BACKGROUND Opportunistic pathogenic yeast species are frequently associated with water habitats that have pollution sources of human or animal origin. Candida albicans has already been suggested as a faecal indicator microorganism for aquatic environments. OBJECTIVES The goal of this study was to investigate the occurrence of C. albicans and other opportunistic yeasts in sand and seawater samples from beaches in Brazil to assess their correlation with Escherichia coli, and to characterise the pathogenic potential of the yeast isolates. METHODS Opportunistic species (yeasts that grow at 37ºC) were isolated from sand and seawater samples from eight beaches in Brazil during the summer and the winter. Opportunistic yeast species were evaluated for their susceptibility to antifungal drugs, virulence factors, and the in vitro and in vivo biofilm formation. Strains were selected to carry out virulence tests using BALB/c mice. FINDINGS Several water samples could be classified as inappropriate for primary contact recreation in relation to E. coli densities. C. albicans was isolated in low densities. Of the 144 opportunistic yeasts evaluated, 61% displayed resistance or dose-dependent sensitivity to at least one tested drug, and 40% produced proteinase. Strains of C. albicans and Kodamaea ohmeri exhibited the highest rates of adhesion to buccal epithelial cells. All the C. albicans strains that were tested were able to undergo morphogenesis and form a biofilm on catheter fragments in both in vitro and in vivo experiments. It was possible to confirm the pathogenic potential of three of these strains during the disseminated infection test. MAIN CONCLUSIONS The identification of opportunistic yeast species in seawater and sand samples from Brazilian beaches suggest a potential risk to the health of people who use these environments for recreational purposes.

Abstract: Background: Seaweeds must survive in highly competitive environments and thus develop defense strategies that may produce highly diversified antioxidant compounds. Goals: The main objective of this work was to assess the antioxidant activity of green seaweeds. Methods: Six species of ulvophycean chlorophytes were collected during spring/summer, between the Antarctic (Monostroma hariotii, Protomonostroma rosulatum and Ulva hookeriana - formerly as U. bulbosa) and the southwestern Atlantic Ocean (Gayralia brasiliensis, Protomonostroma undulatum and Ulva fasciata). They were then tested for their antioxidant activities using the 2.2-diphenyl-picrylhydrazyl (DPPH) radical scavenging method and by quantification of their phenolic (expressed as gallic acid equivalent - GAE - and carotenoid contents. Results: Among the evaluated species, P. rosulatum and U. hookeriana showed high antioxidant potential (77.9±2.8 and 53.1±15.0%, respectively) and high phenolic content (176±6.0 and 144.7±8.9 µg GAE g-1, respectively). These species were collected on King George Island (South Shetland archipelago, around the Antarctic Peninsula) and their higher antioxidant potential may be associated with adaptation to the high incidence of UV rays in this region during summer. In general, tested seaweeds, mainly the samples collected in the Antarctic and Chilean Patagonia, showed higher values of phenolic (from 58.3±2.0 to 144.7±8.9 µg GAE g-1) and carote noid contents (from 23.4±0.2 to 51.5±0.1 µg β-carotene g-1). Conclusions: The presence and levels of these compounds suggest that the target seaweeds may have high antioxidant potential. Also the antioxidant activity could be associated with the occurrence area of the species instead of the order or taxonomic group to which they belong.

Resumen: Antecedentes: Las algas marinas tienen que sobrevivir en entornos altamente competitivos, lo que hace que desarrollan estrategias de defensa que pueden dar lugar a una gran diversidad de compuestos antioxidantes. Objetivos: El principal objetivo de este trabajo fue evaluar la actividad antioxidante de algas verdes. Métodos: Seis especies de clorófitos (Ulvophyceae) recogidos durante el primavera/verano entre la Antártida (Monostroma hariotii, Protomonostroma rosulatum y Ulva hookeriana - antes como U. bulbosa) y el Atlántico Sur (Gayralia brasiliensis, Protomonostroma undulatum y Ulva fasciata) fueron probados por su actividad antioxidante usando el método de secuestro de radicales libres con 2,2-diphenil-picrylhidrazil (DPPH) y pela cuantificación de contenidos fenólicos (expreso como equivalente de ácido gálico (GAE)) y contenidos de carotenoides. Resultados: Entre las especies evaluadas, P. rosulatum y U. hookeriana mostraron alto potencial antioxidante (77,9±2,8 y 53,1±15%, respectivamente) y alto contenido fenólico (176±6,0 y 144,7±8,9 µg GAE g-1, respectivamente). Estas especies fueron recolectadas en la Isla Rey Jorge (cerca de la Península Antártida) y su mayor potencial antioxidante puede estar asociado con la adaptación a la alta incidencia de los rayos UV en esta región. En general, las algas marinas probadas, principalmente las muestras recogidas en la Patagonia Antártida y chilena, mostraron valores más altos de fenólico (de 58,3 ± 2,0 a 144,7 ± 8,9 mg GAE g-1) y el contenido de carotenoides (de 23,4 ± 0,2 a 51,5 ± 0,1 mg g-1 β-caroteno). Conclusiones: La presencia y los niveles de estos compuestos sugieren que las algas marinas diana pueden tener un alto potencial antioxidante. También la actividad antioxidante podría estar asociada con el área de ocurrencia de las especies en lugar de la orden o grupo taxonómico a la que pertenecen.