Evaluation of the Novel Bacteriophage Chage1 and Its Endolysin LysCG1 as Biocontrol Agents against <i>Cronobacter sakazakii</i> in Foods.

Abstract

<i>Cronobacter sakazakii</i> is a foodborne pathogen transmitted through powdered infant formula (PIF) and consequently leads to illness in infants. Owing to the pathogen's occasional antibiotic resistance, bacteriophages offer a promising strategy for controlling this pathogen. Therefore, this study characterized a novel virulent phage (Chage1) that specifically infects <i>C. sakazakii</i> cells. Chage1 exhibited stability across a temperature range of 4-50°C and pH conditions of 4-11. Moreover, Chage1 inhibited bacterial growth for up to 24 h when inoculated into <i>C. sakazakii</i> at a multiplicity of infection (MOI) of 1. Chage1 (MOI of 10⁵) also showed antibacterial activity against two <i>C. sakazakii</i> strains in PIF and milk samples for 8 h at 37°C. Whole genome sequencing of Chage1 revealed a 52,653 bp DNA genome with 72 predicted open reading frames (ORF) containing an endolysin gene (ORF 60). The endolysin LysCG1 was fused with a maltose-binding protein for solubility and its lytic activity against various bacterial strains was evaluated. LysCG1 exhibited a broader lysis spectrum than that of Chage1 by inhibiting the growth of diverse ethylenediaminetetraacetic acid-pretreated Gram-negative bacterial cells. Overall, this study provides a basis for the potential application of Chage1 and its endolysin for the control of <i>C. sakazakii</i> in food production.