Artificial elimination of drug resistance from group A beta-hemolytic streptococci

Ten strains of beta-hemolytic streptococci were tested for elimination of resistance to macrolide antibiotics, tetracycline, and chloramphenicol. Six of the strains lost resistance after cultivation at 41 C or addition of acriflavine (0.2 mug/ml). These results suggest that determinants governing resistance to these antibiotics are located on extrachromosomal genetic elements (plasmids) that are widely distributed in streptococci.