Streptococcal Disease

Group A Streptococcal Disease

Group A streptococci (Streptococcus pyogenes) cause a broad spectrum of disease and are the primary bacterial cause of exudative tonsillitis and pharyngitis. Rheumatic fever, a resulting complication of untreated streptococcus infection, may develop 2-4 weeks after a streptococcal throat infection. In serious cases, rheumatic fever can cause heart disease.

Diagnosis

Indications for Testing

Sore throat, fever, and lymphadenopathy

Laboratory Testing

  • Consider Centor score when testing for group A strep in patient with sore throat
Modified Centor Criteria for Management of Sore Throat
Criteria Points

Absence of cough

1

Swollen and tender anterior cervical nodes

1

Temperature >100.4ºF (38ºC)

1

Tonsillar exudates or swelling

1

Age

 

3-14 years

1

15-44 years

0

≥45 years

-1

Cumulative Score Suggested Management

≤0 

No testing

Risk <10%
Test if high suspicion or recent contact

2-3 

Rapid testing or throat culture

≥4 

Treatment without testing

Recommended by Centers for Disease Control (CDC), American College of Physicians (ACP), and American Academy of Family Physicians (AAFP)

Not recommended by Infectious Diseases Society of America (IDSA) or American Heart Association (AHA) – approach results in unnecessary prescribing of antibiotics

  • Rapid antigen detection with reflex to culture for initial negative antigen testing in children
    • Sensitivity – 70-90%
    • Specificity – >95%
  • Swabbing posterior pharynx increases sensitivity of both rapid antigen test and culture
  • Positive rapid test confirms strep infection in presence of clinical syndrome
  • Throat culture – sensitivity 90-95%
  • Occurrence of strep infection in adults is low (10%); follow-up culture of negative rapid antigen not usually indicated
  • Antibody tests (antistreptolysin O [ASO] and anti-DNase-B) – provide serologic evidence of prior and current infection in suspected poststreptococcal glomerulonephritis or rheumatic fever (Parks, 2015)
    • May be indicated for
      • Patients with suspected acute rheumatic fever and poststreptococcal glomerulonephritis in high-risk settings
        • Either titer (ASO, anti-DNase-B) may be used for glomerulonephritis antibody
        • Both antibody tests should be used to exclude rheumatic heart disease
      • Patients with suspected rheumatic fever and poststreptococcal pharyngitis in low-risk settings – negative or low ASO usually sufficient to rule out disease
    • Not useful in diagnosing acute streptococcal disease (titers rise 7-14 days after infection and peak in 2-3 weeks) – convalescent titers with rise are best evidence of antecedent streptococcal infection
  • Elevated serum ASO titers – found in about 85% of individuals with acute rheumatic fever
    • ASO and anti-DNase-B antibodies – elevated titers in 90-95% of acute rheumatic fever patients
    • Skin infections with group A streptococci
      • Often associated with a poor ASO response
      • Anti-DNase-B titers are increased after skin infection

Differential Diagnosis

Background

Epidemiology

  • Prevalence
    • Streptococcal pharyngitis
      • Represents 1-2% of primary care visits
      • 1 of the top 20 reported diseases
    • Rheumatic fever poststreptococcal pharyngitis – 1-2/100,000
  • Age – usually <20 years
    • Rare in children <3 years old
  • Transmission – direct contact with nasal discharge
    • Seasonally most common in winter and/or early spring

Organism

  • Streptococcus pyogenes bacteria are gram-positive cocci
  • May evoke cross-reacting immune response with human tissue leading to the postinfection sequelae of  
    • Acute rheumatic fever (including rheumatic heart disease) – associated with streptococcal pharyngitis
    • Acute glomerulonephritis – associated with both streptococcal pharyngitis and skin disease
  • Causes a range of human disease
    • Pharyngitis
    • Impetigo
    • Scarlet fever
    • Invasive infections

Risk Factors

  • Young age
  • Crowded conditions

Clinical Presentation

  • Primary symptoms – sudden onset sore throat, fever (>100.4°F), headache
  • Constitutional symptoms – nausea, vomiting, abdominal pain
  • Clinical findings – pharyngeal erythema, exudative tonsillitis, anterior cervical adenopathy, palatine petechiae
    • Presence of cough, hoarseness, pharyngeal ulcers, diarrhea, and/or conjunctivitis are more suggestive of viral pharyngitis
    • Fine papular erythematous (sandpaper) rash – scarlet fever
  • Complications
    • Peritonsillar abscess
    • Toxic shock syndrome – almost exclusively associated with soft tissue infections
    • Rheumatic fever – rheumatic heart disease
    • Poststreptococcal glomerulonephritis
    • Poststreptococcal reactive arthritis

ARUP Lab Tests

Gold standard for confirming group A streptococcal infection

Order when rapid testing is negative and suspicion of streptococcus is moderately high

Confirm current or recent group A streptococcal infection in patients suspected of having a nonsuppurative complication such as acute glomerulonephritis (AGN) or acute rheumatic fever (ARF)

DNase-B and antistreptolysin O (ASO) antibody tests are generally ordered concurrently

Preferred test for rheumatic chorea since it remains elevated longer

Confirm a prior infection with group A streptococcus in patients suspected of having a nonsuppurative complication such as AGN or ARF

DNase-B and ASO antibody tests are generally ordered concurrently

Related Test

Medical Experts

Contributor

Delgado

Julio Delgado, MD, MS
Professor of Clinical Pathology, University of Utah
Chief, Division of Clinical Pathology, University of Utah and ARUP Laboratories
Chief Medical Officer and Director of Laboratories at ARUP Laboratories
Contributor

Fisher

Mark A. Fisher, PhD, D(ABMM)

Associate Professor of Clinical Pathology, University of Utah

Medical Director, Bacteriology, and Special Microbiology, Antimicrobial Susceptibility Testing, at ARUP Laboratories

References

Additional Resources
Resources from the ARUP Institute for Clinical and Experimental Pathology®

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 Lab Tests

Identify potential bacterial cause of pneumonia

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

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, Microbial Immunology, Parasitology and Fecal Testing, and Infectious Disease Antigen Testing at ARUP Laboratories

Contributor

Fisher

Mark A. Fisher, PhD, D(ABMM)

Associate Professor of Clinical Pathology, University of Utah

Medical Director, Bacteriology, and Special Microbiology, Antimicrobial Susceptibility Testing, at ARUP Laboratories

References

Additional Resources
Resources from the ARUP Institute for Clinical and Experimental Pathology®

Group B Streptococcal Disease

Group B Streptococcus (GBS) is one of the major causes of severe maternal and neonatal infections and sepsis. GBS screening by culture or polymerase chain reaction (PCR) is used to identify the presence of GBS in the vaginal/rectal area of a pregnant woman prior to delivery.

Diagnosis

Indications for Testing

  • Nonpregnant patients
    • Infection concerning for GBS
  • Pregnant patients
    • At-risk status (refer to Risk Factors)
    • GBS status unknown at time of delivery

Laboratory Testing

  • Routine culture
    • Identify GBS in blood, cerebrospinal fluid (CSF), tissues, wounds, urine, and other sites
  • Antenatal screening
    • Culture, PCR, nucleic acid amplification test (NAAT) – broth enrichment using combined vagina/rectal swab specimen is recommended
    • Status unknown at time of delivery – assessment of risk (delivery <37 weeks, premature rupture of membranes, and fever of >38°C [100.4°F]) is recommended for determining patient management
    • Susceptibility testing should be performed in women with penicillin allergy and high risk of anaphylaxis
  • Neonatal infection (CDC, 2010)
    • Neonate with signs and symptoms of neonatal infection
      • Initial tests – CBC with differential and platelet count, glucose, proteins, CSF studies, blood culture
    • Neonate born at <37 weeks gestation, or with mother positive for chorioamnionitis or with ruptured membranes ≥18 hours
      • Limited evaluation – CBC with differential and platelet count at birth

Differential Diagnosis

Screening

Screening for Streptococcus group B by PCR or culture is routinely recommended at 35-37 weeks in pregnant women.

Background

Epidemiology

  • Incidence
    • Neonatal – <1/1,000 live births
    • Adult (nonpregnant) – 2-5/100,000 for invasive disease
  • Transmission – vertical from mother to neonate in 75% cases
  • Ethnicity – higher rate of neonatal infections in African Americans

Organism

Group B streptococci (Streptococcus agalactiae) are gram-positive cocci arranged in pairs or chains.

Risk Factors

  • Maternal
    • Vaginal GBS colonization
    • Preterm delivery
    • Prolonged rupture of membranes
    • Intrapartum fever
    • Previous infant with GBS infection
  • Nonpregnant

Clinical Presentation

  • Neonatal infection
    • Early onset (first week of life) – respiratory distress, apnea, bacteremia, pneumonia, septic shock, meningitis (less frequent than in late onset)
    • Late onset (1 week-3 months) – bacteremia and meningitis are the most frequent manifestations
    • Meningitis is often associated with impaired psychomotor development
  • Adult infection (95% of cases are pregnancy related)

Prevention

Group B strep prevention guidelines (CDC, 2010)

ARUP Lab Tests

Initial test for infection

Identify bacteria in CSF

Identify bacteria in wounds

Anaerobe culture is recommended for body fluids, tissue, and deep wound/surgical cultures; refer to anaerobe culture and gram stain

Anaerobe culture is NOT included with this order

Help differentiate viral from bacterial source

Help differentiate viral from bacterial source

Identify bacteria in normally sterile body fluids

May assist in differentiating gout from septic arthritis

Anaerobe culture is recommended for body fluids, tissue, and deep wound/surgical cultures; refer to anaerobe culture and gram stain

For CSF specimens, order CSF culture and gram stain

For blood specimens, order blood culture or blood culture, AFB and fungal

Anaerobe culture is NOT included with this order

Determine genital and rectal GBS in pregnant women

Related Tests

Use to rapidly detect a panel of common viruses, bacteria, and fungi associated with meningitis and encephalitis

Do NOT use as a replacement for CSF bacterial and/or fungal culture and Cryptococcal antigen testing for at-risk patients

A negative result does not exclude a diagnosis of meningitis or encephalitis due to infection

Panel includes Cryptococcus neoformans/gattii, cytomegalovirus (CMV), enterovirus, Escherichia coli K1, Haemophilus influenzae, herpes simplex virus 1 (HSV-1), herpes simplex virus 2 (HSV-2), human herpesvirus 6 (HHV-6), human parechovirus, Listeria monocytogenes, Neisseria meningitidis, Streptococcus agalactiae, Streptococcus pneumoniae, varicella-zoster virus (VZV)

Medical Experts

Contributor

Fisher

Mark A. Fisher, PhD, D(ABMM)

Associate Professor of Clinical Pathology, University of Utah

Medical Director, Bacteriology, and Special Microbiology, Antimicrobial Susceptibility Testing, at ARUP Laboratories

Contributor

Lehman

Christopher M. Lehman, MD
Professor of Clinical Pathology, University of Utah
Co-Medical Director, University Hospitals and Clinics Clinical Laboratory
Contributor

Schlaberg

Robert Schlaberg, MD, MPH
Assistant Professor of Clinical Pathology, University of Utah
Medical Director, Microbial Amplified Detection, Virology, and Fecal Chemistry, and Assistant Medical Director, Virology and Molecular Infectious Disease at ARUP Laboratories

References

Additional Resources
Resources from the ARUP Institute for Clinical and Experimental Pathology®
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