Fungal contamination in residential water systems: A comparative study between hot and cold water samples

Some fungal species are known to have adverse health effects for humans and their presence in water systems may lead to alterations in the taste and odour of the water they occupy. Although a few country-based regulations are known, no universal legal restriction on the presence of fungi in drinking or utility water is present currently. Waterborne fungi have been a neglected part of microbial studies worldwide, and more sudies are needed in the current era of global warming. This study was performed to evaluate (i) the fungal load in randomly selected residential water systems connected to the municipal water supply in Istanbul, Türkiye, and (ii) the possible impact of water temperature on the number and biodiversity of fungi. Additionally, the relationship between bacterial loads, some water parameters and the determined fungi were investigated. Cold and hot water samples were taken from 20 randomly selected buildings in Istanbul and inoculated into SDA using the membrane filtration method for fungal isolation, and onto R2A and Candida Agar using the spread plate method for bacterial and Candida isolation, respectively. More microorganisms were detected in cold water samples than in hot water. The mean fungal and bacterial numbers in cold and hot water samples were 2.4, 1.47, 702.3 and 79.5 cfu/100 mL, respectively. No Candida was found. It was determined that temperature affected the biodiversity and frequency of fungi. Penicillium (41%) and Aspergillus (43.75%) were the dominant fungal genera in cold and hot water, respectively. Aspergillus versicolor was the most common fungal species found in both water samples. 9 of fungi were identified that are known to have the potential to cause allergies and/or opportunistic infections. No relationship was detected between fungal growth and pH and chlorine.