Measurement of the minimal inhibitory concentrations and minimal fungicidal concentrations of antifungal agents against Candida strains isolated from blood cultures

• Published in: Japanese Journal of Chemotherapy Vol. 55; no. 4; pp. 257 - 267
• Main Author: Fujita, Shin-ichi
• Format: Journal Article
• Language: Japanese
• Published: Japanese Society of Chemotherapy 2007; 公益社団法人 日本化学療法学会
• Subjects: Cmdida; MFC; MIC
• ISSN: 1340-7007; 1884-5886
• DOI: 10.11250/chemotherapy1995.55.257

We measured the minimal inhibitory concentrations (MICs) and minimal fungicidal concentrations (MFCs) of micafungin (MCFG), amphotericin B (AMPH-B), flucytosine (5-FC), voriconazole (VRCZ), itraconazole (ITCZ), miconazole (MCZ), and fluconazole (FLCZ) for 57 Candida strains isolated byblood cultures. In the experiment of viable cell counting, polysorbate 80 was added to the sterile saline in order to inhibit the aggregation of fungus cells, and to Sabouraud agar media, in combination with lecithin and histidine, to overcome the carryover effect of antifungal agents. MFC was defined as the lowest concentration of the drug that could kill 99% of viable cells. The MFC90 values of MCFG and AMPH-B for C. albicans (14 strains), C.tropicalis (11 strains), and C.glabrata (14 strains) were 0.03 and 1 μg/mL, 0.125 and 0.5 g/mL, and 0.5 and 2 μg/mL, respectively. Furthermore, MCFG and AMPH-B exhibited superior fungicidal activity against azole-resistant C.albicans (one strain) and azole-resistant C.tropicalis (one strain). While theMIC90 of VRCZ for 16 C. parapsilosis strains was 0.008 μg/mL, showing thegreatest growth-inhibitory activity, the MFCs of VRCZ for C. parapsilosis ranged from 0.03 to≥32 μg/mL, and the MFC of VRCZ was 32 μg/mL or more. In contrast, AMPH-B and MCFG showed marked fungicidal activity, and the MFC90 of AMPH-B and MCFG for C.parapsilosis was 2 and 8 μg/mL, respectively. As compared to MCFG, AMPH-B showed more marked fungicidal activity against two C.guilliermondii strains. The MFC90 of the azoles for Candida strainsbelonging to the five Candida species isolated could not be defined at the concentrations tested. Our results demonstrated that MCFG and AMPH-B exhibit superior fungicidal activity against medically important Candida strains isolated by blood cultures.