Search results for "Virulence"
showing 10 items of 457 documents
Evidence that water transmits the disease caused by the fish pathogen Photobacterium damselae subsp. damselae
2000
The transmission through water of the disease caused by the fish pathogen, Photobacterium damselae subsp. damselae, as well as the role of the skin mucus in the initial steps of the infection, have been studied. All tested strains resisted the bactericidal activity of the mucus and showed an ability to adhere to it, but only those virulent by the intraperitoneal route were infective through water. Moribund fishes showed the typical signs of the disease: haemorrhaged areas on the body surface and ulcerative lesions with mucus degradation. These results suggest that the pathogen can be transmitted to fish through water and use the skin as a portal of entry.
LOCAL ADAPTATION, RESISTANCE, AND VIRULENCE IN A HEMIPARASITIC PLANT-HOST PLANT INTERACTION
2000
Coevolution may lead to local adaptation of parasites to their sympatric hosts. Locally adapted parasites are, on average, more infectious to sympatric hosts than to allopatric hosts of the same species or their fitness on the sympatric hosts is superior to that on allopatric hosts. We tested local adaptation of a hemiparasitic plant, Rhinanthus serotinus (Scrophulariaceae), to its host plant, the grass Agrostis capillaris. Using a reciprocal cross-infection experiment, we exposed host plants from four sites to hemiparasites originating from the same four sites in a common environment. The parasites were equally able to establish haustorial connections to sympatric and allopatric hosts, and…
Molecular organization of the cell wall of Candida albicans and its relation to pathogenicity.
2006
Candida albicans is one of the most important opportunistic pathogenic fungi. Weakening of the defense mechanisms of the host, and the ability of the microorganism to adapt to the environment prevailing in the host tissues, turn the fungus from a rather harmless saprophyte into an aggressive pathogen. The disease, candidiasis, ranges from light superficial infections to deep processes that endanger the life of the patient. In the establishment of the pathogenic process, the cell wall of C. albicans (as in other pathogenic fungi) plays an important role. It is the outer structure that protects the fungus from the host defense mechanisms and initiates the direct contact with the host cells by…
Biosynthesis of fungal melanins and their importance for human pathogenic fungi
2003
For more than 40 years fungi have been known to produce pigments known as melanins. Predominantly these have been dihydroxyphenylalanine (DOPA)-melanin and dihydroxynaphthalene (DHN)-melanin. The biochemical and genetical analysis of the biosynthesis pathways have led to the identification of the genes and corresponding enzymes of the pathways. Only recently have both these types of melanin been linked to virulence in some human pathogenic and phytopathogenic fungi. The absence of melanin in human pathogenic and phytopathogenic fungi often leads to a decrease in virulence. In phytopathogenic fungi such as Magnaporthe grisea and Colletotrichum lagenarium, besides other possible functions in …
Transcriptional Upregulation of Genes Related to Virulence Activation in Entamoeba histolytica
2007
Background To understand the molecular basis of virulence variability in Entamoeba histolytica , this study presents results about differential gene expression induced by E. histolytica trophozoites in liver of hamsters in order to produce experimental amebic liver abscess (ALA) and consequently reactivate its virulence. Methods Amebic cultures were studied before (BALA) and after (AALA) inoculation in hamster peritoneal cavity. Markers of pathogenicity such as the rate of erythrophagocytosis, hemolytic activity, and cytotoxic effects on MDCK cell monolayers were evaluated in order to correlate these phenotypic characteristics to differential gene expression between virulent and non-virulen…
Adaptation to iron deficiency in human pathogenic fungi
2020
Iron is an essential micronutrient for virtually all eukaryotic organisms and plays a central role during microbial infections. Invasive fungal diseases are associated with strikingly high rates of mortality, but their impact on human health is usually underestimated. Upon a fungal infection, hosts restrict iron availability in order to limit the growth and virulence of the pathogen. Here, we use two model yeasts, Saccharomyces cerevisiae and Schizosaccharomyces pombe, to delve into the response to iron deficiency of human fungal pathogens, such as Candida glabrata, Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans. Fungi possess common and species-specific mechanisms to a…
Vibrio vulnificus biotype 2, pathogenic for eels, is also an opportunistic pathogen for humans
1996
We report that the eel pathogen Vibrio vulnificus biotype 2 is also an opportunistic pathogen for humans. Results from a detailed comparative study using reference strains of both biotypes revealed that the clinical strain ATCC 33817, originally isolated from a human leg wound and classified as V. vulnificus (no reference on its biotype is noted), belongs to biotype 2 of the species. As a biotype 2 strain, it is negative for indole and pathogenic for eels and mice, harbors two plasmids of high MrS, and belongs to serogroup E, recently proposed as characteristic of biotype 2 strains. In consequence, appropriate measures must be taken by consumers, particularly by those running a health risk,…
Complete Genome Sequence of the Enterobacter cancerogenus Bacteriophage Enc34
2012
ABSTRACT Enterobacter cancerogenus is widely distributed in nature and is generally recovered from environmental or vegetal sources. In some cases, it has also been associated with human infections. In this study, the complete genomic sequence of virulent E. cancerogenus bacteriophage Enc34 was determined. The Enc34 genome is 60,364 bp in length and contains 80 open reading frames. To our knowledge, this is the first report of a bacteriophage infecting E. cancerogenus .
ACELLULAR PERTUSSIS VACCINE COMPOSED OF GENETICALLY INACTIVATED PERTUSSIS TOXIN: SAFETY AND IMMUNOGENICITY IN 12- TO 24- AND 2-TO 4-MONTH-OLD CHILDREN
1992
To determine whether a nontoxic derivative of pertussis toxin obtained by recombinant DNA technology, PT-9K/129G, is a good candidate for a new pertussis vaccine, we examined the safety and the immunogenicity in children of a vaccine containing 15 micrograms of PT-9K/129G protein and 0.5 mg of aluminum hydroxide per dose. Fifty-three children 12 to 24 months of age and 21 infants aged 2 to 4 months were injected with two and three doses, respectively. The vaccine did not induce significant local or systemic reactions and elicited an increase of antibody titer in more than 98% of the children. The geometric mean of the toxin-neutralizing titers increased after each dose and was 85 units in c…
Relationships between Staphylococcus aureus genetic background, virulence factors, agr groups (alleles), and human disease
2002
ABSTRACT The expression of most Staphylococcus aureus virulence factors is controlled by the agr locus, which encodes a two-component signaling pathway whose activating ligand is an agr -encoded autoinducing peptide (AIP). A polymorphism in the amino acid sequence of the AIP and of its corresponding receptor divides S. aureus strains into four major groups. Within a given group, each strain produces a peptide that can activate the agr response in the other member strains, whereas the AIPs belonging to different groups are usually mutually inhibitory. We investigated a possible relationship between agr groups and human S. aureus disease by studying 198 S. aureus strains isolated from 14 asym…