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Virulence is a pathogen's or microorganism's ability to cause damage to a host. In most cases, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host. [1] The pathogenicity of an organism—its ability to cause disease—is determined by its virulence factors.
Virulence factors (preferably known as pathogenicity factors or effectors in botany) are cellular structures, molecules and regulatory systems that enable microbial pathogens (bacteria, viruses, fungi, and protozoa) to achieve the following: [1] [2] colonization of a niche in the host (this includes movement towards and attachment to host cells ...
Pathogenicity is the potential disease-causing capacity of pathogens, involving a combination of infectivity (pathogen's ability to infect hosts) and virulence (severity of host disease). Koch's postulates are used to establish causal relationships between microbial pathogens and diseases.
Casadevall proposes that pathogenicity should be determined based on the amount of damage caused to the host, classifying pathogens into different categories based on how they function in the host. [16] However, in order to cope with the changing pathogenic environment, treatment methods need to be revised to deal with drug-resistant microbes.
Multiple genetic elements of human-affecting pathogens contribute to the transfer of virulence factors: plasmids, pathogenicity island, prophages, bacteriophages, transposons, and integrative and conjugative elements. [13] [50] Pathogenicity islands and their detection are the focus of several bioinformatics efforts involved in pathogenomics.
In 1988, microbiologist Stanley Falkow developed a set of three Molecular Koch's postulates for identifying the microbial genes encoding virulence factors. First, the phenotype of a disease symptom must be associated with a specific genotype only found in pathogenic strains. Second, that symptom should not be present when the associated gene is ...
Microbial pathogenesis is a field of microbiology that started at least as early as 1988, with the identification of the triune Falkow's criteria, aka molecular Koch's postulates.
E. coli and related bacteria constitute about 0.1% of gut flora, [4] and fecal–oral transmission is the major route through which pathogenic strains of the bacterium cause disease. Cells are able to survive outside the body for only a limited amount of time, which makes them ideal indicator organisms to test environmental samples for fecal ...