Chronic rhinosinusitis (CRS) is one of the most common chronic diseases in the 'westernized world'. The biodiversity of fungi isolated from the nasal mucus of patients suffering from CRS and from healthy persons was monitored over 28 months. Mucus samples were obtained by flushing the noses of patients with saline or by endoscopic sinus surgery. Identification of isolated fungi was performed microscopically and by PCR with subsequent sequencing of the ribosomal internal transcribed spacer region.
Altogether, 619 strains of fungi were cultivated from 233 subjects. Eighty-one species were identified, with a maximum of nine different species per person. The most prevalent isolates belonged to the genera Penicillium, Aspergillus, Cladosporium, Alternaria and Aureobasidium. Whereas Aspergillus and Penicillium spp. occurred in more or less the same numbers throughout the year, Cladosporium spp., Alternaria spp. and Aureobasidium pullulans showed a significantly higher occurrence during late summer and early autumn.
Besides the culture-based techniques, mucus of patients was examined for the presence of fungi by direct microscopy of methenamine-silver stained histological preparations. In parallel, the corresponding histological sections were stained with hematoxylin-eosin for eosinophils. Fungal elements were found in 75.5%, and eosinophilic mucin in 94.6% of patients. In most of the cases the observed eosinophils were clustered around fungi.