# Isolation and Characterization of the New Lytic Bacteriophage KEC4 Against Escherichia coli MDR Strains

## TL;DR

This paper describes a new bacteriophage, KEC4, that can kill drug-resistant Escherichia coli and reduce the minimum inhibitory concentrations of certain antibiotics.

## Contribution

The paper introduces a novel lytic bacteriophage, KEC4, isolated from a Russian river, with potential for treating multidrug-resistant E. coli infections.

## Key findings

- KEC4 can lyse 14 out of 31 E. coli clinical isolates with multiple resistance patterns.
- The presence of KEC4 reduced the MICs of several antibiotics by up to 16-fold in some isolates.
- KEC4 forms round plaques and has a genome of 145,125 bp with no lysogeny-associated proteins.

## Abstract

Being first applied for the treatment of infectious diseases of the gut at the start of the 20th century, bacteriophages are again now considered as alternative antimicrobial tools for targeting antibiotic-resistant enterobacteria. Here, we report the new bacteriophage Escherichia phage KEC4 isolated from the Kukshum River (Chuvash Republic, Russia), lysing Escherichia coli and belonging to the Septuagintavirus genus. The genome consists of 145,125 bp with a GC content of 41.3% and contains 6 tRNA and 303 protein-coding sequences. Among them, only 72 encode proteins with known functions, while no proteins potentially associated with lysogeny can be identified. The bacteriophage forms round and pure plaques 0.3–1 mm in diameter and is capable of lysing 14 of 31 E. coli clinical isolates with multiple resistance patterns. Furthermore, in the presence of KEC4, the MICs of meropenem and kanamycin decreased 16-fold in the reference strain. In clinical multidrug-resistant isolates, a 16-fold decrease in the MIC was observed for aminoglycosides (amikacin and gentamicin) for the isolate NKC1, and an eight-fold drop in the MIC of ceftriaxone was observed for isolate 167, with no increase in the efficiency of aminoglycosides. Finally, a four-fold increase in the efficiency of both azithromycin and gentamicin was detected in isolate 5767. Taken together, these data characterize the new Escherichia phage KEC4 as a promising tool for the treatment of infections associated with Escherichia coli, while a preliminary assessment of both the isolate specificity of the phage and an antimicrobial susceptibility test would be required for successful elimination of the pathogen.