Hydrocortisone, prednisolone and dexamethasone act on Aspergillus fumigatus in vitro susceptibility to itraconazole.

In a previous in vitro investigation from the same laboratory a therapeutic level of hydrocortisone enhanced the itraconazole susceptibility of a sing le strain of Aspergillus fumigatus. In the present work, the influence of t herapeutic levels of hydrocortisone (1 muM), prednisolone (0.125 muM 0.25 m uM and 0.5 muM) and dexamethasone (0.25 muM and 0.5 muM) on the itraconazol e susceptibility of four A. fumigatus strains, was determined. A. fumigatus conidia were germinated either in the absence or in the presence of a gluc ocorticoid. The germinated conidia were then spread onto plates and grown e ither in the presence or in the absence of a glucocorticoid, together with increasing concentrations of itraconazole. The mean colony forming units (C FU) were measured. Two factor analyses of variance showed that hydrocortiso ne significantly (p <0.001) potentiated the action of itraconazole. The cyt otoxic effect of prednisolone on the fungal strains added significantly to the effect of itraconazole (p <0.001). Dexamethasone was also cytotoxic to the fungus but, when used in conjunction with itraconazole, it effectively increased (p <0.01) the number of CFU. This study showed a direct effect of glucocorticoids, currently in use for patient therapy, on in vitro A. fumi gatus susceptibility to itraconazole.