Detection Of Foodborne Pathogens Research Articles

E. coli O157:H7 Detection Using Surface Plasmon Resonance Based Biosensor

The detection of foodborne pathogenic bacteria remains a significant challenge, and the need for fast and sensitive detection methods is becoming increasingly important. Escherichia coli is a prevalent bacteria associated with foodborne illness, and this study aimed to evaluate the ability of a surface plasmon resonance (SPR) based biosensor to detect E. coli O157:H7 at low levels in pure culture and artificially contaminated bay leaves (Laurus nobilis) using different injection methods. To develop a biological sensing surface, the sensor surface was functionalized with 3-aminopropyltriethoxysilane (APTES), and polyclonal antibodies were immobilized on the surface for bacteria detection. Bacterial attachment to the antibodies resulted in a change in resonance angle. The biosensor was able to discriminate between cellular concentrations of 103 to 107 CFU/mL and showed potential in detecting different pathogens in various food samples. Before the SPR detection, the sample preparation step was optimized to ensure complex food matrices were suitable for SPR analysis. The results suggest that the SPR based biosensor is a promising tool for the rapid detection of foodborne pathogens in complex food matrices.

Research progress of aptasensor technology in the detection of foodborne pathogens

In recent years, foodborne pathogenic bacteria have gained increasingly serious public concerns. Therefore, the construction of simple, rapid, effective, and low-cost methods for rapid detection in the field of food safety has become an important topic. Amongst, aptasaenors are emerging biosensors in the field of food safety, detection, and control. Aptamers are single-stranded DNA or RNA sequence that specifically bind to proteins or other small molecules following the systematic evolution of ligands by exponential enrichment (SELEX) and other derivative techniques. Aptamers are widely used in food safety testing because of their wide range of target molecules, high sensitivity, strong specificity, and good stability. This review will provide an overview of recent studies about aptamers against foodborne pathogens, the potential applications and optimization methods of aptasensors in foodborne pathogens. Finally, it is hoped that this review can generate new ideas and approaches for the development and application about aptasensors against foodborne pathogens.

A rapid detection method of three foodborne pathogens based on physical and chemical Raman spectroscopy enhanced

Escherichia coli, Listeria monocytogenes, and Salmonella typhi are three pathogens commonly found in food. Label-free enhanced substrates have limitations in achieving high sensitivity in three bacteria detection. To enable low-concentration detection and differentiation of foodborne pathogens, this research presents an optimized detection strategy using Au @Ag NPs as the enhancing substrate for SERS technology. The impact of the particle size of Au @Ag NPs and the pH of the borate buffer solution on enhancing the Raman signals of these bacteria was investigated through electromagnetic and chemical enhancement mechanisms. By evaluating the intensity of bacterial Raman spectra, and employing chemometric techniques, the concentration and classification of the three bacterial species were predicted and analyzed. The research findings revealed that the optimized detection method was able to detect three pathogens at the concentration lower than 3 lg CFU/mL. Logarithmic fitting of the bacteria enabled prediction correlations above 0.98 and prediction root mean square errors below 0.17. After normalizing, efficient discrimination of low-concentration bacteria was achieved using the PLS-DA, with a classification prediction correlation greater than 0.94. The fabrication process of the proposed enhancement substrate is simple, but the stability of signal detection needs further improvement in subsequent experimental testing steps.

Risk-based detection as a cost-effective strategy to reduce foodborne illness due to salmonella

BackgroundSalmonella, a widespread pathogen, poses a significant threat to global food safety, leading to foodborne diseases and substantial economic losses. The timely and accurate detection of foodborne pathogens is pivotal for averting food contamination and outbreaks across the food production chain. This study assesses the cost-effectiveness of traditional culture-based methods versus risk-based approaches, incorporating polymerase chain reaction (PCR) for Salmonella detection. MethodsWe employed a stochastic scenario tree model to simulate scenarios based on the sampling inspection plan for raw aquatic products conducted by the Guangzhou Center for Disease Control and Prevention from 2018 to 2020. Various detection methods (culture or PCR) were applied to these aquatic products based on their categorized risk level. Sensitivity values were derived from published data, and incremental cost-effectiveness ratios were used to compare the different scenarios against the traditional culture method. ResultsA total of 360 samples were collected for analysis. The cost of culture-based detection alone amounted to 125,423.20 Chinese Yuan (CNY) and yielded nine instances of positive Salmonella detections. The risk-based detection strategy, which combined the more sensitive PCR method with high-risk sample characteristics, while employing the culture method for the remaining combinations, imposed a total cost of 128,775.83 CNY and yielded ten positive detections. This approach cost approximately 3391.74 CNY per additional positive sample detected compared to the culture method alone. Meanwhile, PCR-only detection imposed a total cost of 62,960.03 CNY. ConclusionsIn comparison to traditional culture-based methods, both the risk-based detection strategy and the PCR-only approach demonstrated superior capabilities with respect to detecting contaminated aquatic products. Implementing risk-based detection strategies can enhance cost-effectiveness, not only ensuring food safety but also reducing the incidence and economic burden of foodborne diseases.

Capture antibody imitator MnO2 nanozyme-based dual-signal immunochromatographic assay for rapid detection of Salmonella enteritidis

The sensitive and rapid detection of foodborne pathogens is of great significance to global public health security. Here, with two-dimensional nanomaterial MnO2 NSs as the capture antibody imitator and signal reporter molecules, based on its enzyme-catalyzed signal amplification capability, a label-free, dual-signal output immunochromatographic biosensor was constructed to achieve the sensitive detection of S. enteritidis. The capture antibody imitator of MnO2 capture probe shows an outstanding capture ability, forming a stable immune complex with S. enteritidis. As an in-situ catalytic amplification colorimetric signal trigger, MnO2 NSs exert oxidase-like enzyme activity and obtain satisfactory detection sensitivity. It is worth noting that the proposed dual-signal ICA has high analytical performances for S. enteritidis during the concentration range of 103-107 cfu mL−1 both in standard bacterial solutions and food matrixes.

Plasmonic aptasensor with antifouling dual-functional surface layer for lysozyme detection in food

Antifouling coatings are critically necessary for optical biosensors for various analytical application sectors, from medical diagnostics to foodborne pathogen detection. They help avoid non-specific protein/cell attachment on the active biosensor surface and catch the analytes directly in the complex media. Advances in antifouling plasmonic surfaces have been mainly focused on detecting clinical biomarkers in real biofluids, whereas developing antifouling coatings for direct analysis of analytes in complex media has been scarcely investigated for food quality control and safety.Herein, we propose a new low-fouling poly-l-lysine (PLL)-based surface layer for directly detecting an allergen protein, lysozyme, in the food matrix using surface plasmon resonance. The PLL-based polymer contains densely immobilized anionic oligopeptide side chains to create an electric charge-balanced layer able to repel the non-specific adsorption of undesired molecules on the biosensor surface. It also includes sparsely attached aptamer probes for capturing lysozyme directly in food sources with no pre-analytical sample treatment. We optimized the surface layer fabrication condition and tested the dual-functional surface to evaluate its ability to detect the target protein selectively. The developed analytical approach allowed for achieving a limit of detection of 0.04 μg mL−1 (2.95 nM) and a limit of quantification of 0.13 μg mL−1 (8.95 nM). Lysozyme was successfully quantified in milk samples using the plasmonic dual-functional aptasensor without sample pre-treatment or target isolation, illustrating the device's utility.

Independent evaluation of a DNA microarray system for Salmonella detection in ground beef

A new DNA microarray test kit has been developed to detect foodborne pathogens in various food matrices. This study focuses on evaluating the PathogenDx microarray-based system to detect Salmonella in ground beef and verify critical parameters that could interfere with the method's effectiveness, such as enrichment incubation time, ground beef fat content, inclusivity, exclusivity, and analytical sensitivity. Sample preparation protocols were evaluated at 6, 8, 12, 18, and 24 h enrichment times at varying bacterial levels to identify optimal conditions to detect the invA gene using the PathogenDx microarray. An 8 h enrichment step was selected based on 100% detection when initial inoculum levels were ≥5 CFU/g, and fractional detection was achieved when the concentration was as low as 1 CFU/g. Thus, the detection of Salmonella using the PathogenDx microarray system can be conducted in 12.5 h, including sample preparation, labeling PCR, hybridization, and analysis. Regarding fat content, there was no significant difference in detection rates of PathogenDx protocol among the highest and lowest commercially sold lean-to-fat ratios of ground beef. Inclusivity and exclusivity experiments showed that Salmonella was correctly identified 100% of the time. Using the ground beef matrix, PathogenDx method is comparable to the United States Department of Agriculture's Microbiology Laboratory Guidebook methodology for detection, which correctly identified Salmonella in 100% of the samples. Salmonella was detected between 93.33 and 100% when ground beef was inoculated with 1 and 5 CFU/g, respectively.

Application of quasimetagenomics methods to define microbial diversity and subtype Listeria monocytogenes in dairy and seafood production facilities.

Microorganisms frequently colonize surfaces within food production facilities. Detection of Listeria monocytogenes in this setting relies on culture-dependent methods, but the complex dynamics of bacterial interactions within these environments and their impact on pathogen detection remain largely unexplored. To address this challenge, we applied both 16S rRNA and shotgun quasimetagenomic (enriched microbiome) sequencing of swab culture enrichments from five seafood and seven dairy production environments. Utilizing 16S rRNA amplicon sequencing, we observed variability between 355 samples taken from these 12 production facilities and a distinctive microbiome for each environment. With shotgun quasimetagenomic sequencing, we were able to assemble L. monocytogenes metagenome-assembled genomes (MAGs) from 28 of the 32 culture-positive samples. We compared these MAGs to their corresponding whole-genome sequencing assemblies, which resulted in two polyphyletic clades consisting of L. monocytogenes lineages I and II with 13,195 and 25,556 single-nucleotide polymorphism sites, respectively. The remaining four MAGs did not produce sufficient genome coverage. To understand and establish limits for pathogen detection and subtyping using shotgun quasimetagenomics, these same data sets were downsampled in slilico to produce a titration series of abundances of L. monocytogenes and analyzed. Pathogen detection was achieved for all downsampled data sets, even those with only 3× genome coverage. This study contributes to the understanding of microbial diversity within food production environments and presents insights into the level of genome coverage needed in a metagenome sequencing data set to detect, subtype, and source track a foodborne pathogenIMPORTANCEIn developed countries, the human diet is predominated by food commodities, which have been manufactured, processed, and stored in a food production facility. Little is known about the application of metagenomic sequencing approaches for detecting foodborne pathogens, such as L. monocytogenes, and characterizing microbial diversity in food production ecosystems. In this work, we investigated the utility of 16S rRNA amplicon and quasimetagenomic sequencing for the taxonomic and phylogenetic classification of Listeria culture enrichments of environmental swabs collected from dairy and seafood production facilities. We demonstrated that single-nucleotide polymorphism (SNP) analyses of L. monocytogenes metagenome-assembled genomes (MAGs) from quasimetagenomic data sets can achieve similar resolution as culture isolate whole-genome sequencing. To further understand the impact of genome coverage on MAG SNP cluster resolution, an in silico downsampling approach was employed to reduce the percentage of target pathogen sequence reads, providing an initial estimate of required MAG coverage for subtyping resolution of L. monocytogenes.

A comprehensive review of the applications of bacteriophage-derived endolysins for foodborne bacterial pathogens and food safety: recent advances, challenges, and future perspective.

Foodborne diseases are caused by food contaminated by pathogenic bacteria such as Escherichia coli, Salmonella, Staphylococcus aureus, Listeria monocytogenes, Campylobacter, and Clostridium, a critical threat to human health. As a novel antibacterial agent against foodborne pathogens, endolysins are peptidoglycan hydrolases encoded by bacteriophages that lyse bacterial cells by targeting their cell wall, notably in Gram-positive bacteria due to their naturally exposed peptidoglycan layer. These lytic enzymes have gained scientists' interest in recent years due to their selectivity, mode of action, engineering potential, and lack of resistance mechanisms. The use of endolysins for food safety has undergone significant improvements, which are summarized and discussed in this review. Endolysins can remove bacterial biofilms of foodborne pathogens and their cell wall-binding domain can be employed as a tool for quick detection of foodborne pathogens. We explained the applications of endolysin for eliminating pathogenic bacteria in livestock and various food matrices, as well as the limitations and challenges in use as a dietary supplement. We also highlight the novel techniques of the development of engineering endolysin for targeting Gram-negative bacterial pathogens. In conclusion, endolysin is safe and effective against foodborne pathogens and has no adverse effect on human cells and beneficial microbiota. As a result, endolysin could be employed as a functional bio-preservative agent to improve food stability and safety and maintain the natural taste of food quality.

Aggregative Soil Sampling Using Boot Covers Compared to Soil Grabs From Commercial Romaine Fields Shows Similar Indicator Organism and Microbial Community Recoveries

Aggregative boot cover sampling may be a more representative, practical, and powerful method for preharvest produce soil testing than grab sampling because boot covers aggregate soil from larger areas. Our study tests if boot cover sampling results reflect quality and safety indicator organisms and community diversity of grab sampling. We collected soil samples from commercial romaine lettuce fields spanning 5060 m2 using boot covers (n = 28, m = 1.1 ± 0.4 g; wearing boot covers and walking along the path), composite grabs (n = 28, m = 231 ± 24 g; consisting of 60 grabs of 3–5 g each), and high-resolution grabs (n = 72, m = 56 ± 4 g; taking one sample per stratum). Means and standard deviations of log-transformed aerobic plate counts (APCs) were 7.0 ± 0.3, 7.1 ± 0.2, and 7.3 ± 0.2 log(CFU/g) for boot covers, composite grabs, and high-resolution grabs, respectively. APCs did not show biologically meaningful differences between sample types. Boot covers recovered on average 0.6 log(CFU/g) more total coliforms than both grabs (p < 0.001) where means and standard deviations of log-transformed counts were 3.2 ± 1.0, 2.6 ± 0.6, and 2.6 ± 1.0 log(CFU/g) for boot covers, composite grabs, and high-resolution grabs, respectively. There were no generic E. coli detected in any sample by enumeration methods with LODs of 1.3–2.1 log(CFU/g) for boot covers and 0.5 log(CFU/g) for both grabs. By 16S rRNA sequencing, community species diversity (alpha diversity) was not significantly different within collection methods. While communities differed (p < 0.001) between soil sampling methods (beta diversity), variance in microbial communities was not significantly different. Of the 28 phyla and 297 genera detected, 25 phyla (89%) and 258 genera (87%) were found by all methods. Overall, aggregative boot cover sampling is similar to both grab methods for recovering quality and safety indicator organisms and representative microbiomes. This justifies future work testing aggregative soil sampling for foodborne pathogen detection.

Femtomolar endogenous adenosine triphosphate-responded photoelectrochemical biosensor based on Au@Cu2O core-shell nanocubes for the ultrasensitive determination of Escherichia coli O157:H7 in foods

Sensitive and precise determination of virulent foodborne pathogens is significant for food safety. Herein, an ultrasensitive photoelectrochemical (PEC) bioanalysis was developed using the endogenous adenosine triphosphate (ATP)-responded Au@Cu2O core-shell nanocubes (Au@Cu2O NCs) to measure Escherichia coli O157: H7 (E. coli O157:H7) in food. Briefly, the phage-functionalized gold wire was used to specifically recognize the target pathogen. With the bacteriolysis of lysozyme, the endogenous ATP molecules were emitted from the captured target bacteria and enriched by another ATP aptamer-modified gold wire. Following the exchange with complementary DNA (cDNA) chains, the bonded ATP would be released. It could simultaneously etch the Au@Cu2O NCs and compete with external circuit electrons to combine photogenerated holes on the Au@Cu2O NCs-modified screen-printed electrode. With the synergy of the two signal amplification mechanisms, a significant attenuation of photocurrent signal appeared even with femtomolar ATP. Therefore, the purpose of ultrasensitive determination of E. coli O157:H7 was realized, which depended on the endogenous ATP rather than exogenous signal probes. The proposed biosensor presented a good analysis performance within 10–106 CFU/mL with a detection limit of 5 CFU/mL. Besides, its specificity, repeatability, and stability were also investigated and acceptable. The detection results for food samples matched well with the results detected by the plate counting method. This work gives an innovative and sensitive signal amplification strategy for PEC bioassays in foodborne pathogens detection.

Rapid detection of foodborne pathogens in diverse foodstuffs by universal electrochemical aptasensor based on UiO-66 and methylene blue composites.

Rapid and sensitive detection of foodborne pathogens in complex environments is essential for food protection. A universal electrochemical aptasensor was fabricated for the detection of three common foodborne pathogens, including Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Salmonella typhimurium (S. typhimurium). The aptasensor was developed based on the homogeneous and membrane filtration strategy. Zirconium-based metal-organic framework (UiO-66)/methylene blue (MB)/aptamer composite was designed as a signal amplification and recognition probe. Bacteria were quantitatively detected by the current changes of MB. By simply changing the aptamer, different bacteria could be detected. The detection limits of E. coli, S. aureus and S. typhimurium were 5, 4 and 3CFU·mL-1, respectively. In humidity and salt environments, the stability of the aptasensor was satisfactory. The aptasensor exhibited satisfactory detection performance in different real samples. This aptasensor has excellent potential for rapid detection of foodborne pathogens in complex environments.

Rapid and accurate quantification of viable Bacillus cereus in foods with a Propidium monoazide (PMA) - Fluorescence in situ hybridization (FISH) - Flow cytometry (FCM) method

Fluorescence-labeled antibodies and viability indicators are routinely employed in conjunction with flow cytometry (FCM) to rapidly quantify viable target bacteria, ensuring food safety. However, the specific detection of Bacillus cereus, a prominent bacterium causing food poisoning, proves challenging because of its close phylogenetic relationship with other Bacillus species. Moreover, the accuracy of viability indicators in identifying viable B. cereus has been underexplored. This study established a rapid and specific method for quantifying viable B. cereus. The membrane-permeable dye propidium monoazide was identified as an effective means to differentiate between viable and non-viable B. cereus cells. Subsequently, fluorescence in situ hybridization was introduced to specifically identify viable B. cereus cells. Furthermore, FCM was utilized for the rapid and accurate quantification of labeled viable B. cereus cells. Following optimization, the method demonstrated notable specificity and robust anti-interference ability, with B. cereus recovery rates in milk powder and chicken breast after pretreatment ranging from 96.3% to 97.7%. Viable B. cereus cells were accurately quantified within 1.5 h, with a linear range of 102 to 107 cells/g. In conclusion, this developed method enables the rapid and specific quantification of viable B. cereus, offering a novel approach to the detection of specific foodborne pathogens.

PEC-SERS Dual-Mode Detection of Foodborne Pathogens Based on Binding-Induced DNA Walker and C3N4/MXene-Au NPs Accelerator.

In this paper, a photoelectrochemical (PEC)-surface-enhanced Raman scattering (SERS) dual-mode biosensor is constructed coupled with a dual-recognition binding-induced DNA walker with a carbon nitride nanosheet (C3N4)/MXene-gold nanoparticles (C/M-Au NPs) accelerator, which is reliable and capable for sensitive and accurate detection of Staphylococcus aureus (S. aureus). Initially, a photoactive heterostructure is formed by combining C3N4 and MXene via a simple electrostatic self-assembly as they possess well-matched band-edge energy levels. Subsequently, in situ growth of gold nanoparticles on the formed surface results in better PEC performance and SERS activity, because of the synergistic effects of surface plasmon resonance and Schottky barrier. Furthermore, a three-dimensional, bipedal, and dual-recognition binding-induced DNA walker is introduced with the formation of Pb2+-dependent DNAzyme. In the presence of S. aureus, a significant quantity of intermediate DNA (I-DNA) is generated, which can open the hairpin structure of Methylene Blue-tagged hairpin DNA (H-MB) on the electrode surface, thereby enabling the switch of signals for the quantitative determination of S. aureus. The constructed PEC-SERS dual-mode biosensor that can be mutually verified under one reaction effectively addresses the problem of the low detection accuracy of traditional sensors. Experimental results revealed that the effective combination of PEC and SERS is achieved for amplification detection of S. aureus with a detection range of 5-108 CFU/mL (PEC) and 10-108 CFU/mL (SERS), and a detection of limit of 0.70 CFU/mL (PEC) and 1.35 CFU/mL (SERS), respectively. Therefore, this study offers a novel and effective dual-mode sensing strategy, which has important implications for bioanalysis and health monitoring.

Dual-channel biosensor for simultaneous detection of S. typhimurium and L. monocytogenes using nanotags of gold nanoparticles loaded metal-organic frameworks

Simultaneous detection of multiple foodborne pathogens is of great importance for ensuring food safety. Herein, we present a sensitive dual-channel electrochemical biosensor based on copper metal organic frameworks (CuMOF) and lead metal organic framework (PbMOF) for simultaneous detection of Salmonella typhimurium (S. typhimurium) and Listeria monocytogenes (L. monocytogenes). The MOF-based nanotags were prepared by functionalizing gold nanoparticles loaded CuMOF (Au@CuMOF) and PbMOF (Au@PbMOF) with signal DNA sequences 1 (sDNA1) and sDNA2, respectively. By selecting invA of S. typhimurium and inlA gene of L. monocytogenes as targe sequences, a sandwich-typed dual-channel biosensor was developed on glassy carbon electrodes (GCE) through hybridization reactions. The sensitive detection of S. typhimurium and L. monocytogenes was achieved by the direct differential pulse voltametric (DPV) signals of Cu2+ and Pb2+. Under optimal conditions, channel 1 of the biosensor showed linear range for invA gene of S. typhimurium in 1 × 10−14−1 × 10−8 M with low detection limit (LOD) of 3.42 × 10−16 M (S/N = 3), and channel 2 of the biosensor showed linear range for inlA gene of L. monocytogenes in 1 × 10−13−1 × 10−8 M with LOD of 6.11 × 10−15 M (S/N = 3). The dual-channel biosensor showed good selectivity which were used to detect S. typhimurium with linear range of 5−1.0 × 104 CFU mL−1 (LOD of 2.33 CFU mL−1), and L. monocytogenes with linear range of 10 − 1.0 × 104 CFU mL−1 (LOD of 6.61 CFU mL−1).

Research advances of SERS analysis method based on silent region molecules for food safety detection.

Food safety is a critical issue that is closely related to people's health and safety. As a simple, rapid, and sensitive detection technique, surface-enhanced Raman scattering (SERS) technology has significant potential for food safety detection. Recently, researchers have shown a growing interest in utilizing silent region molecules for SERS analysis. These molecules exhibit significant Raman scattering peaks in the cellular Raman silent region between 1800 and 2800 cm-1 avoiding overlapping with the SERS spectrum of biological matrices in the range 600-1800 cm-1, which could effectively circumvent matrix effects and improve the SERS accuracy. In this review, the application of silent region molecules-based SERS analytical technique for food safety detection is introduced, detection strategies including label-free detection and labeled detection are discussed, and recent applications of SERS analysis technology based on molecules containing alkyne and nitrile groups, as well as Prussian blue (PB) in the detection of pesticides, mycotoxins, metal ions, and foodborne pathogens are highlighted. This review aims to draw the attention to thesilent region molecules-based SERS analytical technique and toprovide theoretical support for its further applications in food safety detection.

Using dCas9 as an intermediate bridge of loop-mediated isothermal amplification-based lateral flow colorimetric biosensor for point-of-care Salmonella detection

Foodborne pathogens pose a serious threat to human health worldwide. Combining isothermal amplification techniques (e.g., loop-mediated isothermal amplification, LAMP) with lateral flow biosensor (LFB) is ideal for point-of-care testing of foodborne pathogens, but challenges remain in distinguishing target amplicons and by-products. Here, we developed a portable lateral flow colorimetric biosensor, termed CALL (dCas9-assisted LAMP-based LFB), using dCas9 as an intermediate bridge to address these challenges. As a proof-of-concept, we chose Salmonella as the model. Strategically, LAMP amplicons of the target gene contain many contiguous repeats that can be recognized and unlocked by dCas9/single-guide RNA, which then serve as scaffolds to assemble many gold nanoparticles (GNPs) into chainlike structures on the test line. This strategy eliminates false positives caused by by-products and enables all repeats of LAMP amplicon to participate in capturing GNPs, greatly improving specificity and sensitivity. The biosensor integrates rapid extraction, LAMP amplification, dCas9-based assembly and LFB analysis without requiring complex equipment, enabling on-site screening of Salmonella as low as 41 CFU/mL in 40 min. The practicability of the biosensor was further demonstrated by testing real foods. The success of CALL provides a promising direction for developing foodborne pathogen detection tools.

Preparation of a multifunctional and ultrasensitive Au@AgNPs-Van/PDMS film SERS substrate for rapid detection of foodborne pathogens in beef

We present a novel and super-sensitive vancomycin (Van) modified Au@AgNP self-assembly with polydimethylsiloxane (PDMS) (Au@AgNPs/Van-PDMS) film surface-enhanced Raman scattering (SERS) substrate for identification of foodborne pathogens in beef, without the need for in vitro bacterial culture. The results illustrated that the Au@AgNPs/Van-PDMS film exhibited high reproducibility and Raman enhancement effect (1.09 × 105). Clostridium perfringens, Bacillus subtilis and Staphylococcus aureus isolated from beef captured by Au@AgNPs/Van-PDMS film exhibited high reproducibility and significant differences. Principal component analysis score plots distinguished classes of foodborne pathogens, and the qualitative identification of linear discriminant analysis was correct at 100%. The detection limit of S. aureus in beef was as low as 3 CFU/mL. This method could provide an effective means and technical support for realizing the application of SERS technology for quick and highly sensitive detection of foodborne pathogens in complex environments.

Implication of Sodium Hypochlorite as a Sanitizer in Ready-to-Eat Salad Processing and Advantages of the Use of Alternative Rapid Bacterial Detection Methods.

The use of disinfection agents in the washing processing of ready-to-eat (RTE) vegetables, especially sodium hypochlorite, is a common industrial practice performed to enhance microbiological quality. However, some studies have reported a restart of bacterial growth and a substantial increase in bacterial load during early storage associated with the use of disinfection agents, which might represent a risk for consumers. We evaluated the effect of sodium hypochlorite on bacterial growth trends during the shelf-life in Lactuca sativa, simulating the industrial procedures for RTE vegetable packaging. Immediately after sodium hypochlorite treatment, an effective abatement of the bacterial load was observed, followed by a restart of growth throughout storage. After 5 days, the bacterial load was close to that reached by the control samples, indicating that the net increase in bacterial load was significantly higher in the treated samples. This might be ascribed to the reduction in competitive microflora and/or to the induction of adaptive responses by resting bacteria, which might select disinfectant-resistant bacteria. These findings elicit some concerns about the actual duration of the shelf-life; products might decrease their microbiological quality earlier during storage, pointing out the need to better clarify the impact of sodium hypochlorite as a sanitizer to closer consider its use in RTE vegetable processing. Furthermore, due to the importance of the rapid estimation of bacterial load and the early detection of foodborne pathogens throughout the food chain, the accuracy of the rapid bacteria detection method, the Micro Biological Survey (MBS), and its effectiveness for microbiological analyses of RTE vegetables were evaluated.

An Integrated Microfluidic Biosensing System Based on a Versatile Valve and Recombinase Polymerase Amplification for Rapid and Sensitive Detection of Salmonella typhimurium.

Detecting foodborne pathogens on-site is crucial for ensuring food safety, necessitating the development of rapid, cost-effective, highly sensitive, and portable devices. This paper presents an integrated microfluidic biosensing system designed for the rapid and sensitive detection of Salmonella typhimurium (S. typhimurium). The biosensing system comprises a microfluidic chip with a versatile valve, a recombinase polymerase amplification (RPA) for nucleic acid detection, and a customized real-time fluorescence detection system. The versatile valve combines the functions of an active valve and a magnetic actuation mixer, enabling on-demand mixing and controlling fluid flow. Quantitative fluorescence is processed and detected through a custom-built smartphone application. The proposed integrated microfluidic biosensing system could detect Salmonella at concentrations as low as 1.0 × 102 copies/µL within 30 min, which was consistent with the results obtained from the real-time quantitative polymerase chain reaction (qPCR) tests. With its versatile valve, this integrated microfluidic biosensing system holds significant potential for on-site detection of foodborne pathogens.