Genetic and phenotypic characterization of macrolide resistance in group Astreptococci isolated from adults with pharyngo-tonsillitis in France

Three hundred and three strains of group A streptococci (GAS) isolated from adults with pharyngitis were tested to evaluate their phenotype of resista nce to macrolides-lincosamides and to search for macrolide resistance genes . MICs of clarithromycin were determined. The overall rate of resistance to both erythromycin and clarithromycin was 9.6%. Constitutive, inducible and M phenotypes of resistance were detected in 4.3, 2 and 3.3% of strains, re spectively. All constitutive phenotypes harboured ermB genes, whereas induc ible phenotypes had the ermTR gene and M phenotypes had the mefA gene. In F rance, the current resistance rate of GAS to erythromycin and clarithromyci n remains low.