Chinese Journal of Dermatology ›› 2008, Vol. 41 ›› Issue (8): 515-518.
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HU Xiao-Yan
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Abstract: Objective To seek a cost-effective method for isolation of dematiaceous fungi from soil. Methods Four concentrations of soil suspension samples were prepared by ten-fold serial dilution (1, 1 ∶ 10, 1 ∶ 100, 1 ∶ 1000). Then, each concentration of sample was divided into two parts: one part supplemented with antibiotics, including chloramphenicol, cycloheximide, penicilin and streptomycin, and the other free of antibiotics. Three culture media were prepared: Sabouraud′s dextrose agar(SDA), potato dextrose agar(PDA) and rose bengal medium (RBM). Various concentrations (0, 100, 200, 300, 500 mg/L) of cycloheximide were added into each culture medium along with defined concentration of penicillin (1000 u/mL) and streptomycin (0.2 g/L). In addition, chloramphenicol (50 mg/L) was added to PDA. The prepared soil samples were inoculated into these media by spread plate and pour plate, respectively. Results The total isolation rate of dematiaceous fungi was 70% (56/80) for PDA, 67.5% (54/80) for RBM and 3.75% (3/80) for SDA. PDA and RBM were more efficient than SDA (both P < 0.05). Significant difference was observed in the isolation rate of dematiaceous fungi between the original and 1:100 diluted soil suspension samples in PDA (50% vs 85%, P < 0.05) and RBM (45% vs 85%, P < 0.05). An increased isolation rate was achieved in PDA (87.50% vs 31.25%) and RBM (81.25% vs 37.5%) with cycloheximide at 200 mg/L compared with those free of cycloheximide. No difference was found in the isolation rate between antibiotic-supplemented and antibiotic-free soil samples. Although there was no difference in the total isolation rate between spead plate and pour plate, a higher isolation rate was observed by pour plate from antibiotic-free soil samples in PDA (80% vs 40%, P < 0.05) and RBM (80% vs 30%, P < 0.05) compared with spread plate. Conclusions The modified PDA and RBM are suitable for the isolation of dematiaceous fungi from soil with the optimal concentration of cycloheximide being 200 mg/L in the medium. Pour plate is more convenient and cost-effective than spread plate for the isolation of dematiaceous fungi from soil.
Key words: Soil, Dematiaceae fungi, Isolation
HU Xiao-Yan . Evaluation of methods for isolation of dematiaceous fungi from soil[J].Chinese Journal of Dermatology, 2008,41(8):515-518.
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