MCPHS Microbiology Self Paced
Which of these conditions would NOT affect the ability of Streptococcus mutans to attach to teeth? -
The absence of Actinomyces, a bacterium that can be part of dental plaque
cell wall components - 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)
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 - 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 - Strep. Pneumoniae, Hib, bacillus anthracis
,Enzymes - Coagulase: coagulates fibrinogen
Kinases: digest fibrin clots
hyaluronidase: hydrolyzes hyaluronic acid
Collagenase: hydrolyzes collagen
IgA proteases: destroys IgA antibodies
antigenic variation - Alteration of surface antigens to avoid detection by host antibodies
Examples: flu, gonorrhea, trypanosoma brucei gambiense
Invasins: Penetration into the host cell cytoskeleton - Salmonella alters host actin to enter a host
cell
Listeria uses actin to move from one cell to the next
Direct damage caused by - disrupting the host cells function
produces waste products
toxins
induce hypersensitive reactions
damage immediate vicinity
use hosts nutrients (iron) -siderophores
Siderophores - proteins that free host stores of iron
Toxin - substance that contributes to pathogenicity
Toxoid - inactivated toxin used in a vaccine
Antitoxin - antibodies against a specific toxin
, Endotoxins - 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 - 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 - 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 - A: Alters cell function by inhibiting protein synthesis
B: Binding compenent
examples: Corynebacterium diphtheria, clostridium botulinum, c. tetani, vibrio cholerae
membrane disrupting exotoxins - lyse host cells by disrupting plasma membranes/disrupt
phospholipid bilayer
Which of these conditions would NOT affect the ability of Streptococcus mutans to attach to teeth? -
The absence of Actinomyces, a bacterium that can be part of dental plaque
cell wall components - 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)
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 - 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 - Strep. Pneumoniae, Hib, bacillus anthracis
,Enzymes - Coagulase: coagulates fibrinogen
Kinases: digest fibrin clots
hyaluronidase: hydrolyzes hyaluronic acid
Collagenase: hydrolyzes collagen
IgA proteases: destroys IgA antibodies
antigenic variation - Alteration of surface antigens to avoid detection by host antibodies
Examples: flu, gonorrhea, trypanosoma brucei gambiense
Invasins: Penetration into the host cell cytoskeleton - Salmonella alters host actin to enter a host
cell
Listeria uses actin to move from one cell to the next
Direct damage caused by - disrupting the host cells function
produces waste products
toxins
induce hypersensitive reactions
damage immediate vicinity
use hosts nutrients (iron) -siderophores
Siderophores - proteins that free host stores of iron
Toxin - substance that contributes to pathogenicity
Toxoid - inactivated toxin used in a vaccine
Antitoxin - antibodies against a specific toxin
, Endotoxins - 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 - 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 - 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 - A: Alters cell function by inhibiting protein synthesis
B: Binding compenent
examples: Corynebacterium diphtheria, clostridium botulinum, c. tetani, vibrio cholerae
membrane disrupting exotoxins - lyse host cells by disrupting plasma membranes/disrupt
phospholipid bilayer
