Emergence of linezolid-resistant Staphylococcus aureus during treatment of pulmonary infection in a patient with cystic fibrosis.

We report the first linezolid-resistant Staphylococcus aureus strain isolated in Brazil. The strain was isolated from a 10-year-old female patient with cystic fibrosis (CF) who received repeated and prolonged courses of low-dose linezolid. The strain belonged to the Brazilian endemic methicillin-resistant S. aureus clone, and the G2576U mutation was identified in domain V of the 23S rRNA. Detection of this mechanism of resistance in a CF patient is very worrisome, as these patients may become a reservoir for further dissemination of resistant strains. Our findings emphasise the importance of optimal dosage of linezolid to prevent the emergence of resistance.