Ch. 24 Microbial Diseases of the Respiratory System

Question 1

What are the parts of the upper and lower respiratory system?

Answer 1

• The upper respiratory system
  
  • Nose
  • Pharynx (throat)
  • Larynx
  • Middle ear
  • Eustachian tubes
• The lower respiratory system
  
  • Trachea
  • • Bronchial tubes
  • Alveoli
  • Pleura

Question 2

What organism causes strep throat and scarlet fever?

Answer 2

• Streptococcal Pharyngitis – Strep Throat – caused by Streptococcus pyogenes
• Scarlet fever is caused by Streptococcus pyogenes

Question 3

3. What does it mean when a lysogenic bacteria produces a toxin?

Answer 3

• Lysogenic bacteria produce erythrogenic toxin
• A bacterial exotoxin from certain strains of Streptococcus pyogenes that produces an erythromatous reaction when injected intradermally and is responsible for the rash in scarlet fever

Question 4

4. What are the characteristics of diphtheria?

Answer 4

• caused by Corynebacterium diphtheria, a Gram-positive rod
• Forms a tough grayish membrane in the throat
• made of Fibrin and dead tissue
• Blocks passage of air to the lungs
• Exotoxin produced by lysogenized bacteria
• Circulates in the blood; damages the heart and kidneys
• Cutaneous diphtheria – infected skin wound leads to slow healing ulcer
• Prevented by DTaP vaccine - Diphtheria toxoid

Question 5

5. What is the causative agent of tuberculosis?

Answer 5

• caused by Mycobacterium tuberculosis (Acid-fast rod; obligate aerobe)
• Other causes
  
  • Mycobacterium bovis
    
    • Bovine tuberculosis; < 1% of U.S. cases
  • Mycobacterium avium-intracellulare complex
    
    • Infects people with late-stage HIV infection

Question 6

6. What is the causative agent of melioidosis and where is it endemic?

Answer 6

• Meliodosis is caused by Burkholderia pseudomallei – gram-negative rod
• Occurs mostly in Southeast Asia and northern Australia (in moist soils)
• Commonly affects those with lowered immune systems
• Transmission by inhalation, puncture wounds, and ingestion

Question 7

7. What are the characteristics of the spikes on the envelope of the influenza virus?

Answer 7

• Hemagglutinin (HA) spikes used for attachment to host cells
• Neuraminidase (NA) spikes used to release virus from cell

Question 8

8. What is the difference between antigenic shift and antigenic drift with regard to influenza?

Answer 8

• Antigenic drift
  
  • Changes in HA and NA spikes
  • Probably due to genetic recombination between different strains infecting the same cell
  • Allow the virus to elude some host immunity
• Antigenic shift
  
  • Point mutations in genes encoding HA or NA spikes
  • May involve only 1 amino acid
  • Allows virus to avoid mucosal IgA antibodies
  • Changes great enough to evade most immunity
  • Leads to pandemics
  • Involve the reassortment of the eight RNS segments

Question 9

9. What are the four fungal diseases of the lower respiratory system listed in the table from lecture and their symptoms?

Answer 9

• Histoplasmosis – resembles tuberculosis
• Coccidiomycosis – fever, coughing, weight loss
• Pneumocystis pneumonia – pneumonia
• Blastomycosis – abscesses, extensive tissue damage