Development of quantitative real-time PCR for detection and enumeration of Enterobacteriaceae

- Enterobacteriaceae has recently been used as food hygiene indicator.
- The rplP-targeted real-time PCR was developed and applied to 51 food samples.
- The real-time PCR method and culture method showed good correlation (r2 = 0.8285).
- The developed method can be used for the microbiological risk analysis of foods.

The family Enterobacteriaceae, members of which are widely distributed in the environment, includes many important human pathogens. In this study, a rapid real-time PCR method targeting rplP, coding for L16 protein, a component of the ribosome large subunit, was developed for enumerating Enterobacteriaceae strains, and its efficiency was evaluated using naturally contaminated food products. The rplP-targeted real-time PCR amplified Enterobacteriaceae species with Ct values of 14.0-22.8, whereas the Ct values for non-Enterobacteriaceae species were > 30, indicating the specificity of this method for the Enterobacteriaceae. Using a calibration curve of Ct = − 3.025 (log CFU/g) + 37.35, which was calculated from individual plots of the cell numbers in different concentrations of 5 Enterobacteriaceae species, the rplP-targeted real-time PCR was applied to 51 food samples. A < 1 log difference between the real-time PCR and culture methods was obtained in a majority of the food samples (81.8%), with good correlation (r2 = 0.8285). This study demonstrated that the rplP-targeted real-time PCR method could detect and enumerate Enterobacteriaceae species in foods rapidly and accurately, and therefore, it can be used for the microbiological risk analysis of foods.