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MCPHS Microbiology Exam II :-Questions & Solutions
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MCPHS Microbiology Exam II :-Questions & Solutions
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MCPHS Microbiology Exam II :-Questions & SolutionsPathogenicity Right Ans - The ability to cause disease
Virulence Right Ans - the extent of pathogenicity
Portals of entry Right Ans - mucous membranes, skin, parenteral route
ID50 (infectious dose) Right Ans - The number of microbes that must enter
the body to establish infection in 50% of test animals is expressed as the ID50
LD50 Right Ans - lethal dose (of a toxin) for 50% of the test population
Adherence Right Ans - Adhesions / ligands bind to receptors on host cells,
form biofims
Glycocalyx: streptococcus mutans
Fimbriae: E.coli
M proteins: Strepoccus pyogenes
Pili, flagella, glycoproteins, lipoproteins
Capsules - resist phagocytosis Right Ans - Strep. Pneumoniae, Hib, bacillus
anthracis
cell wall components Right Ans - M proteins: mediates attachment and
resists phagocytosis (strep. pyogenes)
Opa protein: assist attachment and recept mediated endocytosis, inhibs helper
t cells (n. gonorrhoeae)
Mycolic acid: Waxy, resists digestion (mycobacterium TB)
Enzymes Right Ans - Coagulase: coagulates fibrinogen
Kinases: digest fibrin clots
hyaluronidase: hydrolyzes hyaluronic acid
Collagenase: hydrolyzes collagen
IgA proteases: destroys IgA antibodies
antigenic variation Right Ans - Alteration of surface antigens to avoid
detection by host antibodies
Examples: flu, gonorrhea, trypanosoma brucei gambiense
,Invasins: Penetration into the host cell cytoskeleton Right Ans - Salmonella
alters host actin to enter a host cell
Listeria uses actin to move from one cell to the next
Direct damage caused by Right Ans - disrupting the host cells function
produces waste products
toxins
induce hypersensitive reactions
damage immediate vicinity
use hosts nutrients (iron) -siderophores
Siderophores Right Ans - proteins that free host stores of iron
Toxin Right Ans - substance that contributes to pathogenicity
Toxoid Right Ans - inactivated toxin used in a vaccine
Antitoxin Right Ans - antibodies against a specific toxin
Endotoxins Right Ans - 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 Right Ans - 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 Right Ans - 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 Right Ans - A: Alters cell function by inhibiting protein
synthesis
B: Binding compenent
examples: Corynebacterium diphtheria, clostridium botulinum, c. tetani,
vibrio cholerae
membrane disrupting exotoxins Right Ans - lyse host cells by disrupting
plasma membranes/disrupt phospholipid bilayer
Leukocidins: kill phagocytic leukocytes
Hemolysins: destroy RBCs
-Streptolysins
example: strep. pyogenes
Superantigens Right Ans - 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
Stimulate T cells
LAL Assay - limulus amebocyte lysate assay Right Ans - detects endotoxins
(horseshoe crabs white blood cells) will produce a clot
Commensalism Right Ans - one organism benefits and the other is
unaffected
Etiology Right Ans - study of the cause of disease
Pathogenesis Right Ans - development of disease
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