Platelets enhance activity of antimycotic substances against non-Aspergillus fumigatus Aspergillus species in vitro.

Platelets are known to be part of haemostasis but they are also players in innate host defense. Recently, we observed that platelets attenuate the virulence of Aspergillus spp. in vitro. However, little is known about the antifungal effects of platelets in the presence of antimycotics against non-A. fumigatus Aspergillus species. We therefore investigated whether platelets increase the in vitro activity of amphotericin B, voriconazole, posaconazole and caspofungin against two clinical isolates each of Aspergillus flavus, Aspergillus terreus and Aspergillus niger. The antifungal activity was evaluated by assessing germination percentages, hyphal elongation and hyphal damage by use of XTT. The combination of platelets plus amphotericin B significantly (P < 0.05) enhanced the reduction of germination percentage compared to either substance alone. Among triazoles, voriconazole exhibited significant effects with platelets for all tested aspergilli. Overall, these findings suggest that among the tested antimycotic substances, amphotericin B in combination with platelets has enhancing effects in reducing germination and hyphal elongation in the tested non-A. fumigatus Aspergillus species. These data indicate that platelets act beneficially with antimycotics in an early stage of fungal growth by blocking and/or delaying fungal germination and hyphal elongation; both crucial mechanisms in the development of invasive fungal disease.