PhageScore: A simple method for comparative evaluation of bacteriophages lytic activity

Nowadays, an increasing amount of studies indicate the numerous applications of bacteriophages (e.g. medical, pharmaceutical, use in animal breeding, food processing). However, so far, there is limited availability of simple, efficient, and sensitive methods for evaluation and comparison of the phage's lytic activity against its host. The aim of this paper is the examination of a new methodological approach (PhageScore method) for the comparative evaluation of bacteriophages lytic activity against bacterial host. For this purpose, two model bacteria (gram-positive Staphylococcus aureus and gram-negative Escherichia coli) were cultivated under control conditions and with the presence of proper bacteriophages (three kayviruses for S. aureus and three wildtypes of T4-like phages infecting E. coli) with the different initial multiplicity of infection (MOI, ranging from MOI = 0.1-1 for S. aureus, and MOI = 0.01-1 for E. coli). The experimental data were analyzed using the proposed method, which employed a set of appropriate mathematical expressions. The results obtained by the proposed procedure clearly show differences between phage lytic activity. Thus, the PhageScore method provides a useful tool for bacteriophage characterization, giving a precise rate of lytic activity which can be useful for a comparison between bacteriophages for selected purposes.