Pathology of Respiratory Tract Infections Flashcards
What are the 3 types of microorganisms and explain each one?
Primary
- Invasive
Facultative
- Need assistance to cause infection but mostly independent
Opportunistic
- Increase chance of ordinary infections
- Infection by organisms not normally capably of producing disease in patients with intact lung defences
- Low grade bacterial pathogens, CMV, pneumocystis jirovecii, other fungi and yeasts
What are some common URTI causing organisms?
Strep. pyogenes
Viruses - rhinovirus, adenovirus, parainfluenza, and EB virus
What are the mechanisms for defence in the respiratory system?
Macrophage mucociliary escalator system
General immune system (humoral and cellular immunity)
Respiratory tract secretions
Upper respiratory tract acting as a filter (only if you breath through your nose).
Explain the macrophage mucociliary escalator system.
Mucous membrane of bronchioles/bronchi/trachea form the mucociliary escalator.
Aided by cough reflex which encourages sputum up the tract
Macrophages migrate and enter respiratory bronchioles and onto surface of respiratory epithelium carried as a layer of fluid out of the lungs via cilia.
What happens if respiratory epithelium is damaged/destroyed?
The mucociliary escalator will be damaged or stop working.
This increases chance of secondary infection as sputum/fluid cannot get out of respiratory system.
A viral infection of influenza damages epithelium
What is bronchopneumonia?
Bacterial infection leading to acute inflammation of the bronchi (pus and neutrophils fill alveoli)
Where does bronchopneumonia mostly affect?
Central acinus area
Lower zones/lobes of the lungs
What does bronchopneumonia look like on a CXR?
Focal/patchy areas of consolidation
- White fluffy shadows
- Bilateral basal
What is lobar pneumonia?
Infection involving the whole lobe
How does lobar pneumonia come about?
Hyper response to an infection creates lots of fluid which spreads around the whole lobe. (spreading the infection)
Resulting in soldi consolidation of the whole lobe.
What does lobar pneumonia look like on a CXR?
Complete white out of whole lobe
What are the main outcomes/complications of pneumonia? (6)
- Most resolve!
- Infection spreads to pleura
- Organisation
- Abscess
- Bronchiectasis
- Fatality
What happens when infection spreads to the pleura?
Pleurisy
Pleural effusion
Emphysema
What is the outcome of organisation as a response to pneumonia?
Mass lesion
RARE- Fibrous tissue in air space that used to contain pus (COP - cryptogenic organising pneumonia)
Constructive bronchiolitis
Explain a lung abscess
Caused by obstructed bronchus (tumour), aspiration and particular organisms
Metastatic in pyaemia (infection comes from the blood - uncommon)
Necrotic lung (secondar infection - uncommon)
