Streptococcus pneumoniae

Diagnosis

Indications for Testing

• Invasive disease (eg, pneumonia, meningitis)

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 
  • Legionella pneumophila
  • Mycoplasma pneumoniae
  • Chlamydia pneumoniae

Differential Diagnosis

• Other testing for community-acquired pneumonia 
  • C. pneumoniae
  • M. pneumoniae
  • L. pneumophila
• Asthma
• Exacerbation of chronic obstructive pulmonary disease
• Viral pneumonia (influenza, adenovirus, respiratory syncytial virus)
• Fungal pneumonia
• Pneumonitis

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

Click the plus sign to expand the table of additional tests.

Test Name and Number	Comments
Streptococcus pneumoniae Antibodies, IgG, Polysaccharide Vaccine (11 serotypes) 2005790 Method: Quantitative Multiplex Bead Assay	Quantify antibody levels to 23-valent pure polysaccharides in persons receiving vaccine to determine response to vaccine and whether protective antibody levels are reached at 4 weeks post-immunization
Streptococcus pneumoniae Antibodies, IgG, Conjugate Vaccine (12 serotypes) 2005791 Method: Quantitative Multiplex Bead Assay	Quantify antibody levels to the 13-valent (Prevnar™) pneumococcal polysaccharide vaccine in persons receiving vaccine to determine response to vaccine and whether protective antibody levels are reached at 4 weeks post-immunization
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 (23 Serotypes) 2005779 Method: Quantitative Multiplex Bead Assay
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