Clindamycin treatment of chronic pharyngeal carriage of group A streptococci

We previously demonstrated that chronic pharyngeal carriage of group A β-hemolytic streptococci (GABHS) can be terminated by intramuscular administration of bezathine penicillin plus 4 days of orally administered rifampin. Because an effective oral regimen would be desirable, we compared clindamycin with P+R for treating GABHS carriage. Healthy, symptom-free GABHS carriers were randomly assigned to receive orally administered clindamycin (20 mg/kg per day) three times a day for 10 days or intramuscularly administered benzathine penicillin with oral doses of rifampin (20 mg/kg per day) twice a day for 4 days. Compliance, was documented by antibiotic activity in urine. Throat cultures for GABHS were obtained every 3 weeks for up to 9 weeks after treatment. Patients who had positive throat cultures for their original GABHS T type 3 weeks after randomization were crossed over to the other treatment. Treatment success was defined as eradication of the original GABHS T type, with all follow-up cultures negative. Clindamycin eradicated carriage in 24 (92%) of 26 patients; penicillin plus rifampin was effective in 12 (55%) of 22 patients (p <0.025). Including patients crossed over 3 weeks after enrollment, clindamycin was effective in 28 (85%) of 33 treatment courses compared with 12 of 22 courses of penicillin plus rifampin (p<0.05). We conclude that 10 days of oral clindamycin therapy was significantly more effective than benzathine penicillin plus 4 days of orally administered rifampin for treatment of symptom-free GABHS carriers.