STEC Detection via PCR Amplification of stx1 and stx2 Genes
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Solution Overview
Problem
Current methods for detecting Shiga toxin-producing E. coli (STEC) are time-consuming and lack sensitivity, particularly for non-0157 STEC serotypes, as they require overnight stool specimen enrichment and are not widely capable of detecting multiple STEC strains.
Innovation Solution
The development of methods and kits using specific pairs of amplification oligomers and detection probes for identifying stx1 and stx2 genes through nucleic acid amplification techniques, such as PCR, allowing for rapid and sensitive detection of STEC strains, including those from E. coli, Citrobacter freundii, Aeromononas hydrophile, Aeromononas caviae, and Enterobacter cloacae.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If routine stool culture methods are used to detect STEC, then detection capability is achieved, but the testing time is excessively long (24 hours or more with overnight enrichment required)
Solution Approach 1:
The patent applies preliminary action by performing nucleic acid extraction and PCR amplification directly on stool specimens without requiring overnight broth enrichment. The method prepares detection-ready samples through direct processing, eliminating the time-consuming pre-enrichment step while maintaining detection sensitivity through targeted amplification of stx1 and stx2 genes.
Solution Approach 2:
The patent replaces the mechanical/cultural system of stool culture with a molecular biology system based on nucleic acid amplification. Instead of relying on bacterial growth on selective media over 24 hours, the method uses PCR to directly amplify and detect Shiga toxin genes from stool DNA, achieving rapid detection without cultural enrichment.
2Measurement precision
If selective and differential media are used for identifying 0157:H7, then identification capability is improved, but the versatility to detect non-0157 STEC serotypes is lost
Solution Approach 1:
The patent applies universality by designing PCR primers that target conserved regions of the stx1 and stx2 genes across all STEC serotypes. The amplification oligomers are designed to bind to essential functional regions of the Shiga toxin genes that are conserved among different serotypes, enabling a single assay to detect 0157:H7, O26, O45, and other non-O157 STEC strains with equal effectiveness.
Solution Approach 2:
The patent changes the detection parameter from serotype-specific phenotypic characteristics (which require different media for different serotypes) to genotype-based detection using universal primers. By targeting conserved genetic sequences rather than variable surface antigens, the method achieves broad serotype coverage with a single standardized protocol.
3Loss of time
If enzyme immunoassays are performed directly on stool specimens, then testing time is reduced, but sensitivity is insufficient compared to overnight enrichment methods
Solution Approach 1:
The patent applies preliminary action by performing nucleic acid extraction and concentration from stool specimens before PCR amplification. This pre-concentration step ensures sufficient target DNA is available for detection without requiring overnight enrichment, while the subsequent exponential amplification during PCR provides the necessary sensitivity for direct stool specimen testing.
4Measurement precision
If complex testing procedures such as pulse-field gel electrophoresis typing are used, then detection accuracy is improved, but device complexity and operational difficulty increase beyond capabilities of many labs
Solution Approach 1:
The patent extracts and amplifies only the specific stx1 and stx2 gene regions of interest from the complex bacterial genome, eliminating the need for complex whole-genome analysis methods like pulse-field gel electrophoresis. By focusing on the essential virulence genes rather than entire genomic characterization, the method achieves sufficient detection accuracy with a simpler, more accessible PCR-based approach.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables rapid, sensitive, and specific detection of STEC strains, including those that are not typically identified by standard methods, facilitating timely diagnosis and treatment by amplifying and detecting stx1 and stx2 genes in clinical samples.
Implementation Method 1
specific pairs of amplification oligomers and detection probes for identifying stx1 and stx2 genes through nucleic acid amplification techniques
Implementation Method 2
nucleic acid amplification techniques, such as PCR
Data Source
AI summary
The disclosed invention is related to methods, compositions and kits for targeting nucleic acid derived from Shiga toxin-producing bacteria such as E. coli. Compositions include amplification oligomers and/or detection probe oligomers. Kits and methods comprise at least one pair of amplification oligomers.