Fungi in drinking wáter distribution systems during a stagnation period

SHEILA CORIMAYO; DIEGO GASTÓN SANGUINO JORQUERA; MÓNICA APARICIO; NELI ROMANO ARMADA; VERONICA BEATRIZ RAJAL; MERCEDES CECILIA CRUZ

Congreso; Congreso Conjunto de la Sociedad Argentino Bioquímica (SAIB) y la Asociación Civil de Microbiología General (SAMIGE); 2020

Fungi survive under different environmental conditions, including oligotrophic ecosystems such as chlorinated drinkingwater distribution systems (DWDS). These organisms can be found in the bulk water causing unpleasant odors, cloggedpipes, paint deterioration, and they can grow on the surface of inner-wall pipes forming biofilms. Therefore, they couldharbor pathogens, increase resistance to antibiotics and disinfectant tolerance. These organisms can also producemycotoxins that are harmful to human health. Furthermore, stagnation periods could enhance those undesirable effects.The objective of this work was to evaluate the presence of fungi in DWDS using traditional cultivation techniques. A totalof 48 water samples were collected monthly from six taps points of different buildings, an elevated distribution tank, andthe cistern located at a university campus, in a period of six months (March to August 2020) with low water consumption.To determine the abundance of fungi, drinking water samples of 100 mL were concentrated by a membrane filtrationmethod and cultured on Sabouraud Glucose Agar medium at 30 o C for seven days. The grown colonies were isolated inthe same medium, and their macro- and microscopic characteristics were examined. In addition, 1 L of water wascollected from each site for microbiological and physicochemical analysis, which included the determination of indicatorbacteria and opportunistic pathogens (total coliforms, E. coli, and P. aeruginosa), the quantification of heterotrophicbacteria on Plate Count Agar, and the measurement of temperature, conductivity, salinity, pH, and free chlorine. The eightsites showed different physicochemical characteristics. Chlorine concentration varied significantly (0.2 mg/L - 1.5 mg/L)among the studied sites. As expected, because of seasonality, the temperature decreased along with the study. Thebacteriological quality of the drinking water was acceptable for consumption according to the current legislation. Nosignificant correlations were found between the physicochemical and bacteriological variables and the abundance of fungi(p-value > 0.05). Of the total of samples, 89.6% (43/48) presented fungi. The average abundance of fungi in the DWDSwas 62.8 CFU/mL, while the highest number of fungi determined was 825 CFU/mL in one site in May. Three Fungigenera were constantly observed in one of the sampled points; meanwhile, the other sites showed a more diverse fungalcommunity during the monthly monitoring. The results showed that fungi are widely found in the DWDS, and changes intheir abundance and diversity can be expected at different sites throughout stagnation periods. The occurrence of fungi inwater has no relationship with indicator bacteria tested according to the current legislation. More studies are required toknow the potential impact of fungi on infrastructure and consumers.