Respiratory toxicity of Aspergillus versicolor: the most common indoor mould in Slovakia

摘要

A mould Aspergillus versicolor clearly dominates in damp and mouldy indoor environments under Slovak dwelling/public building conditions (up to 1/3 of all isolates during the last decade's surveys). Nearly all of its isolates are able to synthesize a mycotoxin sterigmatocystin (detected by LC/MS-MS), that showed severe in vitro as well as in vivo toxic potential in animal experiments (after intratracheal instillation to rats). In vitro toxicity of complex chloroform-extractable endo- and exometabolites of 10 indoor, and related outdoor, A. versicolor isolates from a heavily mouldy kids' fashion store in Slovakia with complaints from the occupants of irritation of their airways has been evaluated by a bioassay with tracheal organ cultures of one-day old chicks (20 microg of toxicants per mL of cultivation medium). In the in vivo experiments, respiratory toxicity of the same metabolite mixtures was tested in Wistar rats during three days. The inflammatory and cytotoxic biomarkers were then analyzed in bronchoalveolar lavage fluid. Searching for the fungus possible source, molecular epidemiological study of the isolates was performed using RAMP PCR. Strains colonizing the indoor walls of the shop were the highest correlated to the outdoor airborne ones (Pearson correlation 97%). While indoor airborne isolates correlated to the strains growing on retailed clothes at the levels of 90 or 86% according to Pearson. All micromycetes produced secondary metabolites that ceased ciliary beating in tracheal epithelium in the organ cultures already in 24 hrs of the activity, i.e. in the sense of the method used, they belong to strong toxicants. Two of the isolates tested also produced extrolites without toxic effects detectable by the method. The metabolites also showed certain cytotoxic and inflammation-inducing effects that were in concentration depending on the animal experiments. It has been proven that toxin production in fungi depends not only on the species but may vary between every single isolate as well. The most important outcome of the study is that microscopic filamentous fungi present in the dwelling indoor environment under Slovak (Central European) building/housing conditions might produce compounds even with the potential to damage the airways of occupants, while children remain the most vulnerable population.