Resistance to linezolid in a methicillin-susceptible Staphylococcus aureus clinical isolate without previous exposure to oxazolidinones.

A linezolid-resistant, methicillin-susceptible isolate of Staphylococcus aureus was obtained from an infected surgical wound in an ambulatory patient. The isolate belonged to ST125 and was susceptible to all the antibiotics tested except linezolid (MIC 8 μg/ml) and levofloxacin. Linezolid resistance could be ascribed to the presence of the mutation G2576T in 2 of the 23S rRNA alleles. The mutant alleles were stably maintained in the absence of antibiotic selection.