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Group A Streptococcal Pharyngitis

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Group A Streptococcal Pharyngitis, Streptococcal Pharyngitis, Strep Throat, Strep Pharyngitis, Streptococcus Pyogenes Pharyngitis

  • See Also
  1. Pharyngitis
  2. Pharyngitis Causes
  3. Dysphagia
  4. Tonsillitis
  5. Peritonsillar Abscess
  6. Retropharyngeal Abscess
  7. Lemierre Syndrome
  8. Diphtheria
  9. Chronic Pharyngeal Carriage of Streptococcus pyogenes
  10. Tonsillectomy Indications
  • 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 10 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 years
  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
  • Pathophysiology
  1. Caused by Streptococcus Pyogenes (Group A Beta-hemolytic Streptococcus)
  • 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
  • Signs
  1. See Pharyngitis
  2. Anterior Cervical Lymphadenopathy
  3. Palatal Petechiae (Test Sensitivity 7%, Test Specificity 95%)
  4. Pharyngeal or Tonsillar exudate (Test Sensitivity 26%, Test Specificity 88%)
  • 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
    3. Upper Respiratory Infection (viral)
      1. Cough, congestion, Coryza and Hoarseness
  • 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
  • Diagnosis
  1. See Modified Centor Criteria
  2. See FeverPAIN Streptococcal Pharyngitis Score
  3. Management may be based on Modified Centor or FeverPAIN scoring (or other modifiers)
    1. Low risk findings (score 0-1)
      1. Consider no further testing, and symptomatic management only
      2. Also consider no further testing in age <3 years (Strep Pharyngitis is uncommon in this age group)
    2. Moderate Risk findings (score 2-3)
      1. Test for Streptococcal Pharyngitis and treat if present
    3. High Risk findings (score >=4) OR
      1. Consider treating for Streptococcal Pharyngitis without further testing
      2. Also consider treating patient with Pharyngitis AND close contact (esp. household) with Strep Pharyngitis
  • Management
  • Acute Episode
  1. See Sore Throat symptomatic management (includes Acetaminophen, Ibuprofen)
  2. Prescribe medications in liquid form if odynophagia
  3. Glucocorticoids are NOT routinely recommended (aside from Peritonsillar Abscess)
    1. Corticosteroids may be considered when severe pain risks Dehydration (evaluate for PTA and other complications)
    2. Oral Dexamethasone 0.6 mg/kg up to 10 mg for one dose may be considered (but NOT recommended by IDSA)
      1. Long (2021) Acad Emerg Med 28(4): 470-1 [PubMed]
  4. Return to School, work or daycare Criteria
    1. Fever has resolved AND
    2. Antibiotics have been started for >12 hours
  5. Narrow spectrum antibiotics (esp. Penicillin) are preferred
    1. No Streptococcal Pharyngitis strains have been indentified that are Penicillin resistant
    2. Broad spectrum antibiotics do not prevent Strep Throat recurrence
    3. Amoxicillin is typically used for young children who must use oral suspensions
      1. Despite a century of medical advances, palatable Penicillin suspension has never been achieved
    4. Antibiotics are NOT recommended for non-Group A Streptococcal Pharyngitis
      1. Only Group A Streptococcal Pharyngitis is associated with Rheumatic Fever (the key reason for antibiotics)
      2. Avoid antibiotics for Streptococcal dysgalactiae (Group C or Group G Streptococcus)
  6. Antibiotic Course
    1. Penicillin at standard dosing requires 10 day course
      1. However, Penicillin 800 mg VK four times daily for 5 days (age >6 years) is equivalently effective
      2. Skoog (2019) BMJ 367:15337 [PubMed]
      3. Tell (2022) BMC Infect Dis 22(1): 840 [PubMed]
    2. Five days of alternative antibiotics are effective (however broad spectrum agents are not recommended)
      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]
  7. First Line Antibiotics
    1. Standard Penicillin Regimen
      1. Penicillin VK (250 mg/5cc; tablets: 250 mg, 500 mg)
        1. Repeat course if a dose is missed (when giving only twice daily)
        2. Dosing: 12.5 mg/kg (25 mg/kg if severe) up to 500 mg orally twice daily for 10 days
        3. Child <9 kg: 125 mg (0.5 tsp) orally twice to three times daily for 10 days
        4. Child 10-18 kg: 250 (1 tsp) mg orally twice to three times daily for 10 days
        5. Child 19-27 kg: 375 (1.5 tsp) mg orally twice to three times daily for 10 days
        6. Adult and child >27 kg: 500 mg orally twice to three times 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) orally twice daily for 10 days
          2. Child 10-18 kg: 250 mg (1 tsp) orally twice daily for 10 days
          3. Child 19-27 kg: 375 mg (1.5 tsp) orally twice daily for 10 days
        3. Adult and child >27 kg: 500 mg orally twice daily OR 1000 mg orally daily for 10 days
    2. Cephalosporins fo Penicillin Allergy WITHOUT Anaphylaxis
      1. Beta Lactams are preferred over Macrolides and Clindamycin if non-anaphylactic reaction (Type 4 Hypersensitivity)
      2. Cephalexin (Keflex)
        1. Child: 20 mg/kg/dose (up to 500 mg) orally twice daily for 10 days
        2. Adult:: 500 mg orally twice daily for 10 days
    3. Macrolide for Penicillin Anaphylaxis (2-8% resistance, 30% GI adverse effects)
      1. Consider Throat Culture with sensitivities
      2. 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)
      3. Clarithromycin
        1. Adults: 250 mg orally twice daily for 10 days
        2. Children: 7.7 mg/kg/dose (up to 250 mg) orally twice daily for 10 days
      4. Erythromycin Base
        1. Adult: 500 mg orally every 6 hours for 10 days
      5. Erythromycin Estolate
        1. Children: 20-40 mg/kg divided every 12 hours for 10 days
      6. Erythromycin Ethyl Succinate (EES)
        1. Children: 40 mg/kg divided twice daily (up to 1 g/day) for 10 days
        2. Adult or child >40 kg: 250 mg four times daily or 333 mg orally three times daily for 10 days
    4. Clindamycin for Penicillin Anaphylaxis
      1. Child: 7 mg/kg/dose (up to 300 mg) orally three times daily for 10 days
      2. Adult: 300 mg orally three times daily for 10 days
    5. 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
  • Management
  • Second-Line Antibiotics
  1. Indications: Treatment Failure or Relapse (up to 10% of cases)
    1. Symptom worsening or persistent symptoms >5 days
    2. Consider noncompliance
    3. Consider complications (e.g. Lemierre Syndrome, Peritonsillar Abscess)
    4. Consider comorbid conditions (e.g. Mononucleosis)
    5. Consider Throat Culture with sensitivities (evaluate for Antibiotic Resistance)
      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)
  1. See Tonsillectomy Indications
  • 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]
  • Complications
  • General
  1. See Group A Beta-hemolytic Streptococcus
  2. Airway
    1. Lemierre Syndrome
    2. Airway Compromise
    3. Peritonsillar Abscess
  3. Group A Beta-hemolytic Streptococcus Specific Complications
    1. Rheumatic Fever
    2. Poststreptococcal Glomerulonephritis
    3. Poststreptococcal Reactive Arthritis
    4. Childhood Acute Neuropsychiatric Symptoms (or PANDAS)
    5. Guttate Psoriasis
    6. Sydenham's Chorea
    7. Henoch Schonlein Purpura
  4. Other suppurative complications
    1. Suppurative Otitis Media
    2. Cervical Lymphadenitis
    3. Acute Sinusitis
    4. Mastoiditis
    5. Meningitis
    6. Bacteremia
    7. Endocarditis
    8. Pneumonia
  • Complications
  • Causes of 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
  • 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. Hamilton (2024) Am Fam Physician 109(4): 343-9 [PubMed]
  6. Hayes (2001) Am Fam Physician 63(8):1557-64 [PubMed]
  7. Kalra (2016) Am Fam Physician 94(1): 24-31 [PubMed]
  8. Pichichero (1995) Ann Emerg Med 25:390-403 [PubMed]
  9. Pichichero (1998) Pediatr Rev 19:291-302 [PubMed]
  10. Smith (2023) Am Fam Physician 107(1): 35-41 [PubMed]
  11. Van Driel (2021) Cochrane Database Syst Rev (3): CD004406 +PMID: 27614728 [PubMed]