Faster detection of contaminated foods can prevent adulterated foods from being consumed and mini-
mize the risk of an outbreak of foodborne illness. A sensitive molecular detection method is especially
important for Shigella because ingestion of as few as 10 of these bacterial pathogens can cause disease.
The objectives of this study were to compare the ability of four DNA extraction methods to detect Shigella
in six types of produce, post-enrichment, and to evaluate a new and rapid conventional multiplex assay
that targets the Shigella ipaH, virB and mxiC virulence genes. This assay can detect less than two Shigella
cells in pure culture, even when the pathogen is mixed with background microflora, and it can also
differentiate natural Shigella strains from a control strain and eliminate false positive results due to
accidental laboratory contamination. The four DNA extraction methods (boiling, PrepMan Ultra [Applied
Biosystems], InstaGene Matrix [Bio-Rad], DNeasy Tissue kit [Qiagen]) detected 1.6 103
Shigella CFU/ml
post-enrichment, requiring w18 doublings to one cell in 25 g of produce pre-enrichment. Lower
sensitivity was obtained, depending on produce type and extraction method. The InstaGene Matrix was
the most consistent and sensitive and the multiplex assay accurately detected Shigella in less than
90 min, outperforming, to the best of our knowledge, molecular assays currently in place for this
pathogen.
Faster detection of contaminated foods can prevent adulterated foods from being consumed and mini-mize the risk of an outbreak of foodborne illness. A sensitive molecular detection method is especiallyimportant for Shigella because ingestion of as few as 10 of these bacterial pathogens can cause disease.The objectives of this study were to compare the ability of four DNA extraction methods to detect Shigellain six types of produce, post-enrichment, and to evaluate a new and rapid conventional multiplex assaythat targets the Shigella ipaH, virB and mxiC virulence genes. This assay can detect less than two Shigellacells in pure culture, even when the pathogen is mixed with background microflora, and it can alsodifferentiate natural Shigella strains from a control strain and eliminate false positive results due toaccidental laboratory contamination. The four DNA extraction methods (boiling, PrepMan Ultra [AppliedBiosystems], InstaGene Matrix [Bio-Rad], DNeasy Tissue kit [Qiagen]) detected 1.6 103Shigella CFU/mlpost-enrichment, requiring w18 doublings to one cell in 25 g of produce pre-enrichment. Lowersensitivity was obtained, depending on produce type and extraction method. The InstaGene Matrix wasthe most consistent and sensitive and the multiplex assay accurately detected Shigella in less than90 min, outperforming, to the best of our knowledge, molecular assays currently in place for thisการศึกษา
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