Seasonal distribution of Alternaria, Aspergillus, Cladosporium and Penicillium species isolated in homes of fungal allergic patients.

BACKGROUND: Allergy to airborne fungi can cause rhinitis and severe asthma, hence the exposure to spores inside home is an important factor of sensitization. The aim of this study was to determine the distribution and prevalence of species of Alternaria, Aspergillus, Cladosporium and Penicillium inside and outside of homes of patients allergic to fungi and to evaluate seasonal variations.
METHODS: Air samples were collected in 22 selected homes of patients with allergy to fungi using a volumetric method of impacting plates with culture media. The isolated species were identified and statistical analysis of the presence of the four fungi was carried out.
RESULTS: A total of 431 indoor and 150 outdoor exposed plates were cultured, leading to isolation of 11,843 colonies of fungi (range 0- 1 666 colony-forming units per cubic meter (CFUs/m(3)). 85.5% of total colonies belonged to the four genera considered. The highest presence of Aspergillus, Cladosporium and Penicillium in indoor environment was registered in autumn. Alternaria was more frequent in summer. In the outdoor environment, Penicillium was more abundant in winter and Aspergillus in summer (P= .002). The largest numbers of isolations were of Cladosporium and Penicillium during all four seasons, indoors as well as outdoors. Alternaria was present in all the homes studied both in summer and in autumn. The most prevalent species were: Alternaria alternata, Cladosporium herbarum, Cladosporium cladosporioides, Aspergillus niger and Penicillium chrysogenum.
CONCLUSIONS: The quantitative analysis of the four taxa related with respiratory allergies demonstrated considerable seasonal variability. Statistical differences between the indoor and outdoor prevalence were detected only in Alternaria. In summer and autumn, the greater level of exposure to the four studied taxas occurred inside homes.