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Community-Acquired Acute Pneumonias.

onset is usually abrupt, with high fever, shaking chills, pleuritic chest pain, and a productive mucopurulent cough

Usually as a result of aspiration of pharyngeal flora, esp Pneumococcus

lower lobes or the right middle lobe most frequently involved

In the era before antibiotics, 4 stages used to be seen

the affected lobe is heavy, red, and boggy
M/E vascular congestion with proteinaceous fluid, numerous neutrophils containing the typical gram-positive, lancet-shaped diplococci

red hepatization
lobe has a liver-like consistency
alveolar spaces are packed with neutrophils, red cells, and fibrin

gray hepatization
lung is dry, gray, and firm, because the red cells are lysed, while the fibrinosuppurative exudate persists

exudates within the alveoli are enzymatically digested to produce granular, semifluid debris that is resorbed, ingested by macrophages, coughed up, or organized by fibroblasts
pleuritis may similarly resolve or undergo organization, leaving fibrous thickening or permanent adhesions.
M/E of bronchopneumonia shows
focal suppurative exudate that fills the bronchi, bronchioles, and adjacent alveolar spaces.

Complications of pneumonia

Lung abscess
Empyema thoracic
Bacteremia, causing meningitis, septic arthritis or infective endocarditis

Bronchopneumonia :

Abscess formation

Lobar Pneumonia:

Lobar Pneumonia Gray hep..

Other common organisms causing CAP:

Haemophilus influenzae

in children, often following a respiratory viral infection
most common bacterial cause of acute exacerbation of COPD.
Common cause of epiglottitis and suppurative meningitis in children
In pts with cystic fibrosis, and bronchiectasis

Staphylococcus aureus

after viral respiratory illnesses (e.g., measles in children and influenza in both children and adults)
complications, such as lung abscess and empyema are very common
intravenous drug abusers

Klebsiella pneumoniae

malnourished persons, particularly chronic alcoholics
viscid capsular polysaccharide, which the individual may have difficulty coughing up

Pseudomonas aeruginosa

Neutropenic pts,eg chemotherapy
in victims of extensive burns
those requiring mechanical ventilation
Pseudomonas bacteremia is a fulminant condition
Pseudomonas vasculitis of the pulmonary vessels is common.