Community-Acquired Pneumonia

Harvey B. Simon, M.D., F.A.C.P.
Massachusetts General Hospital

Definition/Key Clinical Features
Differential Diagnosis
Best Tests
Best Therapy
Best References

Definition/Key Clinical Features

• 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 rales, rhonchi, bronchial breath sounds, percussion dullness
• Respiratory rate often > 20/min
• Chest x-ray reveals infiltrates
• Bacterial: abrupt onset of illness, copious sputum production, high temps, chills, signs of consolidation or at least localized rales and rhonchi; patients generally appear sicker than they would with viral pneumonia
• Atypical (Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella pneumophila, various viruses): little or no sputum

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Differential Diagnosis

• Asthmatic bronchitis
• Hypersensitivity pneumonia
• COPD
• Atelectasis
• Pulmonary embolism
• Pulmonary edema
• Tuberculosis
• Hypersensitivity reaction
• Congestive heart failure
• Aspiration
• Lung abscess

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Best Tests

• Chest x-ray—necessary for diagnosis
• Sputum exam for leukocytes and bacteria
• Sputum culture
• Bronchoscopy with bronchoalveolar lavage: consider for immunosuppressed patients and extremely ill patients
• Tracheal aspirate is rarely necessary
• Molecular diagnosis may be helpful to diagnose Legionella, Mycloplasma, or Chlamydia pneumonia
• CT extremely helpful in complex infections

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

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Best Therapy

• Clinical and lab data identify patients who require hospitalization and aggressive therapy and are at greatest risk for death
• Initiate treatment based on clinical setting, chest x-ray, and sputum Gram stain, and then tailor to culture and sensitivity results, clinical response, side effects
• Treat with antibiotics for 7–14 days for Streptococcus pneumoniae and 10–21 days for M. pneumoniae, C. pneumoniae, and Legionella

General Principles

• Adequate hydration/humidification
• Expectorants are ineffective
• Oxygen for hypoxia
• Avoid cough suppressants in bacterial infection
  

Antibiotics

Initial Antibiotic Therapy for Community-Acquired Pneumonia in Outpatients

• Fluoroquinolones: excellent first-line drugs
  • Levofloxacin
    • Dose: 500 mg p.o., q. 24 hr for 10 days
    • Cost/mo: $108
  • Moxifloxacin
    • Dose: 400 mg p.o., q. 24 hr
    • Cost/mo: $300
  • Gemifloxacin
    • Dose: 320 mg p.o., q. 24 hr
    • Cost/mo: N/A
• Macrolides: cost-effective alternative, but GI intolerance is common with erythromycin
  • Erythromycin: inexpensive but GI intolerance common
    • Dose: 250–500 mg p.o., q. 6 hr
    • Cost/mo: $27 or $40, depending on formulation used
  • Clarithromycin: better GI tolerance and activity against Haemophilus and Moraxella; good first-line drug
    • Dose: 250–500 mg p.o., q. 12 hr
    • Cost/mo: $297 or $260, depending on formulation used
  • Azithromycin: better GI tolerance and activity against Haemophilus and Moraxella
    • Dose: 500 mg p.o. day 1, then 250 mg p.o. days 2–5
    • Cost/mo: $276
  • Doxycycline: cost-effective alternative
    • Dose: 100 mg p.o., q. 12 hr
    • Cost/mo: $42

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
• Fluoroquinolones: first-line treatment, either alone or with a third-generation cephalosporin
  • Levofloxacin
    • Dose: 500 mg p.o. or I.V. q. 24 hr
    Cost/mo: $310
  • Moxifloxacin
    • Dose: 400 mg p.o. or I.V. q. 24 hr
    • Cost/mo: $300
• 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
• 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/mo: $3,648

Antibiotic Therapy for Aspiration Pneumonia

• Clindamycin: may be superior to penicillin
  • Dose: 150–300 mg p.o., q. 6 hr to 600 mg I.V. q. 8 hr, depending on severity of infection
  • Cost/mo: $312 or $601, 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/mo: $12
• 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/mo: $28
• Amoxicillin-clavulanate: alternative for oral therapy
  • Dose: 500 mg p.o., q. 8 hr or 875 mg p.o., q. 12 hr
  • Cost/mo: $391
• 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/mo: $300
  • Levofloxacin
    • Dose: 500 mg p.o. or I.V. q. 24 hr
    • Cost/mo: $310

   

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Best References

Castro-Guardiola A, et al: Am J Med 111:367, 2001 [PMID 11583639]

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 37:1405, 2003 [PMID 14614663]

August 2006