Abstract
Salmonella enterica is a pathogenic bacterium that causes foodborne illness. One of the vehicle foods of S. enterica are chicken eggs. Efficient collection of the bacterium is necessary to detect it specifically. We developed a method to detect S. enterica by PCR on a microfluidic disc device using a fluorescent probe. Salmonella enterica cells were isolated in the microchambers on the device, followed by thermal lysis and PCR targeting with the invA gene, a gene specific to S. enterica, were observed by measurement of the fluorescent signal that resulted from gene amplification. However, the developed method was unable to discriminate viable cells from dead cells. Consequently, in this study, magnetic beads modified with anti-Salmonella antibody were utilized to detect viable Salmonella cells from egg yolk prior to PCR on the device. While using the antibody-modified beads, egg yolk components, which inhibit PCR, were removed. The collected cells were subsequently detected by PCR of the invA gene on a microfluidic disc device. This method enabled the detection of viable cells without the inhibition of PCR by any egg component. S. enterica was detected at 5.0×104 cells mL−1 or at a higher concentration of egg yolk within 6 h including the sampling time.
Highlights
Salmonella enterica is a dangerous pathogen that causes outbreaks of foodborne illness [1]
S. enterica cells were separated from chicken meat with the use of a stomacher bag with filter which is useful for separating small bacterial cells from solid samples, such as meat, collected by centrifugation using Percoll® [11]
It was considered that the stomacher bag was not effective to separate bacterial cells from an egg sample, so centrifugation using Percoll® was examined in this study to collect S. enterica cells
Summary
Salmonella enterica is a dangerous pathogen that causes outbreaks of foodborne illness [1]. The vehicle foods of S. enterica are eggs, meat, and foods made of eggs or meat [2,3,4,5]. Cells of S. enterica exist in the intestines of chickens as a coliform bacterium, allowing the easy contamination of chicken meat and eggs [6,7]. Infection of S. enterica can occur from contaminated eggs or meat and from its contamination through food processing, transportation, packaging, sales, cooking, and serving. When contaminated food is consumed, after an incubation period of 6 to 48 h, symptoms such as vomiting, diarrhea, and/or fever appear [8,9]. In order to prevent outbreaks, rapid detection of the origin of this bacterium in food is necessary
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