virulence factor

(noun)

Molecules expressed and secreted by pathogens (bacteria, viruses, fungi and protozoa) that enable them to achieve colonization of a niche in the host, immunoevasion, immunosuppression, entry into and out of the cells, and obtaining nutrition from the host.

Related Terms

Examples of virulence factor in the following topics:

  • Pathogenicity Islands and Virulence Factors

    • Typical examples of PAIs are adherence factors, toxins, iron uptake systems, invasion factors and secretion systems.
    • These mobile genetic elements may range from 10-200 kb, and may encode genes contributing to the virulence of the respective pathogen.
    • Typical examples are adherence factors, toxins, iron uptake systems, invasion factors and secretion systems.
    • PAIs carry genes encoding one or more virulence factors, including, but not limited to, adhesins, toxins, or invasins.
    • They can be transferred as a single unit to new bacterial cells, thus conferring virulence to formerly benign strains.

  • Whooping Cough

    • B. pertussis has the ability to inhibit the function of a host's immune system, through virulence factors.
    • Its virulence factors include pertussis toxin, filamentous hæmagglutinin, pertactin, fimbria, and tracheal cytotoxin.
    • PTx, formerly known as lymphocytosis-promoting factor, causes a decrease in the entry of lymphocytes into lymph nodes.

  • Pathogenicity Islands

    • Pathogenenicity islands are discrete genetic loci that encode factors which make a microbe more virulent.
    • These mobile genetic elements may range from 10-200 kb and encode genes which contribute to the virulence of the respective pathogen.
    • Typical examples are adherence factors, toxins, iron uptake systems, invasion factors, and secretion systems.
    • Pathogenicity islands carry genes encoding one or more virulence factors, including, but not limited to, adhesins, toxins, or invasins.
    • They can be transferred as a single unit to new bacterial cells, thus conferring virulence to formerly benign strains.

  • Virulent Bacteriophages and T4

    • T-4 bacteriophage is a virulent bacteriophage that infects E. coli bacteria; virulent bacteriophages have a lytic life cycle.
    • The pathogenicity of an organism is determined by its virulence factors.
    • Virus virulence factors determine whether an infection will occur and how severe the resulting viral disease symptoms are.
    • Some viral virulence factors confer ability to replicate during the defensive inflammation responses of the host such as during virus-induced fever.
    • Summarize how the T4 life cycle serves as a model for viral virulence

  • Identification of Microbes Based on Molecular Genetics

    • Genes that satisfy molecular Koch's postulates are often referred to as virulence factors (i.e., what makes the pathogen virulent).
    • Once virulent factors have been identified, it is possible to develop a vaccine against the factors. illustrates how the avian flu vaccine was developed using reverse genetic techniques.
    • Testing a candidate virulence gene requires a relevant animal model of the disease being examined and the ability to genetically manipulate the microorganism that causes the disease.

  • Regulating Virulence

    • Virulence regulation is a combination of the specific traits of the pathogen and the evolutionary pressures that lead to virulent traits.
    • The pathogenicity of an organism - its ability to cause disease - is determined by its virulence factors.
    • The ability of a microorganism to cause disease is described in terms of the number of infecting bacteria, the route of entry into the body, the effects of host defense mechanisms, and intrinsic characteristics of the microorganism called virulence factors.
    • The evolution of virulence in pathogens is a balance between the costs and benefits of virulence to the pathogen.
    • But as long as transmission continues despite the virulence, virulent pathogens will have the advantage.

  • Otitis Media

    • A major risk factor for developing otitis media is Eustachian tube dysfunction, which leads to the ineffective clearing of bacteria from the middle ear.
    • TAAs are virulence factors; an infective agent that infects the host cell by attaching to them and secreting the virulence factor by a secretion pathway.

  • Group Translocation

    • Despite that fact, some pathogenic bacteria such as Pseudomonas aeruginosa , Legionella pneumophila, Yersinia pseudotuberculosis, and E. coli O157:H7 rely on a functioning Tat pathway for full virulence in infection models.
    • In addition, a number of exported virulence factors have been shown to rely on the Tat pathway.
    • One such category of virulence factors are the phospholipase C enzymes, which have been shown to be Tat-exported in Pseudomonas aeruginosa and thought to be Tat-exported in Mycobacterium tuberculosis.

  • Adherence

    • Adhesins are a type of virulence factor.
    • Fimbriae are believed to be involved in attachment to solid surfaces or to other cells, and are essential for the virulence of some bacterial pathogens.
    • To effectively achieve adherence to host surfaces, many bacteria produce multiple adherence factors called adhesins.
    • The Dr family of adhesins bind to the Dr blood group antigen component of decay-accelerating factor (DAF).

  • Ecology, Epidemiology, and Evolution of Pathogens

    • Optimal virulence is a concept relating to the ecology of hosts and parasites.
    • However, the host, being the parasite's resource and habitat in a way, suffers from this higher virulence.
    • Thus, there is a natural force providing pressure on the parasite to "self-limit" its virulence.
    • The idea is then, that there exists an equilibrium point of virulence, where parasite's fitness is highest.
    • Any movement on the virulence axis, towards higher or lower virulence, will result in lower fitness for the parasite, and this will be selected against.