Isolate-dependent pathogenicity and host-pathogen interactions of toxigenic Penicillium roqueforti in the Galleria...

This study evaluated pathogen-host interactions of five toxigenic Penicillium roqueforti isolates obtained from artisanal mold-ripened cheeses using an experimentally induced Galleria mellonella infection model, by assessing survival, activity, and melanization together with hemocyte cytology and tissue-level histopathology. The isolates exhibited pronounced isolate-dependent differences in pathogenicity and host responses, despite all isolates originating from food matrices. Among the isolates tested, the larvae infected with Hatay isolate showed an early mortality pattern and, together with the Isparta and Erzurum isolates, produced higher mortality than the Kars and Giresun isolates. The mean survival time was shortest in the Hatay group (5.00 ± 0.52 days), whereas no mortality was observed in the Giresun or PBS control groups. Cytological findings indicated impaired phagocytosis with extracellular fungal elements and oenocytoid-like cells, while histopathology revealed severe fat body degeneration, extensive hemocyte infiltration, widespread necrosis, and diffusely distributed PAS-positive fungal structures. The Isparta- and Erzurum-derived isolates exhibited intermediate pathogenicity, with mortality rates of 46.7% and 53.3%, respectively, characterized by mixed intra- and extracellular fungal forms and moderate melanized nodules with partial tissue invasion. In contrast, the Giresun-derived isolate had the lowest pathogenic effect, showing 100% larval survival with predominant phagocytic plasmatocytes indicative of effective fungal containment and minimal tissue damage with limited melanization. The Kars-derived isolate displayed relatively low pathogenicity, with 26.7% mortality and a prolonged mean survival time of 6.2 days, accompanied by moderate histopathological findings. In conclusion, the present findings suggest that P. roqueforti isolated from artisanal mold-ripened cheeses can induce isolate-dependent immune and histopathological responses in a live host model and may reflect aspects of pathogenic potential. This points to the need for more comprehensive, isolate-level evaluation of the biological behavior of food-derived isolates.