Group A strep in the pediatric ED: from strep throat to invasive disease and toxic shock.
Ellen Duncan, MD, PhD
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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 petechiaeStrawberry tonguePerioral pallorScarlet 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 / Workup
Centor / Modified (McIsaac) Score
Centor Score (Modified/McIsaac) — MDCalcOne 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 Failure
The kid who finishes amox and is back a week later. Sort into three buckets:
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 glomerulonephritis (PIGN) — several weeks out; hematuria / “Coca-Cola” urine. Note strep impetigo can also seed PIGN.The pearl: we treat strep to prevent rheumatic fever — but treatment does NOT prevent PIGN.Invasive Group A Strep (iGAS)
Why it’s on the radar
Rates have been climbing since 2014, and preliminary 2023 data hit a 20-year high (CDC). A CDC/ABCs analysis flagged a roughly 3-fold pediatric increase in Colorado/Minnesota in late 2022 (MMWR).Keep it in mind when a child isn’t following the typical strep course or just looks sicker than expected.The spectrum
STSS, necrotizing fasciitis, meningitis, bacteremia, peritonitis.Increasingly common and worth highlighting: bone and joint disease — septic arthritis, osteomyelitis — often traveling with pyomyositis.The trap — nonspecific early presentation
Symptoms are often nonspecific: fever, “not acting like themselves,” localized pain.Septic joint/osteo may show a limp or focal pain — but not always.When your gut fires, cast a wide net.Workup
Blood cultures, CBC, chemistries, CRP, ESR.Imaging — tailor to the suspected site:Suspected joint → start with X-ray + ultrasound.Worried about osteomyelitis or pyomyositis → MRI (the recommended modality for pyomyositis per IDSA SSTI).Management
Broad-spectrum: vancomycin + piperacillin-tazobactam (concordant with IDSA SSTI).In shock / STSS: ADD clindamycin or linezolid for toxin suppression — this is on top of vanc/zosyn, not a coverage swap. (IDSA: penicillin plus clindamycin for documented GAS necrotizing infection; consider IVIG in STSS.)The Kawasaki overlap
Meaningful overlap between iGAS and Kawasaki disease.Proposed mechanism: strep superantigens activate a shared inflammatory (T-cell) pathway that may contribute to KD; some data suggest kids with iGAS may be at higher risk of developing Kawasaki.Get rheumatology involved early — they’ll want those inflammatory markers and can help sort KD from mimics.Take-Home Points
Adult tools don’t translate to peds. Centor was built for ≥16 and is unreliable in young kids — diagnose on exam, the eponyms, and testing. Low threshold to swab the febrile kid with abdominal pain or headache.The bounce-back is a triage problem — carrier (2–20%) vs. new infection vs. true failure. True failure is usually the shield effect (beta-lactamase co-colonizers, not resistance) → switch to amox-clav or a first-gen cephalosporin.Treatment prevents rheumatic fever, NOT PIGN — and impetigo can cause PIGN too.iGAS is rising and hides behind nonspecific symptoms. When your gut fires, work it up broadly and escalate to MRI for osteo/pyomyositis. Treat with vanc + pip-tazo, and in shock add clindamycin/linezolid for toxin suppression. Keep Kawasaki in the differential and call rheum early.Links & References
Calculators
Centor Score (Modified/McIsaac) for Strep Pharyngitis — MDCalcGuidelines
Shulman ST, et al. Clinical Practice Guideline for the Diagnosis and Management of Group A Streptococcal Pharyngitis: 2012 Update. IDSA / Clin Infect Dis. 2012;55(10):e86–e102. — IDSA · Full textStevens DL, et al. Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update. IDSA / Clin Infect Dis. 2014;59(2):e10–e52. (necrotizing infection, STSS, clindamycin adjunct, MRI for pyomyositis) — IDSA · Full textGewitz MH, et al. Revision of the Jones Criteria for the Diagnosis of Acute Rheumatic Fever in the Era of Doppler Echocardiography. AHA / Circulation. 2015;131:1806–1818. — Circulation · ACC “10 Points to Remember”CDC
Group A Strep Disease Surveillance and Trends (invasive disease rising since 2014; 2023 20-year high)MMWR — Increase in Pediatric Invasive Group A Streptococcus Infections, Colorado and Minnesota, Oct–Dec 2022Diagnosing Acute Rheumatic Fever (clinician guidance)
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