Monocytogenes In Food Samples Research Articles

LAMP based electrochemical sensor for extraction-free detection of Listeria monocytogenes in food samples

Listeria monocytogenes (LMO) represents one of the most serious hazards for food health due to the high mortality rate and its ability to survive at limiting conditions. In this study, an electrochemical sensor for the detection of LMO in food samples using loop mediated isothermal amplification (LAMP) technique is presented. The extraction step for the release of the nucleic acids of the sample was simplified using three different alternatives (QuickExtract buffer lysis, heating method and an extraction-free option). The three protocols were tested with the LAMP reaction in seven different food matrices (Dairy milk, fresh cheese, ham, hummus, lettuce, milk powder and pâté) and were able to detect 1 cfu/25 g as stipulated by the food safety regulations. It was proved that all three alternatives were compatible with the electrochemical detection using methylene blue redox-active molecule in dairy milk samples. The final validation of the sensor was carried out with the extraction-free option in nine different food matrices, which were able to detect 1 cfu/25 g of food sample in all cases. This validation demonstrates the feasibility of the sensor for its application in the food industry as a point-of-test solution.

Quartz crystal microbalance–based aptasensor integrated with magnetic pre-concentration system for detection of Listeria monocytogenes in food samples

A fast and accurate identification of Listeria monocytogenes. A new quartz crystal microbalance (QCM) aptasensor was designed for the specific and rapid detection of L. monocytogenes. Before detection of the target bacterium from samples in the QCM aptasensor, a magnetic pre-enrichment system was used to eliminate any contaminant in the samples. The prepared magnetic system was characterized using ATR-FTIR, SEM, VSM, BET, and analytical methods. The saturation magnetization values of the Fe3O4, Fe3O4@PDA, and Fe3O4@PDA@DAPEG particles were 57.2, 40.8, and 36.4 emu/g, respectively. The same aptamer was also immobilized on the QCM crystal integrated into QCM flow cell and utilized to quantitatively detect L. monocytogenes cells from the samples. It was found that a specific aptamer-magnetic pre-concentration system efficiently captured L. monocytogenes cells in a short time (approximately 10 min). The Fe3O4@PDA@DA-PEG-Apt particles provided selective isolation of L. monocytogenes from the bacteria-spiked media up to 91.8%. The immobilized aptamer content of the magnetic particles was 5834 µg/g using 500 ng Apt/mL. The QCM aptasensor showed a very high range of analytical performance to the target bacterium from 1.0 × 102 and 1.0 × 107 CFU/mL. The limit of detection (LOD) and limit of quantitation (LOQ) were 148 and 448 CFU/mL, respectively, from the feeding of the QCM aptasensor flow cell with the eluent of the magnetic pre-concentration system. The reproducibility of the aptasensor was more than 95%. The aptasensor was very specific to L. monocytogenes compared to the other Listeria species (i.e., L. ivanovii, L. innocua, and L. seeligeri) or other tested bacteria such as Staphylococcus aureus, Escherichia coli, and Bacillus subtilis. The QCM aptasensor was regenerated with NaOH solution, and the system was reused many times.Graphical

Development and Application of Four Foodborne Pathogens by TaqMan Multiplex Real-Time PCR.

A TaqMan multiplex real-time PCR (mRT-PCR) was developed to detect simultaneously Salmonella spp., Escherichia coli O157, Staphylococcus aureus, and Listeria monocytogenes in food samples. The method involves four sets of primers and probes tailored to the unique DNA sequences found in the invA, nuc, rfbE, and hly genes of each pathogen. The generated standard curves, correlating gene copy numbers with Ct values, demonstrated high accuracy (R2 > 0.99) and efficiency (92%-104%). Meanwhile, the limit of detection was 100 CFU/mL for the four target bacteria in artificially contaminated food samples after 6-8 h of enrichment. The assay's effectiveness was further verified by testing 80 naturally contaminated food samples, showing results largely in agreement with traditional culture methods. Overall, this newly developed TaqMan mRT-PCR, inclusive of a pre-enrichment step, proves to be a dependable and effective tool for detecting single or multiple pathogens in diverse food items, offering significant potential for in vitro diagnostics.

Development of Optical Label-Free Biosensor Method in Detection of Listeria monocytogenes from Food.

The present work describes an alternative method for detecting and identifying Listeria monocytogenes in food samples by developing a nanophotonic biosensor containing bioreceptors and optical transducers. The development of photonic sensors for the detection of pathogens in the food industry involves the implementation of procedures for selecting probes against the antigens of interest and the functionalization of the sensor surfaces on which the said bioreceptors are located. As a previous step to functionalizing the biosensor, an immobilization control of these antibodies on silicon nitride surfaces was carried out to check the effectiveness of in plane immobilization. On the one hand, it was observed that a Listeria monocytogenes-specific polyclonal antibody has a greater binding capacity to the antigen at a wide range of concentrations. A Listeria monocytogenes monoclonal antibody is more specific and has a greater binding capacity only at low concentrations. An assay for evaluating selected antibodies against particular antigens of Listeria monocytogenes bacteria was designed to determine the binding specificity of each probe using the indirect ELISA detection technique. In addition, a validation method was established against the reference method for many replicates belonging to different batches of meat-detectable samples, with a medium and pre-enrichment time that allowed optimal recovery of the target microorganism. Moreover, no cross-reactivity with other nontarget bacteria was observed. Thus, this system is a simple, highly sensitive, and accurate platform for L. monocytogenes detection.

Detection of Listeria monocytogenes in foods with a textile organic electrochemical transistor biosensor

Foods contaminated by pathogens are responsible for foodborne diseases which have socioeconomic impacts. Many approaches have been extensively investigated to obtain specific and sensitive methods to detect pathogens in food, but they are often not easy to perform and require trained personnel. This work aims to propose a textile organic electrochemical transistor-based (OECT) biosensor to detect L. monocytogenes in food samples. The analyses were performed with culture-based methods, Listeria Precis™ method, PCR, and our textile OECT biosensor which used poly(3,4-ethylenedioxythiophene) (PEDOT):polystyrene sulfonate (PSS) (PEDOT:PSS) for doping the organic channel. Atomic force microscopy (AFM) was used to obtain topographic maps of the gold gate. The electrochemical activity on gate electrodes was measured and related to the concentration of DNA extracted from samples and hybridized to the specific capture probe immobilized onto the gold surface of the gate. This assay reached a limit of detection of 1.05 ng/μL, corresponding to 0.56 pM of L. monocytogenes ATCC 7644, and allowed the specific and rapid detection of L. monocytogenes in the analyzed samples.Keypoints• Textile organic electrochemical transistors functionalized with a specific DNA probe• AFM topographic and surface potential maps of a functionalized gold gate surface• Comparison between the Listeria monocytogenes Precis™ method and an OECT biosensor

Phenyllactic acid application to control Listeria monocytogenes biofilms and its growth in milk and spiced beef

Listeria monocytogenes, as a food-associated pathogen, is able to develop biofilms on different surfaces of food contact, which seriously threatens food safety. Phenyllactic acid (PLA) exhibits excellent inhibitory effects on many bacterial strains including L. monocytogenes. Our study aimed to investigate effects of PLA on L. monocytogenes biofilms and its growth in milk and on spiced beef. Biofilm biomass was measured by the microplate method and biofilm structure was observed by electron microscopy. Growth of L. monocytogenes in food samples was determined by colony counting. Results from the agar dilution method demonstrated that L. monocytogenes 10403S had a PLA minimum inhibitory concentration (MIC) value of 6 mg/ml. Sub-inhibitory concentrations of PLA could inhibit biofilm formation by reducing the secretion of exopolysaccharides and extracellular proteins in L. monocytogenes. PLA at concentrations above 1/2MIC could destroy mature biofilms of L. monocytogenes by decreasing the exopolysaccharides and extracellular proteins in the biofilm framework. Both swimming and swarming motilities of L. monocytogenes were inhibited by PLA. The hemolytic activity of L. monocytogenes was inactivated by PLA. However, the capacity to attach and invade Caco-2 cells was not affected by PLA. The results displayed that PLA had no effect on the expression of genes associated with motility, but reduced the expression level of the hly gene encoding Listeria hemolysin. When added to ultra-high temperature (UHT) whole and pasteurized milk, PLA at 3 mg/ml inhibited L. monocytogenes growth through 14 days of storage at 4 °C. PLA at concentrations ≥3 mg/ml significantly reduced L. monocytogenes counts on spiced beef samples during storage. PLA has potential as an alternative antimicrobial to control L. monocytogenes contamination and its biofilms in food industry.

A novel lateral flow immunoassay strip based on a label-free magnetic Fe3O4@UiO-66-NH2 nanocomposite for rapid detection of Listeria monocytogenes.

Listeria monocytogenes (L. monocytogenes) is one of the most lethal pathogenic bacteria. Although the traditional microbial culture method has high sensitivity and selectivity for the diagnosis of L. monocytogenes, it is time-consuming and not suitable for on-site detection. A rapid, convenient and visualized on-site detection method is particularly needed. In this work, Fe3O4@UiO-66-NH2 was prepared for both magnetic separation and lateral flow immunoassay (LFIA) for the detection of L. monocytogenes by taking advantage of the easy separation of the magnetic core Fe3O4 and the high surface area of the outer layer UiO-66-NH2. Fe3O4@UiO-66-NH2 with a high surface area and good water-dispersibility and optical properties was synthesized by a simple hydrothermal process. It could directly adsorb on the surface of target bacteria and form Fe3O4@UiO-66-NH2-bacteria conjugates, without the labeling of an antibody. After magnetic separation and concentration, the Fe3O4@UiO-66-NH2-bacteria conjugates were detected by the antibody on the test line of the LFIA strip, resulting in a visible orange band. The capture efficiency and LFIA detection of Fe3O4@UiO-66-NH2 were optimized in this study. Under the optimal conditions, a good linear correlation between the test line intensity and the concentration of L. monocytogenes was obtained in the range of 105-108 CFU mL-1, and the limit of detection was 2.2 × 106 CFU mL-1 by the naked eye. The Fe3O4@UiO-66-NH2-based LFIA strip showed strong specificity for L. monocytogenes, and the detection took 45 min without culture enrichment. Therefore, the proposed Fe3O4@UiO-66-NH2-based strip showed the advantages of simple synthesis, being label-free, low cost, good selectivity and convenience.

Ultrasensitive Detection of Salmonella and Listeria monocytogenes by Small-Molecule Chemiluminescence Probes.

Detection of Salmonella and L. monocytogenes in food samples by current diagnostic methods requires relatively long time to results (2-6 days). Furthermore, the ability to perform environmental monitoring at the factory site for these pathogens is limited due to the need for laboratory facilities. Herein, we report new chemiluminescence probes for the ultrasensitive direct detection of viable pathogenic bacteria. The probes are composed of a bright phenoxy-dioxetane luminophore masked by triggering group, which is activated by a specific bacterial enzyme, and could detect their corresponding bacteria with an LOD value of about 600-fold lower than that of fluorescent probes. Moreover, we were able to detect a minimum of 10 Salmonella cells within 6 h incubation. The assay allows for bacterial enrichment and detection in one test tube without further sample preparation. We anticipate that this design strategy will be used to prepare analogous chemiluminescence probes for other enzymes relevant to specific bacteria detection and point-of-care diagnostics.

Ultrasensitive Detection of Salmonella and Listeria monocytogenes by Small‐Molecule Chemiluminescence Probes

AbstractDetection of Salmonella and L. monocytogenes in food samples by current diagnostic methods requires relatively long time to results (2–6 days). Furthermore, the ability to perform environmental monitoring at the factory site for these pathogens is limited due to the need for laboratory facilities. Herein, we report new chemiluminescence probes for the ultrasensitive direct detection of viable pathogenic bacteria. The probes are composed of a bright phenoxy‐dioxetane luminophore masked by triggering group, which is activated by a specific bacterial enzyme, and could detect their corresponding bacteria with an LOD value of about 600‐fold lower than that of fluorescent probes. Moreover, we were able to detect a minimum of 10 Salmonella cells within 6 h incubation. The assay allows for bacterial enrichment and detection in one test tube without further sample preparation. We anticipate that this design strategy will be used to prepare analogous chemiluminescence probes for other enzymes relevant to specific bacteria detection and point‐of‐care diagnostics.

Development and application of Peptide Nucleic Acid Fluorescence in situ Hybridization for the specific detection of Listeria monocytogenes

Listeria monocytogenes is one of the most important foodborne pathogens due to the high hospitalization and mortality rates associated to an outbreak. Several new molecular methods that accelerate the identification of L. monocytogenes have been developed, however conventional culture-based methods still remain the gold standard. In this work we developed a novel Peptide Nucleic Acid Fluorescence in situ Hybridization (PNA-FISH) method for the specific detection of L. monocytogenes. The method was based on an already existing PNA probe, LmPNA1253, coupled with a novel blocker probe in a 1:2 ratio. The method was optimized for the detection of L. monocytogenes in food samples through an evaluation of several rich and selective enrichment broths. The best outcome was achieved using One Broth Listeria in a two-step enrichment of 24 h plus 18 h. For validation in food samples, ground beef, ground pork, milk, lettuce and cooked shrimp were artificially contaminated with two ranges of inoculum: a low level (0.2–2 CFU/25 g or mL) and a high level (2–10 CFU/25 g or mL). The PNA-FISH method performed well in all types of food matrices, presenting an overall accuracy of ≈99% and a detection limit of 0.5 CFU/25 g or mL of food sample.

Concentration of Listeria monocytogenes in skim milk and soft cheese through microplate immunocapture

Microplate immunocapture is an inexpensive method for the concentration of foodborne pathogens using an antibody-coated microplate. The objective of this study was to determine the efficacy of microplate immunocapture as an alternative to traditional enrichment for concentrating Listeria monocytogenes to levels detectable with selective plating or real-time PCR. L. monocytogenes isolates serologically characterized as Type 1 (1/2a) and Type 4 (untypeable) were grown overnight and diluted to 100 to 106 colony-forming units (CFU)/mL. The isolates were used to optimize microplate immunocapture in tryptic soy broth with 0.6% yeast extract (TSBYE), skim milk, and queso fresco samples. Following microplate immunocapture, the bacteria were streaked onto polymyxin-acriflavine-LiCl-ceftazidime-aesculin-mannitol (PALCAM) agar, followed by incubation at 37 °C for 24 ± 2 h. The bacteria also underwent real-time polymerase chain reaction (PCR). The optimized microplate immunocapture method was tested in triplicate for its ability to capture L. monocytogenes in broth and food samples. Overall recovery rates for L. monocytogenes in food samples at cell populations of 100, 102, and 104 CFU/25 g using microplate immunocapture with real-time PCR were 88.9%, 94.4%, and 100%, respectively. Recovery in these matrices using microplate immunocapture with selective plating was comparatively lower, at 0%, 44.4%, and 100%, respectively. Conventional culture method showed 100% detection at each inoculation level. Microplate immunocapture combined with real-time PCR shows high potential to reduce the time required for detection, with concentration of L. monocytogenes to detectable levels within 1–4 h. The incorporation of a short enrichment step may improve recovery rates at low cell levels.

Optimization of a Viability PCR Method for the Detection of Listeria monocytogenes in Food Samples.

Rapid detection of Listeria and other microbial pathogens in food is an essential part of quality control and it is critical for ensuring the safety of consumers. Culture-based methods for detecting foodborne pathogens are time-consuming, laborious and cannot detect viable but non-culturable microorganism, whereas viability PCR methodology provides quick results; it is able to detect viable but non-culturable cells, and allows for easier handling of large amount of samples. Although the most critical point to use viability PCR technique is achieving the complete exclusion of dead cell amplification signals, many improvements are being introduced to overcome this. In the present work, the yield of dead cell DNA neutralization was enhanced by incorporating two new sample treatment strategies: tube change combined with a double light treatment. This procedure was successfully tested using artificially contaminated food samples, showing improved neutralization of dead cell DNA.

Rapid and sensitive detection of viable Listeria monocytogenes in food products by a filtration-based protocol and qPCR

Listeria monocytogenes continues to be one of the most important foodborne pathogens worldwide, either due to its incidence and/or to its high mortality rate. In the present study, a filtration-based protocol was applied for the screening of viable bacteria. Additionally, a complete method (enrichment, filtration, DNA extraction and real-time PCR detection) was evaluated in order to determine the capacity of this protocol to detect viable L. monocytogenes in food samples. A new multiplex qPCR detection system was designed, including an internal amplification control, both targets were detected with hydrolysis probes. It was demonstrated that the method could reliably detect this pathogen, reaching a limit of detection of 9.5 cfu/25 g. The evaluation of the relative sensitivity, specificity, accuracy, positive and negative predictive values, as well as the index kappa of concordance obtained values higher than 90.0% after 24 h sample enrichment. Furthermore, it was demonstrated that with a secondary enrichment step, the limit of the detection could be further decreased to 4.6 cfu/25 g without significantly affecting the performance parameters. The present study demonstrates the reliability of the proposed methodology for the detection of viable L. monocytogenes, and the possibility of its direct implementation for routine analyses in the food industry.

Actuation of chitosan-aptamer nanobrush borders for pathogen sensing.

We demonstrate a sensing mechanism for rapid detection of Listeria monocytogenes in food samples using the actuation of chitosan-aptamer nanobrush borders. The bio-inspired soft material and sensing strategy mimic natural symbiotic systems, where low levels of bacteria are selectively captured from complex matrices. To engineer this biomimetic system, we first develop reduced graphene oxide/nanoplatinum (rGO-nPt) electrodes, and characterize the fundamental electrochemical behavior in the presence and absence of chitosan nanobrushes during actuation (pH-stimulated osmotic swelling). We then characterize the electrochemical behavior of the nanobrush when receptors (antibodies or DNA aptamers) are conjugated to the surface. Finally, we test various techniques to determine the most efficient capture strategy based on nanobrush actuation, and then apply the biosensors in a food product. Maximum cell capture occurs when aptamers conjugated to the nanobrush bind cells in the extended conformation (pH < 6), followed by impedance measurement in the collapsed nanobrush conformation (pH > 6). The aptamer-nanobrush hybrid material was more efficient than the antibody-nanobrush material, which was likely due to the relatively high adsorption capacity for aptamers. The biomimetic material was used to develop a rapid test (17 min) for selectively detecting L. monocytogenes at concentrations ranging from 9 to 107 CFU mL-1 with no pre-concentration, and in the presence of other Gram-positive cells (Listeria innocua and Staphylococcus aureus). Use of this bio-inspired material is among the most efficient for L. monocytogenes sensing to date, and does not require sample pretreatment, making nanobrush borders a promising new material for rapid pathogen detection in food.

Detection of Listeria monocytogenes based on combined aptamers magnetic capture and loop-mediated isothermal amplification

Rapid detection of Listeria monocytogenes (L. monocytogenes) is important to ensure timely treatment and to prevent outbreaks of listeriosis. Here, we reported an efficient and accurate system using aptamers magnetic capture and loop-mediated isothermal amplification (AMC-LAMP) for sensitive detection of L. monocytogenes. A set of combined aptamers (including four individual aptamers with high binding affinity to L. monocytogenes) was conjugated to magnetic beads, used for capture L. monocytogenes. After incubation at room temperature for 45 min, the captured L. monocytogenes cells were directly used for DNA extraction (1 h). Subsequently, the LAMP assays were carried out at 63 °C for 40 min, and the amplification products were visualized via SYBR Green® I staining. The AMC-LAMP had a detection limit of 5 CFU/mL, and the total assay time was approximate 3 h. By the protocols developed in this study, 17 food samples was test for L. monocytogenes without prior culture enrichment. The accuracy of AMC-LAMP was shown to be 100% when compared with culture-biotechnical examination, while PCR failed to detect L. monocytogenes in one of five positive samples. These results indicate the developed AMC-LAMP is a potential useful method for rapid screening and on-site detection of L. monocytogenes in food samples.

A 3-year multi-food study of the presence and persistence of Listeria monocytogenes in 54 small food businesses in Ireland

The problem of assessing the occurrence of the food-borne pathogen Listeria monocytogenes in the food chain, and therefore the risk of exposure of the human population, is often challenging because of the limited scope of some studies. In this study the occurrence of L. monocytogenes in food from four major food groups, dairy products, meats, seafood and vegetables, and associated food processing environments in Ireland was studied over a three-year period. Fifty-four small food businesses participated in the study and sent both food and environmental samples every 2months between 2013 and 2015. L. monocytogenes was isolated using the ISO11290 standard method. Confirmation of L. monocytogenes and identification of serogroups were achieved using a multiplex PCR assay, and for some isolates serotype was determined using commercial antisera. Pulsed- field gel electrophoresis (PFGE) analysis was performed on all isolates allowing the relatedness of isolates from different food businesses to be compared nationwide. In total, 86 distinct pulsotypes were identified. The overall occurrence of L. monocytogenes in food samples was 4.2%, while in environmental samples it was 3.8%. In general, the occurrence of L. monocytogenes in food businesses decreased over the course of the study, presumably reflecting increased awareness and vigilance. The majority of the pulsotypes detected were unique to a particular food group (63/86), while only three pulsotypes were found in all four food groups investigated. The highest occurrence in food was found in the meat category (7.5%) while seafood had the lowest rate of occurrence (1.8%). Seventeen of the pulsotypes detected in the study were persistent, where persistence was defined as repeated isolation from a single facility with a minimum time interval of 6months. Using PFGE, 11 of the pulsotypes identified in this study were indistinguishable from those of 11 clinical isolates obtained from patients in Ireland over the last 4years, highlighting the fact that these pulsotypes are capable of causing disease. Overall, the study shows the diversity of L. monocytogenes strains in the Irish food chain and highlights the ability of many of these strains to persist in food processing environments. The finding that a significant proportion of these pulsotypes are also found in clinical settings highlights the need for continued vigilance by food producers, including frequent sampling and typing of isolates detected.

Establishment and Application of a Visual DNA Microarray for the Detection of Food-borne Pathogens.

The accurate detection and identification of food-borne pathogenic microorganisms is critical for food safety nowadays. In the present work, a visual DNA microarray was established and applied to detect pathogens commonly found in food, including Salmonella enterica, Shigella flexneri, E. coli O157:H7 and Listeria monocytogenes in food samples. Multiplex PCR (mPCR) was employed to simultaneously amplify specific gene fragments, fimY for Salmonella, ipaH for Shigella, iap for L. monocytogenes and ECs2841 for E. coli O157:H7, respectively. Biotinylated PCR amplicons annealed to the microarray probes were then reacted with a streptavidin-alkaline phosphatase conjugate and nitro blue tetrazolium/5-bromo-4-chloro-3'-indolylphosphate, p-toluidine salt (NBT/BCIP); the positive results were easily visualized as blue dots formatted on the microarray surface. The performance of a DNA microarray was tested against 14 representative collection strains and mock-contamination food samples. The combination of mPCR and a visual micro-plate chip specifically and sensitively detected Salmonella enterica, Shigella flexneri, E. coli O157:H7 and Listeria monocytogenes in standard strains and food matrices with a sensitivity of ∼10(2) CFU/mL of bacterial culture. Thus, the developed method is advantageous because of its high throughput, cost-effectiveness and ease of use.

Multi-Province Listeriosis Outbreak Linked to Contaminated Deli Meat Consumed Primarily in Institutional Settings, Canada, 2008.

A multi-province outbreak of listeriosis occurred in Canada from June to November 2008. Fifty-seven persons were infected with 1 of 3 similar outbreak strains defined by pulsed-field gel electrophoresis, and 24 (42%) individuals died. Forty-one (72%) of 57 individuals were residents of long-term care facilities or hospital inpatients during their exposure period. Descriptive epidemiology, product traceback, and detection of the outbreak strains of Listeria monocytogenes in food samples and the plant environment confirmed delicatessen meat manufactured by one establishment and purchased primarily by institutions was the source of the outbreak. The food safety investigation identified a plant environment conducive to the introduction and proliferation of L. monocytogenes and persistently contaminated with Listeria spp. This outbreak demonstrated the need for improved listeriosis surveillance, strict control of L. monocytogenes in establishments producing ready-to-eat foods, and advice to vulnerable populations and institutions serving these populations regarding which high-risk foods to avoid.

Taq Man Real Time PCR detection of Listeria monocytogenes: A study of enrichment incubation time affecting sensitivity in experimental dry fermented sausages

Listeria monocytogenes is a facultative intracellular Gram positive, catalase positive bacterium, ubiquitous in nature and capable of causing listeriosis in humans and animals. Conventional microbiological techniques and modern molecular approaches are currently used for the isolation and detection of Listeria monocytogenes in food samples. The aim of this study was to investigate the influence of enrichment incubation time on the sensitivity of Taq Man Real Time PCR method. For that purpose, dry fermented sausages were artificially inoculated with serial dilutions of L. monocytogenes ATCC 19111. The obtained results indicated that incubation time is an important factor affecting the sensitivity of Real-Time PCR detection. The best results were obtained after 24 h of pre-enrichment, with primers and probe complementary to the listeriolysin (hlyA) gene, when it was possible to detect less than 10 CFU/g of L. monocytogenes.

Gold Nanoparticle-Modified Carbon Electrode Biosensor for the Detection of Listeria monocytogenes

Abstract Conventional detection methods for Listeria monocytogenes contamination in food are time-consuming and expensive, creating a need for a more inexpensive and efficient detection method. The objective of this study was to develop an inexpensive biosensor to detect L. monocytogenes in food samples. Screen-printed carbon electrode (SPCE) strips previously used by diabetic patients for glucose monitoring were modified with gold nanoparticles (AuNPs) and specific antibodies to L. monocytogenes. To facilitate detection L. monocytogenes was amplified by conjugating secondary enzyme-labeled antibodies with AuNPs. This assay has the ability to detect L. monocytogenes at 2 log CFU/g in wild blueberry samples and exhibits significant specificity over other enteric pathogens such as Escherichia coli O157:H7 and Salmonella Typhimurium. These results indicate that modifying the electrodes with AuNPs is crucial in the development and production of SPCE biosensors. The use of this optimized amperometric immuno-bi...