-t ...200818310044
characterization of the periplasmic domain of motb and implications for its role in the stator assembly of the bacterial flagellar motor.mota and motb are integral membrane proteins that form the stator complex of the proton-driven bacterial flagellar motor. the stator complex functions as a proton channel and couples proton flow with torque generation. the stator must be anchored to an appropriate place on the motor, and this is believed to occur through a putative peptidoglycan-binding (pgb) motif within the c-terminal periplasmic domain of motb. in this study, we constructed and characterized an n-terminally truncated variant ...200818310339
identification of novel genes and pathways affecting salmonella type iii secretion system 1 using a contact-dependent hemolysis assay.we screened 5,700 salmonella enterica serovar typhimurium mutants for defects in type iii secretion system 1 (t3ss-1)-mediated contact-dependent hemolysis to identify novel genes and pathways affecting the activity of t3ss-1. our data suggest that previously unrecognized factors such as type i fimbriae may modulate the expression, activity, or deployment of this key virulence factor.200818310344
Refresh
firstprev
...61626364656667686970...
nextlast
Displaying items 6701 - 6800 of 11731