Best Dx/Best Rx: Community-Acquired Pneumonia

Community-Acquired Pneumonia

Joel T. Katz, MD, FACP
Harvard Medical School, Brigham and Woman's Hospital and Dana-Farber Cancer Institute, Boston, MA

Cough (with or without sputum), fever (with or without chills), chest pain (usually pleuritic), dyspnea, hypoxia
High fever, tachypnea, confusion, hypoxia, and hypotension indicate more severe illness
Physical exam often nonspecific but may reveal crackles, rhonchi, bronchial breath sounds, egophany, percussion dullness
Respiratory rate often elevated (> 20/min)
Chest x-ray reveals infiltrates
Bacterial: abrupt onset of illness, copious sputum production, high fevers, chills, localized lung findings (such as crackles, rhonchi, and percussion dullness); patients generally appear sicker than they would with viral pneumonia
Atypical (Mycoplasma pneumoniae, Chlamydophilia pneumoniae, Legionella pneumophila, various viruses): little or no sputum, extrapulmonary symptoms (such as diarrhea, abdominal pain, nasal congestion)

Differential Diagnosis

Best Tests

Chest x-ray—necessary for diagnosis
Sputum exam for leukocytes and bacteria
Sputum culture
Blood culture
Bronchoscopy with bronchoalveolar lavage: consider for immunosuppressed patients and extremely ill patients
Molecular diagnosis may be helpful to diagnose Legionella, Mycloplasma, or Chlamydia (Chlamydophila) pneumonia
CT extremely helpful in complex or non-resolving infections or to exclude associated findings such as an adjacent lung mass

Clinical Pearls

Consider Legionnaires disease with segmental, lobar, or interstitial pneumonia with no etiologic agent evident on Gram stain
Nonbacterial infection: scant quantities of thin sputum with scant cellular response and few bacteria
True interstitial infiltrate suggests nonbacterial pneumonia

Best Therapy

Clinical and laboratory data can be used to identify patients who require hospitalization and aggressive therapy and are at greatest risk for death (e.g., Pneumonia Severity Index)
Initiate treatment based on clinical setting, chest x-ray, and sputum Gram's stain when available, and then tailor to culture and sensitivity results, clinical response, side effects
Treat with antibiotics for 7–14 days for Streptococcus pneumoniae, M. pneumoniae, C. pneumoniae, and 21 days for Legionella

General Principles

Antibiotics

Initial Antibiotic Therapy for Community-Acquired Pneumonia in Outpatients

Initial Antibiotic Therapy for Community-Acquired Pneumonia in Hospitalized Patients

Cephalosporins: first-line treatment for severely ill patients when combined with a second agent
- Cefotaxime or ceftriaxone + a macrolide or a fluoroquinolone
  - Dose: cefotaxime, 1–2 g I.V. q. 4 hr; ceftriaxone, 1–2 g I.V. q. 12–24 hr
  - Cost/day: $18
Fluoroquinolones: first-line treatment, either alone or with a third-generation cephalosporin
- Levofloxacin
  - Dose: 500 mg p.o. or I.V. q. 24 hr
- Moxifloxacin
  - Dose: 400 mg p.o. or I.V. q. 24 hr
  - Cost/14 days: $238 or $616
Vancomycin + a macrolide or a fluoroquinolone: alternative for severely ill patients who are allergic to β-lactams
- Dose: vancomycin, 1 g I.V. q. 12 hr
- Cost/day: $15
Linezolid + a macrolide or a fluoroquinolone: for severely ill patients who cannot tolerate β-lactams or vancomycin
- Dose: Linezolid, 600 mg p.o. or I.V. q. 12 hr
- Cost/14 days: $548 or $3,332

Antibiotic Therapy for Aspiration Pneumonia

Clindamycin: preferred treatment; does not promote MRSA emergence
- Dose: 150–300 mg p.o., q. 6 hr to 600 mg I.V. q. 8 hr, depending on severity of infection
- Cost/14 days: $70 or $630, depending on formulation used
Penicillin: traditional drug of choice
- Dose: 500 mg p.o., q. 6 hr to 1–2 million units I.V. q. 4 hr, depending on severity of infection
- Cost/14 days: $28
Metronidazole: excellent alternative
- Dose: 500 mg p.o., q. 8 hr to 500 mg I.V. q. 6 hr, depending on severity of infection
- Cost/14 days: $224 to $266
Amoxicillin-clavulanate: alternative for oral therapy
- Dose: 500-125 mg p.o., q. 8 hr or 875-125 mg p.o., q. 12 hr
- Cost/14 days: $266
Ampicillin-sulbactam: alternative useful in hospitalized patients
- Dose: 1–2 g ampicillin + 0.5–1 g sulbactam I.V. q. 6 hr
Imipenem: alternative useful in hospitalized patients
- Dose: 0.5–1 g. I.V. q. 6–8 hr
Meropenem: alternative useful in hospitalized patients
- Dose: 1 g I.V. q. 8 hr
Fluoroquinolones: excellent for community-acquired pneumonias but less active against oral anaerobes than penicillin, clindamycin, and metronidazole
- Moxifloxacin
  - Dose: 400 mg p.o., q. 24 hr
  - Cost/14 days: $238
- Levofloxacin
  - Dose: 500 mg p.o. or I.V. q. 24 hr
  - Cost/14 days: $210 or $630

Best References

Cunha BA: Chest 125:1913, 2004 [PMID 15136407]

Dunbar LM, et al: Clin Infect Dis 37:752, 2003 [PMID 12955634]

Mandell LA, et al: Clin Infect Dis 44 Suppl 2:S27, 2007 [PMID 17278083]

Yandiola PP, et al: Chest 135:1572, 2009 [PMID 19141524]

October 2009