Lecture 16: Pneumonia

Question 1

Describe the basic triad of infectious disease;

Answer 1

• Host
• Pathogen
• Environment

Question 2

What is a characteristic of pneumonia on CXR?

Answer 2

• Infection of air spaces -> Terminal bronchioles and alveoli (pus in lobes, consolidation)

Question 3

What are the risk factors of the host for pneumonia?

Answer 3

Host:

• Chronic lung disease
• Smoking
• Alcohol excess (Inc. change of aspiration, Dec. immune system function)
• Poor swallowing
• Very young/very old
• Immune supression

Question 4

What are some factors about germs / an example?

Answer 4

S. pneumoniae

• Ability to colonise oropharynx
• Polysaccharide capsule
• Avoids complement deposition (C3B, polysacc avoids this)
• Toxins that lyse neutrophils and epithelial cells

Question 5

What are some environmental factors?

Answer 5

• Cluster of sick people?

- Exposure i.e birds, AC, potting mix

Question 6

What are the primary innate immune cells?

Answer 6

Alveolar macrophages

Question 7

Describe the first couple days of pneumonia development?

Answer 7

Bacteria in the alveoli start early immune response
- Cap dilate, inc. BF, WBC movement, Cap congest
- Congestion day 1-2
- Neutrophils extravasate
= Exudate in alveoli (pus = proteins, dead/alive bacteria & WBC)

Question 8

Describe days 2-4 of pneumonia development:

Answer 8

“Red hepatisation” Days 2-4

• Lots of RBC in extravasation
• More neutrophils
• Fibrin stranding

(At this stage the lung resembles a red liver)

Question 9

Describe days 4-8 of pneumonia development?

Answer 9

“Grey hepatisation” - Day 4-8

• Alveoli packed with neutrophils
• Dense fibrin stranding

(At this stage the lung resembles a grey liver)

Question 10

How common is s.pneumoniea?

Answer 10

Carriage of s.pneumoniae varies with age, siblings, daycare attendance, recent antibiotic use, time etc

Dynamic! lots of people can have it and not be sick

Question 11

Whats notable about the types of bacteria in the lower and upper airways?

Answer 11

Types of bacteria were similar between the two.

BUT the amount of bacterial DNA was lower in the lungs than the oropharynx (i.e lower airways not sterile)

Question 12

How does bacteria get into the lower RT?

Answer 12

Healthy adults aspirate oropharyngeal contents into lungs while sleeping, Thats how we can get pneumonia.

Question 13

But why dont people get pneumonia more often?

Answer 13

Mucocillary escalator!
Mucus
Cough and sneeze
Alveolar defences

Question 14

What can cause problems with the cilia?

Answer 14

Bronchiectasis and chronic sinusitis

• Congenitial or acquired
• Structure or function

Question 15

Write some notes on the mucocillary escalator

Answer 15

• Ciliated cells to 17th generation of airways
• Effective and recovery strokes
• Co-ordinated by intra-cellular signalling

Question 16

Describe resp. mucus;

Answer 16

Secreted by goblet cells and mucus glands

• Water
• Mucin (anti-bacterial / biofilm properties)
• Proteoglycans
• Lipids
• Proteins (Lysozyme, defensins)

Question 17

What is the role of mucus:

Answer 17

1) Protects epithelium: Physical, dilutes chemicals, absorbs gas
2) Traps particles - removal: Thinner layer and non-continuous in the periphery
3) Suitable environment for luminal immune cells
4) Antimicrobial substances

Question 18

What is the function of cough/sneeze?

Answer 18

Forceful removal of material from upper airways, thin layer of normal mucous not removed by sneezing.

Question 19

How does a cough/sneeze work?

Answer 19

Development of high intra-thoracic pressure with sudden release

• High linear airflow, material removed by sheer forces cough is ineffective in small airways

Question 20

What are some alveolar defences?

Answer 20

No muco-ciliary escalator, no cough mechanism

• Pulmonary alveolar macrophage (resident antigen presenting cell)
• Neutrophils recruited by PAMs
• Immunoglobulin
• Complement
• Adaptive immune cells

Question 21

What are the clincal features of pneumonia?

Answer 21

Fever
- Cytokines/immune response
Cough - Productive, sometimes non-productive
- Clearance of excess mucus
Dyspnoea
- Hypoxia
Solid lung
- Poor expansion, dull, reduced air entry, altered sounds
Problems associated with hypoxia
- Impairment of other organs i.e delerium