Beta-hemolytic streptococcal pharyngitis: uncommon in infectious mononucleosis.

Infectious mononucleosis (IM) and beta-hemolytic streptococcal pharyngitis may present similar clinical pictures and may occur concurrently; however, recent studies have differed sharply with older ones that cited high rates of concurrent disease. Our study of 100 consecutive new patients meeting strict criteria for a diagnosis of IM found only 4% with positive throat cultures for group A beta-hemolytic streptococci at the time of diagnosis. Use of antibiotics for presumed streptococcal pharyngitis in patients with IM is unjustified. Only patients with positive cultures should be treated.