Macrolide and Clindamycin Resistance in Group A Streptococci Isolated from Children With Pharyngitis.

Group A streptococcus (GAS) is responsible for 15%-30% of cases of acute pharyngitis in children. Macrolides such as azithromycin have become popular for treating GAS pharyngitis. We report macrolide resistance rates in a primary care setting in our geographic area over the past 5 years and discuss the implications of resistance in making treatment decisions. Throat swabs were collected from children with pharyngitis from May 2011 to May 2015 in a primary care setting in Madison, Wisconsin. Susceptibility testing was performed for erythromycin and clindamycin using the Kirby-Bauer disk diffusion method. GAS was identified on 143 throat cultures. Overall, 15% of GAS isolates demonstrated nonsusceptibility for both clindamycin and erythromycin. Inducible resistance (positive D-test) was detected in 17 isolates (12%). The rate of detection of nonsusceptibility in each year of the study did not change over time. Azithromycin should only be used for patients with pharyngitis and substantial manifestations of penicillin hypersensitivity and when used, susceptibility testing should always be performed.