Host-Microbe Interactions Flashcards
Define infection
Infection is the process whereby a microbe enters into a relationship with a host. May or may not be pathogenic.
Define infectious disease
An infectious disease is a disease caused by infection with a microbe. Some are communicable, others are not.
Define pathogenicity
Pathogenicity is the ability of a microbe to cause disease. Frank pathogens readily cause disease in normal hosts (Yersinia). Opportunistic pathogens primarily cause disease in compromised hosts (Pseudomonas).
Define virulence
Virulence is the degree of pathogenicity. Highly virulent microbes can cause disease even when introduced in small numbers.
What are Koch’s Postulates?
1) Specific microbes are present regularly in lesions of the disease. 2) The specific microbe can be isolated and grown in vitro. 3) Injection of the cultured microbes into animals reproduces the disease seen in humans. 4) The specific microbes can be re-isolated from lesions of the disease in animals.
What are the overall stages of infection?
Encounter, Entry, Spread, Multiplication, Damage, and Outcome
What are the important features of the Encounter and Entry stages of infection?
Encounter is how the agent meets the host. What is the route of infection? Endogenous or exogenous source? Through contact with humans, animals, food, water? Entry concerns how the agent enters the host. Actively, by invasion, or passively, by injection, bites, transfusions, etc? Colonization of body surfaces is frequently an important first step, mediated by adherence (pili or non-pilus).
What is the importance of the Damage stage of infection?
The damage stage is concerned with how the tissue is damaged by the agent or the immune response. Does the agent have specific virulence factors? Some microbes cause direct damage to the host, others contribute to host damage by interfering with host defense mechanisms. The microbe products that cause this damage are often used to develop vaccines.
What is the importance of the Outcome stage of infection?
The Outcome stage is concerned with whether the microbial agent or the host wins the battle, or whether they eventually coexist. What are the consequences of failure to eliminate the agent?
What is the primary immune defense and mechanism against agents that multiply within tissue cells?
Attachment of antibodies inhibit the microbes ability to enter a cell. The mechanism is production of antibodies IgG, A, and M. Further defense is to kill the infected cell (Antibody+complement, NK cells, cytotoxic cells)
What is the primary immune defense and mechanism against agents that multiply within phagocytes?
The primary defense is to activate the phagocytes and thus render them resistant to infection. This is achieved via T-cell lymphokines. Further defense is achieved through the killing of infected cells (Antibody+complement, NK cells, cytotoxic cells).
What is the primary immune defense and mechanism against agents that multiply outside of cells?
Kill the agents extracellularly via complement mediated lysis or intracellularly via opsonization and phagocytosis.. Additional immune defense may be achieved via neutralizing microbial toxins.
What is the primary immune defense and mechanism against agents that multiply outside cells and need to attach to body surfaces for invasion?
Prevent the attachment by coating microbial surface with specific antibody. This is achieved via Antibody production (Mainly IgA). Additionaly immune defense may be achieved via neutralizing microbial toxins.
What physiologically important roles does the micro biome perform?
1) Effects on tissue/organ differentiation. 2) Production of vitamins by gut flora. 3) Biochemical conversion (bilirubin degradation, drug metabolism, potential carcinogens). 4) Competition with pathogens for colonization of body surfaces/source of agents for endogenously acquired infections.
What is the pathogenic mechanism of cholera?
Toxin mediated disease
