Emergence of Erythromycin-Resistant, Clindamycin-Susceptible Streptococcus pyogenes Isolates in Madrid, Spain

In Spain, the frequency of resistance of group A streptococci (GAS) to erythromycin was very low, increasing from 0 to 0.7% in 1989 and 1990 (1, 7) to approximately 3% in 1991 to 1994 (2). The purpose of the present study was to determine the susceptibilities of recent isolates of GAS to macrolides and, in the case of resistant isolates, to ascertain their patterns of erythromycin resistance. We also studied the in vitro activities of penicillin G and clindamycin.