(316f) Rapid and Sensitive Detection of Salmonella Using An Integrated Microfluidic Chip and Real-Time PCR

Salmonella is one of the leading causes of food-borne illness. Conventionally, the presence of Salmonella in food products is routinely tested by a lengthy and laborious procedure including non-selective pre-enrichment, selective enrichment, selective plating, and subsequent biochemical and serological confirmation, which requires 4 and 6 days for negative and positive samples, respectively. To overcome these issues, we developed a strategy that integrates sample pretreatment steps including cell lysis and DNA purification on a single microfluidic chip in order to reduce the processing time and the number of steps for rapid detection of pathogens. In addition, immunomagnetic separation (IMS) technique and real-time PCR assay were also incorporated in our methods to achieve both high sensitivity and specificity of detection. The target bacterial cells were initially separated from crude food samples using Dynabeads® anti-Salmonella. The bead-Salmonella complex was then delivered into the microfluidic chip and captured by a NdFeB permanent magnet. Subsequently, the bacterial cells could be lysed by electrical pulses with high intensity (1000-1500 V/cm) within only 1-3 minutes. The released DNA was selectively adsorbed onto magnetic ChargeSwitch® beads held by a magnet in the down-stream of microchannel, which greatly removed PCR inhibitors from samples. We were able to detect Salmonella with a high sensitivity level, and the total assay time is only about 6 hr. The results suggest that our approach provides a new tool for rapid, sensitive, accurate and cost-effective identification of pathogens.