New Staphylococcus aureus incompatibility group 1 plasmids encoding penicillinase production and resistance to different antibacterial agents

Eleven Staphylococcus aureus plasmids encoding penicillinase production and resistance to different antibacterial agents were transferred to laborator y recipient strains in mixed-culture transfer and transduction experiments and characterized by restriction endonuclease analysis and incompatibility. The plasmids were differentiated into four types (types A-D) on the basis of their resistance phenotypes and restriction endonuclease patterns. One t ype encoded resistance to cadmium and arsenate. The second type encoded res istance to cadmium, mercuric compounds and nucleic acid-binding compounds. The third type encoded resistance to cadmium, kanamycin, neomycin and strep tomycin while the fourth type encoded resistance to kanamycin, neomycin and ethidium bromide. Plasmids within the same class were structurally related or similar and were different from those in the other classes. Three plasm ids, pWBG626, pWBG628, and gWB6663, representing three of the four plasmid types, belonged to incompatibility group 1. These new plasmids add to the n umber of known incompatibility group 1 plasmids and have resistance phenoty pes which should be useful for studying incompatibility of new S. aureus pl asmids.