Types of Pneumonia.

Histologic:

fibrinopurulent : acute bacterial pneumonias

mononuclear interstitial infiltrates in viral and other atypical pneumonias

granulomas and cavitation seen in chronic pneumonia like TB

Bronchopneumonia:

patchy distribution of inflammation that generally involves more than one lobe.

initial infection of the bronchi and bronchioles with extension into the adjacent alveoli

lobar pneumonia :

the contiguous airspaces of part or all of a lobe are homogeneously filled with an exudate

visualized on radiographs as a lobar or segmental consolidation

Community-Acquired Acute Pneumonia

Streptococcus pneumoniae

Haemophilus influenzae

Moraxella catarrhalis

Staphylococcus aureus

Legionella pneumophila

Enterobacteriaceae (Klebsiella pneumoniae) and Pseudomonas spp.

Community-Acquired Atypical Pneumonia

Mycoplasma pneumoniae

Chlamydia spp. (C. pneumoniae, C. psittaci, C. trachomatis)

Coxiella burnetti (Q fever)

Viruses: respiratory syncytial virus, parainfluenza virus (children); influenza A and B (adults); adenovirus (military recruits); SARS virus

Nosocomial Pneumonia

Gram-negative rods belonging to Enterobacteriaceae (Klebsiella spp., Serratia marcescens, Escherichia coli) and Pseudomonas spp.

Staphylococcus aureus (usually penicillin-resistant)

Aspiration Pneumonia

Anaerobic oral flora (Bacteroides, Prevotella, Fusobacterium, Peptostreptococcus), admixed with aerobic bacteria (Streptococcus pneumoniae, Staphylococcus aureus, Haemophilas influenzae, and Pseudomonas aeruginosa)

Fulminant course

Chronic Pneumonia

Nocardia

Actinomyces

Granulomatous: Mycobacterium tuberculosis and atypical mycobacteria, Histoplasma capsulatum, Coccidioides immitis, Blastomyces dermatitidis

Necrotizing Pneumonia and Lung Abscess

Anaerobic bacteria (extremely common), with or without mixed aerobic infection

Staphylococcus aureus, Klebsiella pneumoniae, Streptococcus pyogenes

Pneumonia in the Immunocompromised Host

Cytomegalovirus

Pneumocystis carinii

Mycobacterium avium-intracellulare

Invasive aspergillosis

Invasive candidiasis

"Usual" bacterial, viral, and fungal organisms.