Group A Streptococcal Pharyngitis

Aka: Group A Streptococcal Pharyngitis, Streptococcal Pharyngitis, Strep Throat, Strep Pharyngitis

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II. Epidemiology

  1. Peak season: Late fall through early spring
    1. Bimodal peaks in November to December and April to May
  2. Prevalence of Streptococcus in peak season
    1. Child <3 years old: Uncommon
    2. Child 3-5 years old: Up to 24% have Group A Beta-hemolytic Streptococcus
    3. Child 5 to 15 years old: Up to 37% have Group A Beta-hemolytic Streptococcus
    4. Adult: Up to 15% with Pharyngitis have Group A Beta-hemolytic Streptococcus
  3. Ages affected
    1. Most commonly affects ages 5 to 12 years old
    2. Not usually seen in children under age 3
  4. Incubation: 24 to 72 hours
  5. Transmission: direct person to person contact
    1. Passed by Saliva and nasal secretions
    2. Increased in crowded settings
    3. May be transmitted with food preparation
    4. Transmission rate from Streptococcus carriers is 3-11%
  6. Infectivity
    1. Decreases 1-3 days after antibiotic started
    2. Return to School and day care recommendations
      1. Antibiotics for minimum of 24 hours
      2. No fever

III. Etiology: Streptococcus Pyogenes

  1. Group A Beta-hemolytic Streptococcus

IV. Complications

  1. Non-suppurative
    1. Rheumatic Fever
    2. Acute post-streptococcal glomerulonephritis
  2. Suppurative
    1. Peritonsillar Abscess
    2. Suppurative Otitis Media
    3. Cervical Lymphadenitis
    4. Acute Sinusitis
    5. Mastoiditis
    6. Meningitis
    7. Bacteremia
    8. Endocarditis
    9. Pneumonia

V. Symptoms

  1. Stretococcal exposure in last 2 weeks (Test Sensitivity 19%, Test Specificity 91%)
  2. Pharyngitis
  3. Fever (Temperature >100.9)
  4. Cough absent
  5. Headache
  6. Myalgia

VI. Signs

  1. See Pharyngitis
  2. Anterior Cervical Lymphadenopathy
  3. Palatal Petechiae (Test Sensitivity 7%, Test Specificity 95%)
  4. Pharyngeal exudate (Test Sensitivity 26%, Test Specificity 88%)

VII. Differential Diagnosis

  1. See Pharyngitis Causes
  2. Common other causes
    1. Infectious Mononucleosis
      1. Posterior cervical adenopathy, Fatigue and prolonged Pharyngitis
    2. Hand, foot and mouth disease
      1. Oral Lesions, hand and foot skin lesions

VIII. Labs

  1. Streptococcal Rapid Antigen Test
    1. Used to distinguish intermediate probability of Streptococcal Pharyngitis (Centor Score 2-3)
    2. Test Sensitivity: 86%
    3. Test Specificity: 96%
  2. Group A Streptococcal PCR (Point-Of-Care GAS Nucleic Acid Amplification Test)
    1. Point of Care, 15 minute test for Group A Streptococcus Test via Nucleic Acid Amplification (NAAT)
    2. More expensive that the Streptococcal Rapid Antigen Test
      1. However, nearly perfect Test Sensitivity and requires no Throat Culture
      2. Group A Streptococcal Colonization will also result in a positive PCR test
      3. Other Bacterial Pharyngitis Causes are not identified by molecular testing
    3. Efficacy
      1. Positive Predictive Value: 97.7%
      2. Negative Predictive Value: 100%
  3. Throat Culture
    1. Used to confirm a negative rapid Antigen test
      1. IDSA recommends confirmatory Throat Culture in children (higher risk of Strep Throat complications)
    2. Some authors argue that Throat Culture is unnecessary
      1. They argue rapid Antigen test is adequately sensative for a very low risk of Rheumatic Fever
      2. Preventing each case of Rheumatic Fever costs $8 Million in U.S.
      3. Lean (2014) Pediatrics 134(4):771-81 [PubMed]
  4. Serology
    1. Consider in complicated cases (e.g. suspected Rheumatic Fever, Poststreptococcal Glomerulonephritis)
    2. Antistreptolysin O titer (ASO Titer)
      1. Confirms diagnosis (with serial values), but not helpful in acute disease
      2. Increases within 1 week of infection and peaks at 4 to 6 weeks after infection
    3. Anti-Deoxyribonuclease B (anti-DNase B)
      1. Increases within 1 week of infection and peaks at 6 to 8 weeks after infection

IX. Diagnosis

  1. See Strep Score

X. Management: Acute Episode

  1. See Sore Throat symptomatic management
  2. Prescribe medications in liquid form if odynophagia
  3. Glucocorticoids are NOT routinely recommended (aside from Peritonsillar Abscess)
  4. Antibiotic Course
    1. Penicillin use requires 10 day course
    2. Five days of alternative antibiotics effective
      1. Amoxicillin Clavulanate (Augmentin)
      2. Ceftibuten
      3. Cefuroxime
      4. Loracarbef
      5. Clarithromycin
      6. Erythromycin estolate
    3. References
      1. Adam (2000) Clin Infect Dis 182:509-16 [PubMed]
  5. First Line Antibiotics
    1. Standard Penicillin Regimen
      1. Penicillin VK (250 mg/5cc; tablets: 250 mg, 500 mg)
        1. Dosing: 12.5 mg/kg (25 mg/kg if severe) up to 500 mg bid for 10 days
        2. Child <9 kg: 125 mg (0.5 tsp) po bid
        3. Child 10-18 kg: 250 (1 tsp) mg po bid
        4. Child 19-27 kg: 375 (1.5 tsp) mg po bid
        5. Adult and child >27 kg: 500 mg orally twice daily for 10 days
      2. Amoxicillin (250 mg/5cc)
        1. Penicillin is preferred first line
        2. Child: 25 mg/kg (up to 500 mg) orally twice daily OR 50 mg/kg (up to 1000 mg) once daily for 10 days
          1. Child <9 kg: 125 mg (0.5 tsp) po bid
          2. Child 10-18 kg: 250 (1 tsp) mg po bid
          3. Child 19-27 kg: 375 (1.5 tsp) mg po bid
        3. Adult and child >27 kg: 500 mg orally twice daily OR 1000 mg orally daily for 10 days
    2. Macrolide for Penicillin Allergic (2-8% resistance, 30% GI adverse effects)
      1. Erythromycin Base
        1. Adult: 500 mg PO q6 hours for 10 days
      2. Erythromycin Estolate
        1. Children: 20-40 mg/kg divided every 12 hours
      3. Erythromycin Ethyl Succinate (EES)
        1. Children: 40 mg/kg divided bid (up to 1 g/day)
        2. Adult or child >40 kg: 250 mg qid or 333 mg tid
      4. Azithromycin (200 mg/tsp; 250 mg tablet)
        1. Child 12 mg/kg/day up to 500 mg for 5 days
        2. Adult or child >40 kg: 500 mg daily for 5 days (or 500 mg day 1, then 250 mg qd for 4 days)
      5. Clarithromycin
        1. Adults: 250 mg orally twice daily for 10 days
        2. Children: 7.5 mg/kg/dose orally twice daily for 10 days
    3. Clindamycin for penicillin Hypersensitivity
      1. Child: 7 mg/kg/dose orally every 8 hours (up to 300 mg/dose) for 10 days
      2. Adult: 300 mg orally every 8 hours for 10 days
    4. Single IM dose regimen (Consider for non-compliant)
      1. Benzathine Penicillin (Bicillin LA)
        1. Adults (over 27 kg) 1.2 MU IM
        2. Pediatric (under 27kg): 600,000 U IM

XI. Management: Second-Line Antibiotics

  1. Indications
    1. Allergy to other other agents
    2. Recurrent Streptococcal Pharyngitis
      1. Cephalosporins have higher rates of clinical cure
      2. Casey (2004) Pediatrics 113:866-82 [PubMed]
  2. Cephalexin (Keflex)
    1. Adult: 500 mg PO bid
    2. Child: 40 mg/kg/day (up to 1000 mg/day) divided bid
  3. Cefadroxil (Duricef)
    1. Adult: 1 gram orally daily
    2. Child: 30 mg/kg/day divided bid
  4. Cefuroxime (Zinacef, Ceftin)
    1. Adult: 250 mg PO bid
    2. Child: 10 mg/kg/dose PO bid
  5. Cefpodoxime (Vantin)
    1. Adult: 100 mg PO bid
    2. Child: 5 mg/kg/dose PO bid
  6. Cefdinir (Omnicef)
    1. Adult: 300 mg orally twice daily OR 600 mg orally once daily
    2. Child: 7 mg/kg/dose orally twice daily OR 14 mg/kg/dose once daily
  7. Loracarbef (Lorabid)
    1. Adult: 200-400mg PO bid
    2. Child: 15 mg/kg/day divided bid
  8. Amoxicillin Clavulanate (Augmentin)
    1. Adult: 500-875 mg PO bid
    2. Child: 40 mg/kg/day divided bid
  9. Bicillin
    1. Single IM shot (dosing as above)

XII. Management: Tonsillectomy

  1. See Tonsillectomy Indications

XIII. Efficacy: Benefits of Antibiotic Treatment

  1. Benefits are at the expense of 10 million antibiotic prescriptions annually for Strep Throat
    1. Risk of serious Allergic Reaction and Diarrheal illness including Clostridium difficile
  2. Prevents Rheumatic Fever
    1. Antibiotics decrease Rheumatic FeverIncidence by 90%
      1. Effective if given in first 9 days of infection
    2. Number Needed to Treat: 3000-4000 patients treated to prevent one case Rheumatic Fever
      1. Data is based on 1940s data, and some estimates estimate NNT at over 1 Million
      2. One third of those Rheumatic Fever patients develop cardiac complications (NNT 12000)
      3. No case reports in U.S. of Rheumatic Fever since 1961
  3. Prevents suppurative complications
    1. Peritonsillar Abscess (variable evidence, NNT 50 to 225)
    2. Acute Sinusitis
    3. Suppurative Otitis Media (NNT 1 in 200)
    4. Cervical Lymphadenitis
  4. Decreases epidemic spread
  5. Decreases duration of disease by about 1 day
  6. Does NOT prevent Post-Streptococcal Glomerulonephritis (PSGN)
  7. References
    1. Del Mar (2006) Cochrane Database Syst Rev (4): CD000023 [PubMed]

XIV. Complications

  1. See Group A Beta-hemolytic Streptococcus
  2. Lemierre Syndrome
  3. Airway Compromise

XV. Complications: Etiologies for recurrent Streptococcal Pharyngitis

  1. Poor Compliance with oral medications (most common)
    1. Day 3: 50% stopped antibiotics
    2. Day 6: 70% stopped antibiotics
    3. Day 9: 80% stopped antibiotics
    4. Families reporting taking all the medication: 80%
  2. Repeat exposure in crowded conditions
    1. School
    2. Daycare
    3. Home or workplace
  3. Eradicated protective throat flora by prior antibiotic
    1. a-hemolytic Streptococcus is protective normal flora
    2. Cephalosporins apparently do less harm
  4. Selected beta-lactam resistance by prior antibiotic
    1. Consider Augmentin for 10 day course
  5. Suppressed Immune response from prior antibiotics
  6. Antibiotic Resistance
    1. Penicillin resistance is infrequent in Strep Throat
    2. Macrolide (Erythromycin, Biaxin, Zithromax)
      1. Resistance 2-8% in U.S.
  7. Chronic Pharyngeal Carriage of Streptococcus pyogenes
    1. Pharyngitis due to another cause

XVI. References

  1. Anderson (2019) Crit Dec Emerg Med 33(9): 3-10
  2. Bisno (1997) Clin Infect Dis 25:574-83 [PubMed]
  3. Choby (2009) Am Fam Physician 79(5): 383-90 [PubMed]
  4. Ebell (2000) JAMA 284(22):2912-8 [PubMed]
  5. Hayes (2001) Am Fam Physician 63(8):1557-64 [PubMed]
  6. Kalra (2016) Am Fam Physician 94(1): 24-31 [PubMed]
  7. Pichichero (1995) Ann Emerg Med 25:390-403 [PubMed]
  8. Pichichero (1998) Pediatr Rev 19:291-302 [PubMed]
  9. Smith (2023) Am Fam Physician 107(1): 35-41 [PubMed]
  10. Van Driel (2021) Cochrane Database Syst Rev (3): CD004406 +PMID: 27614728 [PubMed]

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