ch 19
No description yet. This curated deck is ready for daily study.
Card preview (23)
two endospore-forming genera of medical importance and difference in oxygen requirement
Bacillus= aerobic (can grow in oxygen) Clostridium= anaerobic (do not need oxygen)
What are the two main types of virulence factors involved in Bacillus anthracis pathogenesis?
Capsule (antiphagocytic) Anthrax toxin
How do humans contract anthrax?
Contact with spores from soil, infected animals, animal products Inhalation, skin entry, or ingestion
hat are the three types of anthrax diseases in humans? Which one is the most lethal?
Cutaneous Pulmonary Gastrointestinal Pulmonary is most lethal
What is eschar associated with?
black necrotic sore associated with cutaneous anthrax
gas gangrene and food poisoning: how do they usually occur?
Occurs when spores enter damaged tissue under anaerobic conditions. Bacteria ferment muscle → gas production + tissue destruction Ingestion of food contaminated with spores → enterotoxin → diarrhea
what are the predisposing factors for gas gangrene? Why does hyperbaric treatment help treat and prevent cases of gas gangrene?
predisposing factors: Surgical wounds, crush injuries, diabetic ulcers, puncture wounds, gunshot wounds, devitalized tissue Oxygen inhibits anaerobic growth and reduces toxin production and tissue damage
the role of superinfection in pseudomembranous colitis
Cause (superinfection) Broad-spectrum antibiotics kill normal flora → dysbiosis C. diff overgrows and releases toxins A and B
what is the main route of transmission for C.diff
fecal–oral route Nosocomial transmission
what are the treatments for C.diff?
🟢 Mild, uncomplicated infection: Stop the offending antibiotic (if possible) Fluid and electrolyte replacement→ to manage diarrhea and dehydration 🔴 Severe infection: Oral vancomycin or metronidazole
Why would replacement culture and fecal microbiota transplant help to recover for recurrent cases of C. diff?
restore normal gut microbiota
Clostridium tetani vs. Clostridium botulinum Entry & infection
Tetanus: Spores enter through puncture wounds, burns, umbilical stump Botulism: Foodborne (improper canning), infant ingestion of spores, wound infection
Compare the actions of the two neurotoxins: Why does C. tetani cause lockjaw while C. botulinum causes muscle paralysis?
Tetanus toxin (tetanospasmin) Blocks inhibitory neurons → uncontrolled muscle contraction -Causes lockjaw and spasms Botulinum toxin Blocks acetylcholine release → flaccid paralysis
Why can botulin be used in cosmetic wrinkle-removal procedures?
Controlled paralysis of facial muscles reduces wrinkles
What kind of disease is diphtheria?
toxin-mediated respiratory disease
What is the major virulence factor for this diphtheria?
diphtheria toxin
at does it mean that the diphtheria toxin is an AB toxin?
B subunit: binds host cell receptor A subunit: shuts down 80S ribosomes, kills cells
vaccine for diphtheria?
diphtheria toxoid (DTaP)
How are mycolic acid and other cell wall lipids involved in Mycobacterium tuberculosis pathogenesis?
-Waxy cell wall with mycolic acid -Prevents destruction in macrophages -Induces hypersensitivity and inflammation -No exotoxins → damage is immune-mediated
What is a tubercle (granuloma)?
-Cluster of immune cells surrounding Mtb -Walls off infection; may calcify or become latent
How is TB diagnosed? If a TB skin test turns positive, does it always mean the person has (had) a TB infection?
-Mantoux (PPD) skin test Chest X-ray -Acid-fast stain and culture Positive skin test ≠ active disease -Can reflect past infection or BCG vaccination
What are MDRTB and XDRTB?
mdrtb: resistant to at least 1 main TB drugs XDRTB: resistant to nearly all TB drugs
why is the DOT program necessary in TB drug treatment?
-Ensures patient takes medication -Prevents resistance development