TRANSFER OF DRUG-RESISTANCE-PLASMIDS IN MIXED CULTURES OF STAPHYLOCOCCI

Abstract

Transfer of pen[penicillin-resistance]- and chl[chloramphenicol-resistance]-plasmids occurs between strains of Staphylococcus aureus and between strains of S. aureus and S. epidermidis. In S. aureus the frequency of transfer of a tet[tetracycline resistance]-plasmid is less frequent than the transfer of pen- and chl-plasmids. Lyzogenization of the donor strain by a sero-group-B-phage has no influence on the frequency of transfer. Transfer is not inhibited by .gamma.-globulin although .gamma.-globulin non-specifically inhibits phage adsorption and transduction by phage 80. Transfer is also possible when an encapsulated recipient strain is used. Since phages are inhibited by the capsular material, transduction to an encapsulated strain is impossible. Thus phage-mediated transfer in mixed cultures is not indicated. A dilution of the incubation mixture leads to an unproportional decrease in the transfer frequency. A prerequisite for the transfer is probably a close cell-to-cell contact.