Pneumonia Flashcards
What are the most common causes of acute bacterial pneumonia?
S. pneumoniae (most common) H. influenzae Staph Klebsiella spp. Legionella spp. TB Chlamydophila
What are the common causes of atypical pneumonia?
Mycoplasma pneumoniae Chlamydia pneumoniae Coxiella burnetti Legionella spp. M. catarrhalis Viral (RSV, influenza, adenovirus)
What are some other less common causes of pneumonia?
Histoplasma
Aspergillus
Pneumocystis
How is sputum collected for a laboratory diagnosis of pneumonia?
Transtracheal aspirate Aspiration via tracheostomy, endotracheal tube or bronchoscope Pleural tap to sample effusion Blood culture and serology Rarely lung biopsy
When is serological diagnosis of pneumonia useful (with what causative organisms)?
Mycoplasma pneumoniae
Legionella pneumophilia
Chlamydophila and Chlamydia spaces
Coxiella burnetii
List 5 “must-know” pathogens in the diagnosis of pneumonia
SARS, MERS, etc Influenza (e.g. avian flu) Legionella spp. Bioterrorism agents Community-acquired MRSA
List 2 “should-know” pathogens in the diagnosis of pneumonia
Penicillin G-resistant S. pneumoniae
Gram- rods (e.g. Pseudomonas)
How is community-acquired pneumonia treated?
Usually empirical antibiotics (B-lactam, e.g. penicillin G/amoxycillin, + doxycycline/macrolide)
What vaccines are available to prevent pneumonia?
Influenza (flu is a risk factor for pneumonia)
Pneumococcal (23v for adults, 13v for children)
What is the most common cause of community-acquired pneumonia?
> 50% S. pneumoniae
What are the common pathogens causing nosocomial pneumonias?
Gram-
What pathogens are important in pneumonia in the immune compromised host?
Bacteria (low virulence)
Fungi
Protozoa (e.g. Pneumocystis jiroveci)
What are the 4 possible routes of entry in infective pneumonia?
Inhalation
Aspiration of infected secretions from URT
Aspiration of infected particles
Haematogenous spread
What are the 3 possible microbial aetiologies underlying infective pneumonia?
URT flora
Enteric saprophytes (contaminate airways or via blood)
Environmental pathogens
What are the 2 patterns of infective pneumonia?
Alveolar inflammation
Interstitial inflammation
What causes a pattern of alveolar inflammation in infective pneumonia?
Bacterial pathogens
What causes a pattern of interstitial inflammation in infective pneumonia?
Viruses
Bacterial causes of atypical pneumonia (e.g. mycoplasma)
What is the distinguishing feature of alveolar pneumonia?
Consolidation, a condition in which lung tissue becomes firm and solid due to the accumulation of neutrophils within the alveolar spaces
What are the 2 patterns of consolidation in alveolar pneumonias?
Lobar pneumonia: whole lobe affected +/- inflammation of adjacent pleura
Bronchopneumonia: centered on bronchi or bronchioles and spreads to surrounding alveoli with patchy, multifocal consolidation, often bilateral and affecting >1 lobe
N.B. Patterns can overlap
What causes lobar pneumonia vs. bronchopneumonia?
Bacteria can produce either pattern depending on the virulence of the organism and the state of the host defences
What is the most common cause of lobar pneumonia?
S. pneumoniae
What are the symptoms and signs of lobar pneumonia?
Abrupt onset Fever with chills Raised WCC Cough with sputum and haemoptysis Pleuritic chest pain Gram+ diplococci in sputum Bacteraemia
What are the 4 stages of lobar pneumonia?
Congestion: inflammatory exudate (with fibrin) in alveoli
Red hepatisation: diapedesis of RBCs into alveoli
Grey hepatisation: macrophages invade and remove RBCs and other debris
Resolution
What is the most common pattern of bacterial pneumonia?
Bronchopneumonia
What patients are at risk of acute bronchopneumonia?
Very young and very old
Usually secondary to pre-existing chronic cardiorespiratory disease
Common in hospital patients (frequent post-operative complication)
List 6 possible complications of pneumonia
Pleural fibrosis Empyema Abscess Bronchiectasis Interstitial fibrosis Cysts
What are the common causes of interstitial pneumonia?
Viral
Bacterial, producing an atypical pneumonia
Describe the underlying pathogenesis of interstitial pneumonia
Alveolar septa are widened and infiltrated by lymphocytes, plasma cells and macrophages
Produces bronchiolitis
May be alveolar oedema or haemorrhage but not neutrophils (i.e. there is no consolidation)
What is the presentation of atypical pneumonia?
Systemic symptoms predominant over respiratory (malaise, headaches, diarrhoea)
Dry non-productive cough
Reticulonodular infiltrate on CXR
