Episode 225: Group A Strep

 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](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 / Workup ### Centor / 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 Failure The 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 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 1. **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. 2. **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**. 3. **Treatment prevents rheumatic fever, NOT PIGN** — and impetigo can cause PIGN too. 4. **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 — MDCalc ### Guidelines - 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 text - Stevens 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 text - Gewitz 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 2022 - Diagnosing Acute Rheumatic Fever (clinician guidance) Read More