Streptococcal Pharyngitis

Streptococcal pharyngitis is infection of the pharynx by Streptococcus pyogenes (group A streptococcus), responsible for 15 to 30 percent of sore throats in children and 5 to 10 percent in adults. Antibiotic treatment prevents acute rheumatic fever and suppurative complications, important in Kenya where rheumatic heart disease is common.

• Peak age 5 to 15 years; spread by droplets and close contact in crowded schools and households.
• Carriage of group A streptococci without disease occurs in 5 to 15 percent of school children.

Sudden sore throat with pain on swallowing, fever, headache, abdominal pain and vomiting in children, tender anterior cervical lymph nodes, erythematous pharynx with tonsillar exudate and palatal petechiae; cough and coryza are absent.

• Scarlet fever: fine erythematous sandpaper rash, strawberry tongue, perioral pallor.
• Differential diagnosis: viral pharyngitis, infectious mononucleosis, diphtheria, acute HIV infection, gonococcal pharyngitis, Fusobacterium necrophorum infection, Arcanobacterium haemolyticum, Kawasaki disease, peritonsillar abscess, epiglottitis.
• Complications: peritonsillar and retropharyngeal abscess, cervical lymphadenitis, otitis media, sinusitis, acute rheumatic fever (1 to 3 weeks later), post streptococcal glomerulonephritis (1 to 3 weeks), toxic shock syndrome, PANDAS, invasive disease.

Clinical prediction combined with microbiology.

• Use a clinical score: fever, tonsillar exudate, tender anterior cervical nodes and absence of cough (3 or 4 features favour streptococcal infection); then rapid antigen detection test, with throat culture to confirm negative tests in children and adolescents.
• Anti streptolysin O titres are not useful for acute diagnosis.
• Urinalysis if haematuria or oedema follow; ECG and echocardiography if rheumatic fever is suspected.

Treat with penicillin for 10 days (or one intramuscular dose) to prevent rheumatic fever.

• Supportive: rest, oral fluids, soft diet, warm saline gargles, exclusion from school or work until 24 hours after starting antibiotics.
• Pharmacological: benzathine benzylpenicillin 1.2 million units IM single dose (600,000 units for children under 27 kg); or phenoxymethylpenicillin 500 mg twice daily (or 250 mg four times daily) for 10 days (children 250 mg two to three times daily for 10 days); or amoxicillin 500 mg three times daily or 1 g once daily for 10 days (children 50 mg/kg once daily, maximum 1 g). Penicillin allergy (non severe): cefalexin 500 mg twice daily for 10 days (children 25 to 50 mg/kg/day); severe allergy: azithromycin 500 mg on day 1 then 250 mg daily for 4 days (children 12 mg/kg once daily for 5 days), or clindamycin 300 mg three times daily for 10 days (children 7 mg/kg three times daily), or erythromycin 500 mg four times daily for 10 days. Analgesia: paracetamol 1 g every 6 hours (children 15 mg/kg), ibuprofen 400 mg every 8 hours (children 10 mg/kg).
• Procedures: incision and drainage of peritonsillar abscess; tonsillectomy for recurrent infection.
• Special groups: pregnancy, penicillin or cefalexin; previous rheumatic fever, treat immediately and continue secondary prophylaxis with benzathine benzylpenicillin 1.2 million units IM every 3 to 4 weeks (duration set by cardiac involvement); carriers, no treatment unless risk contacts; HIV, give the usual antibiotic course.
• Red flags: drooling, trismus, uvular deviation, stridor, neck swelling, inability to swallow, joint pain or chorea, dark urine or oedema, shock with rash.
• Follow-up: review at 48 to 72 hours if not improving; no routine post treatment culture; counsel on completing the antibiotic course.