Isolation, visualization and characterization of four somatic coliphages from Egyptian sewage

Somatic coliphages are bacteriophage that infect Escherichia coli and can be used in aquatic environment for risk assessment of viral and fecal pollution. The objective of this work was to isolate bacteriophages specific for E. coli strain (ATCC 13706), as well as characterization and evaluation of their stability. We used enrichment method to isolate phages against E. coli strain (ATCC 13706) from two wastewater treatment plants, and one opened drain. The isolated phages purified by successive single plaque isolation technique and results indicated isolation of 4 phages. The plaque sizes for isolated phages were between 1.0 and 4.0 mm in diameter with high titer ranged from 19 to 55 × 109 PFU/mL. Based on morphology, , all phages were found to be belonging to tailed-phages order, Caudovirales, and identified as members of the Myoviridae and Siphoviridae families. The characterization of these phages revealed high tolerance to temperature ranged from 5 to 75°C, and viability over wide pH values from 3 to 11. Some phages exhibit wide range of hosts, which could be polyvalent phage, while others were host specific. 1.0 was the optimum ratio of Multiplicity Of Infection (MOI) for these phages. In phage efficiency test, MOI of 1.0 resulted in 63.93, 61.20, 69.39 and 79.14% reduction in bacterial cell count with EcoP1, EcoP2, EcoP3 and EcoP4, respectively after 5hrs incubation at 37 °C. In one step growth curve, the latent period and burst size, of these phages were between 10 – 20 min and 44 – 62 PFU/cell, respectively.