Validation of a Commercial Loop-Mediated Isothermal Amplification (LAMP) Assay for the Rapid Detection of Anisakis spp. DNA in Processed Fish Products

Rapid and Ultrasensitive Detection of H. aduncum via the RPA-CRISPR/Cas12a Platform

Hysterothylacium aduncum is one of six pathogens responsible for human anisakiasis. Infection with H. aduncum can cause acute abdominal symptoms and allergic reactions and is prone to misdiagnosis in clinical practice. This study aims to enhance the efficiency and accuracy of detecting H. aduncum in food ingredients. We targeted the internal transcribed spacer 1 (ITS 1) regions of Anisakis to develop a visual screening method for detecting H. aduncum using recombinase polymerase amplification (RPA) combined with the CRISPR/Cas12a system. By comparing the ITS 1 region sequences of eight nematode species, we designed specific primers and CRISPR RNA (crRNA). The specificity of RPA primers was screened and evaluated, and the CRISPR system was optimized. We assessed its specificity and sensitivity and performed testing on commercial samples. The results indicated that the alternative primer ADU 1 was the most effective. The final optimized concentrations were 250 nM for Cas12a, 500 nM for crRNA, and 500 nM for ssDNA. The complete test procedure was achievable within 45 min at 37 °C, with a limit of detection (LOD) of 1.27 pg/μL. The amplified product could be directly observed using a fluorescence microscope or ultraviolet lamp. Detection results for 15 Anisakis samples were entirely consistent with those obtained via Sanger sequencing, demonstrating the higher efficacy of this method for detecting and identifying H. aduncum. This visual detection method, characterized by simple operation, visual results, high sensitivity, and specificity, meets the requirements for food safety testing and enhances monitoring efficiency.

Recombinase polymerase amplification combined with lateral flow dipstick assay for rapid visual detection of A.simplex (s. s.) and A.pegreffii in sea foods

Anisakiasis is a food-borne parasitic disease mainly caused by the third stage of Anisakis simplex (s. s.) and Anisakis pegreffii. Traditional methods for detecting of Anisakis involve morphology identification such as visual inspection, enzyme digestion, and molecular methods based on PCR, but they have certain limitations. In this study, the internal transcribed spacer 1 (ITS 1) regions of Anisakis were targeted to develop a visual screening method for detecting A. simplex (s. s.) and A. pegreffii in fish meat based on recombinase polymerase amplification (RPA) combined with lateral flow dipstick (LFD). Specific primers and probes were designed and optimized for temperature, reaction time, and detection threshold. LFD produced clear visual results that were easily identifiable after a consistent incubation of 10-20 min at 37 °C. The whole process of DNA amplification by RPA and readout by LFD did not exceed 30 min. In addition, the detection limit is up to 9.5 × 10-4 ng/μL, and the detection of the artificially contaminated samples showed that the developed assay can effectively and specifically detect A. simplex (s. s.) and A. pegreffii, which fully meet the market's requirements for fish food safety supervision.

Agarose Hydrogel-Boosted One-Tube RPA-CRISPR/Cas12a Assay for Robust Point-of-Care Detection of Zoonotic Nematode Anisakis

Rapid and accurate detection of the zoonotic nematode Anisakis is poised to control its epidemic. The clustered regularly interspaced short palindromic repeats (CRISPR)/Cas-associated assay shows great potential in the detection of pathogenic microorganisms. The one-tube method integrated the CRISPR system with the recombinase polymerase amplification (RPA) system to avoid the risk of aerosol pollution; however, it suffers from low sensitivity due to the incompatibility of the two systems and additional manual operations. Therefore, in the present study, the agarose hydrogel boosted one-tube RPA-CRISPR/Cas12a assay was constructed by adding the CRISPR system to the agarose hydrogel, which avoided the initially low amplification efficiency of RPA caused by the cleavage of Cas12a and achieved reaction continuity. The sensitivity was 10-fold higher than that of the one-tube RPA-CRISPR/Cas12a system. This method was used for Anisakis detection within 80 min from the sample to result, achieving point-of-care testing (POCT) through a smartphone and a portable device. This study provided a novel toolbox for POCT with significant application value in preventing Anisakis infection.

Re-evaluation of certain aspects of the EFSA Scientific Opinion of April 2010 on risk assessment of parasites in fishery products, based on new scientific data. Part 1: ToRs1-3

Surveillance data published since 2010, although limited, showed that there is no evidence of zoonotic parasite infection in market quality Atlantic salmon, marine rainbow trout, gilthead seabream, turbot, meagre, Atlantic halibut, common carp and European catfish. No studies were found for greater amberjack, brown trout, African catfish, European eel and pikeperch. Anisakis pegreffii, A. simplex (s. s.) and Cryptocotyle lingua were found in European seabass, Atlantic bluefin tuna and/or cod, and Pseudamphistomum truncatum and Paracoenogonimus ovatus in tench, produced in open offshore cages or flow-through ponds or tanks. It is almost certain that fish produced in closed recirculating aquaculture systems (RAS) or flow-through facilities with filtered water intake and exclusively fed heat-treated feed are free of zoonotic parasites. Since the last EFSA opinion, the UV-press and artificial digestion methods have been developed into ISO standards to detect parasites in fish, while new UV-scanning, optical, molecular and OMICs technologies and methodologies have been developed for the detection, visualisation, isolation and/or identification of zoonotic parasites in fish. Freezing and heating continue to be the most efficient methods to kill parasites in fishery products. High-pressure processing may be suitable for some specific products. Pulsed electric field is a promising technology although further development is needed. Ultrasound treatments were not effective. Traditional dry salting of anchovies successfully inactivated Anisakis. Studies on other traditional processes - air-drying and double salting (brine salting plus dry salting) - suggest that anisakids are successfully inactivated, but more data covering these and other parasites in more fish species and products is required to determine if these processes are always effective. Marinade combinations with anchovies have not effectively inactivated anisakids. Natural products, essential oils and plant extracts, may kill parasites but safety and organoleptic data are lacking. Advanced processing techniques for intelligent gutting and trimming are being developed to remove parasites from fish.

Fast and sensitive differential diagnosis of pseudorabies virus-infected versus pseudorabies virus-vaccinated swine using CRISPR-Cas12a

IMPORTANCE

Pseudorabies virus (PRV) causes high mortality and miscarriage rates in the infected swine, and the eradication policy coupled with large-scale vaccination of live attenuated vaccines has been adopted globally against PRV. Differential diagnosis of the vaccinated and infected swine is highly demanded. Our multienzyme isothermal rapid amplification (MIRA)-Cas12a detection method described in this study can diagnose PRV with a superior sensitivity comparable to the quantitative PCR (qPCR) and a competitive detection speed (only half the time as qPCR needs). The portable feature and the simple procedure of MIRA-Cas12a make it easier to deploy for clinical diagnosis, even in resource-limited settings. The MIRA-Cas12a method would provide immediate and accurate diagnostic information for policymakers to respond promptly.

Fast and User-Friendly Detection of Flatfish Species (Pleuronectes platessa and Solea solea) via Loop-Mediated Isothermal Amplification (LAMP)

The detection of a Cytochrome b gene (cytb) for species differentiation in fish is intensively used. A fast alternative to expensive and time-consuming DNA barcoding is loop-mediated isothermal amplification (LAMP) in combination with efficient readout systems. For this reason, we developed LAMP assays for rapid species detection of Pleuronectes platessa and Solea solea, two economically important flatfish species in Europe that are prone to mislabeling. Species-specific primer sets targeting cytb were designed, and LAMP assays were optimized. With the optimized LAMP assays, we were able to detect up to 0.1 and 0.01 ng of target DNA of P. platessa and S. solea, respectively, and in each case up to 1% (w/w) of target species in mixtures with nontarget species. For future on-site detection, a lateral flow assay and a pocket-sized lab-on-phone assay were used as readout systems. The lab-on-phone assay with the S. solea specific primer set revealed cross-reactivity to Solea senegalensis. The assay targeting P. platessa proved to be highly specific. Both assays could be performed within 45 min and provided rapid and easy detection of fish species.

An update and ecological perspective on certain sentinel helminth endoparasites within the Mediterranean Sea

The Mediterranean Sea is recognized as a marine biodiversity hotspot. This enclosed basin is facing several anthropogenic-driven threats, such as seawater warming, pollution, overfishing, bycatch, intense maritime transport and invasion by alien species. The present review focuses on the diversity and ecology of specific marine trophically transmitted helminth endoparasites (TTHs) of the Mediterranean ecosystems, aiming to elucidate their potential effectiveness as ‘sentinels’ of anthropogenic disturbances in the marine environment. The chosen TTHs comprise cestodes and nematodes sharing complex life cycles, involving organisms from coastal and marine mid/upper-trophic levels as definitive hosts. Anthropogenic disturbances directly impacting the free-living stages of the parasites and their host population demographies can significantly alter the distribution, infection levels and intraspecific genetic variability of these TTHs. Estimating these parameters in TTHs can provide valuable information to assess the stability of marine trophic food webs. Changes in the distribution of particular TTHs species can also serve as indicators of sea temperature variations in the Mediterranean Sea, as well as the bioaccumulation of pollutants. The contribution of the chosen TTHs to monitor anthropogenic-driven changes in the Mediterranean Sea, using their measurable attributes at both spatial and temporal scales, is proposed.

Rapid visual detection of anisakid nematodes using recombinase polymerase amplification and SYBR Green I

Anisakidosis is a food-borne parasitic disease (FBPD) caused by the third-stage larvae of the family Anisakidae. Therefore, it is important to develop a simple, rapid and equipment-free detection method for anisakids in fish samples or seafood since current methods are time-consuming and require complex instruments. In this study, a recombinase polymerase amplification (RPA)-based method was established for the first time to detect anisakids by targeting the internal transcribed spacer (ITS) regions. The detection results were visualized by including SYBR Green I (SG) in the method. The sensitivity of RPA-SG assay was 102 copies per reaction of recombinant plasmid (within 20 min at 37°C), similar to quantitative real-time PCR (qPCR). The assay had high specificity for detecting anisakids against other related parasites and host fish. In addition, the assay was further used to detect fresh marine fish contaminated with anisakids and it showed high precision. These results indicate that the novel RPA-SG assay suitable for visual detection of anisakids in the field and food safety control.

Rapid identification of Takifugu genus using visual loop-mediated isothermal amplification

Some Takifugu species are commonly found in the coastal areas of China, Japan, Thailand, and Korea and cause pufferfish poisoning, which is toxic and even lethal to humans. From 2010 to 2015, there were 430 cases of pufferfish poisoning worldwide, resulting in 52 deaths. Identification of Takifugu species is imperative to reduce financial losses and ensure food safety. Here, visual loop-mediated isothermal amplification (LAMP) was applied to identify Takifugu species. Conserved regions within the mitochondrial DNA among different Takifugu species were selected to design LAMP primers. In 55 min of amplification, sufficient DNA was obtained to observe the results with the naked eye, without the need for complicated instruments. The method was highly specific, with no cross-detection of 17 other fish species, namely, 7 Tetraodontiformes species and 10 commercially important fish. The method showed a detection limit of 0.1 ng Takifugu DNA and was successfully validated to detect Takifugu in cooked fish and the vomitus of poisoned patients. This rapid and visual LAMP method is a useful tool to prevent false labeling, protect consumer rights, and reduce the risk of pufferfish poisoning. PRACTICAL APPLICATION: The loop-mediated isothermal amplification method established in this study can identify cooked or digested fish products containing 1% or more of Takifugu. Therefore, it can be used for the visual detection of Takifugu products and the medical diagnosis of Takifugu poisoning.

Rapid, Sensitive, Specific, and Visual Detection of Salmonella in Retail Meat with Loop-Mediated Isothermal Amplification, Targeting the invA Gene

ABSTRACT

Salmonella is one of the major pathogenic bacteria causing foodborne diseases. The rapid detection of Salmonella in food is of great significance to food safety. In this study, the loop-mediated isothermal amplification (LAMP) method was developed, and primers were designed targeting the invA gene of Salmonella. Standard samples of recombinant invA-plasmid and 100 retail meat samples were tested by LAMP and compared with the results tested by conventional PCR and the routine Chinese National Food Safety Standard-Microbiological Examination of Food-Examination of Salmonella, respectively. The results showed that Salmonella strains of eight different serotypes were amplified successfully by the developed LAMP assay, and it was 1,000-fold more sensitive than conventional PCR, with the analytical sensitivity of 8 × 102 copies per μL of the standard sample of invA-plasmid. The results were visualized directly by adding calcein and MnCl2 in the LAMP reaction tube, and the positively amplified products turned green after an incubation of 2 min. In parallel detection, the positive rate of Salmonella by the LAMP assay was highly correlated with the routine Chinese national standard method. The results of the study demonstrated that the developed LAMP assay is a simple, rapid, strongly specific, highly sensitive, and visual detection method for Salmonella.

HIGHLIGHTS

Intrinsic properties of anisakid nematode larvae as a potential tool for the detection in fish products

Anisakid nematode larvae (NL) in fish products comprise a risk to human health and, if visible, lead to the rejection of these products by consumers. Therefore, great efforts are being made for the identification of these anisakid larvae to estimate the potential consumer health risk as well as to develop effective detection methods in order to prevent the introduction of heavily infected fish products into the market. The tasks of national reference laboratories include the improvement of detection methods and to promote their further development. As a prerequisite for improved detection, it is important to understand the structural properties of anisakid NL and compounds produced during host-parasite interactions. This review provides an overview of the intrinsic properties of anisakid NL and reports the latest detection methods in published literature. First, in order to define the potentially interesting intrinsic properties of anisakid nematodes for their detection, anatomy and compounds involved in host-parasite interactions are summarised. These can be used for various detection approaches, such as in the medical field or for allergen detection in fish products. In addition, fluorescence characteristics and their use as both established and promising candidates for detection methods, especially in the field of optical sensing technologies, are presented. Finally, different detection and identification methods applied by the fish processing industries and by control laboratories are listed. The review intends to highlight trends and provide suggestions for the development of improved detection and identification methods of anisakid NL in fish products.

Negligible risk of zoonotic anisakid nematodes in farmed fish from European mariculture, 2016 to 2018

BackgroundThe increasing demand for raw or undercooked fish products, supplied by both aquaculture and fisheries, raises concerns about the transmission risk to humans of zoonotic fish parasites. This has led to the current European Union (EU) Regulation No 1276/2011 amending Annex III of Regulation (EC) No 853/2004 and mandating a freezing treatment of such products. Zoonotic parasites, particularly anisakid larvae, have been well documented in wild fish. Data on their presence in European aquaculture products, however, are still scarce, except for Atlantic salmon (Salmo salar), where the zoonotic risk was assessed as negligible, exempting it from freezing treatment.AimTo evaluate the zoonotic Anisakidae parasite risk in European farmed marine fish other than Atlantic salmon.MethodsFrom 2016 to 2018 an observational parasitological survey was undertaken on 6,549 farmed fish including 2,753 gilthead seabream (Sparus aurata), 2,761 European seabass (Dicentrarchus labrax) and 1,035 turbot (Scophthalmus maximus) from 14 farms in Italy, Spain and Greece. Furthermore, 200 rainbow trout (Oncorhynchus mykiss) sea-caged in Denmark, as well as 352 seabream and 290 seabass imported in Italy and Spain from other countries were examined. Fish were subjected to visual inspection and candling. Fresh visceral organs/fillet samples were artificially digested or UV pressed and visually examined for zoonotic anisakid larvae.ResultsNo zoonotic parasites were found in any of the fish investigated.ConclusionsThe risk linked to zoonotic Anisakidae in the examined fish species from European mariculture appears negligible. This study laid the groundwork for considerations to amend the current EU regulation.

Development and Application of Novel Chemiluminescence Immunoassays for Highly Sensitive Detection of Anisakis simplex Proteins in Thermally Processed Seafood

The third-stage larvae (L3) of Anisakis simplex are the most important source of hidden allergens in seafood products. However, there exist no commercial methods for detecting Anisakis proteins in food. Furthermore, only a few methods have been validated for the detection of A. simplex in thermally processed food. The aims of our study are (i) the development and validation of high-sensitivity chemiluminescent (CL) immunoassays for the detection of A. simplex proteins in processed seafood, (ii) and A. simplex antigen detection in common seafood products from Polish markets. We developed and validated CL sandwich ELISA (S-ELISA) and CL competitive ELISA (C-ELISA) methods for A. simplex proteins detection in food, with respective detection limits of 0.5 and 5 ng/mL. The usefulness of the assays for detecting A. simplex proteins in highly processed food was evaluated by examination of autoclaved canned fish spiked with A. simplex larvae (1–8 larvae/200 g). Commercial real-time PCR was unable to detect A. simplex in autoclaved samples at all levels of enrichment with Anisakis larvae. CL-S-ELISA was used to test various types of seafood products from Polish markets. Among all tested products (n = 259), 28% were positive. A. simplex antigens were found mostly (n = 39) in smoked fish products: mackerel, herring, cod, and hake. Other positive samples were found in marinated herrings, canned cod livers, canned mackerels, and surimi sticks. In tuna, Atlantic argentine, anchovy, sardine, sprat, and squid products, A. simplex antigens were not detected. This study provides novel effective tools for the detection of A. simplex proteins in processed food and highlights the potential allergic hazards for Anisakis-sensitized Polish consumers of seafood.

Rapid Methods for Assessing Food Safety and Quality

Food safety represents a central issue for the global food chain and a daily concern for all people. Contaminated food by physical, biological or chemical hazards can harm consumers, increasing demand for health services, government expenditure on public health and other social costs. The quality assurance programs are based on the continuous monitoring of raw matter, production process, storage and distribution of the end products, including the purpose for which they are intended. Such programs represent an important objective for food producers, not only for the potential risk to human health, but also for the economic losses to which they can be subjected. The development and use of rapid analytical methods able to identify the main failures in food production can benefit food companies by saving time and costs for the good and fast control of products through the entire food chain.