the potency of the pathogen indicated by the ratio of the number of cases of disease in a population compared with the number of people exposed to the microorganism.
proportion of exposures needed to cause infection in an individual based on the pathogen's ability to enter, survive in, and multiply in the host.
the ability of the pathogen to produce harmful toxins that increase host cell and tissue damage.
the level to which a pathogen is viewed by the host immune system as foreign.
Antigenic variability is:
a process of eluding the human host defenses and is often a result of altering the antigens present within or on the surface of the microorganism.
Pathogenic defense mechanisms are:
the ways in which many pathogens have developed ways in which many pathogens have developed ways to avoid destruction by the host, such as through thick protective capsules, which prevent phagocytosis.
Coinfection is a:
phenomenon of hosting two or more pathogens simultaneously.
when an infection arises in addition to on that is already present.
Four types of pathogens:
bacteria, fungi, viruses, and protozoa
require the host for metabolism and reproduction
may live on the host but can also survive independently
single celled microorganisms that can reproduce outside of host cells.
The innermost cell membrane, also called the cell envelope, has 3 functions:
1. Formation of a barrier surrounding the bacterial cell 2. Protein and DNA synthesis 3. Cell division
Most bacteria include a ___________cell wall that surrounds an _________membrane.
Humans do not have a cell _________; therefore, antibiotics are aimed at ___________________________
wall: inhibiting synthesis of the bacterial cell wall during bacterial replication.
Name four structural properties critical to the pathogenicity of bacteria:
1. Independent survival: they can survive outside the host and can infect and reinfect. 2. Stimulation of an inflammatory response: Bacteria can stimulate an inflammatory and immune response that will destroy surrounding host tissues. 3. Bacterial capsule: Encapsulated bacteria are adherent and highly resistant to phagocytosis. 4. Endotoxin: the presence of endotoxin in the gram negative bacterial cell envelope activates the plasma protein systems.
What is an endotoxin?
a complex of phospholipid-polysaccharide molecules that form from the structural component of the gram-negative cell wall.
pyogenic bacteria are:
bacteria that can induce fever.
Bacteria that produce spores that survive in a latent state that is resistant to environmental extremes and lack of nutrients.
toxin produced by bacteria which causes cell dysfunction or lysis.
obligate intracellular parasites. They cannont replicate outside of the host cell
How do viruses work?
1. They bind specific receptors on the host cell and then move into the host cell. 2. Once inside the host cell, the virus converts the host cellular metabolism to nucleic acids and proteins that are encoded and controlled by the virus. 3. They either directly kill the cell or modify cellular functions. 4. Cells then proliferate rapidly and randomly. 5. Cell ultimately loses its ability to function. 6. Virus then releases particles outside the cell which enter and infect nearby cells.
released particles by a virus outside of the cell to infect nearby cells.
Factors that support chronic infection with a virus include:
1. the size of the virus that is inoculated into the body 2. The process of viral replication 3. the viral genotype 4. Host susceptibility