Pneumonia, Bacterial

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Bacterial pneumonia is an infection of the pulmonary parenchyma by a bacterial organism.


Bacterial pneumonia can be classified as the following:

  • Community-acquired pneumonia (CAP): lower respiratory tract infection not acquired in a hospital, long-term care facility, or during other recent contact with the health care system
  • Medical care–associated pneumonia
    • Hospital-acquired pneumonia (HAP): pneumonia within ≥48 hours after admission and did not appear to be incubating at time of admission
    • Ventilator-associated pneumonia (VAP): pneumonia that develops >48 hours after endotracheal intubation
    • Health care–associated pneumonia (HCAP): Pneumonia that occurs in a nonhospitalized patient with extensive health care contact, such as the following:
      • IV therapy/wound care within past 30 days
      • Residing in a nursing home/long-term care
      • Hospitalization in an acute care hospital for ≥2 days within the past 90 days; hemodialysis clinic within the past 30 days


  • Influenza and pneumonia are the eighth leading causes of death in the United States with about 53,282 deaths in 2013.
  • HAP is the leading cause of death among nosocomial infections and is one of the leading causes of death in the ICU.
  • Rates of infection are 3 times higher in African Americans than in whites and are 5 to 10 times higher in Native American adults and 10 times higher in Native American children.
  • Mortality rate in children is approximately 1.6 million a year. Hospitalization rate for children with CAP is still highest among the very young ages (<18 months). Respiratory viruses are the most commonly detected causes of pneumonia (1).

  • CAP: 5 to 11 cases per 1,000 persons with increased incidence occurring in the winter months
  • HAP: 5 to 10 cases per 1,000 admissions; incidence increases 6- to 20-fold in ventilated patients (2)[A].

Etiology and Pathophysiology

  • Adults, CAP
    • Typical (85%): Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, group A Streptococcus, Moraxella catarrhalis
    • Atypical (15%): Legionella sp., Mycoplasma pneumoniae, Chlamydophila pneumoniae
  • Adults, HCAP/HAP/VAP
    • Aerobic gram-negative bacilli: Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and Acinetobacter sp.
    • Gram-positive cocci: Streptococcus sp. and S. aureus (including MRSA)
  • Children
    • Birth to 20 days: E. coli, group B streptococci, Listeria monocytogenes
    • 3 weeks to 3 months: Chlamydia trachomatis, S. pneumoniae
    • 4 months to 18 years
      • Typical: S. pneumoniae
      • Atypical: C. pneumoniae, M. pneumoniae

Risk Factors


  • Age >65 years
  • HIV/immunocompromised
  • Recent antibiotic therapy/resistance to antibiotics
  • Asthma, CAD, COPD, chronic renal failure, CHF, diabetes, liver disease, VAP, HAP, HCAP
  • Hospitalization for ≥2 days during past 90 days
  • Severe illness
  • Antibiotic therapy in the past 6 months
  • Poor functional status as defined by activities of daily living score
  • Immunosuppression (including steroid users) (3)

General Prevention

  • All children 2 to 59 months of age should be routinely vaccinated with pneumococcal conjugate (PCV13); given at 2, 4, and 6 months of age; a fourth dose at 12 to 15 months of age
  • Adults ≥65 years who have not received vaccine naïve, ACIP currently recommends PCV13 followed by pneumococcal polysaccharide (PPSV23) ≥1 year interval. If they received PPSV23 vaccine before age 65 years, they should receive a dose of PCV13 followed by a subsequent PPSV23 ≥1 year after PCV13 and at least 5 years have passed since their previous PPSV23 dose.
  • For adults ≥65 years old who have already received PPSV23, a dose of PCV13 is indicated after ≥1 year.
  • Adults 19 to 64 years who have chronic diseases, including alcoholism and tobacco use, should receive PPSV23.
  • Adults ≥19 years old with immunocompromising conditions, asplenia, CSF leaks, cochlear implants who have not received PPSV23 or PCV13 should receive 1 dose of PCV13 followed by PPSV23 after ≥8 weeks. If a second dose of PPSV23 is recommended, it should be given 5 years after first dose. Adults >19 years, previously given PPSV23 should receive a PPCV13 dose ≥1 year after last PPSV23. If additional PPSV23 is required, it should be given ≥8 weeks after PCV13 and 5 years after most recent dose of PPSV23.
  • Annual influenza vaccine

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