Synergy of human neutrophils with fluconazole in killing Candida species

The killing of Candida species by human neutrophils in a long-term 24-h assay and possible synergy with fluconazole (FCZ) for killing was investigated. The test medium (TM) consisted of RPMI-1640, penicillin and streptomycin (P/S), and 10% fresh autologous serum. TM alone was highly fungistatic for Candida species compared to TM without serum. When neutrophils were cocultured in TM with Candida species for 24 h the inoculum colony-forming units (CFU) were always significantly reduced (killing) by 58 to 99%. FCZ was tested over a range of 1-500 mu g/ml, and though almost always fungistatic itself, it synergized with neutrophils for significantly increased killing of C. albicans (isolate Sh27) (P < 0.01) and C. albicans (isolate 94-20) (P < 0.05). Killing of non-albicans Candida species was so efficient in the absence of FCZ that demonstration of synergy with FCZ was difficult.