Effect of the Prophage and Penicillinase Plasmid of the Recipient Strain Upon the Transduction and the Stability of Methicillin Resistance in Staphylococcus aureus

Abstract

Transduction of a methicillin-resistance determinant ( mec ) in Staphylococcus aureus RN450 was dependent on its prior lysogenization with an appropriate temperate phage. In addition, an appropriate transduced penicillinase plasmid was usually required. Some phage 80-resistant variants of RN450 or of its parental lysogenic strain, NCTC 8325, were also effective recipients for transduction of mec . Elimination of prophage from RN450 abrogated its effectiveness as a transductional recipient of mec . Elimination of prophage from a methicillin-resistant transductant of RN450 reduced resistance to undetectable levels in six of seven phage-eliminated strains. In four of these a variable number of clones again became phenotypically resistant after lysogenization alone or lysogenization combined with reintroduction of a penicillinase plasmid. In two prophage-eliminated strains, no evidence of residual mec could be adduced. The establishment, expression, or stability of the transduced mec in strain RN450 appeared to depend on some function determined by a prophage or a prophage and a penicillinase plasmid.