In vitro determination of phagocytosis and intracellular killing of Aspergillus species by mononuclear phagocytes

We investigated phagocytosis and intracellular killing of clinical and environmental isolates of Aspergillus spp. by human monocyte-derived macrophages (MDMs). Serial pathogens such as Aspergillus fumigatus, Aspergillus flavus and Aspergillus terreus were examined with a microbiological assay. Phagocytosis for resting conidia of Aspergillus spp. was similar for all isolates tested. During 30 min of incubation phagocytosis ranged from 49.9% to 85.5% for clinical isolates and from 40.3% to 87.1% for environmental isolates. MDMs killed A. fumigatus, A. flavus and A. terreus conidia after ingestion for 120 min, as shown by a decrease in colony forming units (cfu) count of intracellular fungi. The killing index for all isolates of Aspergillus spp., ranged from 12.1 ± 1.1% to 90.3 ± 10.4%; isolate-dependent (P < 0.01) differences against the fungicidal action of MDMs were observed. In conclusion, significant differences were noted for killing indices between several strains of Aspergillus spp. whereas phagocytosis was similar for all isolates tested in vitro. No differences were observed within environmental and clinical isolates.