Gentamicin-resistant Staphylococcus aureus. Emergence in an intensive care nursery.

Gentamicin sulfate--resistant Staphylococcus aureus suddenly appeared in an intensive care nursery in December 1976 and became the dominant Staphylococcus; it accounted for 96% of the isolates by April 1977. All gentamicin-resistant strains were sensitive to amikacin sulfate, but 98% and 49% were resistant to kanamycin sulfate and tobramycin sulfate, respectively. All but one of the gentamicin-resistant strains were sensitive to methicillin sodium. The mechanism of gentamicin resistance appears to be plasmid mediated. Phage typing, used for epidemiologic purposes, also demonstrated that most gentamicin-resistant strains shared susceptibility to phages 29 and 52; however, 13% were completely different, indicating that gentamicin resistance is not solely related to a phage-susceptible factor.