This young man presents with a sore throat, fatigue, fever, tender lymphadenopathy, and an erythematous oropharynx with exudate. A rapid strep test confirms that he has streptococcal pharyngitis, which is caused by group A streptococcus (Streptococcus pyogenes), a gram-positive, ß-hemolytic coccus that is sensitive to bacitracin. The patient’s medical history of hospitalization for anaphylaxis after a previous course of penicillin indicates that he is allergic to penicillin.
Penicillin is the treatment of choice for streptococcal pharyngitis. However, in patients who cannot tolerate penicillin, a macrolide or clindamycin can be prescribed. The macrolide of choice for treating streptococcal pharyngitis is azithromycin. Like other macrolides (including erythromycin and clarithromycin), azithromycin acts by binding to the 23S rRNA portion of the 50S ribosomal subunit within bacteria, inhibiting protein synthesis by preventing transpeptidation.
Cephalosporins may be used to treat streptococcal pharyngitis in individuals who have a mild penicillin allergy. These antibiotics would be contraindicated for use in this patient because of the severity of his allergy and because there is an increased rate of cross-reactivity to cephalosporins in patients with penicillin allergy. This is due to the structural similarity of the two drug classes (both are ß-lactamase agents).
Timely treatment of streptococcal pharyngitis is important because it reduces the risk of postinfectious rheumatic fever. Treatment has not been shown to reduce the risk of poststreptococcal glomerulonephritis.
Amoxicillin and cephalexin should not be given to this patient because he has a history of severe penicillin allergy (anaphylaxis). Moxifloxacin, trimethoprim-sulfamethoxazole, and doxycycline should not be used to treat streptococcal pharyngitis because S. pyogenes has a high rate of resistance to all three of these antibiotics.