Ultrafast bacterial cell lysis using a handheld corona treater and loop-mediated isothermal amplification for rapid detection of foodborne pathogens

Colony and bacterial LAMP: Simple alternative methods for bacterial determination

In this study, we developed colony and bacterial LAMP, which directly use bacterial colony and bacterial culture as the templates without DNA extraction for rapid and simple detection of bacteria. The end-point readouts were determined by naked eye under ultraviolet light, and real-time fluorescence curve was also used to confirm that the sensitivity of this method to Salmonella typhimurium and Bacillus cereus was 102 and 103 CFU/reaction, respectively. Results presented here provide alternative methods for colony and bacterial PCR that can greatly contribute to reliable and cost-effective diagnosis in resource-poor settings.

Rapid detection methods for foodborne pathogens based on nucleic acid amplification: Recent advances, remaining challenges, and possible opportunities

This article presents a review of recent advancements in the utilization of NAA-based techniques for detecting foodborne pathogens in food products, focusing on studies conducted within the past five years. This review revealed that recent research efforts have primarily aimed at enhancing sensitivity and specificity by improving sample pre-treatment/preparation, DNA isolation, and readout methods. Isothermal-based amplification methods, such as LAMP, RPA, RAA, and RCA, have emerged as promising approaches, providing rapid results within one h and often demonstrating comparable or superior sensitivity to conventional or qPCR methods. However, the attention paid to specific pathogens varies, with Salmonella spp., Listeria spp., E. coli, and V. parahaemolyticus receiving more focus than norovirus and other similar pathogens. NAA-based methods have the potential to significantly contribute to food safety and public health protection. However, further advancements are necessary to fully realize their benefits.

Chemical Trends in Sample Preparation for Nucleic Acid Amplification Testing (NAAT): A Review

Nucleic acid amplification testing facilitates the detection of disease through specific genomic sequences and is attractive for point-of-need testing (PONT); in particular, the early detection of microorganisms can alert early response systems to protect the public and ecosystems from widespread outbreaks of biological threats, including infectious diseases. Prior to nucleic acid amplification and detection, extensive sample preparation techniques are required to free nucleic acids and extract them from the sample matrix. Sample preparation is critical to maximize the sensitivity and reliability of testing. As the enzymatic amplification reactions can be sensitive to inhibitors from the sample, as well as from chemicals used for lysis and extraction, avoiding inhibition is a significant challenge, particularly when minimising liquid handling steps is also desirable for the translation of the assay to a portable format for PONT. The reagents used in sample preparation for nucleic acid testing, covering lysis and NA extraction (binding, washing, and elution), are reviewed with a focus on their suitability for use in PONT.

Preparation and antimicrobial mechanism of Maillard reaction products derived from ε-polylysine and chitooligosaccharides

Chitooligosaccharides can be combined with amino acids or polypeptide to form Maillard reaction products (MRPs) with the antibacterial characteristics through Maillard reaction. This research aims to clarify the structure, antimicrobial effect and mechanism against Shewanella putrefaciens (S. putrefaciens) of ε-polylysine and chitooligosaccharides Maillard reaction products (LC-MRPs). The results of intrinsic fluorescence (IF) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction, proton nuclear magnetic resonance (¹H NMR) spectra and scanning electron microscope (SEM) indicated Maillard reaction occurred between ε-polylysine and chitooligosaccharides. The observation of confocal laser scanning microscopy (CLSM), SEM and growth curves of S. putrefaciens evidenced that LC-MRPs have the strongest antibacterial effects. The leakage of alkaline phosphatase (AKP) and lactate dehydrogenase (LDH) implied that LC-MRPs sabotaged bacterial barrier (cell wall and cell membrane). The changes in content of nucleic acids, reactive oxygen species (ROS) level, lipid peroxidation content (LPO), succinate dehydrogenase (SDH) activity and adenosine triphosphate (ATP) content showed LC-MRPs will affect bacterial genetic gene transcription, material and energy metabolism. Therefore, the LC-MRPs were effective antibacterial agents to inhibit S. putrefaciens, which will help to preserve food with S. putrefaciens as the main spoilage bacteria.

Influence of Surface Corona Discharge Process on Functional and Antioxidant Properties of Bio-Active Coating Applied onto PLA Films

PLA (polylactic acid) is one of the three major biopolymers available on the market for food packaging, which is both bio-based and biodegradable. However, its performance as a barrier to gases remains too weak to be used for most types of food, particularly oxygen-sensitive foods. A surface treatment, such as coating, is a potential route for improving the barrier properties and/or providing bioactive properties such as antioxidants. Gelatin-based coating is a biodegradable and food-contact-friendly solution for improving PLA properties. The initial adhesion of gelatin to the film is successful, both over time and during production, however, the coating often delaminates. Corona processing (cold air plasma) is a new tool that requires low energy and no solvents or chemicals. It has been recently applied to the food industry to modify surface properties and has the potential to significantly improve gelatin crosslinking. The effect of this process on the functional properties of the coating, and the integrity of the incorporated active compounds were investigated. Two coatings have been studied, a control fish gelatin-glycerol, and an active one containing gallic acid (GA) as a natural antioxidant. Three powers of the corona process were applied on wet coatings. In the test conditions, there were no improvements in the gelatin crosslinking, but the corona did not cause any structural changes. However, when the corona and gallic acid were combined, the oxygen permeability was significantly reduced, while free radical scavenging, reduction, and chelating properties remained unaffected or slightly improved.

Novel integrating polymethylene blue nanoparticles with dumbbell hybridization chain reaction for electrochemical detection of pathogenic bacteria

Pathogenic bacteria infections pose a major threat to human health which can be found in contaminated food and infected humans. Herein, an electrochemical sensor was developed for pathogenic bacteria assay using a dual amplification strategy of polymethylene blue nanoparticles (pMB NPs) and dumbbell hybridization chain reaction (DHCR). The strong binding ability of aptamer to targets endowed outstanding performance in identifying Staphylococcus aureus (S. aureus) among other typical bacteria. The released T strands were hybridized with capture DNA on electrode surface which triggered DHCR in the presence of two dumbbell-shaped helper DNA, leading to the formation of extended and tight dsDNA polymers. In combination with pMB NPs (redox indicators), S. aureus was quantitatively detected in a range of 10-10⁸ CFU/mL and the detection limit reached 1 CFU/mL. Moreover, this sensor was successfully applied for S. aureus detection in human serum and foods, demonstrating the reliability in practical applications.

Nucleic acid extraction without electrical equipment via magnetic nanoparticles in Pasteur pipettes for pathogen detection

The outbreak of COVID-19 makes epidemic prevention and control become a growing global concern. Nucleic acid amplification testing (NAAT) can realize early and rapid detection of targets, thus it is considered as an ideal approach for detecting pathogens of severe acute infectious diseases. Rapid acquisition of high-quality target nucleic acid is the prerequisite to ensure the efficiency and accuracy of NAAT. Herein, we proposed a simple system in which magnetic nanoparticles (MNPs) based nucleic acid extraction was carried out in a plastic Pasteur pipette. Different from traditional approaches, this proposed system could be finished in 15 min without the supports of any electrical instruments. Furthermore, this system was superior to traditional MNPs based extraction methods in the aspects of rapid extraction and enhancing the sensitivity of a NAAT method, accelerated denaturation bubbles mediated strand exchange amplification (ASEA), to the pathogens from various artificial samples. Finally, this Pasteur pipette system was utilized for pathogen detection in actual samples of throat swabs, cervical swabs and gastric mucosa, the diagnosis results of which were identical with that provided by hospital. This rapid, easy-performing and efficiency extraction method ensures the applications of the NAAT in pathogen detection in regions with restricted resources.