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Chapter 16 - Host-Microbe Interactions
Terms in this set (58)
a host with a weakness or defect in the innate or adaptive defenses
relationship in which two species live closely together
an association in which both partners benefit
an association in which one partner benefits, but the other remains unharmed
an association in which one organism benefits at the expense of the other
disease producing microorganisms
the population of microorganisms that normally grow on the healthy human body or other specified environment; protects humans by covering binding sites that might otherwise be used for attachment, consuming available nutrients, and producing compounds toxic to other bacteria. it also stimulates the adaptive immune system.
The proposition that increasing allergies among children are the result of decreased exposure to microbes, such as those found in dirt.
refers to a microbe establishing itself and multiplying on a body surface.
colonization of a pathogen on or within the body; does not equal illness
colonization of a pathogen that does NOT produce symptoms, or the symptoms are too mild to be noticed
an infection that results in disease (a noticeable impairment of body function) and are characterized by symptoms and signs
subjective effects of the the disease experienced by the patient (e.g. pain and nausea)
objective evidence of disease (e.g. rash, pus formation, and swelling)
the initial infection (can leave a person predisposed to developing another)
additional infection that occurs as a result of the primary infection
(aka pathogen) a microbe or virus that causes disease in otherwise healthy individuals (e.g. plague, malaria, measles, influenza, diptheria, etc.)
(aka opportunist) causes disease only when the body's innate or adaptive defenses are compromised, or when introduced into an unusual location. as healthcare system improves many organisms not previously known to cause disease are now showing to do so in severely immuncompromised patients
refers to the degree of pathogenicity of an organism. an organism that is highly virulent is more likely to cause disease, particularly severe disease, than might otherwise be expected.
traits of a microorganism that specifically allow it to cause disease
communicable or contagious diseases
infectious diseases that spread from one host to another
the number of microbes necessary to establish an infection (partly reflects the ease with which a contagious disease spreads)
Infectious dose for 50% of the test population
the time between introduction of a microbe to a susceptible host and the onset of illness
follows the incubation period; during this period a person will experience the signs and symptoms of the disease.
early, vague symptoms of disease (e.g. malaise and headache)
stage of recuperation and recovery from the disease
individuals that harbor an infectious agent for months or years and continue to spread the pathogen, even though they show no signs or symptoms of the disease
infection characterized by symptoms that develop quickly, but only last a short time. e.g. is strep throat
infections that develop slowly and last for months or years. e.g. tuberculosis
infections that are never completely eliminated. the microbe continues to exist in host tissues, often within host cells, without causing symptoms. if there is a decrease in immunity, the latent infection may become reactivated and symptomatic. an illness may be stopped by an effective immune response, leaving the host immune to reinfection. the virus, however, is not completely eliminated.
infection where the microbe is limited to a small area. e.g. a boyle
infection that is spread throughout the body. e.g. measles.
refers to a disease in the blood
originally used to determine anthrax. four guidelines that provide a foundation for establishing that given microbe causes a specific infectious disease:
1. the microorganism must be present in every case of the disease
2. the organism must be grown in pure culture from diseased hosts.
3. the same disease must be produced when a pure culture of the organism is introduced into susceptible hosts.
4. the organism must be recovered from the experimentally infected hosts
PROBLEMS with it though: cannot be carried out if organism can't be grown in laboratory, some diseases don't have symptoms, and some symptoms are caused by more than one disease
molecular koch's postulates
used to study a microbe's virulence factors
1. the virulence factor gene or its product shoudl be found in pathogenic strains of the organism
2. mutating the virulence gene to disrupt its function should reduce the virulence of the pathogen
3. reversion of the mutated virulence gene or replacement with a wild-type version should restore virulence to the strain
mechanisms of pathogenisis
1. ingestion (e.g. foodborne intoxication)
2. colonization of mucous membranes of the host followed by toxin production. adheres to lining of intestine or respiratory tracts and multiplies to high numbers
3. invasion of host tissues. penetration of 1st-line defenses and then multiplies within tissues
4. invasion of host tissues, followed by toxin production. same as 3, but in addition to invading, they also make toxins.
pathogens and their hosts generally evolve over tme to a state where pathogen becomes less virulent and the host simultaneously becomes less susceptible.
bacteria use these to attach to the host cells. often located at the tips of pili; the molecule to which the adhesin attaches is the RECEPTOR
produced by pathogens; take the iron away from iron-transport proteins by binding the iron even more tightly
enzyme that destroys igA antibodies
type III secretion system
a specialized bacterial secretion system consisting of a needle complex that allows the pathogen to directly inject proteins into a target host cell and reprogram it for the needs of the pathogen. aka injectisome
characteristic mechanism of engulfment that some bacteria induce by triggering rearrangements of a cell's actin
bacteria that use mechanisms to avoid killing by the complement proteins
ways some pathogens avoid phagocytosis
1. some prevent phagocytosis by avoiding macrophages and neutrophils altogether
2. some avoid being recognized by phagocytes (e.g capsules, M protein, and FC receptors)
3. some survive within phagocytes. allows them to hide from antibodies, control some aspects of the immune response, and be transported to other locations in the body.
kill phagocytes and other cells, often by forming pores in their membranes
pathogens avoid antibodies
1. IgA protease cleaves the antibody
2. Antigenic variation - alter the structure of their surface
3. Mimicking host molecules
proteins produced by bacteria that have very specific damaging effects on the host. either secreted by the bacterium or leak into the surrounding fluid following lysis. can act locally, or they can be carried in the bloodstream throughout the body. many are so powerful that fatal damage occurs before an adequate immune response is mounted. this is why vaccination is important
Toxins that have been deliberately inactivated by heat or chemical treatment so that they are no longer toxic but can still provoke a protective immune response on vaccination.
an antibody that can neutralize a specific toxin
toxins that damage the nervous system causing symptoms such as paralysis
toxins that cause symptoms associated with intestinal disturbance
damage a variety of different cell types, either by interfering with essential cellular mechanisms or by lysing cells
3 general categories of exotoxins
1. A-B toxins
2. membrane-damaging toxins
toxins that lyse red blood cells
overide the specificity of helper T-cell response, causing toxic effects due to the massive release of cytokines by Th cells
toxin that destroys skin
A normal component of the outer membrane of Gram-negative bacteria. Endotoxins produce extreme immune reactions (septic shock), particularly when many of them enter the circulation at once.
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