Occurrence of a nonplasmid-located determinant for gentamicin resistance in strains of Staphylococcus aureus

The occurrence of resistance to gentamicin in strains of Staphylococcus aureus with different phage patterns in two hospitals is described. The data suggest transfer of gentamicin resistance between different strains. In the strains investigated the determinant for resistance to gentamicin (parallel resistance to kanamycin and tobramycin) is located on the chromosome. The transfer of this resistance determinant in a mixed culture of donor and recipient cells in vitro is mediated by transduction because it is dependent upon lysogenicity of the donor for a serogroup-B phage and because it can be inhibited by gamma-globulin. The transfer is always associated with lysogenization of the recipient cells by this phage.