- Pneumonia is an abnormal inflammatory condition of the lung
- Typical symptoms associated with pneumonia include cough, chest pain, fever, and difficulty in breathing
Early classification schemes
• lobar pneumonia
• Multilobar pneumonia
• Bronchial pneumonia
• Interstitial pneumonia
Combined clinical classification (now the most commonly used classification schem).
• community-acquired pneumonia
• hospital-acquired pneumonia.
• healthcare-associated pneumonia
community-acquired pneumonia (CAP)
Streptococcus pneumoniae is the most common cause of community-acquired pneumonia worldwide.
CAP is the fourth most common cause of death in the United Kingdom and the sixth in the United States
CAUSE:
- Virus (~ 20%): influenza, parainfluenza, respiratory syncytial virus, metapneumovirus, adenovirus...
- Bacteria:
+ Streptococcus pneumoniae (both penicillin-sensitive and -resistant strains), H influenzae (both ampicillin-sensitive and -resistant strains), and Moraxella catarrhalis (all strains penicillin-resistant). These 3 pathogens account for approximately 85% of CAP cases.
+ Importantly, Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa are not causes of CAP in typical hosts.
* S aureus causes CAP in the setting of postviral influenza.
* K pneumoniae CAP occurs primarily in persons with chronic alcoholism.
* P aeruginosa is a cause of CAP in patients with bronchiectasis or cystic fibrosis.
+ Other gram(-) pathogens rarely cause CAP.
- Atypical pneumonias : zoonotic and nonzoonotic atypical pathogens.
+ Zoonotic atypical pathogens : Chlamydia psittaci (psittacosis), Francisella tularensis (tularemia), and Coxiella burnetii (Q fever).
+ Nonzoonotic atypical pneumonias : Legionella species, M pneumoniae, or C pneumoniae.(~ 15% of all CAP cases)
COMPLICATIONS
- Sepsis: Streptococcus pneumoniae is the most common cause
- Respiratory failure
- Pleural effusion and empyema
- Abscess
