Bacteria US Medical PG Flashcards - Medical Study Cards
Master Bacteria with OnCourse flashcards. These spaced repetition flashcards are designed for medical students preparing for NEET PG, USMLE Step 1, USMLE Step 2, MBBS exams, and other medical licensing examinations.
Bacteria Flashcard Deck - 10 Cards
Flashcard 91: Compare the antigenicity of exotoxins and endotoxins.
Answer: exo - high antigen response
endo - low antigen response
Flashcard 92: What are the major mechanisms of action of bacterial exotoxins?
Answer: 1. Protein synthesis inhibition (e.g., Diphtheria, Pseudomonas)\n2. Increase fluid secretion/Cyclic nucleotide modulation (e.g., Cholera, ETEC)\n3. Inhibition of neurotransmitter release (e.g., Tetanus, Botulinum)\n4. Cell membrane disruption (e.g., C. perfringens alpha toxin, S. aureus PVL)\n5. Superantigens (e.g., S. aureus TSST-1, S. pyogenes Exotoxin A)
Extra: Bacterial exotoxins are secreted proteins that can be categorized by their mechanism: \n- A-B toxins (Active-Binding structure)\n- Cytolysins (membrane-damaging)\n- Superantigens (nonspecific T-cell activation)
Flashcard 93: What are the key characteristics and clinical effects of bacterial **Exotoxins**?
Answer: - **Source:** Certain Gram-positive and Gram-negative bacteria.
- **Secreted from cell:** Yes.
- **Chemistry:** Polypeptide.
- **Location of genes:** Plasmid or bacteriophage.
- **Toxicity:** High (fatal dose is very low).
- **Clinical effects:** Various (e.g., paralysis in botulism, diarrhea in cholera).
- **Mode of action:** Various (e.g., Protein synthesis inhibition, increased cAMP, superantigen).
- **Antigenicity:** High (induces high-titer antibodies called antitoxins).
- **Vaccines:** Toxoids used as vaccines.
- **Heat stability:** Destroyed rapidly at 60°C (except Staphylococcal enterotoxin).
Extra: Endotoxin (LPS), by contrast, is found only in Gram-negative bacteria, is poorly antigenic, heat stable, and usually causes fever and shock through TNF/IL-1 induction.
Flashcard 94: Compare the toxicity of exotoxins and endotoxins.
Answer: exo - higher toxicity
endo - lower toxicity
Flashcard 95: Where do the genes for bacterial endotoxins reside?
Answer: bacterial chromosome
Flashcard 96: How can Treponema be visualized microscopically?
Answer: Dark-field microscopy or Direct Fluorescent Antibody (DFA) staining.
Flashcard 97: spore
Answer: resistance to dehydration, heat, chemicals
Extra: keratin, dipicolinic acid, peptidoglycan
Flashcard 98: What is the primary function and protein component of bacterial **flagella**?
Answer: Motility; composed of **flagellin** protein.
Extra: Bacterial flagella are highly antigenic and represent the **H antigen** (used for serotyping, e.g., *E. coli* O157:H7).
Flashcard 99: pilus/fimbria
Answer: mediate adherence to host cells, formation of sex pilus
Extra: glycoprotein
Flashcard 100: capsule
Answer: protects against phagocytosis
Extra: polysaccharide
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