Pharyngitis

Essentials of Diagnosis

Abrupt onset of sore throat, fever, malaise, nausea, andheadache.

Throat red and edematous, with or without exudate; cervicalnodes tender.

Diagnosis confirmed by culture of throat.

General Considerations
Group A beta-hemolytic streptococci (Streptococcus pyogenes) are the most common bacterial cause of pharyngitis. Transmission occurs by droplets of infected secretions. Group A streptococci producing erythrogenic toxin may cause scarlet fever in susceptible persons.
Clinical Findings
SYMPTOMS AND SIGNS
"Strep throat" is characterized by a sudden onset of fever, sore throat, pain on swallowing, tender cervical adenopathy, malaise, and nausea. The pharynx, soft palate, and tonsils are red and edematous. There may be a purulent exudate. The Centor clinical criteria for the diagnosis of streptococcal pharyngitis are temperature > 38 °C, tender anterior cervical adenopathy, lack of a cough, and pharyngotonsillar exudate.
The rash of scarlet fever is diffusely erythematous, resembling a sunburn, with superimposed fine red papules, and is most intense in the groin and axillas. It blanches on pressure, may become petechial, and fades in 2–5 days, leaving a fine desquamation. The face is flushed, with circumoral pallor, and the tongue is coated with enlarged red papillae (strawberry tongue).
LABORATORY FINDINGS
Leukocytosis with neutrophil predominance is common. Throat culture onto a single blood agar plate has a sensitivity of 80–90%. Rapid diagnostic tests based on detection of streptococcal antigen are slightly less sensitive than culture.
Complications
Suppurative complications include sinusitis, otitis media, mastoiditis, peritonsillar abscess, and suppuration of cervical lymph nodes.
Nonsuppurative complications are rheumatic fever and glomerulonephritis. Rheumatic fever may follow recurrent episodes of pharyngitis beginning 1–4 weeks after the onset of symptoms. Glomerulonephritis follows a single infection with a nephritogenic strain of streptococcus group A (eg, types 4, 12, 2, 49, and 60), more commonly on the skin than in the throat, and begins 1–3 weeks after the onset of the infection.
Differential Diagnosis
Streptococcal sore throat resembles (and cannot be reliably distinguished clinically from) pharyngitis caused by adenoviruses, Epstein-Barr virus, Arcanobacterium haemolyticum (which also may cause a rash), and other agents. Pharyngitis and lymphadenopathy are common findings in primary HIV infection. Generalized lymphadenopathy, splenomegaly, atypical lymphocytosis, and a positive serologic test distinguish mononucleosis from streptococcal pharyngitis. Diphtheria is characterized by a pseudomembrane; candidiasis shows white patches of exudate and less erythema; and necrotizing ulcerative gingivostomatitis (Vincent’s fusospirochetal disease) presents with shallow ulcers in the mouth. Retropharyngeal abscess or bacterial epiglottitis should be considered when odynophagia and difficulty in handling secretions are present and when the severity of symptoms is disproportionate to findings on examination of the pharynx.
Treatment
Antimicrobial therapy has a modest effect on resolution of symptoms and primarily is administered for prevention of complications. Antibiotic therapy can be safely delayed until the diagnosis is established on the basis of a positive antigen test or culture. Empiric therapy usually is not a cost-effective approach to the management of most adults with pharyngitis because in typical clinical settings, the prevalence of streptococcal pharyngitis is likely to be no more than 10–20% and the positive predictive value of clinical criteria is low. Clinical criteria, such as the Centor criteria, are useful for identifying patients in whom a rapid antigen test or throat culture is indicated. Patients who meet two or more of these criteria merit further testing. When three of the four are present, laboratory sensitivity of rapid antigen testing exceeds 90%. When only one criterion is present, streptococcal pharyngitis is unlikely. In high-prevalence settings or if clinical suspicion for streptococcal pharyngitis is high, a negative antigen test or culture should be confirmed by a follow-up culture.
BENZATHINE PENICILLIN G
Benzathine penicillin G, 1.2 million units intramuscularly as a single dose, is optimal therapy.
PENICILLIN VK
Penicillin VK, 500 mg orally four times a day (or amoxicillin, 750 mg orally twice daily), is effective, but compliance may be poor after the patient becomes asymptomatic in 2–4 days.
MACROLIDES
Erythromycin, 500 mg orally four times a day, or azithromycin, 500 mg orally once daily for 3 days, is an alternative for the penicillin-allergic patient. Macrolides are less effective than penicillins and are considered second-line agents. Macrolide-resistant strains almost always are susceptible to clindamycin, a suitable alternative to penicillins; a 10-day course of 300 mg orally twice daily is effective.
Prevention of Recurrent Rheumatic Fever
Effectively controlling rheumatic fever depends on identification and treatment of primary streptococcal infection and secondary prevention of recurrences. Patients who have had rheumatic fever should be treated with a continuous course of antimicrobial prophylaxis for at least 5 years. Effective regimens are erythromycin, 250 mg orally twice daily, or penicillin G, 500 mg orally daily.

Mahakit P et al. Oral clindamycin 300 mg BID compared with oral amoxicillin/clavulanic acid 1 g BID in the outpatient treatment of acute recurrent pharyngotonsillitis caused by group a beta-hemolytic streptococci: an international, multicenter, randomized, investigator-blinded, prospective trial in patients between the ages of 12 and 60 years. Clin Ther. 2006 Jan;28(1):99–109. [PMID: 16490583]

Smith A et al. Invasive group A streptococcal disease: should close contacts routinely receive antibiotic prophylaxis? Lancet Infect Dis. 2005 Aug;5(8):494–500. [PMID: 16048718]