STREPTOCOCCUS, GROUP A


See also under "Group B Streptococcus" in OB/GYN section
I. Classification of Streptococcus species
  1. All strep are gm-pos. cocci; divided into
  1. Alpha-hemolytic
  2. Beta-hemolytic, inc. Gp. A (see below); Gp. B (neonates, vag. flora), Gp. G
  3. Gamma-hemolytic
  1. Lancefield groups typed according to surface CHO moieties
II. Group A Strep Pathophysiology
  1. Part of normal skin flora
  2. Makes tissue-munching enzymes: DNAase, hyaluron-idase, streptokinase, streptolysin O (can check anti-SLO titers to see if recent infection occurred)
III. Suppurative infections--rare before age 3yo
  1. Pharyngitis--nonspecific presentation
  1. Usual onset over 24h
  2. Can begin with vomiting, headache, malaise, fever102'F
  3. Exam typically shows beefy red tonsils; uvular petechiae, greenish-grey exudate, painful submandibular lymphadenopathy
  4. Can get purulent nasopharyngitis
  5. Lasts about 4d untreated
  6. Treatment with Penicillin V Potassium
  1. Shortens course & can prevent acute rheumatic fvr if start by day 9
  2. 7d course superior to 3d course (fewer recurrences of sx) in a randomized trial of 561 adults (BMJ 320:150, 2000--AFP)
  3. In a meta-analysis of 6 randomized controlled trials studying frequency of dosing, cure rate was no diff. between BID and TID or QID schedules BUT QD was ass'd with a 12% lower cure rate (Peds. 105:e19, 2000--JW)
  1. Treatment with Amoxicillin (750mg QD x 10d) as good as TID PCN VK in a study of 152 kids 3-18yo with Group A Strep pharyngiti
  2. Treatment with systemic corticosteroids
    1. In a study in 125 children 5-18yo with moderate-to-severe pain from acute pharyngitis randomized to oral dexamethasone 0.6mg/kg (max 10mg) PO x 1 vs. placebo, dexamethasone recipients had sig. improvement in time to inital pain relief; among group A strep-negative pts, there were also sig. reductions in time to complete resolution of pain and degree of improvement in the first 24h after treatment (Arch. Pediat. Adol. Med. 159:278, 2005--JW)
  3. Differential diagnosis includes inf. mono (get other URI sx); adenovirus (high fvr); enterovirus, diptheria, HSV
  4. 451 children age 2-13 w/ sore throat and pharyngeal erythema had clinical features recorded & throat cx done (Lancet 350:918, 1997-JW) & the following correlative features were found:
    1. Fever had sens. 37% and spec. 66%
    2. Exudate on tonsils had sens 31% and spec. 81%
    3. Tender cervical lymph nodes had sens 34% and spec. 82%
    4. Presence of a large cervical lymph node had sens 81% but spec. 45%
    5. (Exudate + large cervical node) had sens 84% and spec. 40%
  5. Adenotonsillectomy for recurrent Group A Streptococcal pharyngitis
    1. In a study of 300 children 2-8yo (mean age 4.5y) with recurrent GAS pharyngitis randomized to adenotonsillectomy vs. no tx, there was no sig. diff. in primary outcome of # of fever episodes in ensuing 22mos, but sxurgery group had sig. fewer mean throat infections in the subsequent year (0.56/yr vs. 0.77/yr) (BMJ 329:651, 2004--AFP)
  1. Scarlet fever--a sequela of strep pharyngitis
  1. Strawberry tongue
  2. "Sandpapery" rash, esp. in intertriginous folds ("Pastilla's lines")
  3. Circumoral pallor/red cheeks
  4. 4 types of erythrogenic toxins
  1. Impetigo--honey-crusted lesions, all lesions in a region of skin look the same
  2. Cellulitis--more common even than staph; lymphatic spread; painful lymphadenopathy
  3. Erysipelas--basically facial cellulitis; very virulent
  4. Toxic Shock Syndrome
    1. Mortality incidence is 30-70%
    2. In a randomized trial of Intravenous Immune Globulin vs. placebo in 21 pts with streptococcal toxic shock syndrome (all of whom received standard antibiotics and supportive care), the IVIG group had nonsig. lower 28d mortality (10% vs. 36%) (Clin. Inf. Dis. 37:333, 2003--JW)
    3. See also Sepsis and Septic Shock
IV. Sequelae of Group A Streptococcus infections
  1. Post-streptococcal glomerulonephritis
    1. Occurs 1-2wks after untreated GAS pharyngitis or 2-4wks after skin infection due to GAS
    2. Most cases are in children < 10yo
    3. Common clinical features-Usually abrupt onset and resolves after 2wks
      1. Edema (particularl in periorital region)
      2. Hypertension
      3. Dark urine ("tea-colored')
      4. Microscopic hematuria (can persist up to 1y)
    4. In some cases may also have:
      1. Gross hematuria
      2. Pulmonary edema
      3. Arthralgias and joint swelling
      1. Severe hypertension and oliguria acute renal failure with hyperkalemia
    5. Long-term sequelae (from one longitudinal series over 15y:
      1. Proteinuria (7%)
      2. Microhematuria (5%)
      3. Hypertension (3%)
      4. Azotemia (1%)
    6. Laboratory findings
      1. Low serum levels of C3 complement-Return to normal 2-3mos after presentation
      2. Serum anti-streptolysin O can confirm recent GAS infection if throat culture is negative
      3. antiDNase B titer can confirm recent skin infection
      4. Urinalysis showing proteinuria, RBC cases, and dysmorphic RBCs.
    7. Treatment
      1. Antibiotics (preferably penicillin)
      2. Treat edema with restriction of dietary Na and loop diuretics
      3. Treat hypertension with antihypertensives
      4. Corticosteroids are not helpful
      5. Screen household contacts for GAS
  2. Acute rheumatic fever--a sequela of GAS pharyngitis but not of skin infection; click link for more details
  3. Pediatric Autoimmune Neuropsychiatric Disorders (PANDAS)
    1. A pattern of neuropsychiatric disturbances, e.g. obsessive-compulsive disorder and tics, associated with GAS infections (Arch. Ped. Adol. Med. 156:356, 2002--JW)
    2. Studies examining strength of association between PANDAS-like symptoms and GAS
      1. In a prospective study of 399 children with symptomatic GAS pharyngitis treated with antibiotics, 207 children with nonstreptococcal pharyngitis treated symptomatically, and 196 well children, whose parents completed PANDAS symptom scores for 12 weeks after enrollment, PANDAS sx were more prevalent in both groups of sick kids than the well kids, but there was no diff. between the GAS pharyngitis group and the non-GAS pharyngitis group (Arch. Pediat. Adol. Med. 158:848, 2004--JW)
      2. In a case-control study of 144 children 4-13yo recently diagnosed with OCD, tics, or Tourette syndrome and matched controls, streptococcal throat infections in the prior 3mos and 1y were associated with significantly increased risk of the neuropsychiatric diagnosis (RR 2.22 and 1.91, respectively) (Pediatrics 116:56, 2005--JW)
(Sources include Core Content Review of Family Medicine, 2012)