We next studied the effect of ketamine pre-incubation on macrophage TNF secretion after stimulation with daptomycin-exposed MW2 or LAC. Once again, the addition of ketamine resulted in significant inhibition of macrophage TNF secretion in response to MW2 (23,185 ± 1,267 pg/mL to 17,354 ± 853 pg/mL, a reduction of approximately 25%; p < 0.05) or LAC (approximately 18% reduction, p < 0.05; Figure 2 ). Adding ketamine after the MRSA inocula did not alter the response. Figure 1 The CA-MRSA isolates LAC (USA300) and MW2 (USA400) stimulated less TNF secretion by RAW264.7 murine macrophages when exposed to daptomycin (DAP) than when exposed to vancomycin (VAN). LAC or MW2 were added to RAW264.7 cells at a final concentration of 10 5 to 10 7 CFU/mL (retrospective confirmation) in the presence of either vancomycin or daptomycin at 20 μg/mL. Cells were incubated for 18 hours; supernatants were collected and analyzed for TNF content by an enzyme-linked immunosorbent assay (ELISA). Results are depicted as means with 95% confidence intervals shown as "error bars" (See Methods). The "*" indicates significance at p < 0.05. Control represents the mean TNF macrophage production by macrophages not stimulated with bacteria.