Molecular characterization of mprF genes in daptomycin-resistant clones recovered in multistep selection

StrainTime of MICaDaptomycin MIC (μg/ml)bMprF amino acid changec
SA525 (VSSA)Initial1E44V
Final (passage no.)8 (20)
After subculture2
SA547 (VSSA)Initial1S295L
Final (passage no.)8 (21)
After subculture4
SA262 (VSSA)Initial1I420T
Final (passage no.)8 (16)
After subculture4
SA248 (VSSA)Initial0.5
Final (passage no.)4 (41)
After subculture0.5
SA618 (hVISA)Initial2I506M
Final (passage no.)16 (14)
After subculture8
SA770 (VISA)Initial1I420S
Final (passage no.)8 (35)
After subculture4
  • a Time the MIC was measured.

  • b The MIC values in boldface type indicate that the clones were stable, which was defined as meaning that the MIC after the drug-free passages was within one dilution of the MIC before the drug-free passages.

  • c A minus sign means that no mutation was detected.