Human albumin promotes germination, hyphal growth and antifungal resistance by Aspergillus fumigatus.

Invasive aspergillosis is one of the most common deep-seated fungal infections among patients with an impaired immune system. Albumin is a serum protein commonly administered to critical patients. Our objective was to evaluate the in vitro effect of human albumin upon germination and hyphal growth of Aspergillus species, especially the most pathogenic, Aspergillus fumigatus, as well as its influence on antifungal drug activity. Human albumin induced, at normal serum concentrations (2-4%), a significant promotion of conidial germination by A. fumigatus, but not by Aspergillus flavus and Aspergillus niger. However, mycelium growth following germination was enhanced in all Aspergillus species. Minimal inhibitory concentrations (MIC) of all strains tested to amphotericin B and itraconazole increased in the presence of physiological concentrations of human albumin. Voriconazole activity was not, however, significantly affected by the presence of the protein. Conidial germination represents a crucial initial step in the progression to invasive disease, involving metabolic pathways that may differ considerably among Aspergillus species. Our results support the concept that human albumin may promote a faster onset and enhanced dissemination of invasive aspergillosis.