**13. Daptomycin and linezolid**

There are no CLSI defined sensitivity breakpoints for Daptomycin and Linezolid for NVS. Albierti et al. found that Daptomycin MICs appear to be relatively high for NVS. Daptomycin MIC90 was >4 μg/ml for *A. defectiva*, 4 μg/ml for *G adiacens* and 0.5 μg/ml for *G. elegans*. According to the CLSI breakpoint of susceptibility for viridans group Streptococci is MIC ≤1 μg/ml, majority of the tested isolates (89.4%) would be considered resistant to Daptomycin [62, 69]. The reason for relatively high Daptomycin MICs for *A. defectiva* and *G. adiacens* is not clear. This may be due to an inherent resistance of these bacteria to Daptomycin potentially due to differences in cell wall composition [62]. In a prior study a smaller number of NVS isolates (n = 10) were found to have MICs ≤0.125–2 [73]. The reason for the discrepancy in the findings of these two studies is not known and merits further investigation.

When the breakpoint of Linezolid susceptibility for viridans group streptococci (MIC ≤2 μg/ml) is applied to NVS, all NVS would be considered susceptible to Linezolid according to one study of 132 isolates [62, 69]. It was noted that *G*. *adiacens* MIC90 for Linezolid is higher (2 μg/ml) than that of *A. defectiva* and *G. elegans* (1 μg/ml) [62].
