Effects of abiotic factors on the stability and infectivity of polyvalent coliphage

Bacteriophage has attracted growing interest as a promising therapeutic agent for pathogenic bacteria, especially for antibiotic-resistant bacteria. However, the various abiotic conditions could impact the stability of phages and further threat host-virus interactions. Here, we investigated the stability and lytic activity of virulent polyvalent coliphage (named PE1) by double-layer plaque assay. PE1 can efficiently infect both the drug-sensitive Escherichia coli K12 and multidrug-resistant E. coli NDM-1 even after prolonged storage at 4 °C for up to two months. Results showed that PE1 exhibits an outstanding stability to infect E. coli strains under a wide range of thermal (4 °C-60 °C) and pH (4-11) conditions, which covers the thermal and pH variations of most wastewater treatment plants. Moreover, PE1 exhibited high resistibility to heavy metals exposure including Cu²⁺, Cd²⁺, Co²⁺, and Cr³⁺ at the concentrations below 0.5 mM, and an excellent resistant ability to the variation of ionic strength, which still retained strong infectious ability even treated with saturated sodium chloride solution (350 g/L). This work shows that polyvalent phage PE1 has a strong adaptive capacity to various abiotic factors and should be a good candidate of being an antibacterial agent, especially for antibiotic-resistant bacteria control in sewage.