Water quality and diversity of yeasts from tropical lakes and rivers from the Rio Doce basin in Southeastern Brazil

Yeast communities were assessed in 14 rivers and four lakes from the Doce River basin in Brazil, during the rainy and dry seasons of the years 2000 and 2001. Water samples were collected at the subsurface in all sites. The following physical and chemical parameters were measured: temperature, dissolved oxygen, pH, electrical conductivity, total phosphorus, ortho-phosphate, ammonium, nitrate, nitrite and total nitrogen and the counts of faecal coliforms and heterotrophic bacteria were carried out to characterize the aquatic environmental sampled. The yeast counts were higher in aquatic environments with the highest counts of coliform and heterotrophic bacteria. These environments receive a high influx of domestic and industrial waste. A total of 317 isolates identified in forty eight yeast species were recorded in the sites sampled and the specie Aureobasidium pullulans were found in eleven out of eighteen sites sampled and some opportunistic pathogens such as the yeast species Candida krusei were isolated only in the polluted rivers with a positive correlation with the biotic and abiotic parameters that indicate sewage contamination.

Water quality and diversity of yeasts from tropical lakes and rivers from the Rio Doce basin in Southeastern Brazil.

Yeast communities were assessed in 14 rivers and four lakes from the Doce River basin in Brazil, during the rainy and dry seasons of the years 2000 and 2001. Water samples were collected at the subsurface in all sites. The following physical and chemical parameters were measured: temperature, dissolved oxygen, pH, electrical conductivity, total phosphorus, ortho-phosphate, ammonium, nitrate, nitrite and total nitrogen and the counts of faecal coliforms and heterotrophic bacteria were carried out to characterize the aquatic environmental sampled. The yeast counts were higher in aquatic environments with the highest counts of coliform and heterotrophic bacteria. These environments receive a high influx of domestic and industrial waste. A total of 317 isolates identified in forty eight yeast species were recorded in the sites sampled and the specie Aureobasidium pullulans were found in eleven out of eighteen sites sampled and some opportunistic pathogens such as the yeast species Candida krusei were isolated only in the polluted rivers with a positive correlation with the biotic and abiotic parameters that indicate sewage contamination.

Diversity and antifungal susceptibility of yeasts from tropical freshwater environments in Southeastern Brazil.

Yeast communities were isolated from water and sediment samples of two unpolluted natural lakes, located inside Rio Doce State Park, and two rivers located outside of this Park in Southeastern Brazil. A total of 134 yeast isolates were obtained and identified as belonging to 36 species. The numbers of fecal coliforms and yeast species were higher in rivers than in lakes. The genus Candida had the highest number of species with the presence of opportunistic pathogens such as Candida krusei, C. tropicalis, C. guilliermondii and C. parapsilosis. Yeasts able to grow at 37 degrees C were tested in relation to their susceptibility to common used antifungal drugs. Yeast isolates (13%) were susceptible to ketoconazole, 79% to fluconazole, 31% to terbinafine and 78% of the strains were susceptible to amphotericin B. Seven isolates from different Candida species were resistant to all antifungals tested. The high number of fecal coliforms found in these aquatic environments and the presence of resistant yeast strains to common used antifungal drugs suggest that these environments can pose potential health risks for people utilizing the contaminated waters.