Recombination proficiency influences frequency and locus of mutational resistance to linezolid in Enterococcus faecalis

Abstract

In vitro linezolid resistance was selected at a higher frequency in Enterococcus faecalis JH2-2 than in recombination-deficient E. faecalis UV202. Resistance in JH2-2 was related to accumulated G2576T mutations in 23S rRNA genes, with the least resistance conferred by mutations in two of four copies. UV202 resistance was associated with a G2505A mutation present in a single copy in mutants with different MICs.

FIG. 1.

Southern hybridization of EcoRV-digested genomic DNA from E. faecalis with a 23S rRNA probe. The position of the 23S rRNA gene copy that acquires the mutation is indicated by the arrow with the asterisk to the left of the gel. The positions of the two bands resulting from EcoRV digestion of the 23S rRNA gene that acquires the G2505A mutation in the two resistant UV202 mutants are indicated by the arrows to the right of the gel. Lane 1, E. faecalis UV202; lane 2, linezolid-resistant UV202 mutant (MIC of 2 μg/ml); lane 3, linezolid-resistant UV202 mutant (MIC of 16 μg/ml).