1. Respiratory Infection : Pathology of Respiratory Tract Infection Flashcards
What are lung infections a result of?
An interaction between human host and an infectious agent
Why are lung infections considered multifactorial situations?
Dependent on:
- Microorganism pathogenicity
- Capacity to resist infection
- Population at risk
What are the 3 types of microorganism pathogenicity?
- Primary: no matter how healthy you are, these ones will make you sick
- Opportunistic: attack the severely immunocompromised
- Facultative: need a bit of help in order to cause harm
What affects a host ability to resist infection?
- The state of host defence mechanism i.e immune system
- Age of patient
What are examples of upper respiratory tract infections?
- Coryza: common cold
- Sore throat syndrome
- Acute laryngotracheobronchitis: croup
- Laryngitis
- Sinusitis
- Acute epiglottitis
What is acute epiglottitis caused by?
- Group A beta-haemolytic streptococci
- Haemophilus influenza (type b -Hib)
What are examples of lower respiratory tract infections?
- Bronchitis
- Bronchiolitis
- Pneumonia
- Consequences
- Possible complications
What respiratory tract defences are there?
- Macrophage-mucociliary escalator skeleton
- General immune system
- Respiratory tract secretions
- Upper respiratory tract acts as a filter
What are the 3 components of the MMES?
- Alveolar macrophages
- Mucociliary escalator
- Cough reflex
What is normally sterile?
Lower respiratory tract
How are particles cleared via the MMES?
- Foreign bodies are phagocytised by macrophages. -Macrophages migrate towards the cilia.
- The cilia beat up and outwards
- Digestions of foreign bodies get trapped in the mucous which is swept up the respiratory tract by the cilia and coughed out or swallowed.
- Alternatively macrophages take the interstitial pathway via the lymph to the lymph nodes
What happens if the MMES fails?
Anything inhaled is retained in the lung
What can cause the MMES to fail?
Viral infection as it can lead to the loss of cilia
How can pneumonia be classified?
- Anatomical: understand how it looks
- Aetiological: understand the cause
- Microbiological: understand what is appropriate for treatment
What are the aetiological classes of pneumonia?
- Community acquired pneumonia
- Hospital acquired pneumonia
- Pneumonia in the immunocompromised
- Atypical pneumonia
- Aspiration pneumonia
- Recurrent pneumonia
What are the patterns of pneumonia?
- Bronchopneumonia
- Segmental/lobar
- Hypostatic
- Aspiration
- Obstructive, retention, endogenous lipid
Hypostatic pneumonia
Pneumonia due to bacterial growth in lung where there is a collection of secretions due to lack of draining
How does bronchopneumonia appear?
Often bilateral basal patchy opacification, relating to the focal nature of the consolidation
What happens in lobar pneumonia?
It is more invasive and aggressive. Organisms are washed throughout the lung until it reaches the pleura where it can go no further
What are the outcomes/complications of pneumonia?
- Most resolve
- Pleurisy, pleural effusion and empyema
- Organisation
- Lung abscess
- Bronchiectasis
- Potentially fatal
What can cause a lung abscess?
- Obstructed bronchus ( possibly due to tumour)
- Aspiration
- Particular organism
- Metastatic in pyaemia
- Necrotic lung as secondary infection
What organisms are likely to be involved in the formation of an abscess?
- Staph aureus
- Some pneumococci
- Klebsiella
What is bronchiectasis?
Pathological dilatation of bronchi due to:
- Severe infective episode
- Recurrent infections
- Proximal bronchial obstruction
- Lung parenchymal destruction
What are the symptoms of bronchiectasis?
- Cough
- Abundant purulent foul sputum
- Haemoptysis
- Signs of chronic infection
- Coarse crackles
- Clubbing
How is bronchiectasis diagnosed?
-Thin section CT
How is bronchiectasis treated?
- Postural drainage,
- Antibiotics
- Surgery
What can cause local bronchial obstruction?
- Tumour
- Foreign body
What can cause local pulmonary damage?
Bronchiectasis
What can cause generalised lung disease?
- Cystic fibrosis
- COPD
What can cause non-respiratory disease?
- Immunocompromised
- Aspiration
What can aspiration pneumonia cause?
- Vomiting
- Oesophageal lesion
- Neuromuscular disorders
- Obstetric anaesthesia
- Sedation
What is an opportunistic infection?
Infection by organisms not normally capable of producing disease in patients with intact lung defences
What are examples of opportunistic pathogens?
- Low grade bacterial pathogens
- CMV
- Pneumocystitis jirovecii
- Other fungi and yeasts
