Rapid emergence of resistance to linezolid and mutator phenotypes in Staphylococcus aureus isolates from an adult cystic fibrosis patient

Abstract

Linezolid has emerged as an important therapeutic option for the treatment of Staphylococcus aureus in patients with cystic fibrosis. We report the rapid emergence, upon treatment with linezolid, of linezolid-resistant S. aureus clinical isolates through the accumulation of resistance-associated 23S rRNA mutations, together with acquisition of an altered mutator phenotype.

Fig 1

Characteristics of the MRSA strains isolated over the period of treatment with LZD. LZD MICs (listed in parentheses after the isolate names) were determined by Etest; a thick dotted line shows the 4-μg/ml cutoff value. Mutations in domain V of the 23S rRNA gene are indicated for each MRSA isolate (Sa-A to Sa-G), as are the relative numbers of mutated copies (in parentheses). MutS and MutL genotypes are indicated for all isolates. LZD total therapy from first use to isolation of LRSA was 28 days. wt, wild type.