Pneumonia Flashcards
What is pneumonia? Give a brief description and outline how is it classified?
Pneumonia is any infection of the lung parenchyma. It can be caused by viruses, bacteria, mycoplasma and funghi.
Pneumonia occurs when the local defence mechanisms of the lung are impaired and/or the systemic resistance of the host is lowered.
Local defences can be impaired by:
- Loss or suppression of the cough reflex - Red’d GCS, drugs, pain
- Injury to the cilliary function - Kartagner’s Syndrome
- Accumulation of secretions - CF, obstruction
- Interference of normal phagocytic or bactericidal action of macrophages - ciggarette smoke, ETOH, O2 toxicity
- Pulmonary congestion and/or oedema
Systemic defences can be lowered by:
- immunodeficiency
- chronic disease (DM, COPD, CCF)
- immunosuppressive agents
- leukopaenia (splenectomy)
Pneumonia is classified by either the infective agent and/or the setting in which the pneumonia was contracted (syndromes).
Pneumoniacauses an inflammatory infiltrate to enter the lung parenchyma -> consolidation.
List the seven pneumonia syndromes. Give examples of the common infective agents in each.
- Community acquired:
- S. pneumoniae
- H. influenzae
- Moraxella catarrhalis
- S. aureus
- Legionella pneumophila
- Enterobacteriaceae (Klebsiella pneumoniae)
- Community acquired, atypical
- Mycoplasma pneumoniae
- Chlamydia species
- Coxiella burnetii (Q fever)
- Viruses (RSV, parainfluenza, influenza A and B, adenovirus, SARS
- Hospital acquired
- Gram -ve rods (Klebsiella species, E. Coli and pseudomonas species)
- S. aureus (penicillin resistant)
-
Aspiration
* Anaerobic oral flora
Mixed with:
- Aerobic bacteria (S. pneumonia, S. aureus, H. influenza, pseudomonas aeruginosa)
1. Chronic - Nocardia
- Actinomyces
- M. Tb
- Necrotising and lung abcess
- Anaerobics
- S. aureus, klebsiella pneumonia, Strep pyogenes
- Pneumonia in the immunocompromised host
- CMV
- Aspergillosis
- Candidiasis
- “Normal” basterial, viral and fungal agents (above)
List some of the features of pneumonia resulting from infection by S. pneumoniae.
- Most common cause of community acquired pneumonia - 90-95%
- Sputum contains Gram +ve diplococci
- S. pneuomnia resides in 20% of pop’n without causing disease
List some of the features of pneumonia resulting from infection by H. influenzae.
- Gram -ve
- Causes life-threatening lower resp’y tract infections and meningitis in children
- V.common cause of community acquired pneumonia in adults
- Ubiquitous coloniser of the pharynx
- Capsulated (5%) or non-capsulated forms (95%)
- Causes lobular, patchy consolidation
List some of the features of pneumonia resulting from infection by moraxella catarrhalis.
- More common in the elderly
List some of the features of pneumonia resulting from infection by staph aureus.
- Common cause of secondary pneumonia post viral illness (measels and influenza)
- High incidence of complications - abcess and empyema
- IV drug users at high risk of staphylococcal pneumonia and endocarditis
- Common cause of hospital acquired pneumonia
List some of the features of pneumonia resulting from infection by klebsiella pneumoniae.
- Most common Gram -ve pneumonia
- Affects debilitated, malnourished ppl - esp chronic alcoholics
- List some of the features of pneumonia resulting from infection by legionella pneumophila.
- Legionnaires disease
- Flourishes in aquatic environments eg wwater cooling towers
- Aspiration of aerosol or aspiration of fluid containing the microbe -> disease
- Severe - 50% mortality in immunocompromised
List some of the features of pneumonia resulting from infection by pseudomonas aeruginosa.
- Usually causes hospital acquired pneumonia but can be community acquired in CF patients
- Propensity to extrapulmonary spread
What are the two patterns of anatomic distribution in pneumonia?
- Bronchomonia - patchy
- Lobar - confluent part of lobe or entire lobe
Patterns may overlap.
Describe the four stages of the inflammatory response in lobar pneumonia.
- Congestion - heavy, boggy and red:
- vascular engorgement
- intra-alveolar fluid with few neutrophils
- presence of many bacteria
- Red hepatisation - red, firm and airless:
- massive confluent exudation
- neutrophils, red cells and fibrin fill the alveoli
- Gray hepatisation - grayish-brown, dry
- Disintegration of RBCs
- fibrinosuppurative exudate
- Resolution - return to normal parenchyma
- Enzymatic action breaks down the exudate
- Produces granular, semifluid debris - resorbed, ingested by macrophages, expectorated or organised by fibroblasts
- Can resolve completely but usually results in adhesions
Describe the morphology of bronchopneumonia.
- Consolidated aeras of accute suppurative inflammation
- May be patchy in one lobe but usually multilobular
- Usually bi-basal due gravity
List the complications of pneumonia.
- Tissue destruction and necrosis -> abcess formation
- Spread to pleural cavity -> empyema
- Bacteremic dissemination -> heart valves, pericardium, brain, kidneys, spleen or joints -> metastatic abcesses, endocarditis, meningitis or suppurative arthritis
Describe the clinical course of community acquired pneumonia.
- abrupt onset of high fevers
- rigors
- cough productive of mucopurulent sputum
- haemoptysis
- pleuritis, pleural rub
Resolves rapidly with appropriate antibiotics.
