Culturable mycobiota of drinking water in Goteborg (Sweden) in comparison to Ljubljana (Slovenia) with implications on human health

European Union has currently no specific regulation on fungi in water. The only country where fungi are listed as the parameter is Sweden, with the maximal number of 100 CFU per 100 mL. The present study thus compared culturable mycobiota from Swedish drinking water with Slovenian, which has no specific requirements for fungi. Fungi were isolated with up to 38 CFU/L from 75% of Swedish samples. The most common were the genera Varicosporellopsis (27.3%), Paracremonium (14.5%), and black yeasts Cadophora, Cyphellophora, and Exophiala (18.2%). Using the same sampling and isolation methods, 90% of tap water samples in Slovenia were positive for fungi, with Aspergillus spp. (46%), Aureobasidium melanogenum (36%), and Exophiala spp. (24%) being the most common. The observed differences between countries are likely the consequence of geographical location, the use of different raw water sources, and water treatment methods. However, the core species and emerging fungi Aspergillus fumigatus, Candida parapsilosis sensu stricto, Exophiala phaeomuriformis, Bisifusarium dimerum, and Rhodotorula mucilaginosa have been isolated in both studies. These findings point out the relevance of tracking the presence of emerging fungi with known effects on health in drinking water and encourage further studies on their transmission from raw water sources to the end-users.

Automated summary

Currently, there is no specific regulation on fungi in water by the European Union. However, Sweden has set a maximum limit of 100 CFU per 100 mL for fungi in drinking water. A study compared the culturable mycobiota in Swedish drinking water, which has specific requirements, with Slovenian drinking water, which does not. The results showed differences in fungal isolates between the two countries, likely due to geographical location, raw water sources, and water treatment methods.