Hypervirulent C. difficile Detection via Multiplex PCR
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Solution Overview
Problem
Current PCR-based assays for detecting Clostridium difficile strains lack specificity and reliability in identifying hypervirulent strains, particularly toxin-producing strain 027, due to PCR inhibitors in sample matrices like stool samples, which affect amplification efficiency and bias.
Innovation Solution
A PCR-based method using specific oligonucleotide primers and probes targeting the C. difficile hydR, tcdB, and putative conjugative transposon DNA recombination protein genes, allowing for the detection of hypervirulent strains without enrichment culture, using real-time PCR assays and kits containing these primers and reagents for nucleic acid amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional PCR-based assays are used for detecting C. difficile strains, then the detection speed is improved, but the specificity and reliability for identifying hypervirulent strains deteriorates due to PCR inhibitors in stool samples
Solution Approach 1:
The assay divides the detection task into multiple independent PCR reactions, each targeting specific genetic markers (tedB gene for C. difficile detection, and additional markers for hypervirulent strain identification). This segmentation allows each reaction to be optimized for its specific target while maintaining overall detection speed and improving specificity through multiple verification points.
Solution Approach 2:
The patent applies local quality by designing primers and probes with specific characteristics tailored to each target sequence. Different primer sets are optimized for different genes (tedB, hypervirulent markers), with specific melting temperatures, lengths, and affinities to ensure reliable detection of hypervirulent strains while minimizing interference from PCR inhibitors present in stool samples.
2Ease of operation
If PCR amplification is performed directly on stool samples, then the workflow simplicity is improved, but the amplification efficiency deteriorates due to PCR inhibitors
Solution Approach 1:
The patent introduces an intermediary step of nucleic acid extraction and purification before PCR amplification. This intermediary process removes PCR inhibitors from the stool sample matrix, creating a cleaner template DNA that enables efficient amplification while maintaining the simplicity of a single-tube workflow. The extraction kit serves as the intermediary that bridges the complex stool sample and the sensitive PCR reaction.
Solution Approach 2:
The assay optimizes PCR parameters including annealing temperature, extension time, primer concentrations, and cycle numbers to compensate for the presence of inhibitors. By adjusting these parameters, the system maintains high amplification efficiency directly on stool samples or after minimal processing, balancing workflow simplicity with productivity.
3Measurement precision
If multiple genetic markers are targeted in a single PCR assay, then the detection specificity is improved, but the assay complexity increases
Solution Approach 1:
The patent merges multiple detection functions into a single multiplex PCR assay by incorporating multiple primer sets and fluorescent probes that target different genetic markers (tedB gene, hypervirulent strain markers) within one reaction tube. This combining approach improves detection specificity by simultaneously evaluating multiple criteria while avoiding the complexity of multiple separate assays through automated fluorescence-based detection.
Solution Approach 2:
The assay uses fluorescent probes with distinct emission wavelengths (different colors) to detect different genetic markers simultaneously. Each probe is designed with a specific fluorophore that can be detected by the instrument, allowing multiple targets to be visualized and differentiated by color, thereby improving specificity without requiring separate detection systems.
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
The method provides high specificity and reliability in detecting hypervirulent Clostridium difficile strains, including toxin-producing strain 027, with minimal false positives and negatives, improving clinical management and infection control by differentiating between non-toxigenic and hypervirulent strains.
Implementation Method 1
performing a nucleic acid amplification reaction comprising DNA extracted from the biological sample as a template, a first oligonucleotide primer set specific for amplifying a target sequence in the C. difficulte hydR gene in the reaction
Data Source
AI summary
The present invention provides a nucleic acid amplification based method for detecting a hypervirulent Clostridium difficile strain in a biological sample. The present invention is based on the use of oligonucleotide primers and probes specific to negative and positive markers in hypervirulent Clostridium difficile genome.