MCPHS Microbiology Self Paced
Pathogenicity - answerThe ability to cause disease
Virulence - answerthe extent of pathogenicity
Portals of entry - answermucous membranes, skin, parenteral route
ID50 (infectious dose) - answerThe number of microbes that must enter the body to establish
infection...
Pathogenicity - answer✔✔The ability to cause disease
Virulence - answer✔✔the extent of pathogenicity
Portals of entry - answer✔✔mucous membranes, skin, parenteral route
ID50 (infectious dose) - answer✔✔The number of microbes that must enter the body to establish
infection in 50% of test animals is expressed as the ID50
LD50 - answer✔✔lethal dose (of a toxin) for 50% of the test population
Adherence - answer✔✔Adhesions / ligands bind to receptors on host cells, form biofims
Glycocalyx: streptococcus mutans
Fimbriae: E.coli
M proteins: Strepoccus pyogenes
Pili, flagella, glycoproteins, lipoproteins
antigenic variation - answer✔✔Alteration of surface antigens to avoid detection by host
antibodies
Examples: flu, gonorrhea, trypanosoma brucei gambiense
Invasins: Penetration into the host cell cytoskeleton - answer✔✔Salmonella alters host actin to
enter a host cell
Listeria uses actin to move from one cell to the next
Direct damage caused by - answer✔✔disrupting the host cells function
produces waste products
toxins
induce hypersensitive reactions
damage immediate vicinity
use hosts nutrients (iron) -siderophores
Siderophores - answer✔✔proteins that free host stores of iron
Toxin - answer✔✔substance that contributes to pathogenicity
Toxoid - answer✔✔inactivated toxin used in a vaccine
Antitoxin - answer✔✔antibodies against a specific toxin
Endotoxins - answer✔✔the lipid portions of lipopolysaccharides (LPS) that are part of the outer
membrane of the cell wall of gram-negative bacteria. The endotoxins are liberated when the
bacteria die and the cell wall breaks apart.
PART OF BACTERIAL CELL NOT A PRODUCT
Lipid NOT proteins
all produce same SS
Exotoxins - answer✔✔specific for a structure or function in host cell
Can be gram pos or neg
Are proteins, enzymes
secreted into medium during log phase
most lethal
produce SS
Classification of exotoxins - answer✔✔1. Based on host cell attacked (cardiotoxin)
2. Disease they are associated with: tetanus
3. Bacterium that produces it: botulinum
4. Structure/function: A-B, Membrane-disrupting, superantigens
A-B exotoxin - answer✔✔A: Alters cell function by inhibiting protein synthesis
B: Binding compenent
examples: Corynebacterium diphtheria, clostridium botulinum, c. tetani, vibrio cholerae
Superantigens - answer✔✔cause an intense immune response due to release of cytokines from
host cells
Symptoms: fever, nausea, vomiting, diarrhea, shock, death
Example: Staph. aureus
Combine with macrophages
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