Lecture 16: Pneumonia Flashcards
Describe the basic triad of infectious disease;
- Host
- Pathogen
- Environment
What is a characteristic of pneumonia on CXR?
- Infection of air spaces -> Terminal bronchioles and alveoli (pus in lobes, consolidation)
What are the risk factors of the host for pneumonia?
Host:
- Chronic lung disease
- Smoking
- Alcohol excess (Inc. change of aspiration, Dec. immune system function)
- Poor swallowing
- Very young/very old
- Immune supression
What are some factors about germs / an example?
S. pneumoniae
- Ability to colonise oropharynx
- Polysaccharide capsule
- Avoids complement deposition (C3B, polysacc avoids this)
- Toxins that lyse neutrophils and epithelial cells
What are some environmental factors?
- Cluster of sick people?
- Exposure i.e birds, AC, potting mix
What are the primary innate immune cells?
Alveolar macrophages
Describe the first couple days of pneumonia development?
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)
Describe days 2-4 of pneumonia development:
“Red hepatisation” Days 2-4
- Lots of RBC in extravasation
- More neutrophils
- Fibrin stranding
(At this stage the lung resembles a red liver)
Describe days 4-8 of pneumonia development?
“Grey hepatisation” - Day 4-8
- Alveoli packed with neutrophils
- Dense fibrin stranding
(At this stage the lung resembles a grey liver)
How common is s.pneumoniea?
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
Whats notable about the types of bacteria in the lower and upper airways?
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)
How does bacteria get into the lower RT?
Healthy adults aspirate oropharyngeal contents into lungs while sleeping, Thats how we can get pneumonia.
But why dont people get pneumonia more often?
Mucocillary escalator!
Mucus
Cough and sneeze
Alveolar defences
What can cause problems with the cilia?
Bronchiectasis and chronic sinusitis
- Congenitial or acquired
- Structure or function
Write some notes on the mucocillary escalator
- Ciliated cells to 17th generation of airways
- Effective and recovery strokes
- Co-ordinated by intra-cellular signalling
Describe resp. mucus;
Secreted by goblet cells and mucus glands
- Water
- Mucin (anti-bacterial / biofilm properties)
- Proteoglycans
- Lipids
- Proteins (Lysozyme, defensins)
What is the role of mucus:
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
What is the function of cough/sneeze?
Forceful removal of material from upper airways, thin layer of normal mucous not removed by sneezing.
How does a cough/sneeze work?
Development of high intra-thoracic pressure with sudden release
- High linear airflow, material removed by sheer forces cough is ineffective in small airways
What are some alveolar defences?
No muco-ciliary escalator, no cough mechanism
- Pulmonary alveolar macrophage (resident antigen presenting cell)
- Neutrophils recruited by PAMs
- Immunoglobulin
- Complement
- Adaptive immune cells
What are the clincal features of pneumonia?
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
