Research progress on detection techniques for point-of-care testing of foodborne pathogens

Development of Immunoassays for Foodborne Pathogenic Bacteria Detection Using PolyHRP for Signal Enhancement

The rapid and accurate detection of foodborne pathogens is essential for ensuring food safety. Escherichia coli O157:H7 (E. coli O157:H7) and Salmonella Typhimurium (S. Typhimurium) are major foodborne pathogenic bacteria that pose significant public health risks, highlighting the need for effective detection methods. In this study, highly sensitive double-antibody sandwich-based enzyme-linked immunosorbent assays (ELISAs) were developed for the rapid detection of E. coli O157:H7 and S. Typhimurium, utilizing a streptavidin-polymerized horseradish peroxidase (SA-PolyHRP)-based signal enhancement system. Systematic optimization was performed on key parameters, including the capture antibody concentration, detection antibody, and blocking agent. Compared to the method using SA-HRP, substitution with SA-PolyHRP significantly improved detection sensitivity, achieving limits of detection (LODs) of 1.4 × 104 CFU/mL for E. coli O157:H7 and 6.0 × 103 CFU/mL for S. Typhimurium, with sensitivity enhancements of 7.86-fold and 1.83-fold, respectively. Specificity tests confirmed no cross-reactivity with non-target or closely related pathogenic strains. The matrix effect was effectively mitigated through 10-fold and 100-fold dilutions for E. coli O157:H7 and S. Typhimurium, respectively. Both pathogens were successfully detected in beef samples spiked with 5 CFU after 5 h of incubation. This study demonstrates the effectiveness of PolyHRP-based signal enhancement for the highly sensitive and specific detection of foodborne pathogens, offering a promising approach for rapid food safety monitoring and public health protection.

Application Progress of Carbon Quantum Dot Composites in Fluorescent Detection of Food Safety

Carbon quantum dots (CQDs) have emerged as promising nanomaterials due to their unique optical properties, excellent biocompatibility, and cost-effectiveness. This review highlights recent advances in CQD-based composite materials and their applications in fluorescence detection, particularly in food safety. Combining CQDs with diverse materials enhances their fluorescence performance, stability, and selectivity, enabling the sensitive detection of various food contaminants. CQD composites offer significant improvements over conventional methods, including lower detection limits, faster response times, and broader applicability. Key areas of focus include the detection of pesticide residues, veterinary drug residues, heavy metal ions, and pathogenic bacteria in complex food matrices. Advanced doping and hybridization strategies, such as heteroatom incorporation, further optimize their optical and chemical properties. These innovations address critical challenges in food safety monitoring, paving the way for more effective and accessible detection technologies. Future developments in CQD composites are expected to expand their applications, ensuring enhanced food quality and public health protection.

Self-protective DNAzyme-based dual-responsive three-way Y-probe for simultaneous determination of multiple pathogenic bacteria

Foodborne pathogens, a major cause of foodborne illness due to their high virulence, pose a serious threat to public health. Consequently, identification of foodborne pathogens is essential for the prevention and treatment of foodborne infections. Consequently, there is an immediate need to establish a highly specific and precise approach for the concurrent detection of several foodborne pathogens. Herein, we developed a DNAzyme-based self-protecting dual-response nanoprobe for the simultaneous detection of two foodborne pathogens. The technique utilizes nanostructures to achieve logical signal input and output. In the presence of the target pathogen, the pathogen binds to the arch probe and releases the activation chain, which in turn activates a strand-displacement reaction and DNAzyme for signal amplification, producing different output signals to complete the simultaneous detection of multiple pathogens. The limits of detection for E. coli O157:H7 and S. typhimurium were determined to be 3.7 cfu/mL and 3.2 cfu/mL, with a measurement response time of 2 h. This approach enables ultrasensitive, specific, and simultaneous detection of two foodborne pathogens and is applicable for identifying foodborne pathogens in actual biological samples. The fluorescence detection of foodborne pathogens with a three-way Y-probe and DNAzyme coupling represents a novel approach for the concurrent identification of several foodborne diseases.

A Dual-Recognition Electrochemical Sensor Using Bacteria-Imprinted Polymer and Concanavalin A for Sensitive and Selective Detection of Escherichia coli O157:H7

The accurate detection and quantification of pathogenic bacteria is crucial for ensuring public health. In this work, we propose a sensitive and selective sandwich electrochemical sensor for detecting Escherichia coli O157:H7 (E. coli O157:H7). The sensor employs a dual-recognition strategy that combines a bacteria-imprinted polymer (BIP) and concanavalin A (ConA). The BIP is formed in situ on the electrode surface as the capture probe, while gold nanoparticles co-functionalized with ConA and the electroactive molecule 6-(ferrocenyl)hexanethiol (Au@Fc-ConA) serve as the signaling probe. When E. coli O157:H7 is present, the bacteria are selectively captured by the BIP. The captured bacteria interact with Au@Fc-ConA through ConA's sugar-binding properties, triggering Fc oxidation and generating a current proportional to the bacterial concentration. The sensor exhibits a linear detection range of 101-105 CFU mL-1 and a low detection limit of 10 CFU mL-1. Additionally, it demonstrates high sensitivity in complex milk samples, detecting E. coli O157:H7 at concentrations as low as 10 CFU mL-1, with recoveries ranging from 94.16% to 110.6%. Even in the presence of a 100-fold higher concentration of E. coli O6, the sensor effectively distinguishes E. coli O157:H7 from it. Moreover, it exhibits high reproducibility with a relative standard deviation of 2%. This study proposes a unique dual recognition strategy that combines simplicity and high performance. This method enables the selective detection of E. coli O157:H7 in real samples, providing a promising tool for food safety monitoring.

Principles, Methods, and Real-Time Applications of Bacteriophage-Based Pathogen Detection

Bacterial pathogens in water, food, and the environment are spreading diseases around the world. According to a World Health Organization (WHO) report, waterborne pathogens pose the most significant global health risks to living organisms, including humans and animals. Conventional bacterial detection approaches such as colony counting, microscopic analysis, biochemical analysis, and molecular analysis are expensive, time-consuming, less sensitive, and require a pre-enrichment step. However, the bacteriophage-based detection of pathogenic bacteria is a robust approach that utilizes bacteriophages, which are viruses that specifically target and infect bacteria, for rapid and accurate detection of targets. This review shed light on cutting-edge technologies about the novel structure of phages and the immobilization process on the surface of electrodes to detect targeted bacterial cells. Similarly, the purpose of this study was to provide a comprehensive assessment of bacteriophage-based biosensors utilized for pathogen detection, as well as their trends, outcomes, and problems. This review article summaries current phage-based pathogen detection strategies for the development of low-cost lab-on-chip (LOC) and point-of-care (POC) devices using electrochemical and optical methods such as surface-enhanced Raman spectroscopy (SERS).

Fast detection of bacterial gut pathogens on miniaturized devices: an overview

INTRODUCTION

Gut microbes pose challenges like colon inflammation, deadly diarrhea, antimicrobial resistance dissemination, and chronic disease onset. Development of early, rapid and specific diagnosis tools is essential for improving infection control. Point-of-care testing (POCT) systems offer rapid, sensitive, low-cost and sample-to-answer methods for microbe detection from various clinical and environmental samples, bringing the advantages of portability, automation, and simple operation.

AREAS COVERED

Rapid detection of gut microbes can be done using a wide array of techniques including biosensors, immunological assays, electrochemical impedance spectroscopy, mass spectrometry and molecular biology. Inclusion of Internet of Things, machine learning, and smartphone-based point-of-care applications is an important aspect of POCT. In this review, the authors discuss various fast diagnostic platforms for gut pathogens and their main challenges.

EXPERT OPINION

Developing effective assays for microbe detection can be complex. Assay design must consider factors like target selection, real-time and multiplex detection, sample type, reagent stability and storage, primer/probe design, and optimizing reaction conditions for accuracy and sensitivity. Mitigating these challenges requires interdisciplinary collaboration among scientists, clinicians, engineers, and industry partners. Future efforts are essential to enhance sensitivity, specificity, and versatility of POCT systems for gut microbe detection and quantification, advancing infectious disease diagnostics and management.

An All-in-One Platform for On-Site Multiplex Foodborne Pathogen Detection Based on Channel-Digital Hybrid Microfluidics

Recently, significant progress has been made in the development of microdevices for point-of-care infectious disease detection. However, most microdevices only allow limited steps, such as DNA amplification on the chip, while sample preparation, such as lysis and DNA extraction, is conducted off the chip using the traditional method. In this study, an all-in-one platform was developed, which incorporated all necessary procedures for nucleic acid detection. Our on-chip DNA extraction method utilized the magnetic bead-based technology on a hybrid channel-digital microfluidics (C-DMF) microdevice. It yielded high recovery rates, varying from 88.43% to 95.83%, with pathogen concentrations of 103-106 CFU/mL. In particular, the on-chip method exhibited significantly higher efficacy compared to the traditional off-chip manual method, for the DNA extraction of E. coli and S. aureus, representing Gram-negative and Gram-positive bacteria, respectively, at a sample concentration of 103 CFU/mL. To address the need for rapid and accessible diagnostics, colorimetric LAMP amplification was integrated into the proposed microdevice. The results were visually detectable with the naked eye, making it user-friendly for non-specialists. In addition, this platform demonstrated impressive sensitivity in simultaneously detecting common foodborne pathogens in spiked meat samples, achieving the LOD of 102-103 CFU/mL. The entire process, from sampling to result, was fully automated and only required approximately 60 min, offering promising applicability in resource-limited and on-site testing scenarios.

Multi-aptamer-mediated hairpin allosteric and aptamer-assisted CRISPR system for detection of S. pneumoniae and S. aureus

A novel nucleic acid aptamer nanoprobes-mediated hairpin allosteric and aptamer-assisted CRISPR system for detection of Streptococcus pneumoniae and Staphylococcus aureus is presented. In this fluorescence assay system, utilizing the hairpin allosteric effect caused by the aptamer binding to the target bacteria, the detection of S. pneumoniae is first achieved through changes in fluorescence due to FRET. Subsequently, a Cas12a protein mixture is added to detect S. aureus. The amplified output signal is triggered by two methods to ensure the sensitivity of the method: the synergistic FRET effect is achieved by the assembly of multi-aptamer through the conjugation of streptavidin-biotin, and the trans-cleavage function of CRISPR/Cas 12a. Under the optimized conditions, the proposed hairpin allosteric aptasensor could achieve high sensitivity (a detection limit of 135 cfu/mL) and broad-concentration quantification (dynamic range of 103-107 cfu/mL) of S. pneumoniae. The aptamer-assisted CRISPR system for S. aureus detection showed good linearity (R2 = 0.996) in the concentration range 102-108 cfu/mL, with a detection limit of 39 cfu/mL. No cross-reactivity with other foodborne pathogenic bacteria was observed in both systems. Taking only 55 min, this method of multiple pathogen detection proved to be promising.

Label-free multidimensional bacterial characterization with an ultrawide detectable concentration range by microfluidic impedance cytometry

Rapid and accurate identification of bacteria is of great importance to public health in various fields, including medical diagnostics, food safety, and environmental monitoring. However, most existing bacterial detection methods have very narrow detectable concentration ranges and limited detection information, which easily leads to wrong diagnosis and treatment. This work presents a novel high-throughput microfluidic electrical impedance-based multidimensional single-bacterium profiling system for ultrawide concentration range detection and accurate differentiation of viability and Gram types of bacteria. The electrical impedance-based microfluidic cytometry is capable of multi-frequency impedance quantification, which allows profiling of the bacteria size, concentration, and membrane impedance as an indicator of bacterial viability and Gram properties in a single flow-through interrogation. It has been demonstrated that this novel impedance cytometry has an ultrawide bacterial counting range (102-108 cells per mL), and exhibits a rapid and accurate discrimination of viability and Gram types of bacteria in a label-free manner. Escherichia coli (E. coli) has been used as an analog species for the accuracy assessment of the electrical impedance-based bacterial detection system in an authentic complex beverage matrix within 24 hours. The impedance-based quantifications of viable bacteria are consistent with those obtained by the classical bacterial colony counting method (R2 = 0.996). This work could pave the way for providing a novel microfluidic cytometry system for rapid and multidimensional bacterial detection in diverse areas.

Magnetic nanobead chain-assisted real-time impedance monitoring using PCB interdigitated electrode for Salmonella detection

Pathogen testing is effective to prevent food poisoning. Here, an electrochemical biosensor was explored for Salmonella detection by combining magnetic grid based bacterial separation with enzymatic catalysis based signal amplification on a PCB interdigitated electrode in a microfluidic chip. First, immune magnetic nanobeads, target bacteria, and immune polystyrene microspheres decorated with glucose oxidase were sufficiently mixed to form nanobead-bacteria-microsphere sandwich conjugates. Then, these conjugates were injected into the chip to form conjugate chains right over the electrode under an iron grid enhanced magnetic field. After non-conductive glucose was injected and catalyzed by glucose oxidase on the conjugate chains, conductive glucose acid and non-conductive hydrogen peroxide were continuously produced and rapidly diffused from the conjugate chains to the electrode. Finally, the impedance change was real-timely monitored and used to determine the bacterial amount. This sensor enabled detection of 50 CFU/mL Salmonella typhimurium in 1 h.

Molecular Targets for Foodborne Pathogenic Bacteria Detection

The detection of foodborne pathogenic bacteria currently relies on their ability to grow on chemically defined liquid and solid media, which is the essence of the classical microbiological approach. Such procedures are time-consuming and the quality of the result is affected by the selectivity of the media employed. Several alternative strategies based on the detection of molecular markers have been proposed. These markers may be cell constituents, may reside on the cell envelope or may be specific metabolites. Each marker provides specific advantages and, at the same time, suffers from specific limitations. The food matrix and chemical composition, as well as the accompanying microbiota, may also severely compromise detection. The aim of the present review article is to present and critically discuss all available information regarding the molecular targets that have been employed as markers for the detection of foodborne pathogens. Their strengths and limitations, as well as the proposed alleviation strategies, are presented, with particular emphasis on their applicability in real food systems and the challenges that are yet to be effectively addressed.