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Bacterial pharyngitis Apurva
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I now have comprehensive content. Here is a thorough overview of bacterial pharyngitis for Apurva:
Bacterial Pharyngitis
Overview
Pharyngitis is inflammation of the pharynx and/or tonsils. Bacteria account for roughly 30–40% of pharyngitis in children and 5–15% (up to 23%) in adults. The dominant pathogen is Streptococcus pyogenes (Group A β-hemolytic Streptococcus, GABHS/GAS).
Causative Organisms
| Organism | Notes |
|---|---|
| Group A β-hemolytic Streptococcus (S. pyogenes) | Most common bacterial cause; Lancefield Group A |
| Group C & G streptococci (S. dysgalactiae subsp. equisimilis) | Mirrors GAS clinically; no rheumatic fever risk; penicillin-sensitive |
| Fusobacterium necrophorum | Gram-negative anaerobe; risk of Lemierre's syndrome |
| Neisseria gonorrhoeae | Associated with genital infection; sexually active patients |
| Corynebacterium diphtheriae | Diphtheria; rare in immunized populations |
| Arcanobacterium haemolyticum | Adolescents; may cause a scarlatiniform rash |
GAS Pharyngitis — The Main Focus
Pathogenesis
S. pyogenes is a rapidly growing gram-positive coccus arranged in chains. Virulence is determined by:
- Anti-phagocytic factors: capsule, M protein, C5a peptidase
- Adhesins: M protein, lipoteichoic acid, F protein
- Toxins: streptococcal pyrogenic exotoxins (SPE-A, B, C), streptolysin O & S, streptokinase, DNases
Spread is via respiratory droplets. After colonization, disease occurs before protective anti-M protein antibodies develop.
Clinical Features
After an incubation of 2–5 days, sudden onset of:
- Sore throat, painful swallowing (odynophagia)
- Fever, chills, headache, nausea/vomiting
- Tonsillar swelling (62%), tonsillar exudate (39%), tender anterior cervical lymphadenopathy (76%)
- Uvular edema, myalgias, malaise
- Absent: rhinorrhea, conjunctivitis (these favour viral)
Diagnosis
Modified Centor Score (McIsaac Score)
Step 1 — Calculate score:
| Criterion | Points |
|---|---|
| Temperature > 38°C | +1 |
| Absence of cough | +1 |
| Swollen, tender anterior cervical nodes | +1 |
| Tonsillar swelling or exudate | +1 |
| Age 3–14 years | +1 |
| Age > 44 years | −1 |
Step 2 — Management by score:
| Score | Risk of GAS | Action |
|---|---|---|
| ≤ 0 | 1–2.5% | No testing, no antibiotics |
| 1–2 | 5–17% | Rapid antigen test; treat if positive |
| 3 | 28–35% | Rapid antigen test; treat if positive |
| ≥ 4 | 51–53% | Empirical antibiotics, no testing needed |
Laboratory Tests
- Rapid antigen detection test (RADT): sensitivity ~85–86%, specificity 94–96%
- Throat swab culture: gold standard
- Rapid nucleic acid testing: sensitivity 97.5%, specificity 95% — preferred when available
- If RADT negative in children/adolescents → send culture
- If RADT negative in adults → culture usually not needed (low GAS incidence + low rheumatic fever risk)
- ASO titre: confirms rheumatic fever / post-streptococcal GN
- Anti-DNase B: confirms GN after pharyngitis or pyoderma
Clinical diagnosis alone is only ~75% accurate, even with all classic features — laboratory testing is essential.
Treatment
GAS Pharyngitis
- Penicillin VK 500 mg twice daily × 10 days — first line (GAS has never been resistant to penicillin)
- Benzathine penicillin G 1.2 million units IM single dose — excellent compliance
- Amoxicillin — acceptable alternative; palatable for children
- Penicillin allergy: first-generation cephalosporin or clindamycin
- Adjunct: Single dose of PO/IM dexamethasone in moderate-to-severe cases → faster pain relief, reduced time to resolution (no significant side effects)
Untreated, symptoms resolve in 7–10 days. Antibiotics shorten illness by ~24–48 hours and, critically, prevent rheumatic fever (if started within 10 days). Antibiotics do not prevent post-streptococcal GN.
Non-GAS Bacterial Pharyngitis
- Groups C & G streptococci: penicillin (60% asymptomatic colonisers → treat only symptomatic patients); clindamycin or fluoroquinolones as alternatives
- Diphtheria: diphtheria antitoxin + metronidazole
- Gonococcal: same as genital gonorrhoea treatment
- F. necrophorum: metronidazole + ceftriaxone (or piperacillin-tazobactam) — high macrolide resistance
Complications
Suppurative
| Complication | Notes |
|---|---|
| Peritonsillar abscess | Most common; polymicrobial; F. necrophorum #1 in age 15–24 |
| Retropharyngeal abscess | Especially children |
| Lemierre's syndrome | F. necrophorum; suppurative thrombophlebitis of internal jugular vein; septic emboli |
| Otitis media, sinusitis | Less common |
Non-Suppurative (Immunological — GAS only)
| Complication | Notes |
|---|---|
| Rheumatic fever | Immunologically mediated; delayed 1–5 weeks; PREVENTED by antibiotics |
| Post-streptococcal GN | Associated with pharyngitis AND pyoderma; NOT prevented by antibiotics |
| Streptococcal toxic shock syndrome | Uncommon sequela |
| Scarlet fever | GAS + pyrogenic exotoxin; "sandpaper" rash, strawberry tongue, Pastia's lines; children 2–8 years |
Key Distinctions
| Feature | Bacterial (GAS) | Viral |
|---|---|---|
| Onset | Sudden | Gradual |
| Fever | Often high | Variable |
| Cough | Absent | Present |
| Rhinorrhea | Absent | Present |
| Conjunctivitis | Absent | May be present (adenovirus) |
| Exudate | Common | Less common |
Sources: Tintinalli's Emergency Medicine 9e, Goldman-Cecil Medicine 2 Volume Set, Medical Microbiology 9e
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