Table 1.

MICs of macrolides (14-, 15-, and 16-membered) for wild-type E. faecium TX1330 and two msrCdisruption mutants

OrganismcErythromycinAzithromycinTylosinQuinupristin
MICaE-test MICbE-test MICbMICaMICa
TX13300.750.251.561696
TX13300.50.381.561696
TX13300.750.381.561696
msrCmutant 10.090.0940.38864
msrC mutant 10.090.0940.38864
msrC mutant 10.060.0940.38848
msrC mutant 20.060.0940.38864
msrC mutant 20.060.0940.38864
  • a By broth microdilution method. The ERY concentrations tested were 0.04, 0.06, 0.09, 0.125, 0.187, 0.25, 0.37, 0.5, and 0.75 μg/ml; the quinupristin concentrations tested were 32, 48, 64, and 96 μg/ml.

  • b Performed using inocula as recommended by the manufacturer.

  • c TX1330 and msrC mutant 1 were evaluated in triplicate, and mutant 2 was evaluated in duplicate.