crAssphage DNA Primers for Human Fecal Source Identification
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Solution Overview
Problem
Current methods for detecting human fecal contamination in environmental samples lack specificity and sensitivity, as they often target bacterial indicators rather than viral indicators, and existing genetic markers for the Cross-Assembly phage (crAssphage) are not adequately validated for human fecal source identification.
Innovation Solution
Development of DNA primers and probes that specifically hybridize to human-associated regions of the crAssphage metagenome, allowing for the determination of human fecal waste presence using molecular biology techniques, with a multistep strategy involving PrimerBLAST design, end-point PCR testing, and adaptation to quantitative PCR technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If bacterial indicator bacteria (e.g., enterococci, Escherichia coli) are used for fecal contamination detection, then the detection method is well-established and easy to operate, but the method lacks specificity to identify human fecal pollution sources
Solution Approach 1:
The patent applies local quality by targeting specific human-associated genetic regions within the crAssphage virus genome rather than using general bacterial indicators. The primers and probes are designed to hybridize to specific sequences (e.g., ORF00024, ORF00025) that are uniquely associated with human fecal contamination, thereby achieving high specificity while maintaining operational feasibility through standardized PCR techniques
2Measurement precision
If viral indicators like crAssphage are used for human fecal contamination detection, then specificity for human sources is improved, but the method requires more complex molecular biology techniques
Solution Approach 1:
The patent applies preliminary action by pre-designing and validating specific primer pairs and probe sequences before actual detection. The primers (e.g., crAss056_F1, crAss056_R1) and probes (e.g., crAss056_P1) were previously characterized to ensure they specifically target human-associated crAssphage regions. This preliminary preparation allows the detection method to achieve high specificity while using standard, readily available molecular biology equipment and protocols
3Measurement precision
If existing crAssphage genetic markers are used for source tracking, then human fecal pollution can be detected, but the markers are not adequately validated for reliable identification
Solution Approach 1:
The patent applies feedback by systematically testing and validating the primer-probe sets against a comprehensive panel of samples with known fecal sources. The performance metrics (specificity, sensitivity, accuracy) were determined through iterative evaluation where results from controlled samples fed back into the method optimization process. This feedback-driven validation ensures that the markers are adequately tested and reliable for identifying human fecal pollution across diverse environmental matrices
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 solution provides a fast, sensitive, and specific assay for human fecal contamination, identifying human-specific genetic regions in environmental samples with high specificity and sensitivity, enabling effective human fecal source identification in various samples.
Implementation Method 1
Development of DNA primers and probes that specifically hybridize to human-associated regions of the crAssphage metagenome
Implementation Method 2
allowing for the determination of human fecal waste presence using molecular biology techniques, with a multistep strategy involving PrimerBLAST design, end-point PCR testing
Data Source
AI summary
Methods and reagents are used to determine the presence of human fecal contamination. These relate to detection of human crAssphage, a bacteriophage present in Bacteroides.