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For further information, see CMDT Part 33-03: Pneumococcal Infections

Key Features

Essentials of Diagnosis

  • Productive cough, fever, rigors, dyspnea, early pleuritic chest pain

  • Consolidating lobar pneumonia on chest radiograph

  • Lancet-shaped gram-positive diplococci on Gram stain of sputum

General Considerations

  • The most common cause of community-acquired pyogenic bacterial pneumonia

  • Predisposing factors

    • Alcoholism

    • Asthma

    • HIV infection

    • Sickle cell disease

    • Splenectomy

    • Hematologic disorders

  • Up to 40% of infections are caused by pneumococci resistant to at least one drug and 15% are due to a strain resistant to three or more drugs


  • Until 2000, Streptococcus pneumoniae infections caused 100,000–135,000 hospitalizations for pneumonia, 6 million cases of otitis media, and 60,000 cases of invasive disease, including 3300 cases of meningitis

  • Disease figures are now changing due to conjugate vaccine introduction

Clinical Findings

Symptoms and Signs

  • High fever, productive cough, occasional hemoptysis, and pleuritic chest pain

  • Rigors may occur initially but are uncommon later in the course

  • Bronchial breath sounds are an early sign

  • Differentiating pneumococcal from other bacterial pneumonias is not possible clinically or radiographically because of significant overlap in presentations

Differential Diagnosis

  • Pneumonia due to other causes, eg, Haemophilus influenzae, influenza

  • Aspiration pneumonia or lung abscess

  • Pulmonary embolism

  • Myocardial infarction

  • Acute exacerbation of chronic bronchitis

  • Acute bronchitis

  • Hypersensitivity pneumonitis


Laboratory Tests

  • A good-quality sputum sample (less than 10 epithelial cells and more than 25 polymorphonuclear leukocytes per high-power field) shows gram-positive diplococci in 80–90% of cases

  • Blood cultures are positive in up to 25% of selected cases and much more commonly so in HIV-positive patients

Imaging Studies

  • Chest radiograph shows findings of consolidation, often with a lobar distribution, infiltrates, pleural effusion



  • Initial antimicrobial therapy of pneumonia is empiric pending isolation and identification of the causative organism (Table 9–8)


  • Amoxicillin, 750 mg twice daily orally for 7–10 days

  • Cephalosporins may also be used

    • Cefpodoxime, 200 mg orally twice daily

    • Cefdinir, 300 mg twice daily

  • Alternatives include

    • Azithromycin, one 500-mg dose orally on the first day and 250 mg orally for the next 4 days

    • Clarithromycin, 500 mg twice daily orally for 10 days

    • Doxycycline, 100 mg twice daily orally for 10 days

    • Levofloxacin, 750 mg orally for 5 days

    • Moxifloxacin, 400 mg orally for 7–14 days


  • Aqueous penicillin G (susceptible strains), 2 million units every 4 hours intravenously

  • Ceftriaxone, 1 g every 24 hours intravenously

  • For a highly penicillin-resistant strain, vancomycin, 1 g ...

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