What investigations should be done for a child with streptococcal bacteremia from pneumonia?

Investigations for a Child with Streptococcal Bacteremia from Pneumonia

Blood cultures should be performed in all children with suspected bacterial pneumonia, and repeat blood cultures should be obtained in children with Streptococcus pneumoniae bacteremia who remain febrile or unwell after initial treatment. 1

Essential Diagnostic Tests

Microbiological Investigations

• Blood cultures: Must be obtained before starting antibiotics whenever possible 1

  • For confirmed streptococcal bacteremia:
    • Repeat blood cultures if the child remains febrile or shows clinical deterioration 1
    • Note: Repeat blood cultures are not necessary to document resolution of pneumococcal bacteremia if there is clear clinical improvement 1

• Sputum collection: If the child can produce sputum (rare in young children), obtain for culture and Gram stain 1

  • Consider tracheal aspiration for bacterial culture if the child undergoes general anesthesia 1

• Nasopharyngeal aspirates: Should be collected from all children under 18 months for viral antigen detection with or without viral culture 1

  • Important to identify potential viral co-infections which are common (8-40% of CAP cases) 1

Pleural Fluid Analysis

• If significant pleural fluid is present, it should be aspirated for:

  • Microscopic examination and culture
  • Gram stain
  • Bacterial antigen detection
  • Differential cell count 1

• Additional pleural fluid tests to consider:

  • PCR techniques for specific pathogens (e.g., S. pneumoniae) 1
  • Culture in anaerobic blood culture bottles to improve yield 1
  • Cytological analysis if there's any suspicion the effusion is not infectious 1

Radiological Investigations

• Chest radiography: Indicated for hospitalized children with pneumonia 1

  • Not routinely needed for mild uncomplicated cases 1
  • Follow-up chest radiography only needed for:
    • Lobar collapse
    • Round pneumonia
    • Continuing symptoms 1

• Ultrasound: Should be used if pleural effusion is suspected to:

  • Confirm presence of fluid
  • Guide thoracocentesis or drain placement 1

General Investigations

• Pulse oximetry: Should be performed in every child admitted with pneumonia 1
• Complete blood count: Not necessary for all outpatients but should be obtained for patients with severe pneumonia 1, 2
• Acute phase reactants (CRP, ESR): Not routinely recommended as they don't reliably distinguish between bacterial and viral infections 1

Additional Considerations

For Complicated Pneumonia

• If the child is not responding to appropriate antibiotics within 48-72 hours, consider complications such as:

  • Parapneumonic effusion
  • Empyema
  • Necrotizing pneumonia 3

• For these cases, additional investigations may include:

  • Ultrasound to assess for pleural fluid
  • Pleural fluid drainage and analysis if present 3

Special Circumstances

• Persistent bacteremia: Children who did not receive antibiotics at initial evaluation or those treated with oral antibiotics but remain febrile are at highest risk for persistent bacteremia 4

• Immunocompromised patients or those with unusual presentations:

  • Consider broader testing for atypical pathogens
  • Mantoux testing and sputum for acid-fast bacilli if risk factors for tuberculosis are present 1

Pitfalls to Avoid

• Urinary antigen detection tests are not recommended for diagnosing pneumococcal pneumonia in children due to common false-positive results 1
• Antibiotics given before blood cultures can mask bacteremia and lead to false-negative results 5
• CT scans should not be performed routinely; they're rarely needed and expose children to unnecessary radiation 1
• Biochemical analysis of pleural fluid is unnecessary in uncomplicated parapneumonic effusions/empyema 1

Remember that S. pneumoniae is the most common bacterial cause of pneumonia in childhood, but a significant proportion of cases (8-40%) represent mixed infections with viruses, making comprehensive testing important for optimal management 1.