Family Medicine & Pediatrics & Otolaryngology
Pharyngitis and tonsillitis
Pharyngitis — a general term for inflammation of the pharynx — and tonsillitis — a common term in Quebec and France for acute pharyngotonsillitis — constitute the most frequently encountered upper respiratory tract infection in primary care medicine, accounting for 10 to 15 % of all medical consultations in family medicine and up to 50 % of outpatient antibiotic prescriptions — the vast majority of which are unnecessary because 80 to 90 % of pharyngitis cases are viral in origin. The central clinical challenge is not to treat throat pain — which resolves spontaneously in 5 to 7 days in almost all cases regardless of the etiology — but to identify the 10 to 30 % of cases caused by group A beta-hemolytic Streptococcus (GAS) — Streptococcus pyogenes) which justify antibiotic treatment to prevent non-suppurative (rheumatic fever) and suppurative (peritonsillar abscess + otitis + mastoiditis) complications. The distinction between viral pharyngitis (rhinovirus + adenovirus + influenza virus + Epstein-Barr virus in infectious mononucleosis + herpes simplex) and group A streptococcal bacterial pharyngitis is impossible to make with sufficient certainty based on clinical examination alone. This underscores the importance of the McIsaac score (a Canadian, validated version of the Centor score) and rapid antigen detection tests (RADTs) to guide antibiotic therapy decisions rationally and avoid systemic antibiotic prescriptions for viral infections, a major source of bacterial resistance and adverse effects with no clinical benefit for the patient.
McIsaac Score — antibiotic therapy decision aid
| Clinical criterion | Points |
|---|---|
| Fever ≥ 100.4 °F (measured or reported) | +1 |
| No cough | +1 |
| Painful anterior cervical lymphadenopathy | +1 |
| Tonsillar exudate or swelling | +1 |
| Ages 3–14 | +1 |
| Ages 15-44 | 0 |
| Age ≥ 45 years | -1 |
| Score less than or equal to 0 : very low probability of SGA (< 2–3 %) → no test + no antibiotic + symptomatic treatment | |
| Score 1–2 low to moderate probability (5–15 %) → TDRSA recommended → antibiotic only if test is positive | |
| Score 3–4 moderate to high probability (30-50% %) → TDRSA recommended → antibiotic if positive + culture if negative (child) or empirical treatment questionable (adult) | |
| Score 5 or greater high probability (> 50% %) → possible empirical antibiotic without testing if very suggestive presentation |
Etiological agents and clinical presentation
| Agent | Characteristic clinical presentation | Frequency and management |
|---|---|---|
| Group A Streptococcus (GAS) | Sudden onset + high fever (39–40 °C) + intense odynophagia + red tonsils with yellowish-white exudate (strep throat or exudative pharyngitis) + painful anterior cervical adenopathy + absence of cough + palatine enanthem (petechiae) + strawberry tongue (associated scarlet fever) + no rhinorrhea or cough | 10–30 % pharyngitis (more frequent in children 5–15 years old) + RADT + amoxicillin if positive + complications if untreated: ARF (rare in Canada) + peritonsillar abscess + post-streptococcal glomerulonephritis |
| Virus (rhinovirus + adenovirus + influenza + parainfluenza + coronavirus) | Gradual onset + moderate or absent fever + rhinorrhea + cough + erythematous pharynx without exudate + moderate adenopathy + possible conjunctivitis (adenovirus) + epidemic context + other household members affected | 70–80 % des pharyngites + traitement symptomatique uniquement (analgésiques + AINS + pastilles + miel) + pas d'antibiotiques + guérison spontanée en 5–7 jours |
| Epstein-Barr virus (infectious mononucleosis) | Adolescent + adulte jeune + triade : pharyngite exsudative sévère + fièvre + adénopathies cervicales bilatérales (postérieures ++) + splénomégalie + asthénie profonde + syndrome mononucléosique à l'hémogramme (lymphocytose atypique) + éruption maculo-papuleuse après amoxicilline (95 % des cas — réaction immunologique à distinguer d'une allergie) | Monospot test (heterophile) + EBV serology (IgM anti-VCA) if Monospot is negative + NO amoxicillin or ampicillin + symptomatic treatment + avoid contact sports if splenomegaly (risk of splenic rupture) + corticosteroids if severe airway obstruction |
| GonococcusNeisseria gonorrhoeae) | Sexually active adult + often asymptomatic or mild pharyngitis + context of unprotected oral-genital practices + possible exudate | Chocolate agar culture + throat TAAN (PCR) + ceftriaxone 500 mg IM single dose + screening for other STIs |
| Arcanobacterium haemolyticum | Adolescent + young adult + exudative pharyngitis + scarlet rash on trunk + can mimic strep throat + rapid strep test negative | Blood agar culture + sensitive to penicillin and macrolides + treatment identical to GAS |
Antibiotic treatment
- Amoxicillin — first choice against GAS: Adult: 500 mg twice daily (or 1,000 mg once daily) for 10 days + Child: 50 mg/kg daily in 2 doses for 10 days (max 1 g/dose) + GAS remains universally susceptible to penicillin and amoxicillin — no resistance documented in Canada + prefer amoxicillin over penicillin V (better compliance with twice-daily dosing + more palatable taste in children) + a 10-day duration is necessary to eradicate pharyngeal carriage and prevent ARF — short courses (5 days) have higher rates of microbiological failure
- Penicillin allergy: mild non-IgE-mediated allergy (simple rash) → cefadroxil 500 mg × 2/day × 10 days (1st gen cephalosporin — cross-reactivity < 2 %) + severe IgE-mediated allergy (hives + anaphylaxis) → azithromycin 500 mg D1 then 250 mg D2–D5 × 5 days + or clarithromycin 250 mg × 2/day × 10 days + caution: GAS resistance to macrolides in Canada 5–10 %
- Recurrent tonsillitis (≥ 7 episodes in 1 year or ≥ 5/year × 2 years): Indications for tonsillectomy (Paradise criteria) + ENT referral + tonsillectomy reduces the number of episodes but does not completely eliminate the risk of pharyngitis
- Symptomatic treatment (viral and bacterial): Paracetamol 1g x 4/day + ibuprofen 400mg x 3/day (adult - more effective than paracetamol for odynophagia according to meta-analyses) + anesthetic lozenges + warm salt gargles + honey (child > 1 year) + ice pops
ℹ️
The rash after amoxicillin in patients with pharyngitis is NOT a penicillin allergy in the vast majority of cases—it is a specific immunological reaction to infectious mononucleosis (EBV) in the presence of amoxicillin, occurring in 95% of cases of mono treated with amoxicillin. This reaction does not recur with subsequent administration of amoxicillin once mononucleosis has resolved. It should not be labeled as penicillin allergy—this over-labeling often deprives patients of first-choice antibiotics for the rest of their lives.
Complications of untreated or undertreated strep throat
- Peritonsillar abscess (quinsy): Suppurative regional complication + pus collection between tonsil and lateral pharyngeal wall + «hot potato» voice + trismus + uvula deviated to the healthy side + very marked tonsillar asymmetry + severe dysphagia + surgical drainage + IV amoxicillin-clavulanate + hospitalization
- Acute Rheumatic Fever (ARF) non-suppurative immune complication occurring 2 to 4 weeks after a group A beta-hemolytic streptococcal pharyngitis (untreated or insufficiently treated) + migratory polyarthritis + carditis (mitral valve disease++) + Sydenham's chorea + erythema marginatum + subcutaneous nodules + diagnosed according to revised Jones criteria + prolonged antibiotic treatment + anti-inflammatories + rheumatic fever has become very rare in Canada (1–2 cases/100,000) but remains a major problem in low-income countries
- Post-streptococcal glomerulonephritis: immune renal complication + 1 to 3 weeks after tonsillitis (or 3 to 6 weeks after streptococcal impetigo) + hematuria + proteinuria + hypertension + edema + low C3 + high ASO + generally spontaneous resolution + preventive antibiotic therapy does not prevent this complication (unlike Rheumatic Fever)
- Lemierre's Syndrome rare but very serious complication + septic thrombophlebitis of the internal jugular vein secondary to tonsillitis + often caused by Fusobacterium necrophorum (anaerobic) + lateral neck pain + indurated mass along the anterior border of the sternocleidomastoid + pulmonary septic emboli + treatment: prolonged IV antibiotics (metronidazole + piperacillin-tazobactam)
Situations requiring urgent medical attention
Go to the emergency room immediately if a sore throat is accompanied by difficulty swallowing saliva, a muffled voice (hot potato voice), trismus (difficulty opening the mouth), significant tonsil asymmetry, and a deviated uvula – these signs suggest a peritonsillar abscess requiring urgent drainage. Also seek emergency care if intense lateral neck pain appears a few days after a sore throat – this may indicate Lemierre's syndrome. Call 911 if severe shortness of breath or airway obstruction occurs (complicated mononucleosis + epiglottitis).
For the assessment of the McIsaac score, the rapid test for SGA (RT-SGA), and the prescription of amoxicillin if indicated, Clinique Omicron offers medical consultations at its service points in Quebec and via telemedicine. To book an appointment, visit cliniqueomicron.ca.
Consult at Clinique Omicron
Clinique Omicron's physicians and nurse practitioners (NPs) assess pharyngitis using the McIsaac score, perform rapid streptococcal detection tests (RSDT) on-site, prescribe amoxicillin for 10 days if a streptococcal infection is confirmed, provide symptomatic treatment for viral pharyngitis, screen for infectious mononucleosis (Monospot + EBV serology) if clinically indicated, and refer to ENT for recurrent tonsillitis or suppurative complications. Consultations are available at several service points in Quebec and via telemedicine. To book an appointment, visit cliniqueomicron.ca.
The content of this page is for informational purposes only and does not replace the advice of a physician or otolaryngologist. Antibiotic treatment for pharyngitis should be guided by the result of a rapid test or bacterial culture—systematic prescription of antibiotics without microbiological confirmation contributes to antibiotic resistance and exposes the patient to undesirable side effects without proven benefit if the infection is viral.
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