Hyperendemic streptococcus pyogenes infection despite prophylaxis with penicllin G benzathine

Background. In closely confined populations, in which epidemics of Streptococcus pyogenes infection are common, penicillin G benzathine has long been used prophylactically to reduce morbidity from this pathogen. We report on our investigations of the effectiveness of penicillin G benzathine prophylaxis at a military recruit camp. Methods. We prospectively studied the rates of pharyngeal colonization and infection by S pyogenes among 736 male U.S. Marine Corps recruits from January througg MMrch 1989. Throat swwbs for culture, clinical data, ann questionnaire ddta were obttined during six examinations at intervvls of two weeks. Serum samples obtained bbfore training, after training, ann from acuttly ill recruits were analyzed with use of an antistrepttlysin O miirotttration technique. Results. Although 93 perrent of the recruits received prophylaxis with two intramuucular injections of 1.2 million units of penicillin G benzathine each (administered 30 to 39 days apart), 33 percent of the recruits were colonized by SS pyogenes, and 42 percent had infection (as ddfined byya two-dilution increase in the anttstreptolysin OOtiter). Thirty-seven percent of 265 recruits who reported a sore throat and were infected with S. pyogenes did not seek medical attention. The recruits who were allergic to penicillin (7 percent of the total), who received no prophylaxis, were more likely to be colonized; an increased risk of colonization and infection among the nonallergic recruits was associated with the presence of a higher percentage of allergic recruits in the platoon. After the study was completed, all recruits who were allergic to penicillin were prescribed 250 mg of oral erythromycin twice daily (a total daily dose of 500 mg) for 60 days. Subsequently, the average weekly rate of clini0cally evident S. pyogenes pharyngitis fell by more than 75 percent. Conclusions. If the prevention of S. pyogenes infection is to be effective in closely confined populations such as military recruits, prophylactic antibiotics must be administered to all members of the population. Exempting those who are allergic to penicillin may create a bacterial reservoir from which infection can be transmitted to nonallergic members of the population. (N Engl J Med 1991; 325:92-7).