[From when on can fungi be identified in nasal mucus of humans?]

Fungal spores are frequent in air and their occurrence in the nasal mucus appears to be a common finding within the adult population, as we were able to show in recent studies. 91,3 % of CRS patients but also healthy controls grew positive fungal cultures out of their nasal mucus. The potential role of fungal elements in nasal mucus for the pathogenesis of CRS, with or without polyposis, is currently investigated intensely and discussed very controversially. However, it was still unknown, as of when fungi could be cultured from nasal mucus in humans. We attempted to identify this point of time, in the nasal mucus of neonates.

In our study we examined nasal mucus from 30 neonates immediately after birth, on the first and fourth day post partum, and after two and four months of life. The samples obtained with sterile cotton swabs were cultured on agar plates. Fungal cultures were identified either conventionally by microscopy or with molecular techniques. To show whether fungi in nasal mucus of newborns were acquired by contamination during birth, mucus of the maternal vagina was examined as well.

Just after birth we found in 6 of 30 (20 %) of our neonates positive fungal cultures out of their nasal mucus, in 3 of them Candida albicans, probably due to contamination passing the maternal vagina as cultures of vaginal mucus of their mothers were positive for Candida albicans too. Positive fungal cultures were obtained in 2 of 29 (7 %) neonates on the second and in 4 of 26 (15 %) neonates on the fifth day of life. In all our cases initial presence in nasal mucus contamination just after birth or on the second day of life was limited to one day only. None of the 12 of 30 (40 %) neonates with positive fungal cultures from nasal mucus in the first 5 days of life showed clinical symptoms of nasal fungal colonisation. Besides Candida albicans, Penicillium sp., Cladosporium cladosporioides, Acremonium polychromum, Beauveria bassiana and Epicoccum nigrum could be detected in the first 5 days of life. After the second month of life, examination of nasal mucus yielded positive fungal cultures in 8 of 11 (72 %), after four months even 17 of 18 (94 %) of babies, with a wide array of different species.

Fungi can be cultured from nasal mucus as soon as contact with the environmental air exists. Furthermore, a transfer of fungi from the mother's birth canal into the nose during birth is possible. Presence of fungal spores is common but not persistent in the nose of babies in the first days of life. However, after four months the situation is similar to the one in adults: fungal cultures can be obtained from almost everyone's nose. Therefore fungal spores must be considered a normal content of nasal mucus. Fungal spores are inhaled with every breath, some stick to the mucus, are transported to the nasopharynx and swallowed. This does not cause any clinical symptoms and is therefore not a pathological finding at all.