Fellow's quick read · Infectious Diseases
Group A streptococcal pharyngitis
IDSA 2025 update (Part 1: risk assessment) + IDSA 2012 (treatment, still operative) · reviewed 2026-07-04
Personal study digest for a new ID fellow. The 2025 IDSA update (Linder/Barshak, Clin Infect Dis, PMID 41343363, doi:10.1093/cid/ciaf668) is Part 1 only — it covers clinical-scoring/testing decisions and does not revise treatment. Treatment recommendations below are drawn from the still-operative 2012 IDSA guideline (Shulman, Clin Infect Dis 2012;55:e86-e102, PMID 22965026) as summarized in CDC's current clinical guidance (cdc.gov, last updated Nov 2025). The "What's changed" section is reviewer synthesis of newer evidence, each claim cited. Not a substitute for the full guideline.
In one line
Strep throat is over-tested and over-treated — use a validated clinical score (Centor or McIsaac) to decide who needs a RADT/culture, but test anyway when a patient is HIGH-RISK regardless of score, and reserve antibiotics for a confirmed positive in a patient with a compatible clinical picture.◆When to suspect / diagnose
- GAS causes ~20–30% of pharyngitis in children and ~5–15% in adults; viruses cause the rest. Clear viral symptoms (cough, rhinorrhea, hoarseness, oral ulcers, conjunctivitis) argue AGAINST testing.
- Centor / McIsaac criteria (nearly identical; McIsaac adds an age term): fever >100.4°F, tonsillar exudate/swelling, tender anterior cervical adenopathy, absence of cough. Score 0–1 = low risk (~7–13% test positive), 2–3 = intermediate, 4(–5) = high (~50–70%).
- IDSA 2025 (conditional recommendation, very-low-certainty evidence): use a clinical scoring system to decide who gets tested — it performs comparably or slightly better than clinician judgment alone. Doesn't apply to children <3 y (atypical presentation).
◆Workup the fellow drives
- Low score → don't test (unless high-risk, see below). This is the main value of scoring: keeping low-probability patients off the testing/antibiotic conveyor belt.
- High-risk overrides a low score — test regardless of score if: household exposure to a person with GAS, a personal history of rheumatic fever, or signs of complicated/invasive local or systemic disease (peritonsillar/retropharyngeal abscess, scarlet fever, toxic shock).
- Positive RADT or throat culture = confirmation. A negative RADT in a child ≥3 y should be followed by a back-up culture (rare in older ages/adults — ARF is very uncommon there).
- Don't test asymptomatic contacts or do test-of-cure — up to ~26% of school-aged children are GAS pharyngeal carriers who will test positive without needing treatment (Shaikh, Pediatrics 2010, cited directly in the 2025 update).
◆Empiric & definitive therapy
| Scenario | Drug / dose / route | Duration |
|---|---|---|
| First-line | Penicillin V 250 mg PO BID–TID (child) or 250 mg QID / 500 mg BID (adolescent/adult) | 10 days |
| First-line, alt | Amoxicillin 50 mg/kg once daily (max 1 g) | 10 days |
| Adherence concern | Benzathine penicillin G IM — 600,000 U if <27 kg, 1,200,000 U if ≥27 kg | Single dose |
| Penicillin allergy (non-severe) | Cephalexin or cefadroxil (avoid both if immediate-type/anaphylactic penicillin allergy) | 10 days |
| Penicillin allergy (severe) | Clindamycin or clarithromycin (10 d); azithromycin 12 mg/kg day 1 then 6 mg/kg | 10 d (5 d for azithromycin) |
- Treating a confirmed positive prevents acute rheumatic fever and suppurative complications (peritonsillar/retropharyngeal abscess, cervical lymphadenitis, mastoiditis), shortens symptoms, and cuts transmission.
◆Key decisions a fellow owns
- Whether to test at all — apply the score, then check for a high-risk override before deciding not to test.
- Recognizing when "just a sore throat" isn't — scarlet fever, peritonsillar/retropharyngeal abscess, or streptococcal toxic shock bypass the entire testing algorithm and need urgent escalation.
- Not treating carriers or asymptomatic contacts — a positive test in the wrong clinical context doesn't mean treat.
◆Duration & stopping
- 10 days for oral penicillin/amoxicillin/cephalosporin/clindamycin/clarithromycin regimens; 5 days for azithromycin; benzathine penicillin G is a single IM dose.
- Patients may return to school/work/daycare once afebrile and ≥12–24 h after starting an appropriate antibiotic.
What's changed since 2012 (and what's still Part 1-only)
Reviewer synthesis of newer evidence — not the guideline. Each claim cited.
- This IS the newest IDSA guidance, but it's a fraction of the topic. The 2025 update covers ONLY the testing-decision question (clinical scoring). Treatment, penicillin-allergy alternatives, and complication management are still governed by the 2012 guideline — a treatment-focused "Part 2" has not been published as of this review (confirm before relying on this note past mid-2026). Linder/Barshak, Clin Infect Dis 2025, PMID 41343363, doi:10.1093/cid/ciaf668
- Invasive GAS disease is at a 20-year high. National surveillance across 10 US states found invasive GAS rates rose sharply through 2023, driven largely by adults — especially people experiencing homelessness or injection drug use. A fellow evaluating "just a sore throat" should keep a low threshold for invasive disease red flags. Gregory et al, JAMA 2025;333:1498-1507, doi:10.1001/jama.2025.0910
- Penicillin/amoxicillin susceptibility is unchanged and total — no penicillin- or amoxicillin-resistant GAS clinical isolate has ever been reported — but roughly 1 in 3 invasive GAS isolates in CDC's Active Bacterial Core surveillance are now macrolide/clindamycin-resistant (2023 data). This matters for penicillin-allergic patients and for adjunctive clindamycin in severe disease. CDC Group A Strep Surveillance and Trends, updated Aug 2025
- Linezolid — an emerging fallback for adjunctive toxin suppression in invasive GAS/STSS when clindamycin is limited by resistance or intolerance. A multicenter retrospective cohort (5,841 clindamycin vs 1,426 linezolid, TriNetX) found no significant 90-day mortality difference (12.0% vs 13.8%; OR 0.854, 95% CI 0.685–1.065). Retrospective, not an RCT — clindamycin remains first-line. Hashimoto et al, J Glob Antimicrob Resist 2025;46:241-245, PMID 41443505, doi:10.1016/j.jgar.2025.12.013
- Open / unresolved — the 2025 systematic review found no study comparing the FeverPAIN score (used in UK NICE guidance) against clinician judgment, so it couldn't be included despite being in wide use elsewhere.
◆Anki cards minted this run
- High-risk override — test despite a low score for household GAS exposure, prior rheumatic fever, or complicated/invasive disease.
- GAS pharyngeal carriage (~26% of school-aged children) — positive test without treatment need.
- Zero penicillin/amoxicillin resistance ever reported, vs ~1-in-3 invasive-isolate macrolide/clindamycin resistance.
- Linezolid as a retrospective-evidence fallback to clindamycin for invasive GAS toxin suppression.
Sources: IDSA 2025 GAS pharyngitis update, Part 1 (Linder/Barshak, Clin Infect Dis, PMID 41343363, doi:10.1093/cid/ciaf668); IDSA 2012 GAS pharyngitis guideline (Shulman, Clin Infect Dis 2012;55:e86-e102, PMID 22965026); CDC Clinical Guidance for GAS Pharyngitis (cdc.gov/group-a-strep, updated Nov 2025); CDC Group A Strep Surveillance and Trends (cdc.gov/group-a-strep, updated Aug 2025); Gregory et al, JAMA 2025;333:1498-1507 (doi:10.1001/jama.2025.0910); Shaikh et al, Pediatrics 2010;126:e557-64 (doi:10.1542/peds.2009-2648); Hashimoto et al, J Glob Antimicrob Resist 2025;46:241-245 (PMID 41443505, doi:10.1016/j.jgar.2025.12.013).