Characterization of a macrolide, lincosamide, and streptogramin resistance plasmid in Staphylococcus epidermidis.

A strain of Staphylococcus epidermidis was transduced to erythromycin resistance, and all of the transductants exhibited the macrolide, lincosamide, streptogramin B resistance phenotype. Curing and antibiotic disk studies also indicated that these resistances were controlled by a single plasmid determinant and were constitutive. Agarose gel electrophoresis of plasmid deoxyribonucleic acid (DNA) from donor, cured, and transduced strains showed that a single plasmid was responsible. This plasmid, designated pNE131, was examined for sequence homology to two other plasmids, pE194 and p1258, from Staphylococcus aureus, which also code for erythromycin resistance. DNA from plasmids pNE131 and pE194 hybridized with one another, but no extensive homology to pI258 with either pNE131 or pE194 was found. Restriction endonuclease digests of pNE131 and pE194 showed no common fragments. However, sequence homology was localized to the nucleotides in pE194 that code for the 29,000-dalton protein responsible for erythromycin resistance. pNE131 was calculated to have 2,220 base pairs and is the smallest naturally occurring plasmid with a known function yet reported in S. epidermidis.