Back to Basics: Community Acquired Pneumonia

Back to Basics - Community Acquired Pneumonia

By: Kristen Adorno

Pneumonia Basics

  • Infection of the alveoli
  • 8th leading cause of death in the United States
  • Most common cause of sepsis
  • Presentation: cough (79-91%), fatigue (90%), fever (71-75%), dyspnea (67-75%), sputum production (60-65%) and pleuritic chest pain (39-49%)

Work Up

  • Chest x-ray
  • Consider labs based on history and severity of illness
  • For severe patients, consider blood cultures, sputum cultures
  • Diagnosis made by history in conjunction with abnormal lung exam and/or characteristic opacifications on radiograph

Common Pathogens

  • Common bacterial pathogens:
    • Typical: Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus (MSSA), Moraxella catarrhalis
    • Atypical: Mycoplasma pneumonia, Legionella species, Chlamydia pneumoniae
  • Common viral pathogens: influenza, respiratory syncytial virus, adenovirus, parainfluenza and corona viruses (SARS, MERS, COVID-19)


  • Outpatient treatment:
    • Amoxicillin or Doxycycline or Macrolide (azithromycin, clarithromycin)
    • If comorbidities or recent abx use:
      • Combination therapy: Augmentin or cephalosporin AND macrolide or doxycycline OR
      • Monotherapy with a respiratory fluoroquinolone (levofloxacin, gemifloxacin, or moxifloxacin)
  • Inpatient treatment, non-ICU/non-Severe:
    • Combination therapy: beta-lactam (ceftriaxone, cefotaxime, or ampicillin/sulbactam) AND a macrolide OR
    • Monotherapy with a respiratory fluoroquinolone (levofloxacin, gemifloxacin, or moxifloxacin)
  • Inpatient treatment, ICU/Severe:
    • Combination therapy: Beta-lactam + macrolide OR respiratory fluoroquinolone + macrolide
  • If risk factors for MRSA: Add vancomycin or linezolid
  • If risk factors for Pseudomonas: Add zosyn, cefepime, ceftazidime, imipenem, meropenem or aztreonam
  • If concern for influenza: Consider adding oseltamivir
  • If +COVID-19 and hypoxic:  Add dexamethasone


  • Dependent on severity of illness - two common prediction tools:
    • Pneumonia Severity Index (PSI)
      • More complex, uses 20 categories to risk-stratify patients
      • Identifies larger proportions of patients as low risk and has a higher discriminative power in predicting mortality when compared to CURB-65
    • CURB-65
      • Uses 5 criteria: confusion, BUN >19, respiratory rate ≥30, SBP <90, age ≥65


American College of Emergency Physicians., Tintinalli, J. E., et al. (2016). Tintinalli's emergency medicine manual (8th ed.). New York: McGraw-Hill Medical. Kalil AC et al.

Management of adults with hospital-acquired and ventilator-associated pneumonia: 2016 clinical practice guidelines by the Infectious Diseases Society of America and the American Thoracic Society. Clinical Infectious Diseases. 2016; 63(5):61–111.

Kaysin, A. Community-acquired pneumonia in adults: Diagnosis and management. American Family Physician. 2016; 94(9):698-706.

Lionel A. Mandell. Community-acquired pneumonia: An overview. Postgraduate Medicine. 2015; 127:6, 607-615.

Metlay JP, Waterer GW, Long AC, et al. Diagnosis and treatment of adults with community-acquired pneumonia: An official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir Crit Care Med. 2019; 200(7):45-67.

Sievert DM et al. Antimicrobial-resistant pathogens associated with healthcare-associated infections: summary of data reported to the National Healthcare Safety Network at the Centers for Disease Control and Prevention, 2009-2010. Infect Control Hosp Epidemiol. 2013; 34(1):1-14.

RECOVERY Collaborative Group, Horby, P., Lim, W. S., Emberson, J. R., Mafham, M., Bell, J. L., Linsell, L., Staplin, N., Brightling, C., Ustianowski, A., Elmahi, E., Prudon, B., Green, C., Felton, T., Chadwick, D., Rege, K., Fegan, C., Chappell, L. C., Faust, S. N., Jaki, T., … Landray, M. J. (2020). Dexamethasone in Hospitalized Patients with Covid-19 - Preliminary Report. The New England journal of medicine, NEJMoa2021436. Advance online publication.