Flashcards in MIP: Introduction to Microbiology and Infectious Disease Deck (14):
What are Koch's Postulates? What are their limitations?
1) The microbe must be associated with lesions of the disease and not found in the healthy (Some pathogens can be found in healthy individuals) 2) Microbe must be isolated from the lesions of the disease and grown in pure culture (not all bacteria can be grown in a petri dish) 3) A pure culture should cause disease if inoculated into a susceptible host (suitable animal models not always available; not all infected will develop disease) 4) Microbe must be re-isolated 5) Effective chemotherapy should eradicate the microbe and cure disease (doesn't address molecular mimicry)
What is the current 'definition' of infection?
Acquisition of a microbe with several possible outcomes
What is a pathogen?
A microbe capable of causing host damage, often through elaboration of virulence factors
What is a commensal?
A microbe that induces either no damage or clinically unapparent damage after primary infection
In which condition is S. mutans pathogenic and what are the outcomes?
With high sucrose content, S. mutans can turn sucrose into acids and cause cavities
True or False: Small bronchi and alveoli are normally sterile?
What is virulence?
The relative capacity of a microbe to cause damage
True or False: Virulence is solely a microbial trait
What makes a microbe virulent?
Capacity to overcome host defenses, severity of disease, LD50, invasiveness of microbe in host, infectivity or damage induced in host, capacity to grow and multiply in host
What is a virulence factor?
A microbial characteristic that allows a microorganism to cause disease
What are the 5 classes of virulence factors and the function of each?
Adhesins- mediate adhesion of microbe to host; invasins- promote the uptake of bacteria into cells that are not normally phagocytic; Impedins- prevent normal functioning of the host immune response without damaging host; aggresins- directly damage host tissue or actively promote spread of a pathogen; modulins- affect host immune response often to the detriment of the host
What class of virulence factor are exotoxins?
What class of virulence factor are super-antigens?