Exam 5 Notes

Exam 5 Notes (4-29-22)

Part 1: Multiple Choice

Question 1: Staphylococcus aureus Portal of Entry

• Question: Which of these is a portal of entry for Staphylococcus aureus?
• Answer: e. All of these (Skin, Eye, GI tract, Respiratory tract)
• Explanation:
  • Staphylococcus aureus can enter through:
    • Skin (cuts)
    • Eyes (conjunctivitis)
    • GI tract (poisoned food)
    • Respiratory tract (pneumonia)

Question 2: Enteropathogenic E. coli Adhesion

• Question: Enteropathogenic E. coli bind to host epithelial cells using the protein:
• Answer: b. Intimin
• Explanation:
  • Intimin tightly adheres to epithelial cells.
  • Incorrect options:
    • Superoxide dismutase: Protects bacteria from oxidative damage, not an adhesin.
    • Chitin: Found in fungi/insect cell walls, irrelevant to E. coli adhesion.
    • Beta-galactosidase: Breaks down lactose (lac operon), unrelated to adhesion.
    • IL-2: Human cytokine, not a bacterial adhesion molecule.

Question 3: Capsule Virulence Factor

• Question: The capsule is an important virulence factor for:
• Answer: e. All of these (Bacillus anthracis, Klebsiella pneumoniae, Haemophilus influenzae, Streptococcus pneumoniae)
• Explanation:
  • Bacillus anthracis: Poly-D-glutamic acid capsule
  • Klebsiella pneumoniae: Thick polysaccharide capsule
  • Haemophilus influenzae: Polyribosylribitol phosphate capsule
  • Streptococcus pneumoniae: Polysaccharide capsule crucial for virulence

Question 4: Actin Polymerization

• Question: Which of these bacteria polymerize actin behind them to propel themselves through eukaryotic cells?
• Answer: c. Listeria monocytogenes
• Explanation:
  • Listeria monocytogenes hijacks the host cell's actin to form "actin tails," pushing itself through the cytoplasm and neighboring cells.
  • Incorrect options:
    • Plasmodium vivax: A protozoan parasite causing malaria and does not use actin polymerization like Listeria.
    • Bacillus anthracis: Causes anthrax, doesn't use actin to move.
    • Escherichia coli: Some strains invade cells but do not polymerize actin like Listeria.

Question 5: Opa Proteins and Immune Evasion

• Question: Which of these bacteria makes Opa proteins that can be variable and allow for immune evasion?
• Answer: c. Neisseria gonorrhea
• Explanation:
  • Neisseria gonorrhea uses opaque proteins (Opa) that can vary their expression to avoid the immune system, helping them persist in host tissues and cause gonorrhea.
  • Incorrect options:
    • Staphylococcus aureus: Immune evasion occurs through factors like protein A, not Opa proteins.
    • Listeria monocytogenes: Doesn't make Opa proteins; uses other virulence mechanisms.
    • Shigella flexneri: Causes dysentery but does not have Opa proteins.
    • Escherichia coli: Doesn't have Opa proteins.

Question 6: Superantigens

• Question: Which of the following are superantigens?
• Answer: c. TSST, SEA, Streptococcal pyrogenic exotoxin
• Explanation:
  • TSST-1 is toxic shock syndrome toxin.
  • SEA is staphylococcal enterotoxin A.
  • Streptococcal pyrogenic exotoxin. All are classified as superantigens

Question 7: Endocytosis

• Question: Which of these bacteria primarily invades by inducing endocytosis?
• Answer: c. Shigella
• Explanation:
  • Shigella tricks host epithelial cells into endocytosing it, allowing it to invade and replicate intracellularly.

Question 8: A-B Toxins

• Question: Which of the following contains an A-B structure?
• Answer: e. Cholera toxin
• Explanation:
  • The "A" component is the active part (enzymatic activity).
  • The "B" component is the binding part (binding to host cells).
  • Cholera toxin is the textbook example. Shiga toxins are phage encoded.

Question 9: Limulus amebocyte lysate (LAL) assay

• Question: Which of the following are not correct names for this assay?
• Answer: a. LPS from Gram-negative bacteria is the LAL assay- none of the options listed are correct names.

Question 10: Lysogeny

• Question: Which disease is lysogeny related?
• Answer: e. Cholera toxin is lysogeny related.

Question 11: Protein Synthesis Inhibition

• Question: Which of the following inhibits protein synthesis?
• Answer: c. Diphtheria toxin
• Explanation:
  • Diphtheria toxin inhibits protein synthesis by ADP ribosylating EF-2.
  • The toxin gene is carried on a bacteriophage.

Question 12: Response to Endotoxin

• Question: Which cytokine is released early in response to endotoxin?
• Answer: d. IL-1
• Explanation:
  • IL-1 is a major pro-inflammatory cytokine released early in response to endotoxin, especially LPS from Gram-negative bacteria.

Question 13: Treatment of Tuberculosis

• Question: Which is harder to treat?
• Answer: d. Tuberculosis
• Explanation:
  • Tuberculosis has a thick waxy cell wall, is intracellular, and requires long-term, multi-drug therapy.

Question 14: Mechanism of Antibiotic Resistance

• Question: What is target site modification?
• Answer: c. MRSA
• Explanation:
  • MRSA acquires the mecA gene, which encodes a modified penicillin-binding protein that does not bind beta-lactam antibiotics effectively. This is a classic example of resistance due to alteration of the drug's target site.

Question 15: Common Antibiotic Target

• Question: The most common antibiotic target?
• Answer: d. Ribosome
• Explanation:
  • The ribosome is the most common antibiotic target because many major antibiotic classes act by disrupting bacterial protein synthesis.

Question 16: Microbe Produced Antimicrobial Compounds

• Question: Which antimicrobial compounds are produced by microbes?
• Answer: e. All of these (Polymyxin B, Chloramphenicol, Tetracycline, Streptamycin)

Question 17: Drugs Targeting Nucleic Acid Synthesis

• Question: Which drug targets the synthesis of nucleic acids?
• Answer: d. Rifampin

Question 18: Systemic Fungal Infection

• Question: Example of a systemic fungal infection?
• Answer: e. Aspergillosis

Question 19: Target for Fungal Infections

• Question: What is a good target for fungal infections?
• Answer: c. Ergosterol

Question 20: Fungi Causing Infections in Mouth or Vagina

• Question: Which fungi can cause infections in the mouth or the vagina?
• Answer: d. Candida

Question 21: Blood Fluke

• Question: Which of these is a blood fluke?
• Answer: b. Schistosoma mansoni

Question 22: Nematodes Causing Disease

• Question: Which of these diseases is caused by nematodes?
• Answer: e. All of these (filariasis, ascariasis, elephantiasis, onchocerciasis)

Question 23: Virulence Factor of Cryptococcus

• Question: What is the primary virulence factor of Cryptococcus?
• Answer: d. Capsule

Question 24: Non-DNA Virus

• Question: Which of these is not a DNA virus?
• Answer: d. Poliovirus

Question 25: Antigenic Shift in Influenza Virus

• Question: The influenza virus can undergo antigenic shift because:
• Answer: c. It has a segmented genome

Question 26: Reactivation of Varicella Zoster

• Question: Latent Varicella zoster can reemerge to cause:
• Answer: d. Shingles

Question 27: Reason for Vaccination Term

• Question: The process of protecting people from future infections is called vaccination because:
• Answer: b. It is based on the use of Vaccinia virus to protect against smallpox.

Question 28 - 50:

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Additional Information Mentioned

• Reverse Transcriptase: Used somen sleeping sickness
• Beta-Lactamases: Type of antimicrobial resistance.
• Efflux Pumps: Type of antimicrobial resistance.
• Trypanosoma cruzi:
• Tapworm infection: Specially taenia solium. It removes its essential helper, leading to the worms death
• CCR5 and CXCR4 Used to Pneumocystis pneumonia
• Superantigens

Discovering New antibiotics

• Start by screening natural sources like soil bacteria or fungi.
• Test its minimum inhibitory concentration.
• Evaluate its toxicity to humans.
• Identify its mechanism of action.
• Test its effectiveness against both drug-sensitive and drug-resistant bacteria.
• Use animal models to study how the compound works in a living system.

Eradication target Example

• Measles should be the next disease targeted for eradication because:
  • It has no animal reservoir.
  • It is easy to diagnose.
  • Effective and affordable vaccine exists.
  • Eradication is achievable with high vaccination coverage.
  • Eliminating measles would prevent thousands of child deaths.