Pediatric Pneumococcal Infections Workup

Updated: Jan 14, 2019
  • Author: Meera Varman, MD; Chief Editor: Russell W Steele, MD  more...
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Workup

Laboratory Studies

Approach Considerations

The following studies are indicated in patients with pneumococcal infections:

WBC count

Elevated WBC count and differential showing a high band count or left shift may suggest bacterial infection.

Young children with a WBC count greater than 15,000 cells/mL and/or an absolute band count greater than 1500/mcL have an increased likelihood of occult bacteremia.

WBC count may be low in children with meningitis and other severe pneumococcal infections.

Antigen tests

The use of CSF and urine antigen tests for pneumococci is limited because of the multitude of S pneumoniae serotypes and the poor sensitivity of the test. At present, these tests should be used only in children in whom blood and CSF cultures were obtained after antibiotic treatment. In these children, antigen test results occasionally are positive when culture results are negative.

A negative result on an antigen test does not exclude pneumococcal infection.

Gram stain

Gram stains of usually sterile body fluids (CSF, synovial fluid, pleural fluid) showing gram-positive diplococci strongly suggest the diagnosis of pneumococcal infection, although alpha-hemolytic streptococci and group B streptococci can look like S pneumoniae.

Results of CSF Gram stains in younger children with meningitis are positive 90-100% of the time, but the CSF Gram stain technique may be slightly less sensitive in older children.

Culture

Culture of S pneumoniae from usually sterile body fluids (eg, blood, CSF, pleural fluid, middle ear effusion, synovial fluid) establishes the diagnosis definitively.

Perform susceptibility testing when an invasive infection is present.

Specific Studies

For each of the following clinical syndromes, specific testing recommendations are as follows:

Otitis media or sinusitis

Tympanocentesis and bacterial cultures of middle ear fluid should be performed in children with chronic otitis media refractory to antibiotic treatment. This requires technical expertise.

Sinus fluid should be obtained and sent for bacterial culture if the sinusitis is refractory to antibiotic treatment.

Upper respiratory tract cultures are not reliable in determining infection because of the high rate of asymptomatic children carrying S pneumoniae.

Occult bacteremia

A blood culture of sufficient volume (minimum of 2 mL) is indicated.

Pneumonia

Sputum cultures are difficult to obtain from children, and results may be falsely positive because of the high rates of upper respiratory colonization in this population.

Blood cultures should be obtained in all patients, although only 25-30% of patients with pneumococcal pneumonia have positive results on blood culture.

Meningitis

When meningitis is suspected, lumbar puncture should be performed. CSF should be sent for cell count, protein levels, glucose levels, Gram stain, and culture. Antigen tests are needed only if the patient was pretreated with antibiotics.

A blood culture also should be obtained to further confirm the diagnosis and the pathogens.

Osteomyelitis/septic arthritis

Procedures include surgical biopsy or joint aspiration; fluid or bone is cultured for the organism.

Perform blood culture because bacteremia is often present as well.

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Imaging Studies

Chest radiographs may reveal lobar or segmental consolidation or typical findings of round pneumonia.

In many centers, a head CT scan is performed in older children with meningitis to exclude increased intracranial pressure prior to performing lumbar puncture. No compelling evidence exists that CT findings are better than physical examination at predicting complications from lumbar puncture, and, in most patients, a CT scan causes unnecessary delay of lumbar puncture. In young children with an open fontanelle, a head CT scan is unnecessary unless physical findings suggest complications or a diagnosis other than meningitis. In children with persistent fevers despite appropriate antimicrobial therapy, a head CT scan, or preferably an MRI, should be performed to exclude subdural empyema. MRI is more sensitive than CT in the detection of subdural or epidural empyema.

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Procedures

Lumbar puncture may be indicated.

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