Rapid and selective detection of E. coli O157:H7 combining phagomagnetic separation with enzymatic colorimetry

- A natural E. coli O157:H7 specific bacteriophage was isolated and purified.
- No interference from S. aureus was observed.
- The method was applied to detect E. coli O157:H7 in spiked skim milk samples.
- It was the first time to utilize a natural phage for E. coli O157:H7 detection.

Mammal IgG antibodies are normally used in conventional immunoassays for E. coli O157:H7, which could lead to false positive results from the presence of protein A producing S. aureus. In this study, a natural specific bacteriophage was isolated and then conjugated with magnetic beads as a capture element in a sandwich format for the rapid and selective detection of E. coli O157:H7. To the best of our knowledge, it was the first time to utilize a natural bacteriophage to develop a phagomagnetic separation combined with colorimetric assay for E. coli O157:H7. The method has an overall time less than 2 h with a detection limit of 4.9 × 104 CFU/mL. No interference from S. aureus was observed. Furthermore, the proposed method was successfully applied to detect E. coli O157:H7 in spiked skim milk. The proposed detection system provided a potential method for E. coli O157:H7 and other pathogenic bacteria in food samples.