Germination dynamics of allergenic fungal spores in respiratory mucus

Mucus and body temperature serve as the first lines of defense against invading pathogens. When the inhaled particles are deposited in the nose, the respiratory mucus and body temperature potentially impact fungal spore germination and prevent pathogen infections. We hypothesized that respiratory mucus and body temperature impact fungal spore germination. This study aimed to investigate the temporal germination dynamics of allergenic Cladosporium, Aspergillus , and Penicillium spp. in respiratory mucus ex situ and the effect of the temperature (28 °C and 37 °C in the upper and lower respiratory tract, respectively) on fungal germination. Fungal spore germination was inhibited at 37 °C in C. oxysporum and C. cladosporioides , but not A. flavus , A. brunneoviolaceus , A. protuberus , P. citrinum , and P. oxalicum. Aspergillus flavus and A. brunneoviolaceus exhibited a high germination rate in the mucus at 28 °C and 37 °C. This indicated that their germination was not limited in the mucus in the upper or lower respiratory tract, where spores of these fungi can overcome the inhibition of germination as in invasive aspergillosis pathogens. The germination rate of A. protuberus in the mucus was very low at both 28 °C and 37 °C. Spore germination of P. citrinum and P. oxalicum occurred at 37 °C (normal body temperature) but was inhibited by the mucus.