Viruses are the most common cause in children under 5 years of age.
PPI use increases the risk of hospital-acquired pneumonia.
Pneumococal (S. pneumoniae) - commonest bact:; elderly, alcoholics, post-splenectomy, immunospressed, pts with CHF or pre-existing lung dz --> lobar p'nia
Staph (Staph. aureus)- young, elderly, iVDU, or pts with underlying dz (e.g Leukemia, Lymphoma, CF); may follow viral syndromes or viral bronchitis/ flu --> bilateral cavitating bronchopneumonia; or necrotizing pneumonia with secondary pneumatoceles (multiple small abscesses)
or empyema in some cases
Px - Flucloxacillin
Haemophilus influenzae - smokers, COPD
Klebsiella (Friedlander's pneumonia)- rare, elderly, DM, alcoholics --> cavitating p'nia esp. upper lobes, Px - Cefotaxime or imipenem
Pseudomonas - common in bronchiectasis and CF, Nosocomial, Px - Ceftazidime, meropenem or Cipro + Aminoglycoside
Legionella - epidemic infection in older smokers, superimposed on COPD pts, particularly when located near infected water sources, such as AC system;
intracellular organism, best visualized by silver stain
CNS manifestations such as confusion, headache, and lethargy. GI - diarrhea & abdominal pain; CXR - bi-basal consolidation, Dx - Legionella serology/ urine Ag; Rx - Clarithro +_Rifampicin or 4quinolone
Moraxella catarrhalis
CAP, often superimposed on COPD pts --> exacerbation
Aspergillus - predisposed by neutropenia and steroid use
Chlamydophila pneumoniae- biphasic illness: pharyngitis, hoarseness, otitis, f/b p'nia; Rx - Clarithro or Tetra