Isolation and characterization of a novel Escherichia coli O157:H7-specific phage as a biocontrol agent.

Abstract

Escherichia coli O157:H7 is one of themajor foodborne pathogens of global public concern. Bacteriophages (phages) have emerged as a promising alternative to antibiotics for controlling pathogenic bacteria. Here, a lytic E. coli O157:H7-specific phage (KFS-EC) was isolated, identified, and characterized to evaluate its potential as a biocontrol agent for E. coli O157:H7. KFS-EC was isolated from slaughterhouse in Korea. Morphological analysis, genomic analysis and several physiological tests were performed to identify and characterize the KFS-EC. A specificity test indicated KFS-EC was strictly specific to E. coli O157:H7 strains among 60 bacterial strains tested. Morphological and phylogenetic analyses confirmed that KFS-EC belongs to the Rb49virus genus, Tevenvirinae subfamily, and the Myoviridae family of phages. KFS-ECgenome consists of 164,725bp and a total of 270 coding sequence features, of which 114 open reading frames (ORFs) were identified as phage functional genes. KFS-EC does not contain genes encoding lysogenic property and pathogenicity, which ensure its safe application. KFS-EC was relatively stable (~1 log decrease) under stressed conditions such as temperatures (20°C-50°C), pHs (3-11), organic solvents (ethanol and chloroform), and biocides (0.1% citric acid, 1% citric acid, and 0.1% peracetic acid). KFS-EC was able to inhibit E. coli O157:H7 efficiently at a multiplicity of infection (MOI) of 0.01 for 8h with greater inhibitory effect and durability and was stable at 4°C and 22°C over a 12-week storage period. Our results suggest that KFS-EC could be used as a biocontrol agent to E. coli O157:H7.