Virulence of Aspergillus flavus and relatives using the Galleria mellonella model

Aspergillus section Flavi encompasses multiple species, with A. flavus being significant for human health because of its dual role as a major aflatoxin producer and opportunist. However, the mechanisms underlying its virulence remain incompletely understood. This study evaluates the pathogenic potential of A. flavus and its relatives using the Galleria mellonella infection model. Twenty-six A. flavus isolates (clinical and environmental) and 17 relatives/domesticated species were tested in G. mellonella, with larval survival monitored over 7 d. Histology, direct microscopy, and culture were used to validate the infection. Growth kinetics and spore sizes were measured to evaluate correlations with pathogenicity. All A. flavus isolates demonstrated high virulence, causing 90%, and 100% mortality of G. mellonella larvae within 3 and 7 d, respectively, with no significant differences between sources. Aflatoxin-producers exhibited higher virulence, resulting in 100% mortality of Galleria larvae within 5 d (p < 0.05). Related species exhibited lower virulence; larval mortalities ranging from 20% to 70% within 3 d, ranked as A. flavus > A. pseudonomiae > A. parasiticus > A. nomiae > A. tamarii > A. pseudocaelatus. Growth kinetics and spore size were correlated with virulence, as rapid growth and smaller spores were associated with increased pathogenicity. Aspergillus flavus exhibits higher virulence than its relatives, with growth rate, and spore size influencing pathogenicity. The G. mellonella model proves effective for comparative virulence studies. These findings highlight the potential health risks of A. flavus, including its domesticated relatives used in food fermentations, necessitating further investigations into their pathogenic potential.