Isolation and characterization of broad host-range of bacteriophages infecting Cronobacter sakazakii and its biocontrol potential in dairy products

Cronobacter sakazakii (C. sakazakii) is an important pathogen contaminating dairy products (e.g., milk powder) and causes high mortality in infants. Bacteriophage as a potential biocontrol agent is a good alternative method for the control of this pathogen in dairy production and its environment. Thus, it is important to complete the C. sakazakii phage library by isolating and characterizing the broad host range of bacteriophage against C. sakazakii for control use. In this study, C. sakazakii strains from different sources were used as hosts to isolate and purify phages from human stool and sewage samples by double-layer plates. The biological characteristics, antibacterial properties, and genomes of these phages were then studied. Finally, ten virulent phages (EspYZU01-EspYZU10) infecting C. sakazakii were isolated and identified as belonging to the Myoviridae, Podoviridae, Tectivirus, and Stylovinidae families. Phage EspYZU08 presented the broadest host range and could infect all the five host strains of C. sakazakii. All 10 phages retained their infectivity at 50°C and pH 5-9. Both genomes of EspYZU05 and EspYZU08 were double-stranded DNAs with sizes of 41723 bp and 145582 bp, G+C contents of 55.69% and 46.75%, and open reading frames of 47 and 103, respectively. No toxins and antibiotic resistance genes were detected in both EspYZU05 and EspYZU08. Phage EspYZU08 and phage cocktail-3 (EspYZU01 + EspYZU03 + EspYZU08 + EspYZU09 + EspYZU10) presented excellent antibacterial efficacy for C. sakazakii in liquid broth and milk at 4°C, 25°C, and 37°C, suggesting that the phages in this study have great potential for the development of biocontrol agents against C. sakazakii in dairy and its processing environment. © 2021 Codon Publications