Effect of levodopa on melanogenesis in and antifungal drug susceptibility of Penicillium marneffei / 中华皮肤科杂志

ABSTRACT

Objective To investigate the effect of levodopa on melanogenesis in Penicillium mameffei (PM),and to determine if melanization affects the antifungal drug susceptibility of PM.Methods A clinical isolate of PM,GXMU121011,was inoculated onto Sabouraud's dextrose agar (SDA) containing different concentrations (0.1-10 mmol/L) of levodopa at an inoculum density of 1.0 × 106 cfu/ml,or onto SDA containing 1 mmol/L levodopa at three inoculum densities (1.0 × 105,1.0 × 106,1.0 × 107 cfu/ml),and cultured at 37 ℃ for 7 days.Subsequently,melanization of PM colonies was observed.The paper-disk method was used for antifungal susceptibility testing,and the diameter of inhibition zones of itraconazole,fluconazole and amphotericin B against 8 clinical strains of PM was determined on SDA with or without levodopa.Results The melanization of PM colonies increased when the concentration of levodopa increased from 0.1 to 1.0 mmol/L,peaked when that reached 1.0 and 3.0 mmol/L,but mildly decreased when that continuously increased beyond 3.0 mmol/L,and a slight shrinkage was observed in PM colonies when that was 10.0 mmol/L.The color of colonies deepened along with the increase in inoculum density of PM.The average diameters of inhibition zones of itraconazole,fluconazole and amphotericin B against PM were all significantly lower on SDA with levodopa than on SDA without levodopa (all P ＜ 0.05).Conclusions Levodopa concentration and inoculum density both affect melanogenesis in PM.Melanization may decrease the susceptibility of PM in yeast phase to itraconazole,fluconazole and amphotericin B in vitro.