Streptococcus pneumoniae

Diagnosis

Indications for Testing

Laboratory Testing

  • Initial testing – CBC, arterial blood gas, chemistry profile
  • Antigen-based testing
    • Immunochromatographic urinary antigen testing in symptomatic adults – 70-80% sensitivity, >90% specificity
      • Most sensitive with bacteremia
      • Prior antibiotic use does not affect antigen test
      • Urine antigen test may stay positive for up to one month; not useful for recurrences or for assessing therapy success
    • Caution: children may asymptomatically shed S. pneumoniae antigen in urine, decreasing clinical specificity of test
  • Culture
    • Gold standard
    • Blood, cerebrospinal fluid (CSF), respiratory sources
  • Nucleic amplification tests and PCR – under investigation
  • Meningitis – Gram stain and CSF culture detect most cases of meningitis
  • Bacteremia and pneumonia
    • Blood cultures are positive in a minority of cases of invasive disease
    • High-quality sputum with gram stain and culture may yield results
  • Other testing for community-acquired pneumonia 

Differential Diagnosis

Clinical Background

Streptococcus pneumoniae causes pneumonia, otitis media, sinusitis, and meningitis.

Epidemiology

  • Incidence – invasive pneumococcal disease (22-25/100,000)
  • Transmission – humans are the natural reservoir for S. pneumoniae; organism colonizes in nasopharynx
    • Most common in winter and early spring

Organism

  • S. pneumoniae are gram-positive, typically lancet-shaped diplococci
  • More than 80 serotypes
  • S. pneumoniae serotypes that are pathogenic in humans are not always heavily encapsulated
    • Virulence determined by composition of capsular polysaccharide
    • Antibodies to capsular polysaccharides confer type-specific immunity

Risk for Invasive Disease

  • Asplenia
  • HIV infection
  • Alaska Native American Indian, African American
  • Immunocompromised state

Clinical Presentation

  • Pneumonia
    • Organism in 50% of community-acquired pneumonia cases
      • Often develops as a secondary pneumonia during upper respiratory tract infections
      • Abrupt onset of fever, shaking chills, cough, dyspnea, tachypnea and fatigue
      • Bacteremia in 25-40%
        • Causes 85% of all cases of bacteremia in pediatric population
        • Mortality rate for bacteremia is 20%; up to 60% in elderly
  • Otitis media (OM)
    • Organism in 30-50% of OM cases
      • ~90% of children in U.S. have ≥1 episode by age 3
      • 50% have >6 episodes/year
      • Penicillin-resistant pneumococcus is the most common cause of recurrent or persistent OM
  • Sinusitis
    • Organism in up to 40% of nonviral sinusitis cases 
  • Meningitis
    • Neurologic sequelae common in survivors

Treatment

  • Effectively treated with antibiotics
  • Complicating factors
    • Delayed treatment
    • Resistant bacteria
    • Presence of debilitating illness
    • Presence of immunosuppression

Prevention

  • Current vaccines recommended by the CDC
    • Adults – 23-valent polysaccharide vaccine (PPV23, Pneumovax)
      • Pneumovax – serotypes 1, 2, 3, 4,  5,  6B, 7F, 8,  9N, 9V, 10A, 11A, 12F, 14, 15B, 17F, 18C, 19F, 19A, 20, 22F, 23F, 33F
    • Infants and toddlers – 7-valent polysaccharide conjugate vaccine (PCV7, Prevnar)
      • Prevnar – serotypes 4, 6B, 9V, 14, 18C, 19F, 23F
    • Clinical trials in progress for 9 and 11 valent-conjugated vaccines that include serotypes 1 and 5, and serotypes 3 and 7F
    • Vaccination pre- and post-titers may be used to assess immune response in evaluation of immunodeficiency

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
Streptococcus pneumoniae Antigen, Urine 0060228
Method: Qualitative Immunochromatography

Rapid diagnostic test for invasive disease caused by S. pneumoniae (bacteremia, pneumonia, meningitis)

False positives may occur because of cross-reactivity with other members of S. mitis group or asymptomatic colonization of S. pneumonia

Clinical correlation is recommended

Patients who have received the S. pneumoniae vaccines may test positive in the 48 hours following vaccination; avoid testing within 5 days of receiving vaccination

 
Streptococcus pneumoniae Antigen, CSF 0061162
Method: Qualitative Immunochromatography

Diagnostic test for pneumonococcal meningitis

False positives may occur because of cross-reactivity with other members of S. mitis group

Clinical correlation is recommended

Patients who have received the S. pneumoniae vaccines may test positive in the 48 hours following vaccination; avoid testing within 5 days of receiving vaccination

 
Respiratory Culture and Gram Stain 0060122
Method: Stain/Culture/Identification

Determine organism of pneumonia

   
Blood Culture 0060102
Method: Continuous Monitoring Blood Culture/Identification

Determine presence of bacteremia

Testing is limited to the University of Utah Health Sciences Center only

 
Cerebrospinal Fluid (CSF) Culture and Gram Stain 0060106
Method: Stain/Culture/Identification

Gold standard for identification of bacterial organism in meningitis

   
Aerobic Organism Identification with Reflex to Susceptibility 0065070
Method: Identification. Methods may include biochemical, mass spectrometry, or sequencing.

Gold standard for identification of S. pneumoniae

For suspected agents of bioterrorism, Salmonella or Shigella, notify your state department of health and refer isolates to your state laboratory for identification; susceptibilities on agents of bioterrorism are not performed at ARUP

 
Additional Tests Available
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
CBC with Platelet Count and Automated Differential 0040003
Method: Automated Cell Count/Differential
Renal Function Panel 0020144
Method: Quantitative Chemiluminescent Immunoassay/Quantitative Enzyme-Linked Immunosorbent Assay

Test for renal function

Panel includes albumin, calcium, carbon dioxide, creatinine, chloride, glucose, phosphorous, potassium, sodium, and BUN

Streptococcus pneumoniae Antibodies, IgG (14 Serotypes) 0050725
Method: Quantitative Multiplex Bead Assay

Quantify antibody levels to pneumococcal polysaccharides in persons receiving vaccine to determine response to vaccine and whether protective antibody levels are reached at 1 month post-immunization

Vaccination pre- and post-antibody titer may aid in diagnosis of patients with suspected antibody deficiency with chronic/recurrent sinopulmonary infections

Test not designed to determine protection against S. pneumoniae based on a single sample

Streptococcus pneumoniae Antibodies, IgG (9 Serotypes) 2008919
Method: Quantitative Multiplex Bead Assay

Quantify antibody levels to pneumococcal polysaccharides in persons receiving vaccine to determine response to vaccine and whether protective antibody levels are reached at 4 weeks post-immunization

Legionella pneumophila Antigen, Urine 0070322
Method: Qualitative Enzyme-Linked Immunosorbent Assay
Mycoplasma pneumoniae by PCR 0060256
Method: Qualitative Polymerase Chain Reaction
Chlamydia pneumoniae by PCR 0060715
Method: Qualitative Polymerase Chain Reaction

Confirm C. pneumoniae as infectious agent in nasal wash, nasopharyngeal aspirate, bronchoalveolar lavage (BAL) or pleural fluid