MDSC 515 COMPREHENSIVE EXAM 2025/2026
QUESTIONS AND SOLUTIONS GRADED A+ TIP
✔✔bacterial factors promoting survival in the environment - ✔✔-cell wall components
-capsule - extra protector
-biofilms
-ability to form spores
-factors promoting survival and transmission from vectors and intermediate hosts
✔✔types of bacteria transmission - ✔✔-airborne
-droplet
-fecal-oral
-direct contact
-sexual
-blood-borne
-inanimate objects
-vector
✔✔bacterial adhesion - ✔✔-adhesion on bacterial cell surface and receptor is on the
mucous cell surface
-pili/fimbriae
-teichoic/lipoteichoic acids
-glycocalyx
✔✔bacteria adhesion and invasion - ✔✔-recognition of host receptor - adhesion
-evade host immunity and acquire essential nutrients - growth
-dissemination/invasion
-transmission to another host - shedding
✔✔bacterial sites of adhesion and invasion - ✔✔-skin
-GI tract
-urogenital tract
-respiratory tract
-conjunctiva
-iatrogenic (medical - surgery, catheter, etc)
✔✔bacteria Invasiveness - ✔✔-ability of microbe to invade tissues
-produce invasins - proteins/enzymes, damage local cells, break through the host
barriers
-evade host defences - avoid contact with immune cells, avoid killing by the immune
cells and kill the immune cells
✔✔how bacteria avoid recognition by the immune system - ✔✔-infect regions not
accessible by the immune system (lumen of glands)
, -capsules and biofilms (cover the cell wall components that the immune system may
recognize)
-destroy host immune factors (complement)
-inhibit the destruction of the bacteria by inhibiting phagocytosis or other immune
signalling processes
-minimize the inflammatory response - cytokine activation or inhibition
✔✔capsules - ✔✔-consist of polysaccharide, polypeptide and 98% water
-protects the bacteria from phagocytosis and/or complement activity
✔✔biofilms - ✔✔-polymer matrix (mostly polysaccharides but some protein and nucleic
acid)
-support complex microbial communities
-stick to surfaces in the environment and in the host
-protects the bacteria from the immune system and antibiotics
-often associated with chronic infections
✔✔exotoxin - ✔✔-bacteria will shoot it out or inject it into the cell
-proteins resemble enzymes
-secreted - into cells or extracellular matrix
-released
-can act at removed site
-denatured by heat/enzymes
-high biological activity
-specific actions
-cytotoxic activity
-antigenic (antitoxin)
✔✔endotoxin - ✔✔eg. lipopolysaccharide (LPS)
-part of cell wall
-released
-systemic effect - pro-inflammatory
-other gram-positive cell wall components such as peptidoglycan and lipoteichoic acid
have similar effects
✔✔endotoxins as pathogen associated molecular patterns (PAMPs) - ✔✔-pathogenic
molecules detected by the innate immune system
-in bacteria they are components of cell wall
-influences the type of immune response to pathogen
-critical to the detection of pathogens (innate immunity)
-role in adaptive immunity - memory
-can also induce damaging inflammatory responses (septic shock)
✔✔Lipid A - ✔✔-main component of LPS that triggers an inflammatory response
-released from the cell in soluble form
-binds to soluble membrane-bound CD14 receptors
QUESTIONS AND SOLUTIONS GRADED A+ TIP
✔✔bacterial factors promoting survival in the environment - ✔✔-cell wall components
-capsule - extra protector
-biofilms
-ability to form spores
-factors promoting survival and transmission from vectors and intermediate hosts
✔✔types of bacteria transmission - ✔✔-airborne
-droplet
-fecal-oral
-direct contact
-sexual
-blood-borne
-inanimate objects
-vector
✔✔bacterial adhesion - ✔✔-adhesion on bacterial cell surface and receptor is on the
mucous cell surface
-pili/fimbriae
-teichoic/lipoteichoic acids
-glycocalyx
✔✔bacteria adhesion and invasion - ✔✔-recognition of host receptor - adhesion
-evade host immunity and acquire essential nutrients - growth
-dissemination/invasion
-transmission to another host - shedding
✔✔bacterial sites of adhesion and invasion - ✔✔-skin
-GI tract
-urogenital tract
-respiratory tract
-conjunctiva
-iatrogenic (medical - surgery, catheter, etc)
✔✔bacteria Invasiveness - ✔✔-ability of microbe to invade tissues
-produce invasins - proteins/enzymes, damage local cells, break through the host
barriers
-evade host defences - avoid contact with immune cells, avoid killing by the immune
cells and kill the immune cells
✔✔how bacteria avoid recognition by the immune system - ✔✔-infect regions not
accessible by the immune system (lumen of glands)
, -capsules and biofilms (cover the cell wall components that the immune system may
recognize)
-destroy host immune factors (complement)
-inhibit the destruction of the bacteria by inhibiting phagocytosis or other immune
signalling processes
-minimize the inflammatory response - cytokine activation or inhibition
✔✔capsules - ✔✔-consist of polysaccharide, polypeptide and 98% water
-protects the bacteria from phagocytosis and/or complement activity
✔✔biofilms - ✔✔-polymer matrix (mostly polysaccharides but some protein and nucleic
acid)
-support complex microbial communities
-stick to surfaces in the environment and in the host
-protects the bacteria from the immune system and antibiotics
-often associated with chronic infections
✔✔exotoxin - ✔✔-bacteria will shoot it out or inject it into the cell
-proteins resemble enzymes
-secreted - into cells or extracellular matrix
-released
-can act at removed site
-denatured by heat/enzymes
-high biological activity
-specific actions
-cytotoxic activity
-antigenic (antitoxin)
✔✔endotoxin - ✔✔eg. lipopolysaccharide (LPS)
-part of cell wall
-released
-systemic effect - pro-inflammatory
-other gram-positive cell wall components such as peptidoglycan and lipoteichoic acid
have similar effects
✔✔endotoxins as pathogen associated molecular patterns (PAMPs) - ✔✔-pathogenic
molecules detected by the innate immune system
-in bacteria they are components of cell wall
-influences the type of immune response to pathogen
-critical to the detection of pathogens (innate immunity)
-role in adaptive immunity - memory
-can also induce damaging inflammatory responses (septic shock)
✔✔Lipid A - ✔✔-main component of LPS that triggers an inflammatory response
-released from the cell in soluble form
-binds to soluble membrane-bound CD14 receptors
