[In vitro antifungal activity of ajoene on five clinical isolates of Histoplasma capsulatum var. capsulatum].

BACKGROUND

The number of histoplasmosis cases have considerably increased since the advent of AIDS, and the therapy for this mycosis is not always effective, as well as having adverse effects.

AIMS: To evaluate the inhibitory effect of ajoene on five clinical isolates of Histoplasma capsulatum, on the mycelial form, using Sabouraud dextrose broth (SDB) and RPMI-1640 culture media.

METHODS

Growth curves and inhibitory activity of the drug (at concentrations of 1.25 ug/ml to 20 μg/ml) were performed at room temperature, under mechanical agitation, and the turbidimetric readings (540 nm) were recorded every 48 h for 14 days, in both culture media. Generation times (GT) were calculated and graphs were constructed to estimate Minimal Inhibitory Concentrations (MIC) and Inhibitory Concentration 50% (IC(50)). The fungicidal minimal concentrations (FMC) were determined by plate cultures. The U-Mann-Whitney and t-test with a significance level of 0.05 were used to evaluate the statistical significance between culture media and GT, MIC, IC(50) MFC and fungistatic effect (FE).

RESULTS

In both media and for all isolates, growth curves showed a GT of 43 to 67 hrs, an FE at 1.25-2.5 μg/ml, and a MFC at 5-10 μg/ml of ajoene. Values of MIC were 2.5-5 in SDB and in RPMI medium these values were 1.25-5 μg/ml of ajoene. For IC(50), in SDB, the values were 1.9-2.6 ug/ml and in RPMI medium, they were of 3.8-4.3 μg/ml of ajoene. There were no significance differences between culture media for GT, FE, MIC, IC(50) and MFC (p>0.05).

CONCLUSIONS

These findings corroborate that ajoene inhibits the growth of the mycelial form of H. capsulatum.