CLINICAL RESISTANCE TO ERYTHROMYCIN AND CLINDAMYCIN IN CUTANEOUS PROPIONIBACTERIA ISOLATED FROM ACNE PATIENTS IS ASSOCIATED WITH MUTATIONS IN 23S RIBOSOMAL-RNA

The genetic basis of erythromycin resistance in cutaneous propionibact eria was determined by comparing the nucleotide sequences of the pepti dyl transferase region in the 23S rRNAs from 9 susceptible and 26 resi stant clinical isolates as well as 4 laboratory-selected erythromycin- resistant mutants of a susceptible strain. In 13 isolates and the 4 la boratory mutants, cross-resistance to macrolides, lincosamides, and B- type streptogramins was associated with an A --> G transition at a pos ition cognate with Escherichia coli 23S rRNA base 2058, These strains were resistant to greater than or equal to 512 mu g of erythromycin pe r ml. Two other mutations were identified, an A --> G transition at ba se 2059 in seven strains, associated with high-level resistance to all macrolides, and a G --> A transition at base 2057 in six strains, ass ociated with low-level resistance to erythromycin, These mutations cor respond to three of four phenotypic classes previously identified by u sing MIC determinations.