Daptomycin Susceptibility of Unusual Gram-Positive Bacteria: Comparison of Results Obtained by the Etest and the Broth Microdilution Method

Abstract

MICs of daptomycin, linezolid, and vancomycin against 212 isolates, including Listeria monocytogenes and Pediococcus, Leuconostoc, Rhodococcus, and Nocardia spp., were determined by the broth microdilution method; daptomycin MICs were also determined by the Etest. Except with those for Leuconostoc spp., daptomycin Etest MICs showed >90% agreement with MICs obtained by the broth microdilution method.

A Current Perspective on Daptomycin for the Clinical Microbiologist

“…Some species of coagulase-negative Staphylococcus display de- (64), and a variety of Gram-positive anaerobes, including the clostridia (62)(63)(64). In vitro MICs to Listeria monocytogenes are elevated compared to those to other Gram-positive bacteria, with an MIC 90 of 4 g/ml (64,65).…”

“…In vitro MICs to Listeria monocytogenes are elevated compared to those to other Gram-positive bacteria, with an MIC 90 of 4 g/ml (64,65). The L. monocytogenes cell membrane is rich in branched fatty acids (66,67), which may prohibit optimal insertion and oligomerization of daptomycin in the cell membrane, but this has not been specifically demonstrated.…”

“…The L. monocytogenes cell membrane is rich in branched fatty acids (66,67), which may prohibit optimal insertion and oligomerization of daptomycin in the cell membrane, but this has not been specifically demonstrated. Daptomycin does not display in vitro activity against the rapidly growing mycobacteria (68) or Rhodococcus or Nocardia species (64).…”

Comparison of Etest, Disk Diffusion, and Broth Macrodilution for In Vitro Susceptibility Testing of Rhodococcus equi

“…Broth macrodilution was selected for use in this study because commercially available microtiter plates have a very limited range of dilutions which would have prevented quantitative comparisons to the Etest over the entire range of possible MICs. There are multiple possible source for mistakes with the broth macrodilution method, and difficulties in reading broth dilution assays at 24 h for some isolates of R. equi have been reported previously (25). A recent publication demonstrated that addition of 2% (vol/vol) lysed horse blood to the cation-adjusted Mueller-Hinton broth facilitates the discrimination between growth and no growth of R. equi (26).…”

Leuconostoc bacteremia in three patients with malignancies

“…for Leuconostoc but which is not authorized in Japan, must be considered a first-line drug for the treatment of Leuconostoc infection 8 .…”