Streptococcus pneumoniae - Pneumococcal Disease

Streptococcus pneumoniae bacteria cause a wide variety of infections, including pneumonia, bacteremia, otitis media (OM), sinusitis, and meningitis. A gram stain of infectious material (pus, sputum) can be performed to demonstrate the presence of the gram-positive, lancet-shaped cocci, followed by culture. Urinary antigen testing may be a useful adjunct to culture in adults.

Diagnosis

Indications for Testing

  • Fever or chills, cough, shortness of breath, tachypnea, tachycardia, infiltrates on chest x-ray, suggesting pneumonia
  • Fever, neck pain and stiffness, headache, suggesting meningitis
  • Fever or chills, hypotension, tachycardia, suggesting bacteremia

Laboratory Testing

  • CDC testing recommendations
  • Initial testing
    • CBC, arterial blood gas, chemistry profile
    • Gram stain and culture
      • Growth of bacteria from infected site is gold standard
      • Gram stain can be performed on cerebrospinal fluid (CSF), sputum, pus, or sites of infection
      • CSF gram stain and culture have good sensitivity for meningitis
    • Antigen-based testing – urine and CSF
      • Immunochromatographic urinary antigen testing in symptomatic adults – 70-80% sensitivity, >90% specificity
        • Most sensitive with bacteremia
        • May remain positive even after prior antibiotic use
        • Urine antigen test may remain positive for months; not useful for recurrences or for assessing therapy success
      • Caution – children may asymptomatically shed S. pneumoniae antigen in urine; this decreases clinical specificity of test
    • Antibiotic resistance testing
      • Identify whether antibacterial resistance is present in the infecting organism
  • Other testing for pneumonia

Differential Diagnosis

Background

Epidemiology

  • Incidence
    • Pneumococcal disease – ~445,000 hospitalizations/year in U.S. (CDC, 2018)
      • Pneumonia – 400,000 hospitalizations/year (CDC, 2017)
      • Bacteremia – 5,000 cases/year, without pneumonia (CDC, 2017)
      • Meningitis – 2,000 cases/year (CDC, 2017)
  • Transmission
    • Most common in winter and early spring
    • Humans are the natural reservoir for S. pneumoniae; organism colonizes the nasopharynx

Organism

  • S. pneumoniae are gram-positive, typically lancet-shaped diplococci and include 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

Clinical Presentation​

  • Pneumonia
    • Recent estimates suggest 27% of community-acquired pneumonia cases are S. pneumoniae (Said, 2013)
      • Often develops as a secondary pneumonia during upper respiratory tract infections
      • Abrupt onset of fever, shaking chills, cough, dyspnea, tachypnea, and fatigue
  • Invasive disease
    • Meningitis
      • Headache, neck stiffness, fever, vomiting, lethargy
      • Early intervention critical to prevent neurologic sequelae
    • Bacteremia 
      • In 25-30% of pneumococcal pneumonia cases (Said, 2013; CDC, 2017)
        • Causes 85% of all cases of bacteremia in pediatric population
        • Mortality rate for bacteremia is 20%, and up to 60% in the elderly (CDC, 2017)
    • Endocarditis
    • Other – pericarditis, abdominal infections (eg, peritonitis), osteomyelitis, septic arthritis
  • OM
    • 30-50% of OM cases are caused by S. pneumoniae
      • ~90% of children in U.S. have one or more episode by 3 years
      • 50% have six or more episodes/year
      • Penicillin-resistant pneumococcus is the most common cause of recurrent or persistent OM
  • Sinusitis
    • Up to 40% of nonviral sinusitis cases are caused by S. pneumoniae

ARUP Laboratory Tests

Identify potential bacterial cause of pneumonia

Important informationLimited to the University of Utah Health Sciences Center only

Detect presence of bacteria in blood

Important informationTesting is limited to the University of Utah Health Sciences Center only

Low volume will result in decreased recovery of pathogens

Identify bacteria in CSF

Important informationLimited to the University of Utah Health Sciences Center only

Aid in the diagnosis of pneumococcal pneumonia

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

Aid in the diagnosis of pneumococcal 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

Reflex panel to identify aerobic bacterial isolate and determine in vitro susceptibility to antimicrobial agents

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

Detect respiratory pathogens in patients with pneumonia

Related Tests

Evaluate for kidney dysfunction in patients with known risk factors (eg, hypertension, diabetes, obesity, family history of kidney disease)

Panel includes albumin, calcium, carbon dioxide, creatinine, chloride, glucose, phosphorous, potassium, sodium, blood urea nitrogen (BUN), and a calculated anion gap value

Evaluate the ability of a patient to produce antibody to pure polysaccharide vaccines (Pneumovax) or protein conjugated vaccines (Prevnar)

Provide retrospective evidence of suspected Legionella pneumophila infection

Detect M. pneumoniae bacteria

Detect C. pneumoniae in bronchoalveolar lavage (BAL), nasal wash, nasopharyngeal swab, or pleural fluid

Medical Experts

Contributor

Couturier

Marc Roger Couturier, PhD, D(ABMM)
Associate Professor of Clinical Pathology, University of Utah
Medical Director, Parasitology/Fecal Testing, Infectious Disease Antigen Testing, Bacteriology, and Molecular Amplified Detection, ARUP Laboratories
Contributor

Fisher

Mark A. Fisher, PhD, D(ABMM)
Associate Professor of Clinical Pathology, University of Utah
Medical Director, Bacteriology, Special Microbiology, and Antimicrobial Susceptibility Testing, ARUP Laboratories

References

Additional Resources