Rapid detection of single viable Escherichia coli O157:H7 cells in milk by flow cytometry

Escherichia coli O157:H7 (E coli O157:H7) is a highly virulent bacterial strain that is present in food, and as few as 10 cells can cause severe diseases. Rapid and sensitive bacterial detection is urgently required. In this study, we report a flow cytometry (FCM)-based method for detecting E coli O157:H7 at the single-cell level. Single E coli O157:H7 cells were obtained by a flow cytometric cell sorter and then artificially added to milk. Next, using BHI for 6.5 hr of enrichment, isolation of target cells, and dual staining, this method could be applied to detect single viable E coli O157:H7 cells in 25 mL of milk. The time to results (TTR) of the FCM-based method was 7 hr. Practical applications The plate-based method is the currently recommended method for detection of single E coli O157:H7 cells in milk because of the ease of operation. However, this method is time-consuming, requiring enrichment of the target organism to attain quantifiable levels. Accordingly, rapid detection of microorganisms in milk would be of great benefit to public health. Flow cytometry (FCM) is a sensitive technique that can be used to rapidly analyze foodborne pathogens. Unfortunately, little attention has been paid to single-cell detection in milk. This study provides a rapid method for detection of single viable E coli O157:H7 cells in milk. This method has the potential to provide effective protection against E coli O157:H7 contamination and is required for rapid detection of microorganisms in dairy products.