PNEUMOCOCCAL PNEUMONIA
 
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PNEUMOCOCCAL PNEUMONIA

 

DEFINITION:

An acute bacterial infection of the lung parenchyma caused by Streptococcus pneumoniae.

EPIDEMIOLOGY:

  • incidence: accounts for >90% of childhood bacterial pneumonia
  • age of onset:
    • all with peak in preschool children (<4years)
  • risk factors:
    • season - late winter, early spring
    • underlying disease - immunocompromised (splenectomy, hypogammaglobulinemia)

PATHOGENESIS:

1. Background

  • Pneumococcal organisms are aspirated into the periphery of the lungs from the nasopharynx. Initially a reactive edema occurs that supports proliferation and distribution of the organisms throughout the lung.
  • out of 84 serotypes, types 1, 6, 14, and 19 are the most commonly involved with pneumococcal pneumoniae

2. Pathology

  • Once at the alveolar level, the involved lobe undergoes 3 stages:

1. Red Hepatization

  • RBC's, PMN's, fibrin, edema fluid, and pneumococcal organisms fill the alveoli

2. Grey Hepatization

  • fibrin, PMN's, phagocytosis fill the alveoli
  • deposition of fibrin over the alveolar surface
  • first 2 stages occur over 7 days

3. Resolution

  • macrophages fill the alveoli
  • PMN's degenerate, fibrin and pneumococci are digested
  • resolution and reexpansion take place over 1-3 weeks

CLINICAL FEATURES:

1. Infants

1. Prodrome

  • upper respiratory tract infection (URTI) - rhinitis, coryza, irritability, anorexia
  • lasts for several days

2. Pneumonia

  • abrupt onset of fever (>39 C)
  • mild-moderate respiratory distress +/- cyanosis
  • toxic appearance - restless, apprehensive
  • associated symptoms:
    • abdominal distension (due to ileus or swallowed air)
    • nuchal rigidity (+/- meningismus)
    • cough - occurs late

2. Children/Teens

1. Prodrome

  • URTI - as above

2. Pneumonia

  • sudden onset of classic features:
    • shaking chills with high fever (>40.5 C)
    • cough - dry, hacking, and unproductive
    • pleuritic chest pain
    • respiratory distress +/- circumoral cyanosis
  • associated symptoms:
    • toxic appearance - drowsy, restless, delirium

3. Complications

  • in both infants and older children:
    • empyema
    • lung abscess
    • mortality <1%
    • pleural effusion
    • pneumatocele

 

Note: The physical signs will change during the course of the illness. Consolidation (dullness, increased fremitus, tubular breath sounds) will not be noted until days 2-3. As resolution occurs, moist crackles are heard and the signs of consolidation disappear with the cough becoming productive with large amounts of blood-tinged sputum.

INVESTIGATIONS:

1. Chest X-Ray

  • children/teens - lobar consolidation
  • infants - bronchial consolidation (i.e., around smaller airways) with patchy and diffuse changes

2. Microbiology

  • samples of tracheal aspirates, sputum, pleural fluid, blood
  • blood cultures - bacteremia (in 30-50%)
  • rapid diagnostic tests available - latex agglutination, etc

3. Serum

  • leukocytosis (15-40) with increased PMN's
  • gas - hypoxia without hypercapnia

MANAGEMENT:

1. Medical

  • Penicillin G IV in infants young children
  • Penicillin V PO in older children/teens (as an outpatient)
  • indications for hospitalization:
    • IV antibiotics and/or rehydration
    • complications (abscess, empyema, effusion)
    • temperature control, oxygen supplementation

 

 

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