FIG 9.

The pH-dependent antifungal activity of methotrexate is species specific. Strains of C. albicans (A), C. glabrata (B), C. tropicalis (C), and C. parapsilosis (D) were seeded into YNB medium buffered at pH 5 or pH 7 at approximately 1 × 10⁴ cells/ml in the presence of a range of MTX concentrations. After 48 h at 30°C, growth was quantified as the OD₆₀₀ and expressed as a percentage of the value for the untreated controls. The values presented here are the average of two replicates and are representative of two experiments. The susceptibility to MTX at the highest concentration at each pH was compared to that of the other pH values using a two-tailed Student's t test (*, P < 0.01; **, P < 0.0001).