Integrating Bacteriophage onto the Magnetic Nanozyme for Effective Enrichment and Colorimetric Detection of Cronobacter sakazakii in Powdered Infant Formula

Cronobacter sakazakii is a dangerous pathogen easily found in powdered infant formula (PIF), causing severe infections and even death in infants. Herein, a bacteriophage-immobilized magnetic nanozyme (Fe3O4@EspYZU13) was prepared for C. sakazakii detection. Bacteriophage EspYZU13 isolated and identified by our group exhibits specific lytic capacity. Fe3O4@EspYZU13 possesses remarkable enrichment capacity towards C. sakazakii, efficiently enriching different concentrations of C. sakazakii from a mixed bacterial solution. Furthermore, Fe3O4@EspYZU13 shows peroxidase-like activity, which can catalyze the 3,3′,5,5′-tetramethylbenzidine (TMB) chromogenic reaction in the presence of H2O2. Upon introduction of C. sakazakii, it can be specifically captured by Fe3O4@EspYZU13, inhibiting its peroxidase-like activity. Based on it, C. sakazakii ranging from 3.2 × 101 to 3.2 × 107 CFU mL−1 can be determined, offering a detection limit (LOD) of 26 CFU mL−1. Moreover, this reaction system keeps high specificity towards C. sakazakii, which can resist interferences of other possible coexisting bacteria. C. sakazakii in the artificially contaminated PIF can be detected, offering good recoveries (96.76% to 103.13%). These results indicate that our proposed reaction system demonstrates its practical application potential for efficient enrichment of C. sakazakii from complex samples and accurate determination of C. sakazakii in PIF.