Engineered M13 Bacteriophage Detects Salmonella with Dual Colorimetric and SERS Signals, Achieving Sub-4 CFU/mL LODs
Background
Rapid and accurate detection of Salmonella is critical for food safety and public health, given its role in widespread foodborne illnesses. Traditional culture-based methods are often time-consuming, delaying intervention and increasing outbreak potential. While molecular methods exist, they can be complex or require specialized equipment, limiting on-site application. Bacteriophage-based detection offers a promising alternative due to their high specificity for bacterial targets and adaptability for various sensing platforms, addressing the need for fast, reliable, and user-friendly diagnostic tools in complex food matrices.
Study Design
Researchers engineered a bifunctional M13 bacteriophage to create a dual-modal detection strategy for Salmonella. A Salmonella-specific binding peptide was genetically fused to the phage's pIII protein, while a streptavidin (SA)-binding nanotag was displayed on the pVIII protein. The assay involved incubating the engineered phage with Salmonella, followed by the addition of SA-HRP (streptavidin-horseradish peroxidase) to leverage the ~2700 copies of pVIII per phage for massive enzymatic loading. This enzyme then catalyzed the conversion of TMB (3,3',5,5'-tetramethylbenzidine) substrate, generating both colorimetric and Surface-Enhanced Raman Spectroscopy (SERS) signals. The detection was optimized at 37 °C for approximately 1.5 hours.
Results
Under optimized conditions, the engineered M13 bacteriophage assay demonstrated high sensitivity and specificity for Salmonella detection. The colorimetric mode achieved a limit of detection (LOD) of 3.4 CFU/mL. The SERS mode, leveraging the enhanced signal from the enzymatic reaction, exhibited an even lower LOD.
The SERS detection mode achieved a superior limit of detection of 2.7 CFU/mL for Salmonella.
Both detection modes displayed excellent specificity, effectively distinguishing Salmonella from other common foodborne pathogens. Furthermore, the method demonstrated satisfactory accuracy when tested in complex food matrices, including Penaeus vannamei (shrimp), beef, and peanuts, indicating its robustness against potential interference from food components. This dual-signal approach provides a reliable and sensitive platform for rapid pathogen identification.
Key Findings
- Engineered M13 bacteriophage detected Salmonella using a dual colorimetric and SERS approach.
- Colorimetric detection achieved a limit of detection (LOD) of 3.4 CFU/mL for Salmonella.
- SERS detection achieved a superior LOD of 2.7 CFU/mL for Salmonella.
- The method exhibited excellent specificity and satisfactory accuracy in complex food matrices (shrimp, beef, peanuts).
- Optimized detection conditions were 37 °C and approximately 1.5 hours.
Why It Matters
This dual-modal M13 bacteriophage assay represents a significant step forward for rapid, on-site food safety testing, potentially reducing the time required to detect Salmonella from days to hours. For food producers and regulatory bodies, this means faster identification of contaminated products, minimizing recalls and public health risks. The ability to use both colorimetric (visual) and SERS (instrumental) signals offers flexibility, allowing for simple, low-cost screening or more sensitive, quantitative analysis as needed. This technology could enable earlier intervention in food supply chains, preventing widespread outbreaks and improving consumer confidence. While currently a proof-of-concept, its application in diverse food matrices suggests strong potential for commercial translation into portable diagnostic kits, enhancing global food safety surveillance.
salmonella
food-safety
m13-bacteriophage
detection
biosensor
colorimetric
