pathogens

(noun)

A pathogen or infectious agent (colloquially known as a germ) is a microorganism (in the widest sense, such as a virus, bacterium, prion, or fungus) that causes disease in its host. The host may be an animal (including humans), a plant, or even another microorganism.

Related Terms

Examples of pathogens in the following topics:

  • Extent of Host Involvement

    • Host-pathogen interactions are the interactions taking place between a pathogen (e.g. virus, bacteria) and their host (e.g. humans, plants).
    • Host-pathogen interactions are the interactions that take place between a pathogen (e.g. virus, bacteria) and their host (e.g. humans, plants).
    • By definition, all pathogens damage their host to some extent.
    • The appearance and severity of disease resulting from the presence of any pathogen depends upon the ability of that pathogen to damage the host as well as the ability of the host to resist the pathogen.
    • Clinicians therefore classify infectious microorganisms or microbes according to the status of host defenses - either as primary pathogens or as opportunistic pathogens.

  • Intracellular Pathogens

    • Not all pathogens are undesirable to humans.
    • In entomology, pathogens are one of the "Three P's" (predators, pathogens, and parasitoids) that serve as natural or introduced biological controls to suppress arthropod pest populations.
    • There are several types of intracellular pathogens.
    • Bacteria can often be killed by antibiotics because the cell wall in the outside is destroyed, expelling the DNA out of the body of the pathogen, therefore making the pathogen incapable of producing proteins, so it dies.
    • According to the prion theory, prions are infectious pathogens that do not contain nucleic acids.

  • Regulating Virulence

    • There are three main hypotheses about why a pathogen evolves as it does.
    • For example, if the host dies, the pathogen population inside may die out entirely.
    • Pathogen strains that kill the host can increase in frequency as long as the pathogen can transmit itself to a new host, whether before or after the host dies.
    • The evolution of virulence in pathogens is a balance between the costs and benefits of virulence to the pathogen.
    • These traits typically arise due to mutations, which occur more frequently in pathogen populations than in host populations, due to the pathogens' rapid generation time and immense numbers.

  • Pathogenicity Islands and Virulence Factors

    • Pathogenicity islands (PAIs) are a distinct class of genomic islands acquired by microorganisms through horizontal gene transfer.
    • Pathogenicity islands (PAIs) are a distinct class of genomic islands acquired by microorganisms through horizontal gene transfer.
    • They are incorporated in the genome of pathogenic organisms, but are usually absent from those nonpathogenic organisms of the same or closely related species.
    • These mobile genetic elements may range from 10-200 kb, and may encode genes contributing to the virulence of the respective pathogen.
    • The GC-content of pathogenicity islands often differs from that of the rest of the genome, potentially aiding in their detection within a given DNA sequence.

  • Airborne Transmission of Disease

    • Airborne diseases are characterized by diseases that are transmitted through the air via the presence of a pathogen.
    • Airborne diseases are characterized by diseases that are transmitted through the air via the presence of a pathogen.
    • These pathogens can include both viruses and bacteria that are spread by coughing, sneezing, laughing, or through personal contact.
    • The airborne transmission that occurs utilizes small particles or droplet nucleithat contains these infectious agents or pathogens.
    • Often times, these airborne pathogens can result in inflammation in the nose, throat, sinuses, and the lungs.

  • Pathogenicity Islands

    • Pathogenicity islands (PAIs) are a distinct class of genomic islands acquired by microorganisms through horizontal gene transfer.
    • They are incorporated in the genome of pathogenic organisms, but are usually absent from those nonpathogenic organisms of the same or closely related species.
    • These mobile genetic elements may range from 10-200 kb and encode genes which contribute to the virulence of the respective pathogen.
    • Pathogenicity islands carry genes encoding one or more virulence factors, including, but not limited to, adhesins, toxins, or invasins.
    • Pathogenicity islands are transferred horizontally, this details some of the ways that occurs.

  • Ecology, Epidemiology, and Evolution of Pathogens

    • Pathogens have evolved to adapt to their environment and their host in order to survive.
    • Ecological competence is the ability of an organism, often a pathogen, to survive and compete in new habitats.
    • If a pathogen does not have this, it will likely become extinct.
    • In the case of plant pathogens, it is also their ability to survive between growing seasons.
    • Diseases can emerge when existing parasites become pathogenic or when new pathogenic parasites enter a new host.

  • Direct Damage

    • The pathogenic organism typically causes damage due to its own growth process.
    • The ability of a pathogen to gain entrance to a host cell is fundamental in the ability of the pathogen to promote and cause disease.
    • However, a successful and destructive pathogen often exhibits the ability to evade phagocytosis.
    • The mechanism(s) utilized by pathogens to avoid phagocytosis include avoiding both contact and engulfment.
    • Describe the different processes used by pathogens to damage the host and ensure infection

  • Overview of Human-Microbial Reactions

    • Human-microbial interactions can be commensal or mutualistic, as with many types of gut flora, or harmful, as with pathogenic bacteria.
    • Skin flora are usually non-pathogenic and either commensal or mutualistic.
    • Infectious disease results from the interplay between those few pathogens and the defenses of the hosts they infect.
    • Primary pathogens cause disease as a result of their presence or activity within the normal, healthy host.
    • The success of any pathogen depends on its ability to elude host immune responses.

  • Plant Pathogens

    • There are four main bacterial pathogenicity factors: cell wall degrading enzymes, toxins, phytohormones, and effector proteins.
    • Most plant pathogenic bacteria are rod shaped (bacilli).
    • In order to be able to colonise the plant they have specific pathogenicity factors.
    • There are 4 main bacterial pathogenicity factors:
    • Necrotrophic fungal pathogens infect and kill host tissue and extract nutrients from the dead host cells.