DUGi

Caracterització fenotípica dels bacteriòfags lítics d’Escherichia coli

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Environmental bacteriophages are the most abundant and diverse biological entities in the biosphere and play a fundamental ecological role in controlling bacterial populations and biogeochemical cycles. This study addresses the investigation of certain virulent bacteriophages, characterized by their lytic cycle, which provides them with properties suitable for an environmental biocontrol strategy: phage therapy. This innovative therapy uses bacteriophages to eliminate pathogens in water, soil, or food, making them a viable alternative to the global threat of antimicrobial resistance. These therapeutic bacteriophages must exhibit high lytic efficiency, a broad host range, or considerable resistance to adverse environmental conditions. In this study, a phenotypic characterization was carried out on four lytic Escherichia coli bacteriophages isolated from wastewater treatment plant effluents: I1.1, E1.3, EUR3.2, and E1.1.A. Initially, the bacteriophages were selected through a host range assay using various E. coli strains. For each virus, lysis curves were evaluated at different MOI values (Multiplicity of Infection) with E. coli WG5. All strains showed reductions greater than 94% at an MOI of 0.1, except for EUR3.2, which required an MOI of 1 to achieve an equivalent effect. Additionally, replication curves were described, showing very long latency periods for all phages—ranging from 30 to 60 minutes—and low burst sizes, with results of 4 to 30 viral particles per infected cell. Finally, the physicochemical stability of the bacteriophages of interest was assessed under the effects of salinity, UV radiation, and temperature, calculating their stability using the D50 parameter (the dose required to reduce the population by 50%). The D50 values for the different tested variables ranged from 7 to >10‰ for salinity, from 7.51 to 116 mJ for UV radiation, and from 24.4 to 54.6°C for temperature. The results demonstrate effective replication in the lysis curves, although the replication assays do not correlate and should be further investigated. On the other hand, the stability values fall within acceptable ranges for application in various environments. This analysis of the studied bacteriophages provides valuable information on their potential use as an innovative tool, contributing to ecosystem balance and the protection of public health

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