Community-Acquired
Pneumonia
Harvey B. Simon, M.D.
Massachusetts General Hospital
Definition/Key Clinical Features
Differential Diagnosis
Best Tests
Best Therapy
Best References
Definition/Key
Clinical Features
- Fever, chills, cough (with or without sputum), chest
pain, hypoxia, dyspnea
- 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 > 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
Differential Diagnosis
- Asthmatic bronchitis
- Hypersensitivity pneumonia
- COPD
- Atelectasis
- Pulmonary embolism
- Pulmonary edema
- Tuberculosis
- Hypersensitivity reaction
- Congestive heart failure
- Aspiration
- Lung abscess
- Emphysema
Best Tests
- Chest x-raynecessary for diagnosis
- Sputum exam for leukocytes and bacteria
- Sputum culture
- Tracheal aspirate is rarely necessary
- Bronchoscopy: consider for immunosuppressed patients
and extremely ill patients
- 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
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, then tailored to culture and sensitivity results,
clinical response, side effects
- Treat with antibiotics for 714 days for Streptococcus
pneumoniae and 1021 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
- Sparfloxacin
- Dose: 400 mg p.o. day 1, then 200 mg p.o., q.
24 hr
- Gatifloxacin
- Dose: 400 mg p.o., q. 24 hr
- Moxifloxacin
- Dose: 400 mg p.o., q. 24 hr
- Macrolides: cost-effective alternative, but GI intolerance
is common
- Erythromycin: better GI tolerance and activity against
Haemophilus and Moraxella; good first-line drug
- Dose: 250500 mg p.o., q. 6 hr
- Clarithromycin: better GI tolerance and activity
against Haemophilus and Moraxella; good first-line drug
- Dose: 250500 mg p.o., q. 12 hr
- Azithromycin: better GI tolerance and activity against
Haemophilus and Moraxella
- Dose: 500 mg p.o. day 1, then 250 mg p.o. days
25
- Doxycycline: cost-effective alternative
- Dose: 100 mg p.o., q. 12 hr
Initial Antibiotic Therapy for Community-Acquired
Pneumonia in Hospitalized Patients
- Cephalosporins: first-line treatment of choice for severely
ill patients
- Cefotaxime or ceftriaxone + a macrolide or a fluoroquinolone
- Dose: cefotaxime, 12 g I.V. q. 4 hr; ceftriaxone,
12 g I.V. q. 1224 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
- Gatifloxacin
- Dose: 400 mg p.o. or I.V. q. 24 hr
- 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
Antibiotic Therapy for Aspiration Pneumonia
- Penicillin: traditional drug of choice
- Dose: 500 mg p.o., q. 6 hr to 12 million units
I.V. q. 4 hr, depending on severity of infection
- 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
- Metronidazole: excellent alternative
- Dose: 500 mg p.o., q. 8 hr to 500 mg I.V. q. 6 hr,
depending on severity of infection
- Ampicillin-sulbactam: alternative useful in hospitalized
patients
- Dose: 12 g ampicillin + 0.51 g sulbactam I.V.
q. 6 hr
- Imipenem: alternative useful in hospitalized patients
- Dose: 0.51 g. I.V. q. 68 hr
- Meropenem: alternative useful in hospitalized patients
- Fluoroquinolones: excellent for community-acquired pneumonias
but less active against oral anaerobes than penicillin, clindamycin, and metronidazole
- Gatifloxacin
- Dose: 400 mg p.o. or I.V. q. 24 hr
- Moxifloxacin
- Dose: 400 mg p.o., q. 24 hr
- Levofloxacin
- Dose: 500 mg p.o. or I.V. q. 24 hr
Best References
Bartlett, et al: Clin Infect Dis 31:347, 2000
Castro-Guardiola, et al: Am J Med 111:367, 2001
Martinez, et al: Clin Infect Dis 36:389, 2003
July 2004
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