Background: In recent studies, we showed that 91.3% of both CRS patients and healthy controls grew positive fungal cultures out of their nasal mucus, which therefore appears to be a common finding within the adult population. However, it still was unknown as of when fungi could be cultured from nasal mucus in human beings. We attempted to ascertain this point of time in the nasal mucus of neonates.
Methods: We examined nasal mucus from 30 neonates immediately after birth, on the 1st and 4th day postpartum and after 2 and 4 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 prove possible contamination during birth, mucus of the maternal birth canal was examined as well.
Results: In 6 of 30 (20%) of our neonates we found positive fungal cultures immediately after birth in (3 of them Candida albicans) most likely because of contamination passing the maternal birth canal. In 2 of 29 (7%) of our neonates, positive fungal cultures were obtained on the 1st day postpartum, and in 4 of 26 (15%) positive fungal cultures were obtained on the 4th day, all limited to 1 day only and without clinical symptoms of colonization. After the 2nd month of life, examination of nasal mucus yielded positive fungal cultures in 8 of 11 (72%), and after 4 months examination of nasal mucus yielded positive fungal cultures in 17 of 18 (94%) of our babies, with a wide array of different species.
Conclusion: Fungi can be cultured from nasal mucus as soon as contact with the environmental air exists but they are not persistent in the 1st day of life. However, after 4 months, the situation is similar to the one in adults: fungal cultures can be obtained from almost everyone's nose. Therefore, fungi must be considered a normal content of nasal mucus.