Group A strep in the pediatric ED: from strep throat to invasive disease and toxic shock.

Host:
Ellen Duncan, MD, PhD
Brian Gilberti, MD

https://media.blubrry.com/coreem/content.blubrry.com/coreem/Group\_A\_Strep.mp3   Download Leave a Comment Tags: Infectious Diseases, Pediatrics    Show Notes Background* **Group A strep = *Streptococcus pyogenes*** — gram-positive organism that colonizes the pharynx, but also the **perianal and genital mucosa** (worth remembering when the source isn’t the throat).

• Extremely common. The episode cites an estimated ~289 million cases/yr of strep pharyngitis in children 5–14 (NIH). For a U.S.-specific, verifiable anchor: the CDC estimates strep throat drives ~5.2 million outpatient visits/yr in people <65.
• No true beta-lactam resistance. GAS remains uniformly susceptible to penicillin and amoxicillin. Note this is not true for macrolides/clindamycin — roughly 1 in 3 invasive isolates are now erythromycin/clindamycin resistant.

Pathophysiology — the throughline Exotoxins (superantigens) tie the whole spectrum together — they drive scarlet fever, streptococcal toxic shock syndrome (STSS), and are implicated in the Kawasaki overlap discussed below. * The organism is the same from a sore throat to a life-threat; what changes is host response and toxin burden.*

Clinical Presentation Core findings: tonsillar inflammation/exudate, tender anterior cervical lymphadenopathy, fever. * Classic strep tells to hunt for: + Palatal petechiae + Strawberry tongue + Perioral pallor * Scarlet fever — fine, sandpapery rash, typically starts on the trunk and spreads outward; later desquamation of the fingers and toes. * Extrapharyngeal clues: kids commonly present with abdominal pain or headache even when the throat looks unimpressive. Low threshold to test with fever + abd pain or fever + headache*.

Diagnosis / WorkupCentor / Modified (McIsaac) Score Centor Score (Modified/McIsaac) — MDCalc * One point each: fever, tonsillar exudates, tender anterior cervical lymphadenopathy, absence of cough. The Modified (McIsaac) version adds age. * Developed and validated in adults (≥16). It is not reliable in young children* — don’t lean on it in peds the way you would in an adult. * For reference, McIsaac culture-positive probabilities: ~2.5% (0 criteria), 6.5% (1), 15% (2), 32% (3), 56% (4).

Testing Rapid PCR — high sensitivity and specificity; increasingly the front-line test. * Rapid antigen detection test (RADT) — highly specific but less sensitive. Per IDSA, a negative RADT in a child/adolescent should be backed up with a throat culture (culture is the more sensitive gold standard). Backup culture is not* required in adults.

Who not to test Generally don’t test/treat children <3 — acute rheumatic fever is rare in this group. * Exception: the symptomatic young child with a close contact recently diagnosed* with strep.

Management First-line: amoxicillin 50 mg/kg once daily, max 1 g/dose. GAS stays beta-lactam susceptible (penicillin and amoxicillin remain treatments of choice per IDSA 2012). * IM penicillin G / benzathine (bicillin) for kids who can’t tolerate oral meds — one shot, done. * Return to school: after one full day of treatment (~12–24 h), provided afebrile and feeling well. * Contact prophylaxis: + Pharyngitis — routine prophylaxis of asymptomatic contacts is not standard; consider it for households with recurrent infection or a history of rheumatic fever. + Invasive GAS — more aggressive. Prophylaxis is recommended for household contacts who are immunosuppressed, pregnant, post-recent-surgery, or have an open wound* (CDC).

The Bounce-Back / Treatment FailureThe kid who finishes amox and is back a week later. Sort into three buckets:

1. Chronic carrier — GAS carriage in children runs 2–20%. Carriers test positive but are asymptomatic, with low risk of transmission or complications. Don’t chase them.
2. New infection.
3. True treatment failure → ask why:
   • The shield effect — the throat is co-colonized with beta-lactamase producers (Staph aureus, H. influenzae, Moraxella) that degrade amoxicillin before it can act, effectively shielding the GAS.
   • This is NOT true resistance — the strep is still beta-lactam susceptible; the neighbors are the problem.
   • Fix: switch to a beta-lactamase–stable agent — amoxicillin-clavulanate or a first-generation cephalosporin.

Complications Suppurative: peritonsillar abscess, sinusitis, meningitis, bacteremia. * Non-suppurative: + Acute rheumatic fever — typically 1–5 wks post-infection; Jones criteria (AHA 2015 revision · ACC summary · CDC). + Post-infectious...*