Group A Streptococcal Pharyngitis

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

1. 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: 40% with Pharyngitis have Streptococcus
      2. Adult: 10% with Pharyngitis have 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: 2 to 5 days
   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
   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. Afebrile
2. Etiology: Streptococcus Pyogenes
   1. Group A Beta-hemolytic Streptococcus
3. 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
4. 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
5. 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%)
6. Differential Diagnosis
   1. See Pharyngitis Causes
7. Labs
   1. Streptococcal Rapid Antigen Test
      1. Used to distinguish intermediate probability of strep
   2. Throat Culture
      1. Used to confirm a negative rapid antigen test
   3. Antistreptolysin O titer (ASO Titer)
      1. Confirms diagnosis, but not helpful in acute disease
8. Diagnosis
   1. See Strep Score
9. Management: Acute Episode
   1. Sore Throat symptomatic management
   2. Prescribe medications in liquid form if odynophagia
   3. 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
   4. First Line Antibiotics
      1. Standard Penicillin Regimen
         1. Penicillin VK (250 mg/5cc; tablets: 250 mg, 500 mg)
            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
            4. Adult and child >27 kg: 500 mg bid for 10 day
         2. Amoxicillin (250 mg/5cc)
            1. Penicillin is preferred first line
            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 bid for 10 day
      2. Macrolide for Penicillin Allergic (2-8% resistance)
         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
         5. Clarithromycin
            1. Adults: 250-500 mg PO bid for 10 days
            2. Children: 15 mg/kg/day divided bid
      3. Single IM dose regimen (Consider for non-compliant)
         1. BenzathinePenicillin (Bicillin LA)
            1. Adults (over 27 kg) 1.2 MU IM
            2. Pediatric (under 27kg): 300,000 - 600,000 U IM
10. Management: Recurrent Streptococcal Pharyngitis
    1. General
       1. Cephalosporins have higher rates of clinical cure
       2. Casey (2004) Pediatrics 113:866-82
    2. Cephalexin (Keflex)
       1. Adult: 500 mg PO bid
       2. Child: 25-50 mg/kg/day divided bid to qid
    3. Cefuroxime (Zinacef, Ceftin)
       1. Adult: 250-500 mg PO bid
       2. Child: 20-30mg/kg/day PO divided bid
    4. Cefpodoxime (Vantin)
       1. Adult: 100-400mg PO bid
       2. Child: 10 mg/kg/day divided bid
    5. Cefadroxil (Duricef)
       1. Adult: 1 gram PO qd
       2. Child: 30 mg/kg/day divided bid
    6. Loracarbef (Lorabid)
       1. Adult: 200-400mg PO bid
       2. Child: 15 mg/kg/day divided bid
    7. Amoxicillin Clavulanate (Augmentin)
       1. Adult: 500-875 mg PO bid
       2. Child: 40 mg/kg/day divided bid
    8. Bicillin
       1. Single IM shot (dosing as above)
11. Efficacy: Benefits of Antibiotic Treatment
    1. Prevents Rheumatic Fever
       1. Antibiotics decrease Rheumatic FeverIncidence by 90%
       2. Number Needed to Treat: 3000-4000 patients treated to prevent one case Rheumatic Fever
       3. Effective if given in first 9 days of infection
    2. Prevents suppurative complications
       1. Peritonsillar Abscess
       2. Suppurative Otitis Media
       3. Cervical lymphadenitis
    3. Decreases epidemic spread
    4. Decreases duration of disease by about 1 day
12. 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
13. References
    1. Bisno (1997) Clin Infect Dis 25:574-83
    2. Choby (2009) Am Fam Physician 79(5): 383-90
    3. Ebell (2000) JAMA 284(22):2912-8
    4. Hayes (2001) Am Fam Physician 63(8):1557-64
    5. Pichichero (1995) Ann Emerg Med 25:390-403
    6. Pichichero (1998) Pediatr Rev 19:291-302