Exam 4: Topic 21

Question 1

Pneumonia is that is the leading cause of death from an infectious agent in the U.S. Describe the pathophysiology of pneumonia; how it develops and why it can be fatal.

Answer 1

evade mechanical defense of upper respiratory tract AND outmaneuver alveolar macrophages

Question 2

Which species is the most common cause of bacterial pneumonia?

Answer 2

• Streptococcus pneumoniae–diplococcus

Question 3

Describe the characteristics of S. pneumoniae (carrier rate, morphology, capsule, drug resistance).

Answer 3

• Carrier rate: varies by age and population group. Decreased with the introduction of childhood conjugate vaccination.
• Morphology: diplococcus
• Capsule: All pathogenic strains are capsulated (virulence factor). Most common
Drug resistance: S. pneumoniae has become resistant to many commonly used antibiotics, including penicillin and cephalosporins.

Question 4

Explain why each of these demographics – the elderly, children under 5, chronic
smokers, and patients with influenza and AIDS respectively have elevated risks
for bacterial pneumonia.

Answer 4

• children under 5: shorter respiratory tract
• Smokers: damaged mucosal ciliary escalated
• Elderly: Immune system weakens in older age
• AIDS: Immune system is compromised
• Influenza: Influenza virus destroys cells of mucosal ciliary escalator.

Question 5

Describe the characteristics of H. influenzae and Mycoplasma pneumoniae, two other bacterial species that can cause pneumonia.

Answer 5

• H Influenzae is actually a bacterial species and does not cause the flu.
• H influenzae most common cause of pneumonia and meningitis in children under 5 that have not been immunized (Hib).
M pneumoniae steals nutrients from a macrophage. Only pathogenic bacteria with no cell wall. Parasitizes alveolar macrophages/causes walking pneumonia

Question 6

What is Legionnaire’s disease and what agent causes it? What is the reservoir for this causative agent?

Answer 6

• Legionella pneumophila
uses pond water as reservoir

Question 7

Explain why alveolar macrophages are invaded by Legionella pneumophila.

Answer 7

invades amoeba and macrophages (since they are similar to amoeba).

Question 8

List two other bacterial species implicated in pneumonia cases.

Answer 8

• Klebsiella pneumoniae
Mycoplasma pneumoniae

Question 9

Name the causative agent of tuberculosis.

Answer 9

• mycobacterium tuberculosis.

Question 10

Describe the characteristics of Mycobacterium as discussed in class

Answer 10

• slow growth rate due to long, skinny porins (17-20 hours); slow process of disease–antibiotics last about 6 months.
• Rifampin

Question 11

Why does mycobacterium have such a long generation time? How does this influence the process of disease?

Answer 11

slow growth rate due to long, skinny porins (17-20 hours); slow process of disease–antibiotics last about 6 months.

Question 12

Big Objective! Describe the disease process of tuberculosis, including the progression of primary, latent, and secondary active TB.

Answer 12

Primary
• Portal of entry: inhalation of TB cells (~10 cells; can be a single cell)
• Alveolar macrophage ingest, does not digest.
• Infected macrophage displays TB antigen on MHC1.
• Induce apoptosis but clean up phagocytosis is not effective (TB cells prevent digestion).
• Immune system attempts containment with a granuloma.
Latent
• As long as granulomas hold, no symptoms.

Secondary active TB Immune system unable to support granulomas

Question 13

At what stage of tuberculosis is a person most infectious?

Answer 13

• Most contagious in secondary active TB
• macrophage ingests bacterial cell
• Is not able to digest bacteria
• Presents invasive signal on MHC1 and attracts Cytotoxic T cell; then induces apoptosis and releases replicated bacterial cells.
• A large amount of bacteria cannot be phagocytized by leukocytes, so white blood cells collect around infected area to form granuloma.
• Tuberculosis granuloma torn. The bacteria spread to other parts of the lung and other organs.

Question 14

Describe the epidemiology of tuberculosis (including % of world population that is
asymptomatic and how many actively infected)

Answer 14

• Highest in areas of crowding and immunosupression coexist
• sub-sahara africa (AIDS ^20%).
• AIDS is a co-epidemic contributors
• Crowding, other immunosuppression factors (e.g. food insecurity)
• Drug resistant strains, antibiotic course too long to be widely accessible

Question 15

With the introduction of antibiotics, TB was all but wiped out. Now, incidences are
back on the rise. List two factors that account for these increased incidences.

Answer 15

Crowding and other immunosuppression factors

Question 16

Once a person progresses to active TB, what percent will die within the next five
years?

Answer 16

50%

Question 17

What does the Mantoux skin test look for? If a person tests positive for the
Mantoux skin test, what is the follow up test to determine if a person is active?

Answer 17

• If a person is positive for the skin test, then the follow up test would be a chest x-ray.
• The test looks for an inflammatory immune response.

Question 18

Describe three reasons that TB has resurged in the past 20 years

Answer 18

Drug resistant strains, antibiotic course too long to be widely accessible