In the realm of food safety, the standard practice involves collecting food product samples and sending them to a central laboratory for microbiological testing. However, this process introduces delays in obtaining the microbiological testing results and subsequently affects the timely delivery of food products to consumers. To further reduce the time-to-detection issue, we propose the development of a self-contained, battery-operated, high-sensitivity optical sensor that can be affixed to the cap of the typical food sample collection container. This device, called MPACT, offers real-time and in-transit monitoring of the contamination status of the food sample, specifically targeting E. coli O157:H7, through a bioluminescence assay. The assay exclusively targets the target pathogen and, when detected, produces minimal luminescence. As the sample is transported in the container, the number of bacterial cells multiplies, and once the luminescent signal reaches a predefined threshold, the sensor reports the results via Bluetooth. This study focuses on the design of the bottle cap sensor and examines its sensitivity by subjecting it to bioluminescence samples.
Luminescence based detection has been widely used in diverse science and engineering applications. The recent development of the smartphone has enabled end users to utilize this communication device as a portable detector and instruments such as a microscope, fluorimeter, colorimeter, and spectrometer. To transform the smartphone into a bioluminescence detector, our group developed an advanced signal processing algorithm and an optical chamber designed for efficient photon capture. This solution was required to overcome the typical sensitivity of the CMOS-based smartphone camera such that sub-nano to pico Watt levels of power can be measured with conventional smartphones. Preliminary experiments conducted with the bioluminescent Pseudomonas fluorescens M3A shows a detection limit of approximately 106 CFU/ml. To achieve sensitive detection while maintaining the portability, we explored using the recently developed silicon photomultiplier (SiPM), and designed a portable bioluminescence sensor which shows a 2-3 order higher sensitivity on calibration sample testing. Finally, for live sample testing, Escherichia coli O157:H7 was inoculated on a ground beef sample and subjected to luminescence phage based detection and a luminescence signal was generated from the bacteriophage infection and detected within 8-10 h after spiking.
Microbial contamination has become a mounting concern the last decade due to an increased emphasis of minimally
processed food products specifically produce, and the recognition of foodborne pathogens such as Campylobacter jejuni,
Escherichia coli O157:H7, and Listeria monocytogenes. This research investigates a detection approach utilizing
bacteriophage pathogen specificity coupled with a bacterial bioluminescent bioreporter utilizing the quorum sensing
molecule from Vibrio fischeri, N-(3-oxohexanoyl)-homoserine lactone (3-oxo-C6-HSL). The 3-oxo-C6-HSL molecules
diffuse out of the target cell after infection and induce bioluminescence from a population of 3-oxo-C6-HSL bioreporters
(ROLux). E. coli phage M13, a well-characterized bacteriophage, offers a model system testing the use of bacteriophage
for pathogen detection through cell-to-cell communication via a LuxR/3-oxo-C6-HSL system. Simulated temperate
phage assays tested functionality of the ROLux reporter and production of 3-oxo-C6-HSL by various test strains. These
assays showed detection limits of 102cfu after 24 hours in a varietry of detection formats. Assays incorporating the
bacteriophage M13-luxI with the ROLux reporter and a known population of target cells were subsequently developed
and have shown consistent detection limits of 105cfu target organisms. Measurable light response from high
concentrations of target cells was almost immediate, suggesting an enrichment step to further improve detection limits
and reduce assay time.
The presence of biologically derived toxins in foods is of utmost significance to food safety and human health concerns. Biologically active amines, referred to as biogenic amines, serve as a noteworthy example, having been implicated as the causative agent in numerous food poisoning episodes. Of the various biogenic amines encountered, histamine, putrescine, cadaverine, tyramine, tryptamine, beta-phenylethylamine, spermine, and spermidine are considered to be the most significant, and can be used as hygienic-quality indicators of food. Biogenic amines can be monitored using whole-cell bioluminescent bioreporters, which represent a family of genetically engineered microorganisms that generate visible light in response to specific chemical or physical agents in their environment. The light response occurs due to transcriptional activation of a genetically incorporated lux cassette, and can be measured using standard photomultiplier devices. We have successfully engineered a lux-based bioreporter capable of detecting and monitoring the biogenic amine beta-phenylethylamine. This research represents a biologically-based sensor technology that can be readily integrated into Hazard Analysis Critical Control Point programs to provide a rugged monitoring regime that can be uniformly applied for field-based and in-house laboratory quality control analyses. Since the bioreporter and biosensing elements are completely self-contained within the sensor design, this system provides ease of use, with operational capabilities realized by simply combining the food sample with the bioreporter and allowing the sensor to process the ensuing bioluminescent signal and communicate the results. The application of this technology to the critically important issue of food safety and hygienic quality represents a novel method for detecting, monitoring, and preventing biologically active toxins in food commodities.
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