17 - Host/Microbe Interactions
Card Set Information
17 - Host/Microbe Interactions
Host Microbe Interactions
17 - Host Microbe Interactions
What are the 3 symbiotic relationships between host and microbe?
Mutualism - Both benefit
Commensalism - One benefits, other is unharmed
Parasitism - One benefits at expense of host
How does our normal microbiota play help us?
Protects us from harmful organisms by covering binding sites, consuming available nutrients and producing toxic compounds, and stimulating our immune systems.
Acquired at birth.
3 Things that can kill normal microbiota:
3. Auto-immune Defeciencies
When is the term "infection" used?
If the colonizing organism has a parasitic relationship with the host.
An infection that results in disease is termed an "infections disease."
What are signs and symptoms?
Symptoms - Experienced by patient, ie pain/nausea
Signs - Can be observed through examination, ie Rash, Swelling, Pus
What are primary and secondary infections?
Primary - Initial infection
Secondary - Additional infections resulting from the primary infection
What is pathogenicity?
The ability of a pathogen to produce an infectious disease in an organism.
What is virulence?
Term referring to a pathogens disease causing ability.
Highly virulent organisms have a high degree of pathogenicity.
What is an opportunistic pathogen?
Microbes that cause disease when the body's defenses are down.
What is the "infectious dose?"
Number of organisms required to establish infection
Diseases with SMALL infectious doses are more easily spread than diseases with HIGH infectious doses because less of the microbe is needed.
What is the course of an infectious disease?
Incubation - Time between infection and onset of symptoms
Illness - Signs and symptoms
Convalescence - Recuperation and recovery; may still be contagious
What are the duration of symptoms?
Acute - Rapid onset, last a short time
Chronic - Develop slowly and persist
Latent - Never completely eliminated, may be reactive
What is a localized infection?
Limited to a small area.
Example - Boil
What is a systemic or generalized infection?
Microbe spreads throughout body
Example - Measles
What is toxemia?
Toxins circulating in the blood stream
What is viremia?
Viruses cirulating in the blood stream
What is septicemia?
Life-threatening illness caused by infectious agent or its products circulating in the blood
What separates disease and non-disease causing organisms?
Their ability to overcome the body's immune system
What is a "mechanism of pathogenicity?"
Mechanism used to overcome the body's immune responses
More than one mechanism is called "Virulence Determinants"
What steps must an organism take to cause disease?
Adherence - Binding to the hosts cells
Colonization - Must successfully multiply, compete for nutrients
Delivery of Effector Molecules - Must be able to deliver colonized cells to host
How do organisms get in to our bodies?
Penetration of skin - most difficult
Penetration of mucous membranes - most common
How do bacteria avoid the hosts defenses?
Hide in a host cell - some can transfer from cell to cell
Avoid being killed by complement protiens - Gram negative cells more susceptible
Avoiding antibodies -
How can a bacteria avoid antibodies?
Antigenic Variation - alternation of surface antigens
Mimicking Host Molecules
What are exotoxins?
Toxins that are leaked or secreted by bacterium
Among most potent toxins known
Can act locally or systemically
What are the 3 types of toxins?
Neurotoxins - damage nervous system
Enterotoxins - damage intestines/digestive tract
Cytotoxins - Damage to variety of cells, cause interference with cell function and lysis
What are membrane damaging toxins?
Disrupt the plasma membrane of a cell
What are superantigens?
Antigens that override T-Cell response and cause toxis effects due to massive release of cytokines by helper t-cells.
Which toxin in responsible for Septic Shock?
What are some damaging effects of immune response?
Drop in blood pressure
What are the mechanisms of viral pathogenesis?
Binding to host cell/Invasion
Avoiding immune responses
What are the mechanisms of Eukaryotic Pathogenesis?
Fungi - Infection begins with inhalation of airborne particles, Spores lodge in lung tissues
Eukaryotic Parasites - Most live in intestinal tract, or enter body via bite of an arthropod, attach to hosts via specialized receptors, some hide within host cells.