Pathology of Pulmonary Infections Flashcards
How can pneumonia be classified?
By clinical setting (e.g. community acquired pneumonia) By organism (mycoplasma, pneumococcal etc) By morphology (lobar pneumonia, bronchopneumonia)
What is pneumonia?
Infection involving the distal airspaces usually with inflammatory exudation/localised oedema
Fluid filled spaces lead to consolidation
Describe the 4 steps of pneumonia?
- Exudation of fibrin-rich fluid
- Neutrophil infiltration
- Macrophage infiltration
- Resolution
What is lobar pneumonia?
Confluent consolidation involving a complete lung lobe which is most often due to Streptococcus pneumoniae (pneumococcus).
Can be seen with other organisms (Klebsiella, Legionella)
What is Bronchopneumonia? Which organisms cause it?
Infection starting in airways and spreading to adjacent alveolar lung.
Most often seen in the context of pre-existing disease.
Strep. Pneumoniae, Haemophilus influenza, Staphylococcus, anaerobes, coliforms
What is Bronchiectasis?
abnormal fixed dilatation of the bronchi, usually due to fibrous scarring following infection - complication of pneumonia
What is Tuberculosis?
Mycobacterial infection. Chronic infection described in many body sites – lung, gut, kidneys, lymph nodes, skin
characterised by delayed type IV hypersensitivity (granulomatous)
What are the main pathogens in TB?
M. tuberculosis
M.bovis
Describe how immunity and hypersensitivity occur in TB?
Immunity = T-cell response to organism enhances macrophage ability to kill mycobacteria
Hypersensitivity = T-cell response causes granulomatous inflammation, tissue necrosis and scarring
Describe the pathology of primary TB - first exposure?
inhaled organism phagocytosed and carried to hilar lymph nodes. Immune activation (few weeks) leads to a granulomatous response in nodes (and also in lung) usually with killing of organism. In a few cases infection is overwhelming and spreads
Describe the pathology of secondary TB - second exposure?
reinfection or reactivation of disease in a person with some immunity, disease tends initially to remain localised, often in apices of lung.
Can progress to spread by airways and/or bloodstream
How is TB diagnosed?
broncho-alveolar lavage
biopsy
Why would TB reactivate?
decreased T-cell function age coincident disease (HIV) immunosuppressive therapy (steroids, cancer chemotherapy) reinfection at high dose or with more virulent organism