among 143 patients aged 21 years or younger observed for 537 patient-years , the number of streptococcal infections ( and number per patient-year ) was 23 ( 0.084 ) in the penicillin group and 12 ( 0.045 ) in the clindamycin group .
C0038395
streptococcal infections
C0008947
clindamycin