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PubMed1996

Note: inhibition of the growth of Yersinia enterocolitica O:3 by the microflora of porcine caecum and ileum in an in vitro model.

The growth of Yersinia enterocolitica O:3 was tested in an in vitro model of the porcine intestine at the physiological temperature of 39 degrees C of growing pigs. The model supported a stable population of Y. enterocolitica at a level 10(8)-10(9) cells ml-1. Plasmid profile analysis and the Ca(2+)-dependent proportion of the population suggested that the great majority of the Y. enterocolitica population retained the 70 kb virulence plasmid, pYV, throughout the experimental period of 5 d. The growth of Y. enterocolitica was substantially inhibited by the ileal and the caecal flora compared to the growth of the bacterium alone. Yersinia enterocolitica was not isolated after 3 d of cultivation.

Animals↗
PubMed2006

Brucella melitensis triggers time-dependent modulation of apoptosis and down-regulation of mitochondrion-associated gene expression in mouse macrophages.

Brucella spp. are facultative intracellular bacteria that cause brucellosis in humans and other animals. Brucella spp. are taken up by macrophages, and the outcome of the macrophage-Brucella interaction is a basis for establishment of a chronic Brucella infection. Microarrays were used to analyze the transcriptional response of the murine macrophage-like J774.A1 cell line to infection with virulent Brucella melitensis strain 16M. It was found that most significant changes in macrophage gene transcription happened early following infection, and global macrophage gene expression profiles returned to normal between 24 and 48 h postinfection. These findings support the observation that macrophages kill the majority of Brucella cells at the early infection stage, but the surviving Brucella cells are able to avoid macrophage brucellacidal activity inside replicative phagosomes at the later infection stage. At 4 h postinfection, macrophage genes involved in cell growth, metabolism, and responses to endogenous stimuli were down-regulated, while the inflammatory response (e.g., tumor necrosis factor alpha and Toll-like receptor 2), the complement system, the responses to external stimuli, and other immune responses were up-regulated. It is likely that the most active brucellacidal activity happened between 0 and 4 h postinfection. Mitochondrion-associated gene expression, which is involved in protein synthesis and transport, electron transfer, and small-molecule transfer, and many other mitochondrial functions were significantly down-regulated at 4 h postinfection. Although there were both pro- and antiapoptosis effects, B. melitensis 16M appears to inhibit apoptosis of macrophages by blocking release of cytochrome c and production of reactive oxygen species in the mitochondria, thus preventing activation of caspase cascades.

Animals↗
PubMed2026

Unveiling microbial risks in Chinese household dust: a comprehensive analysis from absolute abundance to virulence unit.

BACKGROUND: People spend the majority of their lives indoors, yet the risk and virulence potential of household microbiota remain largely unexplored, particularly in developing countries. RESULTS: Here, we conducted a nationwide survey on both dust samples and health information across 118 Chinese households. The microbiota composition and its functional units were analyzed using absolute 16S rRNA/ITS sequencing, metagenomics, and metaproteomics. Cross-domain network analysis of the core microbial communities revealed robust co-occurrence patterns in household dust. The mean absolute abundance of potentially pathogenic bacteria and fungi in households was 2.39 × 105 and 2.83 × 106 DNA copies/g dust. The potentially pathogenic community was primarily influenced by latitude, relative humidity, and average temperature. Although total absolute abundance was substantially lower in urban areas, the relative abundance of potentially pathogenic bacteria was markedly higher compared to rural environments. While urban-rural differences existed, the underlying statistical drivers were the environmental variables. The absolute abundance of potential pathogens was significantly associated with the prevalence of rhinitis, wheeze, and dermatitis in 266 participants. Children were identified as the highest-risk group from inhalation exposure of average daily dose. A total of 170 bacterial, 223 fungal virulence factors (VFs), and 370 antibiotic resistance genes (ARGs) were detected in dust and dust extracellular vesicle (EV)-associated DNA. EV-associated cargoes contributed 47.13% to the bacterial VF profiles, 11.90% to fungal VF profiles, and 44.45% to ARG profiles. Metaproteomic analysis confirmed the presence of VF profiles in dust EVs, which was further verified by curated proteomics data from 35 household pathogens. CONCLUSIONS: This study provides a comprehensive, quantitative framework linking indoor microbial exposure to health risks, highlighting EVs as a non-negligible, novel, extracellular mechanistic pathway for health impact in household environments. Video Abstract.

Child↗
PubMed1999

Indole-positive Vibrio vulnificus isolated from disease outbreaks on a Danish eel farm.

Vibrio vulnificus was isolated in 1996 from 2 disease outbreaks on a Danish eel farm which used brackish water. A characteristic clinical sign was extensive, deep muscle necrosis in the head region. V. vulnificus was isolated from kidney, mucus, spleen, gill and intestine of diseased eels. Thirty-two isolates were examined phenotypically and serologically for pathogenicity to eels and for correlation to ribotype and plasmid profile. Biochemically, the isolates showed properties similar to those described previously for eel-pathogenic strains of V. vulnificus, with the exception of indole production. Virulence was evaluated by LD50 (the 50% lethal dose), which ranged from < 9.4 x 10(3) to 2.3 x 10(5) CFU (colony-forming units) per fish. The isolates which were lethal for eels showed identical ribotypes and serotypes. A relationship between certain plasmids and virulence was not found. A serotyping system based on lipopolysaccharide (LPS)-associated O antigen type and on carbohydrate capsule antigens showed that the eel-virulent isolates shared a common LPS-based homogeneous O serogroup and a capsule antigen. V. vulnificus serovar O4 and capsule type 9 was identical serologically to the Japanese isolate ATCC 33149 and was the agent responsible for the disease outbreaks that occurred on the Danish eel farm. Despite absence of antibiotic resistance, treatment had little effect and disease reoccurred.

Animals↗
PubMed1999

Classification of gastritis--yesterday, today and tomorrow.

The major landmark in the recent history of gastritis was the discovery of Helicobacter pylori as the cause for approximately 90% of cases of chronic gastritis. This was followed by an attempt to rationalise classification from the many conflicting nomenclatures in existence to one, the Sydney System, that might gain more universal acceptance and allow studies from around the world to be compared. In the decade since its inception, including an appropriate update, the system has partially achieved this aim. It is based on documenting the topography of the gastritis, this reflecting the range of possible clinical outcomes and point of progress along the gastritis-metaplasia-dysplasia-carcinoma cascade. The rapidly expanding molecular knowledge about host mucosal immunology, determinants of bacterial virulence and dietary constituents makes it likely "tomorrow's" classification will be an algorithm to include several such factors. From this an exact "peptic" patient profile could be constructed. However one must also speculate that interest in gastritis and its classification could whither just as quickly as it blossomed with the advent of a successful vaccine.

Gastritis↗
PubMed2006

Global analysis of iron assimilation and fur regulation in Yersinia pestis.

Using DNA microarray analysis, mRNA levels from wild-type Yersinia pestis cells treated with the iron chelator 2,2'-dipyridyl were compared with those supplemented with excessive iron, and subsequent to this, gene expression in the fur mutant was compared with that in the wild-type strain under iron rich conditions. The microarray analysis revealed many iron transport or storage systems that had been induced in response to the iron starvation, which is mediated by the Fur protein, using the iron as a co-repressor. The iron-Fur complex also affected some genes involved in various non-iron functions (ribonucleoside-diphosphate reductase, membrane proteins, electron transport and oxidative defense, etc.). The Fur protein still participated in the regulation of genes involved in broad cellular processes (virulence factors, pesticin activity, haemin storage and many proteins with unknown functions) that were not affected by iron depletion conditions. In addition to its classical negative regulatory activities, the Fur protein activates gene transcription. Using bioinformatics tools, we were able to predict the Y. pestis Fur box sequence that was clearly the over-presented motif in the promoter regions of members of the iron-Fur modulon.

Bacterial Proteins↗
PubMed2005

[Screen in vivo induced gene of Mycobacterium tuberculosis by IVIAT].

In order to search new candidates of pharmaceutical target, in vivo induced antigen technology (IVIAT) was used to screen in vivo induced (ivi) genes of Mycobacterium tuberculosis (M. TB). Genomic expression library of M. TB was first constructed with an inducible plasmid pKK223-8; the titer of the library was 1.02 x 10(5) CFU. Sera from ten tuberculosis patients were pooled and absorbed against in vitro-grown M. TB and Escherichia coli, and used to probe the genomic expression library. 16 positive clones were identified by immunological screen, including 22 ORF: two encoding lipid metabolism proteins, five information pathways proteins, two PE/PPE proteins, six intermediary metabolism and respiration proteins, one cell wall and cell processes protein, four conserved hypothetical proteins and two conserved hypothetical proteins with an orthologue in Mycobacterium bovis. Parts of these genes can be used as candidates of pharmaceutical target because they may be relate with virulence.

Antigens, Bacterial↗
PubMed1999

Genotypes of Helicobacter pylori in Polish population.

Here we have studied the genetic diversity of Helicobacter pylori strains recovered from 64 individual patients, 5 family members and 13 unsuccessfully treated patients. The recovered bacteria were finger-printed by the PCR-RFLP and RAPD methods and virulence associated loci (cagPAI, vacA) were PCR studied. Unique differentiation of every independently isolated strain from not-related persons was possible by RAPD technique. In PCR-RFLP technique several profile groups (7 and 15) for particular endonuclease tested were found. Eleven patients carried strains of the same gene profile (PCR-RFLP) and the same overall genotype (RAPD) before and after therapy. In the family studies, essentially the same strain was found in different relatives in three cases, and different strains were found in the other two cases. Island of cagPAI was present in 79% of all strains tested, half and one-fifth of all strains tested presented, s1am2 and s1m1 alleles of vacA gene, respectively. Independently from identity or diversity of pre- and post-treatment strains and strains recovered from the family members we have been observed identical cagPAI/vacA genotypes. These results suggest that H. pylori infections in Poland can be mixed, although just one strain may often predominate, and that inter-family transmission may be significant even in this high risk society. The genetic feature of virulence-associated loci are similar to those seen elsewhere in Europe, although strains that carry the cagPAI and the potentially more toxigenic alleles of the vacA gene are more common. RAPD technique is proven as most differentiating, however PCR-RFLP allows for easy recognition of mixed infection with two or more different strains. Molecular typing study in case of children therapy may allow reduce rate of relapses by reduction of possible transmission from family source.

Adolescent↗
PubMed2006

Whole-genome expression profiling defines the HrpL regulon of Pseudomonas syringae pv. tomato DC3000, allows de novo reconstruction of the Hrp cis clement, and identifies novel coregulated genes.

Pseudomonas syringae pv. tomato DC3000 is a model pathogen of tomato and Arabidopsis that uses a hypersensitive response and pathogenicity (Hrp) type III secretion system (T3SS) to deliver virulence effector proteins into host cells. Expression of the Hrp system and many effector genes is activated by the HrpL alternative sigma factor. Here, an open reading frame-specific whole-genome microarray was constructed for DC3000 and used to comprehensively identify genes that are differentially expressed in wild-type and deltahrpL strains. Among the genes whose differential regulation was statistically significant, 119 were upregulated and 76 were downregulated in the wild-type compared with the deltahrpL strain. Hierarchical clustering revealed a subset of eight genes that were upregulated particularly rapidly. Gibbs sampling of regions upstream of HrpL-activated operons revealed the Hrp promoter as the only identifiable regulatory motif and supported an iterative refinement involving real-time polymerase chain reaction testing of additional HrpL-activated genes and refinements in a hidden Markov model that can be used to predict Hrp promoters in P. syringae strains. This iterative bioinformatic-experimental approach to a comprehensive analysis of the HrpL regulon revealed a mix of genes controlled by HrpL, including those encoding most type III effectors, twin-arginine transport (TAT) substrates, other regulatory proteins, and proteins involved in the synthesis or metabolism of phytohormones, phytotoxins, and myo-inositol. This analysis provides an extensively verified, robust method for predicting Hrp promoters in P. syringae genomes, and it supports subsequent identification of effectors and other factors that likely are important to the host-specific virulence of P. syringae.

Bacterial Proteins↗
PubMed2005

Transcriptional network of multiple capsule and melanin genes governed by the Cryptococcus neoformans cyclic AMP cascade.

Cryptococcus neoformans is an opportunistic human fungal pathogen that elaborates several virulence attributes, including a polysaccharide capsule and melanin pigments. A conserved Galpha protein/cyclic AMP (cAMP) pathway controls melanin and capsule production. To identify targets of this pathway, we used an expression profiling approach to define genes that are transcriptionally regulated by the Galpha protein Gpa1. This approach revealed that Gpa1 transcriptionally regulates multiple genes involved in capsule assembly and identified two additional genes with a marked dependence on Gpa1 for transcription. The first is the LAC1 gene, encoding the laccase enzyme that catalyzes a rate-limiting step in diphenol oxidation and melanin production. The second gene identified (LAC2) is adjacent to the LAC1 gene and encodes a second laccase that shares 75% nucleotide identity with LAC1. Similar to the LAC1 gene, LAC2 is induced in response to glucose deprivation. However, LAC2 basal transcript levels are much lower than those for LAC1. Accordingly, a lac2 mutation results in only a modest delay in melanin formation. LAC2 overexpression suppresses the melanin defects of gpa1 and lac1 mutants and partially restores virulence of these strains. These studies provide mechanistic insights into the regulation of capsule and melanin production by the C. neoformans cAMP pathway and demonstrate that multiple laccases contribute to C. neoformans melanin production and pathogenesis.

Animals↗
PubMed2006

Identification of differentially expressed cDNAs in Acanthamoeba culbertsoni after mouse brain passage.

Free-living amoebae of the genus Acanthamoeba are causative agents of granulomatous amebic encephalitis and amebic keratitis. Because the virulence of Acanthamoeba culbertsoni cultured in the laboratory is restored by consecutive brain passages, we examined the genes induced in mouse brain-passaged A. culbertsoni by differential display reverse transcriptase polymerase chain reaction (DDRT-PCR). Enhanced A. culbertsoni virulence was observed during the second mouse brain passage, i.e., infected mouse mortality increased from 5% to 70%. Ten cDNAs induced during mouse brain passage were identified by DDRT-PCR and this was confirmed by northern blot analysis. BlastX searches of these cDNAs indicated the upregulations of genes encoding predictive NADH-dehydrogenase, proteasomal ATPase, and GDP-mannose pyrophosphorylase B, which have previously been reported to be associated with A. culbertsoni virulence factors.

Acanthamoeba↗
PubMed2005

Genes and molecules involved in Aspergillus fumigatus virulence.

Aspergillus fumigatus causes a wide range of diseases that include mycotoxicosis, allergic reactions and systemic diseases (invasive aspergillosis) with high mortality rates. Pathogenicity depends on immune status of patients and fungal strain. There is no unique essential virulence factor for development of this fungus in the patient and its virulence appears to be under polygenetic control. The group of molecules and genes associated with the virulence of this fungus includes many cell wall components, such as beta-(1-3)-glucan, galactomannan, galactomannanproteins (Afmp1 and Afmp2), and the chitin synthetases (Chs; chsE and chsG), as well as others. Some genes and molecules have been implicated in evasion from the immune response, such as the rodlets layer (rodA/hyp1 gene) and the conidial melanin-DHN (pksP/alb1 gene). The detoxifying systems for Reactive Oxygen Species (ROS) by catalases (Cat1p and Cat2p) and superoxide dismutases (MnSOD and Cu, ZnSOD), had also been pointed out as essential for virulence. In addition, this fungus produces toxins (14 kDa diffusible substance from conidia, fumigaclavin C, aurasperon C, gliotoxin, helvolic acid, fumagilin, Asp-hemolysin, and ribotoxin Asp fI/mitogilin F/restrictocin), allergens (Asp f1 to Asp f23), and enzymatic proteins as alkaline serin proteases (Alp and Alp2), metalloproteases (Mep), aspartic proteases (Pep and Pep2), dipeptidyl-peptidases (DppIV and DppV), phospholipase C and phospholipase B (Plb1 and Plb2). These toxic substances and enzymes seems to be additive and/or synergistic, decreasing the survival rates of the infected animals due to their direct action on cells or supporting microbial invasion during infection. Adaptation ability to different trophic situations is an essential attribute of most pathogens. To maintain its virulence attributes A. fumigatus requires iron obtaining by hydroxamate type siderophores (ornitin monooxigenase/SidA), phosphorous obtaining (fos1, fos2, and fos3), signal transductional falls that regulate morphogenesis and/or usage of nutrients as nitrogen (rasA, rasB, rhbA), mitogen activated kinases (sakA codified MAP-kinase), AMPc-Pka signal transductional route, as well as others. In addition, they seem to be essential in this field the amino acid biosynthesis (cpcA and homoaconitase/lysF), the activation and expression of some genes at 37 degrees C (Hsp1/Asp f12, cgrA), some molecules and genes that maintain cellular viability (smcA, Prp8, anexins), etc. Conversely, knowledge about relationship between pathogen and immune response of the host has been improved, opening new research possibilities. The involvement of non-professional cells (endothelial, and tracheal and alveolar epithelial cells) and professional cells (natural killer or NK, and dendritic cells) in infection has been also observed. Pathogen Associated Molecular Patterns (PAMP) and Patterns Recognizing Receptors (PRR; as Toll like receptors TLR-2 and TLR-4) could influence inflammatory response and dominant cytokine profile, and consequently Th response to infec tion. Superficial components of fungus and host cell surface receptors driving these phenomena are still unknown, although some molecules already associated with its virulence could also be involved. Sequencing of A. fumigatus genome and study of gene expression during their infective process by using DNA microarray and biochips, promises to improve the knowledge of virulence of this fungus.

Animals↗
PubMed2000

Capillary electrophoretic analysis of wild type and mutant Proteus penneri outer membrane proteins.

In this study the virulence factors, outer membrane proteins (OMP), lipopolysaccharides (LPS), hemolysin, and the in vivo and in vitro virulence of wild-type Proteus penneri 357 and its two isogenic mutant variants--a transposon and a spontaneous mutant--were examined. The OMPs of these variants were analyzed by a new and fast technique, "dynamic sieving" capillary electrophoresis (CE). The OMP profiles were dominated by two peaks (39 and 43 kDa). In the P. penneri clone examined, both the transposon and the spontaneous mutations induced significant changes in the OMP patterns (in the relative percentage of the dominant proteins). CE was suitable for the comparative analysis of bacterial protein patterns in the genetic variants of this strain, and provided valuable results in connection with the bacteriological virulence. The LPS composition of the genetic variants also showed alterations. The wild type of P. penneri 357 showed a typical ladder pattern, an "S" form, and the mutants possessed "R" LPS patterns (only few bands) in the gels. In the bacteriological virulence tests the wild type of P. penneri 357 was virulent in the in vivo, and toxic in the in vitro assays, while both mutants showed neither toxicity nor pathogenicity.

Bacterial Outer Membrane Proteins↗
PubMed2004

Multi-virulence-locus sequence typing of Listeria monocytogenes.

A multi-virulence-locus sequence typing (MVLST) scheme was developed for subtyping Listeria monocytogenes, and the results obtained using this scheme were compared to those of pulsed-field gel electrophoresis (PFGE) and the published results of other typing methods, including ribotyping (RT) and multilocus sequence typing (MLST). A set of 28 strains (eight different serotypes and three known genetic lineages) of L. monocytogenes was selected from a strain collection (n > 1,000 strains) to represent the genetic diversity of this species. Internal fragments (ca. 418 to 469 bp) of three virulence genes (prfA, inlB, and inlC) and three virulence-associated genes (dal, lisR, and clpP) were sequenced and analyzed. Multiple DNA sequence alignment identified 10 (prfA), 19 (inlB), 13 (dal), 10 (lisR), 17 (inlC), and 16 (clpP) allelic types and a total of 28 unique sequence types. Comparison of MVLST with automated EcoRI-RT and PFGE with ApaI enzymatic digestion showed that MVLST was able to differentiate strains that were indistinguishable by RT (13 ribotypes; discrimination index = 0.921) or PFGE (22 profiles; discrimination index = 0.970). Comparison of MVLST with housekeeping-gene-based MLST analysis showed that MVLST provided higher discriminatory power for serotype 1/2a and 4b strains than MLST. Cluster analysis based on the intragenic sequences of the selected virulence genes indicated a strain phylogeny closely related to serotypes and genetic lineages. In conclusion, MVLST may improve the discriminatory power of MLST and provide a convenient tool for studying the local epidemiology of L. monocytogenes.

Amino Acid Sequence↗
PubMed2000

The response regulator PhoP is important for survival under conditions of macrophage-induced stress and virulence in Yersinia pestis.

The two-component regulatory system PhoPQ has been identified in many bacterial species. However, the role of PhoPQ in regulating virulence gene expression in pathogenic bacteria has been characterized only in Salmonella species. We have identified, cloned, and sequenced PhoP orthologues from Yersinia pestis, Yersinia pseudotuberculosis, and Yersinia enterocolitica. To investigate the role of PhoP in the pathogenicity of Y. pestis, an isogenic phoP mutant was constructed by using a reverse-genetics PCR-based strategy. The protein profiles of the wild-type and phoP mutant strains, grown at either 28 or 37 degrees C, revealed more than 20 differences, indicating that PhoP has pleiotrophic effects on gene expression in Y. pestis. The mutant showed a reduced ability to survive in J774 macrophage cell cultures and under conditions of low pH and oxidative stress in vitro. The mean lethal dose of the phoP mutant in mice was increased 75-fold in comparison with that of the wild-type strain, indicating that the PhoPQ system plays a key role in regulating the virulence of Y. pestis.

Animals↗
PubMed2003

Isolation and molecular characterization of nalidixic acid-resistant extraintestinal pathogenic Escherichia coli from retail chicken products.

Fluoroquinolone use in poultry production may select for resistant Escherichia coli that can be transmitted to humans. To define the prevalence and virulence potential of poultry-associated, quinolone-resistant E. coli in the United States, 169 retail chicken products from the Minneapolis-St. Paul area (1999 to 2000) were screened for nalidixic acid (Nal)-resistant E. coli. Sixty-two (37%) products yielded Nal-resistant E. coli. From 55 products that yielded both Nal-resistant and susceptible E. coli, two isolates (one resistant, one susceptible) per sample were further characterized. Twenty-three (21%) of the 110 E. coli isolates (13 resistant, 10 susceptible) satisfied criteria for extraintestinal pathogenic E. coli (ExPEC), i.e., exhibited >or=2 of pap (P fimbriae), sfa/foc (S/F1C fimbriae), afa/dra (Dr binding adhesins), iutA (aerobactin receptor), and kpsMT II (group 2 capsule synthesis). Compared with other isolates, ExPEC isolates more often derived from virulence-associated E. coli phylogenetic groups B2 or D (74% versus 32%; P < 0.001) and exhibited more ExPEC-associated virulence markers (median, 10.0 versus 4.0; P < 0.001). In contrast, the Nal-resistant and -susceptible populations were indistinguishable according to all characteristics analyzed, including pulsed-field gel electrophoresis profiles. These findings indicate that Nal-resistant E. coli is prevalent in retail poultry products and that a substantial minority of such strains represent potential human pathogens. The similarity of the Nal-resistant and -susceptible populations suggests that they derive from the same source population, presumably the avian fecal flora, with Nal resistance emerging by spontaneous mutation as a result of fluoroquinolone exposure.

Animals↗
PubMed2000

Evidence of commonality between canine and human extraintestinal pathogenic Escherichia coli strains that express papG allele III.

Although dogs have been proposed as carriers of extraintestinal pathogenic Escherichia coli (ExPEC) with infectious potential for humans, presumed host species-specific differences between canine and human ExPEC strains have cast doubt on this hypothesis. The recent discovery that allele III of papG (the P fimbrial adhesin gene) predominates among human cystitis isolates and confers an adherence phenotype resembling that of canine ExPEC prompted the present reevaluation of the canine-human ExPEC connection. Sixteen paired pap-positive urine and rectal E. coli isolates from dogs with urinary tract infection were studied. papG (adhesin) and papA (pilin) allele type, agglutination phenotypes, virulence factor genotypes, and randomly amplified polymorphic DNA and pulsed-field gel electrophoresis fingerprints were analyzed and compared with those of human ExPEC controls. The 16 canine strains contained predominantly papG allele III. Agglutination phenotypes segregated strictly according to papG allele status and were homogeneous among strains with the same papG allele profile irrespective of their human versus canine origin. Canine and human PapG variant III peptide sequences were highly homologous, without host species-specific differences. The most prevalent canine papA allele was F48, a novel variant recently identified among human urosepsis isolates. In addition to pap, human ExPEC-associated virulence genes detected among the canine strains included sfa/focDE, sfaS, fyuA, hlyA, cnf1, cdtB, kpsMT-II and -III, rfc, traT, ompT, and a marker for a pathogenicity-associated island from archetypal human ExPEC strain CFT073. Molecular fingerprinting confirmed the fecal origin of all but one canine urine isolate and showed one pair of O6 canine urine and fecal isolates to be extremely similar to an O6 human urosepsis isolate with which they shared all other genotypic and phenotypic characteristics analyzed. These data demonstrate that canine ExPEC strains are similar to, and in some instances essentially indistinguishable from, human ExPEC strains, which implicates dogs and their feces as potential reservoirs of E. coli with infectious potential for humans.

Adhesins, Escherichia coli↗
PubMed2005

Regulation of the pspA virulence factor and essential pcsB murein biosynthetic genes by the phosphorylated VicR (YycF) response regulator in Streptococcus pneumoniae.

The VicRK (YycFG) two-component regulatory system (TCS) is required for virulence of the human respiratory pathogen Streptococcus pneumoniae (pneumococcus). The VicR (YycF) response regulator (RR) is essential through its positive regulation of pcsB, which encodes an extracellular protein that mediates murein biosynthesis. To determine other genes that are regulated by VicR, we performed microarray analyses on a unique DeltavicR deletion mutant, which was constructed by uncoupling regulation of pcsB. Results from these microarray experiments support the idea that the VicR RR exerts strong positive regulation on the transcription of a set of genes encoding important surface proteins, including the PspA virulence factor, two proteins (Spr0096 and Spr1875) containing LysM peptidoglycan-binding domains, and a putative membrane protein (Spr0709) of unknown function. To demonstrate direct regulation, we performed band shift and footprinting experiments using purified unphosphorylated VicR and phosphorylated VicR-P, which was prepared by reaction with acetyl phosphate. VicR and VicR-P bound to regions upstream of pcsB, pspA, spr0096, spr1875, and spr0709. Phosphorylation of VicR to VicR-P increased the apparent strength and changed the nature of binding to these regions. DNase I footprinting of VicR and VicR-P bound to regions upstream of pcsB, pspA, spr0096, and spr1875 showed protection of extended regions containing a degenerate sequence related to a previously proposed consensus. These combined approaches did not support autoregulation of the vicRKX operon or substantive direct regulation of fatty acid biosynthesis by VicR or VicR-P. However, the DeltavicR mutant required fatty acids in some conditions, which supports the notion that the VicRK TCS may mediate membrane integrity as well as murein biosynthesis and virulence factor expression in S. pneumoniae.

5' Flanking Region↗