PLASMIDS MEDIATING MULTIPLE DRUG-RESISTANCE IN GROUP-B STREPTOCOCCUS - TRANSFERABILITY AND MOLECULAR-PROPERTIES

Group B β-hemolytic streptococci isolated from a number of geographic locations were investigated with regard to the genetic basis of their drug-resistance determinants. Strains have been identified carrying plasmid-mediated resistance to erythromycin, lincomycin, and streptogramin B (MLS resistance). These MLS-resistance plasmids all have molecular weights of approximately 17 × 106 and are capable of transfer during mixed incubation by a mechanism that appears similar to conjugation. These plasmids were transferable to group B, D, F, and H recipients. Transfer could also be shown from groups F and H to group D recipients. Plasmids DNA isolated from recipient strains following transfer was identical with that of the donor. The similarity of restriction fingerprints of MLS-resistance plasmids from group A, B, and D isolates obtained suggest that they constitute a family of related plasmids. © 1979.