Water quality and antifungal susceptibility of opportunistic yeast pathogens from rivers

Abstract

Yeasts from water sources have been associated with diseases ranging from superficial mucosal infections to life threatening diseases. The aim of this study was to determine the water quality as well as diversity and antifungal susceptibility of yeasts from two rivers. Yeast levels and physico-chemical parameter data were analyzed by principal component analysis to determine correlations between physico-chemical data and yeast levels. Yeast morphotypes were identified by biochemical tests and 26S rRNA gene sequencing. Disk diffusion antifungal susceptibility tests were conducted. Physico-chemical parameters of the water were within target water quality range (TWQR) for livestock farming. For irrigational use, total dissolved solids and nitrates were not within the TWQR. Yeast levels ranged between 27 ± 10 and 2,573 ± 306 cfu/L. Only non-pigmented, ascomycetous yeasts were isolated. Saccharomyces cerevisiae and Candida glabrata were most frequently isolated. Several other opportunistic pathogens were also isolated. A large number of isolates were resistant to azoles, especially fluconazole, but also to other antifungal classes. Candida species were resistant to almost all the antifungal classes. These water sources are used for recreation and religious as well as for watering livestock and irrigation. Of particular concern is the direct contact of individuals with opportunistic yeast, especially the immune-compromised. Resistance of these yeast species to antifungal agents is a further health concern.

Physico-chemical parameters and culturable yeast diversity in surface water: a consequence of pollution

“…TDS values were within TWQR for livestock farming (<1 000 mg/L) but above the recommended values for irrigation use (>40 mg/L). The high TDS values that were found in the NWP rivers by the current and by previous studies (Van Wyk et al, 2012;Monapathi et al, 2017) could have occurred as a result of dolomitic springs which are water sources for some of the river systems (Van Der Walt, 2002).…”

“…The 26S rRNA gene fragments of the extracted DNA were amplified using the polymerase chain reaction (PCR) procedure as described by Monapathi et al (2017). Forward primers, NL1 (5-GCATATCAATAAGCGGAGGAAAAG-3) and reverse primers, NL4 (5-GGTCCGTGTTTCAAGACGG-3) (O'Donnell, 1993) were used.…”

“…Current microbial studies use standard faecal indicator bacteria such as Escherichia coli and intestinal enterococci to determine water pollution levels (Kirschner et al, 2019). However, some studies have also reported high yeast levels and the presence of certain types of yeasts as an indication of contaminated water environments (Van Wyk et al, 2012;Monapathi et al, 2017). Some studies have also deemed yeasts as a complement to faecal indicator bacteria counts when water quality is monitored (Medeiros et al, 2008;Brandão et al, 2010).…”

“…The release of such effluent into aquatic ecosystems escalates antifungal resistance through continuous exposure of pathogenic yeasts. Antifungal resistance has been observed among environmental isolates (Brilhante et al, 2016;Milanezi et al, 2019;Monapathi et al, 2017Monapathi et al, , 2018. According to a report by the UN ad hoc Interagency Coordinating Group on Antimicrobial Resistance, drug-resistant diseases could cause up to 10 million deaths each year by 2050.…”

Collateral consequences of agricultural fungicides on pathogenic yeasts: A One Health perspective to tackle azole resistance

“…Subsequently, Zuza‐Alves et al reported a rate of fluconazole resistance as high as 43% in environmental C tropicalis from a Brazilian sand beach, with 24% of the isolates being multi‐azole resistant 52 . Similar observations were reported from soil samples in Taiwan, 53 and among C albicans isolates from environmental sources in Brazil, Japan and South Africa 54‐56 . Additionally, various levels of resistance to the medical antifungals fluconazole and flucytosine have been described in environmental Cryptococcus isolates 57,58 …”