M250 EXAM 4 2026 COMPREHENSIVE
STUDY GUIDE Q&A REVIEW GRADED A+
⩥ Bacillus: What are the two main types of virulence factors involved in
Bacillus anthracis pathogenesis?
Answer: The two major virulence factors are the polypeptide capsule,
which prevents phagocytosis, and exotoxins (protective antigen, edema
factor, and lethal factor).
⩥ How do humans contract anthrax? What are the three types of anthrax
diseases in humans? Which one is the most lethal? What is eschar
associated with?
Answer: Humans contract anthrax through spores via skin contact,
inhalation, or ingestion. The three forms are cutaneous, inhalation, and
gastrointestinal anthrax. Inhalation anthrax is the most lethal. An eschar
(black necrotic lesion) is associated with cutaneous anthrax.
⩥ Clostridium perfringens - gas gangrene and food poisoning: how do
they usually occur? What are the predisposing factors for gas gangrene?
Why does hyperbaric treatment help treat and prevent cases of gas
gangrene?
Answer: Gas gangrene occurs when spores enter deep, anaerobic
wounds. Predisposing factors include trauma, surgery, and poor
circulation. Hyperbaric oxygen inhibits anaerobic growth and toxin
production.
, ⩥ C. diff: The role of superinfection in pseudomembranous colitis -
what is the cause and main route of transmission (i.e. food poisoning?
zoonotic? nosocomial? respiratory? bloodborne? etc.) What are the
treatments? Why would replacement culture and fecal microbiota
transplant help to recover for recurrent cases of C. diff?
Answer: C. difficile causes pseudomembranous colitis after
antibiotic‑induced superinfection. Transmission is nosocomial via
fecal‑oral route. Treatments include vancomycin or fidaxomicin. Fecal
microbiota transplant restores normal flora displaced by antibiotics.
⩥ Clostridium tetani and Clostridium botulinum: Compare how these
pathogens enter the human body and cause infections (i.e. how do
humans usually contract tetanus and botulism?)
Answer: Tetanus is contracted via spores entering wounds. Botulism is
contracted by ingestion of toxin in contaminated food, infant
colonization, or wound infection.
⩥ Compare the actions of the two neurotoxins: Why does C. tetani cause
lockjaw while C. botulinum causes muscle paralysis? Why can botulin
be used in cosmetic wrinkle-removal procedures?
Answer: C. tetani toxin blocks inhibitory neurotransmitters causing
spastic paralysis (lockjaw). C. botulinum toxin blocks acetylcholine
causing flaccid paralysis. Botulin toxin is used cosmetically to relax
muscles.
STUDY GUIDE Q&A REVIEW GRADED A+
⩥ Bacillus: What are the two main types of virulence factors involved in
Bacillus anthracis pathogenesis?
Answer: The two major virulence factors are the polypeptide capsule,
which prevents phagocytosis, and exotoxins (protective antigen, edema
factor, and lethal factor).
⩥ How do humans contract anthrax? What are the three types of anthrax
diseases in humans? Which one is the most lethal? What is eschar
associated with?
Answer: Humans contract anthrax through spores via skin contact,
inhalation, or ingestion. The three forms are cutaneous, inhalation, and
gastrointestinal anthrax. Inhalation anthrax is the most lethal. An eschar
(black necrotic lesion) is associated with cutaneous anthrax.
⩥ Clostridium perfringens - gas gangrene and food poisoning: how do
they usually occur? What are the predisposing factors for gas gangrene?
Why does hyperbaric treatment help treat and prevent cases of gas
gangrene?
Answer: Gas gangrene occurs when spores enter deep, anaerobic
wounds. Predisposing factors include trauma, surgery, and poor
circulation. Hyperbaric oxygen inhibits anaerobic growth and toxin
production.
, ⩥ C. diff: The role of superinfection in pseudomembranous colitis -
what is the cause and main route of transmission (i.e. food poisoning?
zoonotic? nosocomial? respiratory? bloodborne? etc.) What are the
treatments? Why would replacement culture and fecal microbiota
transplant help to recover for recurrent cases of C. diff?
Answer: C. difficile causes pseudomembranous colitis after
antibiotic‑induced superinfection. Transmission is nosocomial via
fecal‑oral route. Treatments include vancomycin or fidaxomicin. Fecal
microbiota transplant restores normal flora displaced by antibiotics.
⩥ Clostridium tetani and Clostridium botulinum: Compare how these
pathogens enter the human body and cause infections (i.e. how do
humans usually contract tetanus and botulism?)
Answer: Tetanus is contracted via spores entering wounds. Botulism is
contracted by ingestion of toxin in contaminated food, infant
colonization, or wound infection.
⩥ Compare the actions of the two neurotoxins: Why does C. tetani cause
lockjaw while C. botulinum causes muscle paralysis? Why can botulin
be used in cosmetic wrinkle-removal procedures?
Answer: C. tetani toxin blocks inhibitory neurotransmitters causing
spastic paralysis (lockjaw). C. botulinum toxin blocks acetylcholine
causing flaccid paralysis. Botulin toxin is used cosmetically to relax
muscles.
