MCPHS MICROBIOLOGY SELF PACED EXAM II;
QUESTIONS AND ANSWERS
Pathogenicity Correct Answer-The ability to cause disease
Virulence Correct Answer-the extent of pathogenicity
Portals of entry Correct Answer-mucous membranes, skin, parenteral route
ID50 (infectious dose) Correct Answer-The number of microbes that must
enter the body to establish infection in 50% of test animals is expressed as the
ID50
LD50 Correct Answer-lethal dose (of a toxin) for 50% of the test population
Adherence Correct 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 Correct Answer-Alteration of surface antigens to avoid
detection by host antibodies
Examples: flu, gonorrhea, trypanosoma brucei gambiense
Invasins: Penetration into the host cell cytoskeleton Correct 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 Correct Answer-disrupting the host cells function
produces waste products
toxins
induce hypersensitive reactions
damage immediate vicinity
use hosts nutrients (iron) -siderophores
, MCPHS MICROBIOLOGY SELF PACED EXAM II;
QUESTIONS AND ANSWERS
Siderophores Correct Answer-proteins that free host stores of iron
Toxin Correct Answer-substance that contributes to pathogenicity
Toxoid Correct Answer-inactivated toxin used in a vaccine
Antitoxin Correct Answer-antibodies against a specific toxin
Endotoxins Correct 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 Correct 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
, MCPHS MICROBIOLOGY SELF PACED EXAM II;
QUESTIONS AND ANSWERS
most lethal
produce SS
Classification of exotoxins Correct 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 Correct Answer-A: Alters cell function by inhibiting protein
synthesis
B: Binding compenent
examples: Corynebacterium diphtheria, clostridium botulinum, c. tetani, vibrio
cholerae
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