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MCPHS Microbiology Self Paced Exam Questions And Answers
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MCPHS Microbiology Self Paced ExamQuestions And Answers
Pathogenicity - The ability to cause disease
Virulence - the extent of pathogenicity
Portals of entry - Mucous membranes, skin, parenteral route
ID50 (infectious dose) - The number of microbes that must enter the body to establish
infection in 50% of test animals is expressed as the ID50
LD50 - lethal dose of a toxin for 50% of the test population
Adherence-Answer Adhesins / ligands bind to host cell receptors, form biofilms
Glycocalyx: streptococcus mutans
Fimbriae: E.coli
M proteins: Strepoccus pyogenes
Pili, flagella, glycoproteins, lipoproteins
Capsules- avoid phagocytosis- Answer Strep. Pneumoniae, Hib, bacillus anthracis
cell wall components-Answer 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)
,Exoenzymes - Answer Coagulase: coagulates fibrinogen
Kinases: digest fibrin clots
hyaluronidase: hydrolyzes hyaluronic acid
Collagenase: hydrolyzes collagen
IgA proteases: destroys IgA antibodies
antigenic variation - Answer Change 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 disrupts the host cells function
produces waste products
toxins
induces hypersensitive reactions
damages 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
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