Decay comparison of bacteriophages pp7 and p22 in water matrices, under different environmental conditions: detection by culture-based methods and qPCR

CORIMAYO SHEILA; MAIDANA KULEZA NOEL; DOLORES GUTIÉRREZ CACCIABUE; VERÓNICA RAJAL; HUGO R. POMA

Viena

Simposio; 20th International Symposium on Health Related Water (Watermicro); 2019

Virus behaviorin water is usually influenced by different factors. The presence of solidparticles is quite significant since they confer protection to them but thiswill depend on particle type, size and concentration, physicochemicalproperties of virus, ambient conditions, among others. The aim of this work wasto compare the persistence of two phages used as RNA and DNA virus models (pp7and p22) under different ambient conditions. A group synthetic water matriceswere prepared in 500 ml-glass beakers using Phosphate Buffer Solution (PBS). Asmallest particle size found (<0.074 mm) in river bed was chosen and addedin each beaker in two concentrations: 5 and 0.5 g/l (high and lowrespectively). Then, stocks of bacteriophages pp7 (Pseudomonas aeruginosa) orp22 (Salmonella) were prepared and spiked in known concentrations in differentwater matrices. Beakers with virus but without particles were used as controls.Two temperature (25°C and 12 °C) and two conductivities values (130 and 1300µS/cm) were selected to simulate ambient conditions. Water samples were takenfrom the surface of each beaker to evaluate virus disappearance over time.After a while, resuspension was done in all matrices and a last sample wasremoved and analyzed. Turbidity decay was also measured. Virus detection was doneby plate count and qPCR. Kinetic parameters were calculated throughout afirst-order decay model. Results showed that virus persistence was greater atlow temperature, high conductivity and low solids particle concentration inwater (measured through both plate count and qPCR). The persistence of the p22phage was greater than pp7 in all the environmental conditions evaluated, beingmore marked for nucleic acids detection. Phage count did not increase afterresuspension. Knowing virus persistence in water is important as it will allowa better understanding of the health risk involved.