Accelerated Sample Preparation for Fast Salmonella Detection in Poultry Products

Filter-assisted sample preparation for on-site detection using a bi-functional linker-based biosensor demonstrated with Escherichia coli O157:H7

This study presents an advanced food detection platform that integrates filter-assisted sample preparation (FASP) with a bifunctional linker-based biosensor for on-site detection of Escherichia coli O157:H7 as a model case. FASP isolates bacteria from food samples through multi-filter preprocessing, significantly enhancing the specificity, sensitivity, and reproducibility of the subsequent biosensor analysis. This platform can detect E. coli O157:H7 at concentrations as low as 102 CFU per 25 g of tomato with a total processing time of 2.5 h from sampling to testing using an on or off detection method. FASP supports large food processing volumes up to 250 mL, maximizing bacterial capture and minimizing microbial loss during pre-treatment. This integrated approach significantly improves the speed, accuracy, and practicality of pathogen detection, offering a robust solution for onsite microbial detection and enhancing food safety monitoring in the food industry.

Sensitive detection of foodborne pathogens based on CRISPR-Cas13a

Salmonella, being one of the most widespread foodborne pathogens, is a compulsory test item required by national food safety standard of China and many other countries. More sensitive and specific Salmonella detection method is still needed since traditional methods are time consuming and highly dependent on enormous manpower and material resources. In this research, a bacteria detection method based on CRISPR-Cas13a system (where CRISPR is Clustered Regularly Interspaced Short Palindromic Repeats) was proposed. The target DNA was amplified by PCR and transcribed into RNA by T7 transcriptase, which can activate the RNase activity of the Cas13a protein. The self-folding quenched fluorescent probe can be cleaved by the activated Cas13a protein to generate fluorescent signal. We named this method as PCF detection (PCR-CRISPR-Fluorescence based nucleic acid detection). In this study, PCF detection showed excellent sensitivity, which can detect Salmonella genomic DNA with a minimum of 10¹ aM or 10° CFU/ml Salmonella bacteria in 2 hr. It also showed good specificity with no cross-reaction with other common foodborne bacteria. PRACTICAL APPLICATION: The PCF detection method proposed in this article can detect Salmonella sensitively and specifically, providing a novel strategy for the detection of foodborne pathogens in food and has great application potential in other microbial detection fields.

Universal linker Polymerase Chain Reaction-triggered Strand Displacement Amplification visual biosensor for ultra-sensitive detection of Salmonella

Salmonella is a principal causal agent of pathogenic outbreaks via food. A universal, highly sensitive and visual Salmonella detection method was proposed in this paper, based on a universal linker PCR (UL-PCR)-triggered Strand Displacement Amplification (SDA). In this research, the UL-PCR achieved the primary amplification. The universal linker primer was ingeniously designed and composed of two parts, one of which was the binding sequence of the target, and the other was the universal linker. Complementary sequences of the G-quadruplex and the nicking endonuclease recognition sequence were included in the universal linker. Therefore, the G-quadruplexes and nicking sites were successfully introduced into the UL-PCR products, providing a basis for further SDA triggering. SDA achieved the secondary signal amplification and generated a large amount of label-free DNAzymes. Following SDA, DNAzymes catalyzed 3,3',5,5'-tetramethylaniline (TMB) into colored compounds visible to the naked eye. We obtained the best experimental conditions by univariate analysis. Under optimal conditions, this proposed universal label-free method could detect Salmonella genome at level as low as 22 copies mL^-1, with an excellent linear range between 10² copies mL^-1 and 10⁷ copies mL^-1. And the limit of quantification (LOQ) was 10² copies mL^-1. This strategy shows promise for broad applications.