Pneumonia, Adult

Basics

Description

  • Epidemiology:
    • Leading cause of death from infectious disease in the US
  • Highest risk in elderly and patients with the following coexisting conditions:
    • Chronic heart, lung, liver, and kidney disease, eg, COPD
    • Diabetes mellitus
    • Current smoking, alcohol use disorder, and opioid use
    • Malignancy
    • Asplenia
    • Immunosuppression
    • Use of antimicrobials within last 3 mo
  • Classifications:
    • Community acquired (CAP)
    • Hospital acquired (HAP)
    • Ventilator associated (VAP)
    • Bacterial etiology:
      • Typical
      • Atypical
  • Complications:
    • Bacteremia
    • Sepsis
    • Abscess
    • Empyema
    • Respiratory failure

Etiology

  • CAP (typicals):
    • Streptococcus pneumoniae (most common bacterial cause)
    • Haemophilus influenzae
    • Moraxella catarrhalis
    • Staphylococcus aureus
    • Group A streptococci
    • Aerobic gram-negative bacteria (eg, Enterobacteriaceae such as Klebsiella or Escherichia coli)
  • CAP (“atypical” = resistance to β-lactams and inability to visualize on Gram stain or culture using traditional techniques):
    • Legionella
    • Mycoplasma pneumoniae
    • Chlamydia pneumoniae
    • C. psittaci
    • Coxiella burnetii
    • Viral
  • HCAP/HAP/VAP:
    • Gram negatives (Pseudomonas, Stenotrophomonas)
    • Methicillin-resistant S. aureus (MRSA)
  • Immunosuppressed:
    • Mycobacterium tuberculosis
    • Pneumocystis jirovecii
  • Aspiration:
    • Chemical pneumonitis ± oral and gastric anaerobes

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