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Query: UMLS:C0021311 (Infection)
 38,178 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Many higher plants establish symbiotic relationships with arbuscular mycorrhizal (AM) fungi that improve their ability to acquire nutrients from the soil. In addition to establishing AM symbiosis, legumes also enter into a nitrogen-fixing symbiosis with bacteria known as rhizobia that results in the formation of root nodules. Several genes involved in the perception and transduction of bacterial symbiotic signals named "Nod factors" have been cloned recently in model legumes through forward genetic approaches. Among them, DMI3 (Doesn't Make Infections 3) is a calcium- and calmodulin-dependent kinase required for the establishment of both nodulation and AM symbiosis. We have identified, by a yeast two-hybrid system, a novel protein interacting with DMI3 named IPD3 (Interacting Protein of DMI3). IPD3 is predicted to interact with DMI3 through a C-terminal coiled-coil domain. Chimeric IPD3::GFP is localized to the nucleus of transformed Medicago truncatula root cells, in which split yellow fluorescent protein assays suggest that IPD3 and DMI3 physically interact in Nicotiana benthamiana. Like DMI3, IPD3 is extremely well conserved among the angiosperms and is absent from Arabidopsis. Despite this high level of conservation, none of the homologous proteins have a demonstrated biological or biochemical function. This work provides the first evidence of the involvement of IPD3 in a nuclear interaction with DMI3.
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PMID:A novel nuclear protein interacts with the symbiotic DMI3 calcium- and calmodulin-dependent protein kinase of Medicago truncatula. 1772 95

The widespread emergence of human and wildlife diseases has challenged ecologists to understand how large-scale agents of environmental change affect host-pathogen interactions. Accelerated eutrophication of aquatic ecosystems owing to nitrogen and phosphorus enrichment is a pervasive form of environmental change that has been implicated in the emergence of diseases through direct and indirect pathways. We provide experimental evidence linking eutrophication and disease in a multihost parasite system. The trematode parasite Ribeiroia ondatrae sequentially infects birds, snails, and amphibian larvae, frequently causing severe limb deformities and mortality. Eutrophication has been implicated in the emergence of this parasite, but definitive evidence, as well as a mechanistic understanding, have been lacking until now. We show that the effects of eutrophication cascade through the parasite life cycle to promote algal production, the density of snail hosts, and, ultimately, the intensity of infection in amphibians. Infection also negatively affected the survival of developing amphibians. Mechanistically, eutrophication promoted amphibian disease through two distinctive pathways: by increasing the density of infected snail hosts and by enhancing per-snail production of infectious parasites. Given forecasted increases in global eutrophication, amphibian extinctions, and similarities between Ribeiroia and important human and wildlife pathogens, our results have broad epidemiological and ecological significance.
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PMID:Aquatic eutrophication promotes pathogenic infection in amphibians. 1789 32

Cutaneous leishmaniasis of the New World, in particular when caused by Leishmania (L.) braziliensis, harbours the risk of lymphogenic as well as hematogenic dissemination. This may result in mucocutaneous leishmaniasis causing severe destruction of orofacial structures. Dissemination may occur years after the disappearance of the skin lesions. In contrast, cutaneous leishmaniasis of the old world, is typically restricted to the site of inoculation. Therefore, a conservative diagnostic and therapeutic approach is usually sufficient. Infections acquired in the new world should be treated systemically, if infection with Leishmania (Viannia) braziliensis complex cannot be excluded. Here we report on three Austrian soldiers, who, weeks after having participated in an international jungle patrol course in Belize, presented themselves with multiple ulcers on the upper limbs. Diagnosis of cutaneous leishmaniasis was made based upon histological evaluation of biopsies taken from several ulcers revealing the presence of leishmanial bodies, and detection of amastigote leishmania in smears of material obtained from the ulcers. As species phenotyping could not be performed, infection with L. brasiliensis as well as progression into a mucocutaneous form were possible, demanding systemic therapy. Several treatment options including local cryotherapy with liquid nitrogen, paromomycin (Humatis Pulvis, Parke-Davis) 15% topically or oral fluconazole (Diflucan, Pfizer) 200 mg/d were applied, but showed no effect. Hence, a systemic therapy with intravenous pentamidine (Pentacarinat, Gerot), three times in total, 3-4 mg/kg body weight each, led to a complete regression of the lesions within four weeks.
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PMID:[Cutaneous leishmaniasis--an import from Belize]. 1798 67

Pneumococcal meningitis remains a serious disease with a case fatality rate of 15%-25%. Furthermore, long-term residues affect up to 50% of survivors. One of the most frequent sequelae is sensorineural hearing loss, which occurs in 26% of survivors of pneumococcal meningitis. Unfortunately, sufficient treatment regimens are still missing. New insights into the pathology and pathophysiology of meningitis-associated hearing loss have come from animal models of bacterial meningitis. Most likely, bacteria reach the cochlea through the cochlear aquaeduct. Once arrived in the perilymphatic spaces, they induce a severe suppurative labyrinthitis. The blood-labyrinth barrier breaks, hair cells are damaged, and neurons in the spiral ganglion undergo cell death, leading to meningitis-associated hearing loss. Reactive oxygen and nitrogen species, in particular peroxynitrite, seem to be among the crucial mediators of cochlear damage and hearing loss during meningitis. In our rat model of pneumococcal meningitis, adjunctive therapy with the antioxidants and peroxynitrite scavengers Mn(III)tetrakis(4-bencoic acid)-porphyrin (MnTBAP) and N-Acetyl-L-Cystein (NAC) significantly attenuated acute and long-term hearing loss. In several other animal studies of pneumococcal meningitis, adjunctive antioxidant therapy also protected infected animals from intracranial complications. Therefore, the use of antioxidants seems to be a promising future treatment option in pneumococcal meningitis.
Infection 2008 Feb
PMID:Nitrogen and oxygen molecules in meningitis-associated labyrinthitis and hearing impairment. 1808 15

The infection-related expression of a Heterobasidion annosum (Fr.) Bref. sensu lato (s.l.) putative cytochrome P450 gene (CPM2) was analysed with realtime quantitative PCR. CPM2 was highly expressed after 20 days of growth in bark of living spruce trees, and up-regulated by nitrogen starvation on artificial media. Infection of pine seedlings in the presence of high-carbon medium results in low expression levels of CPM2, thus indicating that starvation is the primary regulatory factor for induction of this gene. The predicted cpm2 protein contains 507 amino acids with an estimated molecular mass of 56.1 kDa, and display all conserved amino acids of the cytochrome P450 protein family. The protein has a high similarity to the ord1/ordA O-methylsterigmatocystin oxidoreductases from Aspergillus flavus/A. parasiticus, responsible for catalysing the final step in aflatoxin biosynthesis. Results indicate that cpm2 is potentially important for pathogenicity in H. annosum s.l.
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PMID:A fungal cytochrome P450 is expressed during the interaction between the fungal pathogen Heterobasidion annosum sensu lato and conifer trees. 1829 2

Salmonella Enteritidis is a major food-borne pathogen that causes nontyphoidal diarrhoea in humans. Infection of adult egg-laying hens usually results in symptomless carriage but in young chicks it may cause paratyphoid disease. It is not known whether S. Enteritidis requires genes additional to known virulence genes for systemic infection of young chickens. A transposon insertion library was created using S. Enteritidis 10/02, which yielded 1246 mutants. Of 384 mutants screened in chickens for attenuation (30.8% of insertion library), 12 (3.1%) had a 50% lethal dose at least 100 times that of the parental strain. Sequencing revealed insertions in genes involved in the biosynthesis of lipopolysaccharide, cell membrane, ATP biosynthesis, transcriptional regulation of virulence and the yhbC gene, which has an unknown function. Evaluation of in vitro virulence characteristics of a Delta yhbC mutant revealed that its ability to invade HeLa cells and survive within a chicken macrophage cell line (HD11) was significantly reduced. It was also less resistant to reactive oxygen and nitrogen intermediates and had a retarded growth rate. Chickens challenged with the Delta yhbC mutant cleared the organism from the liver and spleen 1 week faster than the parental strain and were able to develop specific serum IgG antibodies against the Delta yhbC mutant.
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PMID:Identification of novel attenuated Salmonella Enteritidis mutants. 1835 92

Infection of legumes by Rhizobium sp. NGR234 and subsequent development of nitrogen-fixing nodules are dependent on the coordinated actions of Nod factors, proteins secreted by a type III secretion system (T3SS) and modifications to surface polysaccharides. The production of these signal molecules is dependent on plant flavonoids which trigger a regulatory cascade controlled by the transcriptional activators NodD1, NodD2, SyrM2 and TtsI. TtsI is known to control the genes responsible for T3SS function and synthesis of a symbiotically important rhamnose-rich lipo-polysaccharide, most probably by binding to cis elements termed tts boxes. Eleven tts boxes were identified in the promoter regions of target genes on the symbiotic plasmid of NGR234. Expression profiles of lacZ fusions to these tts boxes showed that they are part of a TtsI-dependent regulon induced by plant-derived flavonoids. TtsI was purified and demonstrated to bind directly to two of these tts boxes. DNase I footprinting revealed that TtsI occupied not only the tts box consensus sequence, but also upstream and downstream regions in a concentration-dependent manner. Highly conserved bases of the consensus tts box were mutated and, although TtsI binding was still observed in vitro, gfp fusions were no longer transcribed in vivo. Random mutagenesis of a tts box-containing promoter revealed more nucleotides critical for transcriptional activity outside of the consensus.
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PMID:TtsI regulates symbiotic genes in Rhizobium species NGR234 by binding to tts boxes. 1836 48

Rhizobia can infect roots of host legume plants and induce new organs called nodules, in which they fix atmospheric nitrogen. Infection generally starts with root hair curling, then proceeds inside newly formed, intracellular tubular structures called infection threads. A successful symbiotic interaction relies on infection threads advancing rapidly at their tips by polar growth through successive cell layers of the root toward developing nodule primordia. To identify a plant component that controls this tip growth process, we characterized a symbiotic mutant of Medicago truncatula, called rpg for rhizobium-directed polar growth. In this mutant, nitrogen-fixing nodules were rarely formed due to abnormally thick and slowly progressing infection threads. Root hair curling was also abnormal, indicating that the RPG gene fulfils an essential function in the process whereby rhizobia manage to dominate the process of induced tip growth for root hair infection. Map-based cloning of RPG revealed a member of a previously unknown plant-specific gene family encoding putative long coiled-coil proteins we have called RRPs (RPG-related proteins) and characterized by an "RRP domain" specific to this family. RPG expression was strongly associated with rhizobial infection, and the RPG protein showed a nuclear localization, indicating that this symbiotic gene constitutes an important component of symbiotic signaling.
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PMID:The RPG gene of Medicago truncatula controls Rhizobium-directed polar growth during infection. 1862 93

Hemorrhage is a severe manifestation of dengue disease. Virus strain and host immune response have been implicated as the risk factors for hemorrhage development. To delineate the complex interplay between the virus and the host, we established a dengue hemorrhage model in immune-competent mice. Mice inoculated intradermally with dengue virus develop hemorrhage within 3 days. In the present study, we showed by the presence of NS1 antigen and viral nuclei acid that dengue virus actively infects the endothelium at 12 h and 24 h after inoculation. Temporal studies showed that beginning at day 2, there was macrophage infiltration into the vicinity of the endothelium, increased tumor necrosis factor alpha (TNF-alpha) production, and endothelial cell apoptosis in the tissues. In the meantime, endothelial cells in the hemorrhage tissues expressed inducible nitric oxide synthase (iNOS) and nitrotyrosine. In vitro studies showed that primary mouse and human endothelial cells were productively infected by dengue virus. Infection by dengue virus induced endothelial cell production of reactive nitrogen and oxygen species and apoptotic cell death, which was greatly enhanced by TNF-alpha. N(G)-nitro-L-arginine methyl ester and N-acetyl cysteine reversed the effects of dengue virus and TNF-alpha on endothelial cells. Importantly, hemorrhage development and the severity of hemorrhage were greatly reduced in mice lacking iNOS or p47(phox) or treatment with oxidase inhibitor, pointing to the critical roles of reactive nitrogen and oxygen species in dengue hemorrhage.
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PMID:Enhancement by tumor necrosis factor alpha of dengue virus-induced endothelial cell production of reactive nitrogen and oxygen species is key to hemorrhage development. 1884 37

This study aims to determine the occurrence of Pseudallescheria and Scedosporium species in natural and human-dominated environments. Habitats (136 sampling sites) in a transect with increasing human impact were investigated (natural areas, agricultural soils, urban playgrounds, industrial areas). Physico-chemical parameters were measured to characterize the different areas included in this investigation. Fungal identification was performed by morphology and sequence data analysis. Comparative description of virulence was largely based on the database of the ECMM/ISHAM Working Group on Pseudallescheria/Scedosporium Infections. Pseudallescheria and Scedosporium species were most abundant in industrial areas, followed by urban playgrounds and agricultural areas. None of the species were isolated from natural habitats. The abundance of Pseudallescheria and Scedosporium species could be correlated with increasing nitrogen concentrations (P<0.01) and decreasing pH (P<0.05) within a pH range of 6.1-7.5. In general, frequency of the different Pseudallescheria and Scedosporium species in the environment is strongly enhanced by human activities, and largely differs from species distribution in clinical settings, suggesting that these species have different degrees of virulence. Pseudallescheria boydii is relatively frequently found as agent of human disease, while Scedosporium dehoogii is found almost exclusively in the environment. Scedosporium apiospermum is responsible for the majority of infections and is found at comparable frequency in the environment; S. aurantiacum and P. minutispora showed similar spectra, but at much lower frequencies.
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PMID:Ecology of Pseudallescheria and Scedosporium species in human-dominated and natural environments and their distribution in clinical samples. 1908 59


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