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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

  • Gram-positive diplococci on Gram stain of sputum

General Considerations

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

  • Predisposing factors

    • Alcohol use disorder

    • Asthma

    • HIV infection

    • Sickle cell disease

    • Splenectomy

    • Hematologic disorders

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


Laboratory Tests

  • Diagnosis requires isolation of the organism in culture, although the Gram stain of sputum can be suggestive

  • Sputum and blood cultures, positive in 60% and 25% of cases of pneumococcal pneumonia, respectively, should be obtained prior to initiation of antimicrobial therapy in patients who are admitted to the hospital

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

  • A rapid urinary antigen test for Streptococcus pneumoniae, with sensitivity of 70–80% and specificity > 95%, can assist with early diagnosis


  • Chest radiograph classically shows a lobar pneumonia with consolidation and occasionally effusion

  • Cannot radiographically differentiate pneumococcal pneumonia from other pneumonias because of significant overlap



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

Table 9–8.Characteristics of selected pneumonias.

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