Transfer of drug-resistance-plasmids in mixed cultures of Staphylococci.

Transfer of pen- and chl-plasmids does not only occur between strains of Staph, aureus but also betwen strains of Staph, aureus and Staph, epidermidis. In Staph, aureus, the frequency of transfer of a tet-plasmid is less frequent than the transfer of pen- and chl-plasmids. Lysogenization of the donor strain by a sero-group-B-phage has no influence on the frequency of transfer. The transfer is not inhibited by gamma-globulin. gamma-globulin inhibits unspecifically phage adsorption and also the transduction by phage 80. The transfer is also possible when an encapsulated recipient strain is used. Phages are inhibited by the capsular material (SCHEER and KOFT, 1975); a transduction to an encapsulated strain is impossible. These results speak against a phage-mediated transfer in mixed cultures. A dilution of the incubation mixture leads to an unproportional decrease of the frequency of transfer. A prerequisite to the transfer is probably a close cell-to-cell contact.