Conidial germination in Scedosporium apiospermum, S. aurantiacum, S. minutisporum and Lomentospora prolificans: influence of growth conditions and antifungal susceptibility profiles

In the present study, we have investigated some growth conditions capable of inducing the conidial germination in Scedosporium apiospermum, S. aurantiacum, S. minutisporum and Lomentospora prolificans. Germination in Sabouraud medium (pH 7.0, 37ºC, 5% CO2) showed to be a typically time-dependent event, reaching ~75% in S. minutisporum and > 90% in S. apiospermum, S. aurantiacum and L. prolificans after 4 h. Similar germination rate was observed when conidia were incubated under different media and pHs. Contrarily, temperature and CO2 tension modulated the germination. The isotropic conidial growth (swelling) and germ tube-like projection were evidenced by microscopy and cytometry. Morphometric parameters augmented in a time-dependent fashion, evidencing changes in size and granularity of fungal cells compared with dormant 0 h conidia. In parallel, a clear increase in the mitochondrial activity was measured during the transformation of conidia-into-germinated conidia. Susceptibility profiles to itraconazole, fluconazole, voriconazole, amphotericin B and caspofungin varied regarding each morphotype and each fungal species. Overall, the minimal inhibitory concentrations for hyphae were higher than conidia and germinated conidia, except for caspofungin. Collectively, our study add new data about the conidia-into-hyphae transformation in Scedosporium and Lomentospora species, which is a relevant biological process of these molds directly connected to their antifungal resistance and pathogenicity mechanisms.

El complejo Pseudallescheria/Scedosporium y taxas afines en la rutina del laboratorio micológico clínico / The Pseudallescheria/Scedoporium complex and related taxa in the routine of clinic mycological laboratory

El complejo Pseudallescheria/Scedosporium y taxas relacionados, pertenecientes a un grupo de microhongos con conidios viscosos e integrantes del orden Microascales, se presentan en diversos ambientes comunes asociados a las actividades humanas, ya sea en el suelo como en aguas contaminadas. Actualmente se consideran entre los mayores grupos de hongos filamentosos oportunistas causante de infecciones cutáneas y profundas en el hombre y otros mamíferos. El objetivo principal de este trabajo, consiste en reunir los datos primarios morfofisiológicos más relevantes, útiles para el micólogo médico en el laboratorio, con el aporte adicional de algunos aspectos, biológicos, ecológicos, taxonómicos y moleculares complementarios descritos en la literatura moderna.

The Pseudallescheria/Scedosporium complex and their related taxa are a group of fungus that conidia are presents in viscous mass and belong to the order Microascales. They are in several common enviroment related to human activities either in soil as in contaminated water. Nowadays they are considerated one of the most opportunistic group of filamentous fungus that may cause superficial and deep skin mycoses infections in man and other mammalian. The aim of this work is to gather the primary relevant morphophysiological aspects, usefull to the medical mycologist in the laboratory, plus the contribution of some of biological, ecological, taxonomical and moleculars complementary aspects that are describe in modern literature.