Amoebal coculture and enrichment methods as a proposal for water quality control in Brazil.

Free living amoebae (FLA) can be found in different environments, where they feed on diverse microorganisms. Some bacteria preyed by FLA are called amoeba-resistant bacteria (ARB), as they can resist to lysosomal fusion and are capable of multiplying and evading FLA after internalization, propagating in the environment. Despite the health risks due to the existence of pathogenic and opportunistic species that are ARB and the pathogenicity of some FLA species, there are no water quality protocols to analyze the presence of ARB or FLA. In this sense, our study aimed to isolate FLA through amoebal enrichment and to identify ARB using amoebal coculture in water samples from a public park and two hospitals in southern Brazil. As a result, 9 different microorganisms genera have been identified through amoebal coculture, including fastidious Legionella spp. and Bosea vestrisii. From the positive samples for FLA, by amoebal enrichment, Acanthamoeba spp., Vermamoeba vermiformis and Naegleria spp. were identified in 14 amoebic isolates. The methodologies used in this work proved to be effective as simple and low-cost methods to be used in the implementation in water quality control of anthropogenic environments.

A new continuous-flow solar water disinfection system inactivating cysts of Acanthamoeba castellanii, and bacteria.

Solar water disinfection (SODIS) is an effective and inexpensive microbiological water treatment technique, applicable to communities lacking access to safely managed drinking water services, however, the lower volume of treated water per day (< 2.5 L per batch) is a limitation for the conventional SODIS process. To overcome this limitation, a continuous-flow solar water disinfection system was developed and tested for inactivation of Acanthamoeba castellanii cysts and Escherichia coli, Salmonella Typhimurium, Enterococcus faecalis, and Pseudomonas aeruginosa. The system consisted of a solar heater composed of a cylindrical-parabolic concentrator and a UV irradiator formed by a fresnel-type flat concentrator combined with a cylindrical-parabolic concentrator. Deionized water with low or high turbidity (< 1 or 50 nephelometric turbidity unit (NTU) where previously contaminated by 108 Cysts/L or 105-106 CFU/mL of each of four bacterial species. Then was pumped from the heating tank flowing through the heater and through the UV irradiator, then returning to the heating tank, until reaching 45, 55, 60 or 70 °C. The water was kept at the desired temperature, flowing through the UV irradiator for 0.5 and 10 min. Trophozoites were not recovered from cysts (during 20 days of incubation) when water with < 1 NTU was exposed to UV and 60 °C for 0.5 min. In water with 50 NTU, the same result was obtained after 10 min. In water with < 1 NTU, the inactivation of all bacteria was achieved when the water with < 1 NTU was exposed to 55 °C and UV for 0.5 min; in water, with 50 NTU the same result was achieved by exposure to 60 °C and UV for 0.5 min. The prototype processes 1 L of water every 90s. The system is effective and has the potential to be applied as an alternative to the large-scale public drinking water supply.