Characterization of the broad-spectrum phage vB_CsaM_CBT2 and its inhibition of multidrug-resistant Cronobacter sakazakii in powered infant formula

Abstract

Cronobacter is a group of foodborne pathogens linked to serious and deadly infections in newborns and babies through the consumption of contaminated powdered infant formula (PIF). Meanwhile, antimicrobial misuse has led to emergence of multi-drug resistant (MDR) Cronobacter strains, affecting food safety. Here, a lytic phage vB_CsaM_CBT2 (CBT2) was isolated from a wastewater treatment plant in Hefei as an effective antimicrobial alternative to antibiotics. Phage CBT2 has a broad host spectrum. It can target and lyse 17 strains including MDR clinical strain C. sakazakii GZcsf-1 from four species of C. sakazakii, C. turicensis, C. muytjensii and C. condimenti in the genus Cronobacter. Some Cronobacter phages have a narrow host range and have only been confirmed to infect a single strain of Cronobacter. In addition, excellent tolerance to temperature (25 °C–70 °C) and pH values (3-11) of phage CBT2 were determined. Based on genomic and phylogenetic analyses, the phage CBT2 was successfully identified belonging to the Straboviridae, and genes related with drug resistance and virulence were not observed. After treatment of the phage CBT2 in four brands of rehydrated PIF, the viable counts of host bacteria (C. sakazakii GZcsf-1) were reduced 3.0 log CFU/mL (＞99.9%) after 6 h at 37 °C. The findings in this study provided an alternative tool for prevention and control of Cronobacter contamination in PIF.