Erythromycin resistance in group A beta hemolytic streptococcus.

The incidence of erythromycin resistance and the phenotypic pattern of resistance have been studied in 130 group A beta-hemolytic streptococcus (GABHS) strains, isolated from throat swab obtained in children affected by acute pharyngotonsillitis. A total of 56 (43%) GABHS strains of 130 were resistant to erythromycin. Among these 56 strains, we found that 7 (12.5%), 18 (32.1%) and 31 (55.3%) showed the cMLS, iMLS and M phenotype, respectively. The iMLS and M phenotypes appear to be the most widely represented ones. Their low level of resistance to macrolides could allow the use of the more recent macrolides characterized by higher tissue concentration which could overcome such a resistance.