Effect of subinhibitory concentration of some established and experimental antifungal compounds on the germ tube formation in Candida albicans

The influence of subinhibitory concentrations of six established and 19 newly synthesized antifungal compounds on the dimorphic transition of three C. albicans strains was evaluated in the filamentatation-inducing icing medium. Amphotericin B was found to produce almost complete inhibition in the germination at a concentration of 1/10 of the corresponding MIC and partial inhibition at a concentration as low as MIC/50. Flucytosine and four azole derivatives were proven ineffective. From the newly synthesized drugs, the incrustoporin derivative LN06-22, two phenylguanidine derivatives (PG15, PG45), and four thiosalicylanilide derivatives, in particular, showed results comparable to those of amphotericin B, with a high inhibition of germ tube formation at concentrations of MIC/10. In general, concentrations of MIC/50 had no visible effect.