A novel, simple and low-cost paper-based analytical device for colorimetric detection of Cronobacter spp

Cronobacter spp. are recognized as a world-wide emerging opportunistic food-borne pathogens that can persist in various food and processing environment for a long time. Therefore, the prevention and detection of them are particularly important. In this study, a micro-spot paper-based analytical device (μPADs) was created by combining PVC pad with filter paper. Detection is achieved by measuring the color change (from colorless to indigo) when a species-specific enzyme associated with the Cronobacter spp. of interest reacts with a chromogenic substrate. When combined with the optimization of specific enrichment process, the method allows for a testing time of 10 h or less and is capable of detecting live bacteria on the inoculated surface of samples in concentrations as low as 10¹ CFU cm^-2. We are surprised to discover that C. dublinensis species and their subspecies had the highest ability to produce α-glucosidase in all genus of Cronobacter spp.. This work demonstrated that the manufacturing method is novel, simple, well reproducible (RSD less than 5%) and low-cost (less than $ 0.15 per micro-spot).