Exam 4: Topic 20

Question 1

Describe the mechanical or cellular defenses of the respiratory system. Include the following concepts: nasal eddies, mucociliary escalator, and alveolar macrophages

Answer 1

• Nasal eddies: swirls incoming air
• Mucociliary escalator: bring mucus and microbes from trachea and bronchi into pharynx.
• Alveolar macrophages: phagocytize microbes that make it to the lower respiratory tract.

Question 2

Which respiratory organs should not be colonized with microflora (and are therefore sterile)?

Answer 2

• Bronchi, sinus, and middle ear.

Question 3

Contrast upper and lower respiratory tract infections with respect to (1) incidence
rate and (2) severity

Answer 3

• Upper: lower severity, higher frequency.
Lower: higher severity, lower frequency

Question 4

In order to colonize the lower respiratory tract, name two defenses that a pathogen must successfully evade.

Answer 4

1. Breathing: nasal eddies cause microbes to stick to mucous membranes and nasal hairs capture stuff.
   
   2. Mucociliary escalator: pharynx to bronchi. Cilia beats and moves bacteria back up to pharynx.
   3. Alveolar macrophages: can phagocytize on occasional microbes.

Question 5

Identify three diseases (two localized and one systemic) caused by Streptococcus pyogenes. Briefly describe the symptoms of each disease

Answer 5

• Localized:
1. Strep throat / pharyngitis
2. Impetigo
• Systemic:
1. Childbed fever
2. Toxic shock syndrome
3. Scarlet fever
• Reservoir: human/nasal cavities
• Carrier rate: 10%

Question 6

BIG OBJECTIVE: Characterize S. pyogenes as discussed in class (reservoir, carrier rate, drug resistance, and virulence factors

Answer 6

• Reservoir:
• Carrier rate:
• Drug resistance:
• Virulence factors: capsule made of hyaluronic acid; humans cannot recognize the capsule as foreign. Also have Fimbrae.

Question 7

Although the M protein is strongly antigenic, vaccinations are not given that target the M protein. Why not?

Answer 7

• Often stays hidden behind humans plasma proteins–fibrinogen. Immune system cannot identify M protein and only sees fibrinogen from plasma protein.
G protein forces antibody to sequester around it and binds to it so it cannot bind to anything else.

Question 8

What is rheumatic fever and how does this autoimmune disease relate to Streptococcus pyogenes?

Answer 8

Fever is caused by antibodies that recognize certain types of M protein in S pyrogenes and attack own heart valve

Question 9

Explain why only 10% of S. pyogenes infections lead to Scarlet Fever

Answer 9

• Bacteria cell is infected with a virus containing a gene that codes for erythrogenic exotoxin. Only 10% of bacteria cells carry this gene.