Stability of penicillinase plasmids in Staphylococcus aureus

The isolation of mutants of Staphylococcus aureus that are affected in the stability of penicillinase plasmids is described. One mutation is plasmid borne and results in nonreplication of the plasmid at 42 C. A second type of mutation is host-borne and gives rise to instability of both mcr(I) and mcr(II) penicillinase plasmids but not a tetracycline-resistant plasmid.