Validation and verification of LAMP, ISO, and VIDAS UP methods for detection of Escherichia coli O157:H7 in different food matrices

Establishment of LAMP-CRISPR/Cas12a for rapid detection of Escherichia coli O157:H7 and one-pot detection

Escherichia coli O157:H7 is a pathogenic serotype of Escherichia coli. Consumption of food contaminated with E. coli O157:H7 could cause a range of diseases. Therefore, it is of great importance to establish rapid and accurate detection methods for E. coli O157:H7 in food. In this study, based on LAMP and combined with the CRISPR/cas12a system, a sensitive and specific rapid detection method for E. coli O157:H7 was established, and One-Pot detection method was also constructed. The sensitivity of this method could stably reach 9.2 × 10° CFU/mL in pure culture, and the whole reaction can be completed within 1 h. In milk, E. coli O157:H7 with an initial contamination of 7.4 × 10° CFU/mL only needed to be cultured for 3 h to be detected. The test results can be judged by the fluorescence curve or by visual observation under a UV lamp, eliminating instrument limitations and One-Pot detection can effectively prevent the problem of false positives. In a word, the LAMP-CRISPR/cas12a system is a highly sensitive and convenient method for detecting E. coli O157:H7.

Visual Loop-Mediated Isothermal Amplification (LAMP) Assay for Rapid On-Site Detection of Escherichia coli O157: H7 in Milk Products

(1) Background: Rapid on-site testing is an effective method for the detection of Escherichia coli O157: H7(E. coli O157: H7) in food ingredients and the environment. (2) Methods: In this study, we developed colorimetric loop-mediated isothermal amplification (LAMP) and immunochromatographic test strips (ICTs) for the rapid and visual detection of E. coli O157: H7. This study designed new specific LAMP primers for E. coli O157: H7 virulence island genes. After the LAMP amplification, the double-stranded DNA target sequence labeled with digoxin and fluorescein isothiocyanate (FITC) at both ends was bound to the anti-digoxin antibody on the gold nanoparticles. Subsequently, it was further bound to the anti-FITC antibody at the T line of the ICTs, forming a positive test result. Hydroxynaphthyl blue dye was directly added to the LAMP amplification product. A blue color indicated positive results, while a purple color indicated negative results. (3) Results: Two visualization methods showed high specificity for the target strains. The visualization tests had sensitivities of 5.7 CFU mL-1, and the detection limit of the Escherichia coli O157: H7 in artificially contaminated milk samples was 5.7 × 102 CFU mL-1, which was consistent with the results of the standard method (LAMP-electrophoresis method) used in commercial inspection. (4) Conclusions: Both methods could be useful in remote and under-resourced areas.

From hazard analysis to risk control using rapid methods in microbiology: A practical approach for the food industry

The prevention of foodborne diseases is one of the main objectives of health authorities. To this effect, analytical techniques to detect and/or quantify the microbiological contamination of foods prior to their release onto the market are required. Management and control of foodborne pathogens have generally been based on conventional detection methodologies, which are not only time-consuming and labor-intensive but also involve high consumable materials costs. However, this management perspective has changed over time given that the food industry requires efficient analytical methods that obtain rapid results. This review covers the historical context of traditional methods and their passage in time through to the latest developments in rapid methods and their implementation in the food sector. Improvements and limitations in the detection of the most relevant pathogens are discussed from a perspective applicable to the current situation in the food industry. Considering efforts that are being done and recent developments, rapid and accurate methods already used in the food industry will be also affordable and portable and offer connectivity in near future, which improves decision-making and safety throughout the food chain.

Rapid and highly sensitive detection of Escherichia coli O157:H7 in food with loop-mediated isothermal amplification coupled to a new bioluminescent assay

Testing for bioluminescent pyrophosphate is a convenient method of DNA detection without complex equipments, but it is insufficiently sensitive and offers no particular time advantage over other rapid detection methods. The shortcomings of the traditional bioluminescent pyrophosphate method have been addressed by using 2-deoxyadenosine-5-(α-thio)-triphosphate (dATPαS) instead of dATP for LAMP, thus reducing the high background signal and generating a constant background value. In this study, LAMP coupled to a novel bioluminescent pyrophosphate assay was developed to detect E. coli O157:H7. The new method has a limit of detection of <10 copies/μL or 5 CFU/mL; its sensitivity is higher than that of the conventional LAMP assay. Moreover, a food-borne pathogen can be detected when a single DNA template is included in the LAMP assay, making it 100 times more sensitive than the traditional LAMP method. Three hundred food samples were tested with this assay and the accuracy of detection was verified with a culture method and MALDI Biotyper. The assay only took 90-120 min and detected <10 copies of the pathogen. This method had the advantages of rapidity, sensitivity, and simplicity, so it is very competitive for the rapid and highly sensitive detection of food-borne pathogens.