USMLE Learning checks Exam Questions with
complete Answers 2024/2025
Shiguella - correct answer Inactivate 60S ribosome by
removing adenine from rRNA. enhances cytokine release causing
HUS
EHEC Shiga-like toxin - correct answer Inactivate 60S
ribosome by removing adenine from rRNA. enhances cytokine
release causing HUS
ETEC heat labile - correct answer over activates cAMP >
increase Cl secretion in gut and H2O efflux.
ETEC heat stable - correct answer overactivates cGMP >
decrease reabsorption of NaCl and H2O in gut.
B. anthracis - correct answer Edema factor. increase cAMP.
V. cholera - correct answer over activates cAMP by
permanently activating Gs > increase Cl secretion in gut and
H2O
B. pertusis - correct answer over activates cAMP by disabling
Gi impairing phagocytosis to permit survival of microbe.
C. tetani - correct answer tetanoplasmin. inhibitory (GABA and
Glycine) neurotransmiters from reshaw cells in spinal cord.
,C. Botulinum - correct answer Toxin prevents release of
stimulatory Ach signals at neuromuscular junctions > Flacid
paralysis, floppy baby.
C. perfringens - correct answer alpha toxin. phospholipase
(lecithinase) that degrades tissue cell membrane. degradation of
phospholipids > myonecrosis (gas Gangrene) and hemoptysis
(double zone of hemolysis on blood agar)
S. pyogenes - correct answer Streptolysin O (ASO). protein
that degrades cell membrane. Lyses RBC's contributes to B-
hemolysis; host antibodies against ASO used to dx rheumatic
fever.
S. aureus - correct answer Toxic shock syndrome toxin. Bring
MHC II and TCR in proximity to outside of antigen binding site to
fuse overwhelming release of INF-y and IL-2 leading to shock.
S. pyogenes - correct answer Exotoxin A leading to TSS
Toxic shock syndrome (S.aureus) - correct answer fever, rash,
shock, other toxins cause scalded skin syndrome (exfoliative
toxin) and food poisoning (enterotoxin)
Endotoxin - correct answer an LPS found in outer membrane
of gram (-)
Edema
Nitric oxide
, DIC/Death
Outer membrane
TNF-a
O-antigen
eXtremely heat stable
IL-1
Neutrophil chemotaxis
Phage conversion permitting exotoxin production - correct
answer genes of the 5 following bacterial toxins are encoded in
a lysogenic phage (ABCDE):
shigA-like toxin
Botulinum
Cholera
Diphteria
Erythrogenic toxin of S. pyogenes.
cribiform plate - correct answer CN I
Optic canal - correct answer CNII, ophtalmic artery, central
retinal artery
Superior orbital fissure - correct answer CN III,IV,V1,VI,
ophtalmic vein, sympathetic fibers.
Foramen rotundum - correct answer CN V2
complete Answers 2024/2025
Shiguella - correct answer Inactivate 60S ribosome by
removing adenine from rRNA. enhances cytokine release causing
HUS
EHEC Shiga-like toxin - correct answer Inactivate 60S
ribosome by removing adenine from rRNA. enhances cytokine
release causing HUS
ETEC heat labile - correct answer over activates cAMP >
increase Cl secretion in gut and H2O efflux.
ETEC heat stable - correct answer overactivates cGMP >
decrease reabsorption of NaCl and H2O in gut.
B. anthracis - correct answer Edema factor. increase cAMP.
V. cholera - correct answer over activates cAMP by
permanently activating Gs > increase Cl secretion in gut and
H2O
B. pertusis - correct answer over activates cAMP by disabling
Gi impairing phagocytosis to permit survival of microbe.
C. tetani - correct answer tetanoplasmin. inhibitory (GABA and
Glycine) neurotransmiters from reshaw cells in spinal cord.
,C. Botulinum - correct answer Toxin prevents release of
stimulatory Ach signals at neuromuscular junctions > Flacid
paralysis, floppy baby.
C. perfringens - correct answer alpha toxin. phospholipase
(lecithinase) that degrades tissue cell membrane. degradation of
phospholipids > myonecrosis (gas Gangrene) and hemoptysis
(double zone of hemolysis on blood agar)
S. pyogenes - correct answer Streptolysin O (ASO). protein
that degrades cell membrane. Lyses RBC's contributes to B-
hemolysis; host antibodies against ASO used to dx rheumatic
fever.
S. aureus - correct answer Toxic shock syndrome toxin. Bring
MHC II and TCR in proximity to outside of antigen binding site to
fuse overwhelming release of INF-y and IL-2 leading to shock.
S. pyogenes - correct answer Exotoxin A leading to TSS
Toxic shock syndrome (S.aureus) - correct answer fever, rash,
shock, other toxins cause scalded skin syndrome (exfoliative
toxin) and food poisoning (enterotoxin)
Endotoxin - correct answer an LPS found in outer membrane
of gram (-)
Edema
Nitric oxide
, DIC/Death
Outer membrane
TNF-a
O-antigen
eXtremely heat stable
IL-1
Neutrophil chemotaxis
Phage conversion permitting exotoxin production - correct
answer genes of the 5 following bacterial toxins are encoded in
a lysogenic phage (ABCDE):
shigA-like toxin
Botulinum
Cholera
Diphteria
Erythrogenic toxin of S. pyogenes.
cribiform plate - correct answer CN I
Optic canal - correct answer CNII, ophtalmic artery, central
retinal artery
Superior orbital fissure - correct answer CN III,IV,V1,VI,
ophtalmic vein, sympathetic fibers.
Foramen rotundum - correct answer CN V2
