Escherichia coli ST155 as a production-host of three different polyvalent phages and their characterisation with a prospect for wastewater disinfection

Abstract

Bacteriophages are generally specific, and a cocktail of phages is needed to combat different bacterial targets. Their production usually requires pathogenic isolation hosts. We identified a novel strain, Escherichia coli ST155, that could serve as a production host for three different polyvalent phages (ϕPh_SE03, ϕPh_SD01, and ϕPh_EC01), thus superseding the use of individual isolation hosts. Upon propagation in E. coli ST155, the phages demonstrated differential intergeneric infectivity against Salmonella enterica, E. coli OP50, Shigella dysenteriae, E. coli MDR, and Acinetobacter baumannii. Phages were characterised based on morphology, latent period, burst size, the efficiency of plating, and restriction enzyme profile. Survival assay on Caenorhabditis elegans, the absence of Shiga toxin, and enterotoxigenic E. coli virulence genes indicated that E. coli ST155 could be non-pathogenic. Lack of antibiotic resistance and absence of functional prophages rendered the host suitable for environmental applications. As a proof-of-concept, phage ϕPh_SE03 was produced in ST155 by employing a unique Bacteriophage Amplification Reactor-Lytics Broadcasting System and was simultaneously disseminated into S. enterica augmented wastewater, which resulted in a 3-log reduction in 24 h. The study establishes the potential of E. coli ST155 as a phage production host thereby minimising the possibility of accidental release of pathogenic hosts into wastewater.

Mitigation of biogenic methanethiol using bacteriophages in synthetic wastewater augmented with Pseudomonas putida

“…ɸPh_PP01 and ɸPh_PP02 showed limited polyvalency and were specific towards P. putida, their isolation host, and E. coli ST155. The latter is an established production host that can harbour multiple polyvalent phages, hence bypassing the need to involve pathogenic hosts for their production 56 . High polyvalency is advantageous, because effective malodour mitigation can be carried out with a formulation of limited phages than through a complex cocktail targeting the concerned bacterial population.…”