Pulmonary Respiratory Infections Flashcards
Pneumonia
Infection involving distal airspaces of the lungs, usually with inflammatory exudation/ localised oedema
Lobar Pneumonia
Confluent consolidation involving a complete lobe
What organisms causes lobar pneumonia?
Mainly streptococcus pneumoniae (pneumococcus)
Also can be klebsiella or legionella)
Clinical setting of lobar pneumonia
Usually immunity acquired
Usually in otherwise healthy, young adults
pathology of lobar pneumonia
Classic acute inflammatory response
- secretion of fibrin-rich fluid
- neutrophil and macrophage infiltration
- resolution
Immune system
- antibodies lead to opsonisation, phagocytosis of bacteria
Complications of lobar pneumonia
Organisation eg fibrous scarring
Abscess
Bronchiectasis
Empyema
Bronchopneumonia
Infection staring in airways and spreading to adjacent alveolar lung
Clinical setting of bronchopneumonia
pre existing disease eg COPD, elderly cardiac failure, flu complication
Organisms involved in bronchopneumonia
Streptococcus pneumoniae, haemophiilus influenza, staphylococcus, anaerobes, coliforms
Complications of bronchopneumonia
Organisation eg fibrous scarring
Abscess
Bronchiectasis
Empyema
Lung abscess
tumour-like localised collection of pus, characterised by chronic malaise and fever
Bronchiectasis
Abnormal fixed dilation of bronchi, usually due to fibrous scarring following infection but also in chronic obstruction.
Dilated airways accumulate purulent secretions
TB
Chronic mycobacterial infection
Characterused by type 4/ delayed hypersensitivity (granulomas with neurosis)
Organisms involved in TB?
M. TB, M. Bovis
Pathogenesis of TB
Due to organsims ability to avoid phagocytosis and stimulate a host T-cell response
Which of T-cell responses contributes to immunity in TB?
It enhances organisms macrophage ability to kill mycobacteria
Which of T-cell responses contributes to hypersensitivity in TB?
It causes granulomatous inflammation, tissue necrosis and scarring
When does primary TB occur?
1st exposure, and up to 5 years after
Pathology of primary TB
Inhaled organism is phagocytosed and carried to hilarity lymph nodes Immune activation (few weeks) leads granulomatous response in nodes and lung, usually with killing of organism Infection can spread in some cases
Pathology of secondary TB
Reactivation of disease in person with some immunity, tends to initially stay localised (generally in apices of lung) which can then spread to airways and/ or bloodstream
Tissue changes in primary TB
Small focus in periphery of mid zone of lung and large hilarity nodes which are granulomatous
Tissue changes in secondary TB
Fibrosing and cavitating apical lesion
Why does disease reactivate?
Decreased T cell function due to age, coincident disease (HIV), immunosuppressive therapy
Also reinfection at a high dose/ with a more virulent organism
Diagnosis of TB
Broncho-alveolar lavage
Biopsy
High index of suspicion
