A review on inactivation methods of Toxoplasma gondii in foods

Toxoplasmosis is an infection caused by Toxoplasma gondii, a widespread zoonotic protozoan which poses a great threat to human health and economic well-being worldwide. It is usually acquired by ingestion of water contaminated with oocysts from the feces of infected cats or by the ingestion of raw or undercooked foodstuff containing tissue cysts. The oocyst can contaminate irrigation water and fresh edible produce. It is estimated that approximately one-third of the human population worldwide harbor this parasite. Infection with T. gondii is an important cause of diseases of the central nervous system and the eye in immunocompromised and immunocompetent individuals. The purpose of this study was to evaluate the efficacy and applicability of thermal (heating, cooking, freezing and low temperature), non-thermal (high pressure processing, ionizing irradiation and curing) and chemical and biochemical (disinfection, essential oils and biochemical methods such as enzymes, nanoparticles, antibiotics and immune response) treatments for the inactivation, inhabitation or to kill T. gondii in foodstuff intended for public consumption and under experimental conditions.

Simultaneous detection of four protozoan parasites on leafy greens using a novel multiplex PCR assay

Pathogen contamination of fresh produce presents a health risk for consumers; however, the produce industry still lacks adequate tools for simultaneous detection of protozoan parasites. Here, a simple multiplex PCR (mPCR) assay was developed for detection of protozoan (oo)cysts and compared with previously published real-time PCR assays and microscopy methods. The assay was evaluated for simultaneous detection of Cryptosporidium, Giardia, Cyclospora cayetanensis, and Toxoplasma gondii followed by parasite differentiation via either a nested specific PCR or a restriction fragment length polymorphism (RFLP) assay. Spiking experiments using spinach as a model leafy green were performed for assay validation. Leaf-washing yielded higher recoveries and more consistent detection of parasites as compared with stomacher processing. Lowest limits of detection using the nested mPCR assay were 1-10 (oo)cysts/g spinach (in 10 g samples processed), and this method proved more sensitive than qPCR for parasite detection. Microscopy methods were more reliable for visual detection of parasites in lower spiking concentrations, but are more costly and laborious, require additional expertise, and lack molecular confirmation essential for accurate risk assessment. Overall, the nested mPCR assay provides a rapid (<24 h), inexpensive ($10 USD/sample), and simple approach for simultaneous detection of protozoan pathogens on fresh produce.

A novel multiplex real-time PCR for the detection of Echinococcus multilocularis, Toxoplasma gondii, and Cyclospora cayetanensis on berries

Foodborne parasites (FBP) are of major public health importance and warrant appropriate detection and control strategies. Most of the FBP considered for risk-ranking by a panel of experts are potentially transmitted via consumption of contaminated fresh produce, including berries. In this study we focused on the potential of three FBP, namely Echinococcus multilocularis, Toxoplamsa gondii, and Cyclospora cayetanensis, as contaminants of berries. Surveys to assess these parasites as contaminants of fresh produce in general, and berries in particular, are scanty or non-existent mainly due to the lack of optimized laboratory methods for detection. The aim of the present study was to develop and evaluate a novel multiplex qPCR for the simultaneous detection of E. multilocularis, T. gondii, and C. cayetanensis from berry fruits. The efficiency and linearity of each channel in the multiplex qPCR were within the acceptable limits for the range of concentrations tested. Furthermore, the method was shown to have good repeatability (standard deviation ≤0.2 C_q) and intermediate precision (pooled standard deviation of 0.3-0.6 C_q). The limit of detection was estimated to 10 oocysts for Toxoplasma and Cyclospora, and 5 eggs for Echinococcus per 30 g of raspberries or blueberries. In conclusion, evaluation of the present method showed that the newly developed multiplex qPCR is highly specific, precise, and robust method that has potential for application in food-testing laboratories.

Enhancing the Detection of Giardia duodenalis Cysts in Foods by Inertial Microfluidic Separation

The sensitivity and specificity of current Giardia cyst detection methods for foods are largely determined by the effectiveness of the elution, separation, and concentration methods used. The aim of these methods is to produce a final suspension with an adequate concentration of Giardia cysts for detection and a low concentration of interfering food debris. In the present study, a microfluidic device, which makes use of inertial separation, was designed and fabricated for the separation of Giardia cysts. A cyclical pumping platform and protocol was developed to concentrate 10-ml suspensions down to less than 1 ml. Tests involving Giardia duodenalis cysts and 1.90-μm microbeads in pure suspensions demonstrated the specificity of the microfluidic chip for cysts over smaller nonspecific particles. As the suspension cycled through the chip, a large number of beads were removed (70%) and the majority of the cysts were concentrated (82%). Subsequently, the microfluidic inertial separation chip was integrated into a method for the detection of G. duodenalis cysts from lettuce samples. The method greatly reduced the concentration of background debris in the final suspensions (10-fold reduction) in comparison to that obtained by a conventional method. The method also recovered an average of 68.4% of cysts from 25-g lettuce samples and had a limit of detection (LOD) of 38 cysts. While the recovery of cysts by inertial separation was slightly lower, and the LOD slightly higher, than with the conventional method, the sample analysis time was greatly reduced, as there were far fewer background food particles interfering with the detection of cysts by immunofluorescence microscopy.

A high-throughput sequencing assay to comprehensively detect and characterize unicellular eukaryotes and helminths from biological and environmental samples

BACKGROUND

Several of the most devastating human diseases are caused by eukaryotic parasites transmitted by arthropod vectors or through food and water contamination. These pathogens only represent a fraction of all unicellular eukaryotes and helminths that are present in the environment and many uncharacterized organisms might have subtle but pervasive effects on health, including by modifying the microbiome where they reside. Unfortunately, while we have modern molecular tools to characterize bacterial and, to a lesser extent, fungal communities, we lack suitable methods to comprehensively investigate and characterize most unicellular eukaryotes and helminths: the detection of these organisms often relies on microscopy that cannot differentiate related organisms, while molecular assays can only detect the pathogens specifically tested.

RESULTS

Here, we describe a novel sequencing-based assay, akin to bacterial 16S rRNA sequencing, that enables high-throughput detection and characterization of a wide range of unicellular eukaryotes and helminths, including those from taxonomical groups containing all common human parasites. We designed and evaluated taxon-specific PCR primer pairs that selectively amplify all species from eight taxonomical groups (Apicomplexa, Amoeba, Diplomonadida, Kinetoplastida, Parabasalia, Nematoda, Platyhelminthes, and Microsporidia). We then used these primers to screen DNA extracted from clinical, biological, and environmental samples, and after next-generation sequencing, identified both known and previously undescribed organisms from most taxa targeted.

CONCLUSIONS

This novel high-throughput assay enables comprehensive detection and identification of eukaryotic parasites and related organisms, from a wide range of complex biological and environmental samples. This approach can be easily deployed to many settings and will efficiently complement existing methods and provide a holistic perspective on the microbiome.

Progress on the development of rapid diagnostic tests for foodborne neglected zoonotic helminthiases: A systematic review

BACKGROUND

Foodborne Neglected Zoonotic Helminths (FNZH) are parasites of both economic and public health importance. They include Taenia solium, Echinococcus granulosus sensu lato, Echinococcus multilocularis and Foodborne trematodes (FBT). FNZH are earmarked for major interventions for control, elimination and eradication. This systematic review highlights the progress towards development of rapid tests for the diagnosis of FNZH since 2010 when they were listed as neglected tropical diseases.

METHODOLOGY

A systematic search was conducted in three databases, World of Science, Embase and PubMed using the same search phrase. The search produced 480 hits. Three studies from back referencing were included. Only 22 of these met the inclusion criteria. Data was extracted from these and presented qualitatively.

RESULTS

Twenty-five rapid diagnostic tests were found to have been developed since 2010, eight for diagnosis of T. solium infections, eight for echinococcosis and nine for FBT infections. The rapid tests for diagnosing T. solium infections included six antibody detecting and two antigen detecting tests. They constitute a combination among them, with some tests providing qualitative, others quantitative results. Similarly, seven out of the eight rapid tests developed for Echinococcus infections were antibody detecting tests save for one loop mediated isothermal amplification test. All of them were qualitative tests. For FBT infections, nine rapid tests were described; two antibody and one nucleic acid detecting test for diagnosis of Fascioliasis; three nucleic acid detecting tests for Opisthorchiasis; one antibody detecting test for Paragonimiasis; and for Clonorchiasis, one antibody and one nucleic acid detecting test. The FBT infection rapid tests were all qualitative in nature. Most of these tests have not undergone field evaluation in endemic areas where they will be used most.

CONCLUSION

This review describes the development and evaluation of rapid diagnostic tests, while highlighting the need for in depth validations of the tools to determine how well they can perform in endemic areas.

Use of Tunisian flavored olive oil as anisakicidal agent in industrial anchovy marinating process

BACKGROUND

Natural compounds are more frequently used against Anisakis, responsible for the important fish-borne disease anisakidosis. The aim of the study was to evaluate the effectiveness of enriched Tunisian olive oil with different spices (cumin, turmeric, clove, thyme, and lemon) against Anisakis larvae type 1.

RESULTS

In vitro experiment: larvae were submerged separately in the aforementioned oils and then examined to check viability. For each oil, LT50 and LT100 were calculated. Turmeric and cumin oils are the most effective against the parasites; followed by lemon, thyme and clove oils. For the in vivo experiment, turmeric and cumin oils were tested in anchovy fillets previously artificially parasitized with L3 larvae. Cumin was the most effective against parasites (dead after 5 days) compared with turmeric (8 days). For the two oils, the resulting odor was pleasant, as was the taste, while changes in color were much more evident in turmeric fillets.

CONCLUSION

All the flavored oils demonstrated a good nematodical action against Anisakis. Cumin oil was the most effective against encysted larvae. Turmeric oil showed the best activity in the in vitro experiment. The use of flavored oils in the marinating process could represent an efficient strategy to devitalize Anisakis. © 2017 Society of Chemical Industry.

Development and application of loop-mediated isothermal amplification assays based on ITS-1 for rapid detection of Toxoplasma gondii in pork

The loop-mediated isothermal amplification (LAMP) assay is a novel method that rapidly amplifies DNA with high specificity and sensitivity under isothermal conditions. In this study, we established a LAMP assay with six primers targeting a highly conserved region of Toxoplasma gondii ITS-1 sequence. The amplification protocol completes within 30 min under isothermal condition in a 65°C water bath while specificity tests confirmed no cross-reactivity with DNA templates of Neospora caninum, Eimeria tenella, Cryptosporidium parvum, Listeria monocytogenes and Streptococcus suis. The detection limit of the LAMP assay was 0.9 fg T. gondii genomic DNA, a sensitivity that was 10-fold higher than that of a conventional PCR assay. Both LAMP assay and conventional PCR were applied to detect T. gondii genomic DNA in 118 diaphragm samples obtained from pig farms in Zhejiang Province, China. Our results showed that the LAMP assay is more sensitive than conventional PCR (13.56% and 9.32%). The LAMP assay established in this study provides a simple, specific, sensitive and rapid method of T. gondii genomic DNA detection, hence is expected to plays an important role in the monitoring of T. gondii contamination in various food products.

Detection of Adult Beetles Inside the Stored Wheat Mass Based on Their Acoustic Emissions

The efficacy of bioacoustics in detecting the presence of adult beetles inside the grain mass was evaluated in the laboratory. A piezoelectric sensor and a portable acoustic emission amplifier connected with a computer were used. Adults of the most common beetle pests of stored wheat have been detected in varying population densities (0.1, 0.5, 1, and 2 adults per kilogram of wheat). The verification of the presence of the insect individuals was achieved through automated signal parameterization and classification. We tried out two different ways to detect impulses: 1) by applying a Hilbert transform on the audio recording and 2) by subtracting a noise estimation of the recording from the spectral content of the recording, thus allowing the frequency content of possible impulses to emerge. Prediction for infestation was rated falsely negative in 60-74%, 48-60%, 0-28%, and 0-4% of the cases when actual population density was 0.1, 0.5, 1, and 2 adults per kilogram, respectively, irrespective of pest species. No significant differences were recorded in positive predictions among different species in almost all cases. The system was very accurate (72-100%) in detecting 1 or 2 insects per kilogram of hard wheat grain, which is the standard threshold for classifying a grain mass "clean" or "infested." Our findings are discussed on the basis of enhancing the use of bioacoustics in stored-product IPM framework.

A PCR procedure for the detection of Giardia intestinalis cysts and Escherichia coli in lettuce

Giardia intestinalis is a pathogen associated with foodborne outbreaks and Escherichia coli is commonly used as a marker of faecal contamination. Implementation of routine identification methods of G. intestinalis is difficult for the analysis of vegetables and the microbiological detection of E. coli requires several days. This study proposes a PCR-based assay for the detection of E. coli and G. intestinalis cysts using crude DNA isolated from artificially contaminated lettuce. The G. intestinalis and E. coli PCR assays targeted the β-giardin and uidA genes, respectively, and were 100% specific. Forty lettuces from local markets were analysed by both PCR and light microscopy and no cysts were detected, the calculated detection limit was 20 cysts per gram of lettuce; however, by PCR, E. coli was detected in eight of ten randomly selected samples of lettuce. These data highlight the need to validate procedures for routine quality assurance. These PCR-based assays can be employed as alternative methods for the detection of G. intestinalis and E. coli and have the potential to allow for the automation and simultaneous detection of protozoa and bacterial pathogens in multiple samples. Significance and impact of the study: There are few studies for Giardia intestinalis detection in food because methods for its identification are difficult for routine implementation. Here, we developed a PCR-based method as an alternative to the direct observation of cysts in lettuce by light microscopy. Additionally, Escherichia coli was detected by PCR and the sanitary quality of lettuce was evaluated using molecular and standard microbiological methods. Using PCR, the detection probability of Giardia cysts inoculated onto samples of lettuce was improved compared to light microscopy, with the advantage of easy automation. These methods may be employed to perform timely and affordable detection of foodborne pathogens.

An alternative method to recover Toxoplasma gondii from greenery and fruits

Toxoplasma gondii oocysts are an important form of contamination with a high dispersion in the environment, but their detection is still a challenge. This study evaluated the recovery of oocysts from strawberries and crisphead lettuce. Samples (250 g of strawberries or one head of lettuce) were experimentally inoculated with 10, 10(2), 10(3) and 10(4) T. gondii oocysts, by two separate processes, spot dripping and immersion. Then, 50 g of each sample was washed, filtered through a cellulose ester membrane, and concentrated by centrifugation. Three aliquots were taken for DNA extraction in a direct way, after freeze-thaw (FT) cycles or ultrasound (US), followed by PCR (B22-B23 and Tox4-Tox5 primers). The T. gondii DNA was amplified with the primers B22-B23 in all samples contaminated by dripping and when DNA extraction was carried out after FT or US. These techniques may be useful in epidemiological surveillance in the control of this zoonosis.

Sensitivity of candling as routine method for the detection and recovery of ascaridoids in commercial fish fillets

Ascaridoids are one of the main parasitic hazards in commercial fish. Candling is the current industrial screening method whereby visible ascaridoid larvae are detected on a light table and manually removed. The aim of this study was to assess the sensitivity (Se) and negative predictive value (NPV) of this method. To make targeted recommendations to the fish industry, the Se was calculated per fish part, larval genus, and fish species. All fish parts (n = 615) were first candled, and larvae were collected, followed by enzymatic digestion to recover the remaining larvae. A fish part was considered positive if at least one larva was detected using candling and/or enzymatic digestion, with both methods combined as reference standard. The overall Se of candling was 31% (95% CI 23-41%) and NPV was 87% (95% CI 85-90%). The Se increased with higher numbers of larvae/100 g infected muscle. A low NPV was found for the belly flaps, therefore we either advise the removal or proper freezing of this part. Lastly, the Se and larval recovery was the highest for the darker and larger Pseudoterranova spp. larvae. Due to the low overall efficacy of candling, further assessment of its cost-benefit and impact on consumers' health risk should be conducted.

Ability of near-infrared spectroscopy for non-destructive detection of internal insect infestation in fruits: Meta-analysis of spectral ranges and optical measurement modes

The feasibility of utilizing near-infrared (NIR) spectroscopy has been recently assessed for rapid and non-destructive detection of internal insect infestation in some fruits. Based on the findings, this technology can be used for on/in-line inspection of the fruits in terms of insect infestation if suitable instrument is selected for accurate spectral measurements and system development. The spectral range and optical measurement mode are two of the most important factors which can affect the accuracy of the spectral measurements and detection models. The aim of this study is meta-analysis of these factors' effects on the ability of NIR-based spectroscopy for non-destructive detection of hidden insect infestation in fruits. Eight studies (65 observations) were extracted based on the criteria of this study. Overall, utilizing NIR-based spectroscopy led to 13.98% error (95% CI = 10.69-17.27%) for non-destructive detection of hidden insect infestation in fruits. Spectral ranges of Vis/SWNIR (above 300 up to 1100 nm), NIR (above 780 up to 2500 nm), and Vis/NIR (above 300 up to 2500 nm) showed errors of 21.71% (95% CI = 16.56-26.86%), 13.30% (95% CI = 5.24-21.36%), and 13.65% (95% CI = 5.9-21.4%), respectively. It was noted that wavelengths above 1100 nm (NIR region) are more useful to detect insect infestation in fruit. Results also indicated that optical measurement modes of interactance, reflectance, and transmittance had errors of 6.66% (95% CI = 4.18-9.14%), 15.73% (95% CI = 10.99-20.47%), and 16.04% (95% CI = 7.26-24.82%), respectively. This meta-analysis suggests that utilizing interactance mode for spectra measurement in NIR-based spectroscopy can increase the accuracy of discrimination of insect infested fruits especially when the spectral range of the spectrometer is Vis/SWNIR. Moreover, it should be selected a spectrometer with the wavelength range of NIR or Vis/NIR when using reflectance or transmittance mode is necessary for developing an in/on-line system to detect insect infestation in fruits.

Multi-laboratory validation of a modified real-time PCR assay (Mit1C) for the detection of Cyclospora cayetanensis in fresh produce

Cyclospora cayetanensis is a foodborne protozoan parasite that causes the human diarrheal disease cyclosporiasis. Recently, the US FDA developed a modified real-time PCR method based on a specific mitochondrial target gene (Mit1C) to detect C. cayetanensis in fresh produce. The method was validated by single laboratory validation (SLV) studies in Romaine lettuce, cilantro, and raspberries. The present study aimed to evaluate the performance of the new real-time Mit1C (Mit1C qPCR) method by comparing it with the current BAM Chapter 19b qPCR (18S qPCR) as the reference method for the detection of the protozoan parasite C. cayetanensis in fresh produce in a multi-laboratory validation (MLV) setting with the participation of 13 collaborating laboratories. Each laboratory analyzed twenty-four blind-coded Romaine lettuce DNA test samples that included: two unseeded samples, three samples seeded with five oocysts, and one sample seeded with 200 oocysts in the first round and five unseeded samples, eight samples seeded with five oocysts, and five samples seeded with 200 oocysts in the second round. The overall detection rates across laboratories for Romaine lettuce samples inoculated with 200 and 5 oocysts and un-inoculated samples were 100% (78/78), 69.23% (99/143), and 1.1% (1/91), respectively, for Mit1C qPCR, and 100% (78/78), 61.54% (88/143) and 0% (0/91), respectively, for 18S qPCR. The relative level of detection (RLOD = LOD50, Mit1C/LOD50, 18S) was 0.81 with a 95% confidence interval (0.600, 1.095), which included 1. Thus, Mit1C qPCR and 18S qPCR had statistically similar levels of detection. Mit1C qPCR was highly reproducible as the between-laboratory variance in the test results was nearly zero (0) and showed a high specificity at 98.9%. In conclusion, this study demonstrated that the new, more specific Mit1C qPCR method is an effective alternative analytical tool for detection of C. cayetanensis in fresh produce.

An inexpensive feeding bioassay technique for stored-product insects

ABSTRACT We used the red flour beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae), to compare three feeding bioassay techniques using flour disks. The area (scanner or digital photographs) and mass (sensitive balance) of the same flour disks were measured daily for 1 or 2 wk to assess feeding by insects. The loss in mass and area over 4 h was measured, as some variation over time was noticed in the disks with no insects feeding on them. The gravimetric method correlated well with both measurements of the area for the disks held in a growth chamber: scanner (R2 = 0.96), digital photography (R2 = 0.96). There was also a high correlation (R2 = 0.86) between the disk weight and area scanned at normal lab conditions. There were differences in the percentage of the disks remaining over time depending on the temperature and whether they were weighed or scanned. Measuring the mass of the disks resulted in a relatively larger percent of disk remaining compared with the scanned area. Mass measurements required a sensitive balance, handling of the disks and the insects, and appeared slightly more sensitive to humidity and temperature changes over time. Scanning the disks requires flat bed scanner access but less handling of both insects and disks. Digital photographs could be taken quickly, requiring less equipment, although photographs had to be further processed to determine area Scanning or taking digital photographs of flour disk area was an effective technique for measuring insect feeding.

[(COMPARATIvE EVALUATION OF THE EFFICIENCY OF MANUAL AND AUTOMATIC SCANNING MICROSCOPY IN THE PARASITOLOGICAL STUDIES OF FOODSTUFFS)]

The paper gives the results of experimental studies, as well as sanitary parasitological ones investigating meat and fish, which have been performed using manual microscopy and Mecos-C2 automated digital microscopy and scanning micro- scopy. It shows the effectiveness of automated versus manual microscopy in performing parasitological studies of foods and the possibility of rationalizing production labor. The investigation has been conducted to develop the reform of labora- tory services of the healthcare system in the Russian Federation and proposes to introduce a hardware technology into a group of mass methods for parasitological analyses in sanitary-epidemiological, veterinary and environmental areas.

[Comparative analysis of parasite detection methods in vegetables for human consumption]

INTRODUCTION

vegetable contamination is a persistent health problem. The different methods of processing and diagnosis make it difficult to determine the most effective and sensitive technique.

OBJECTIVE

a comparative analysis of parasitological technique sensitivity in vegetable samples.

METHODS

a total of 30 samples were harvested -lettuce (Lactuca sativa), rocket (Eruca sativa) and watercress (Nasturtium officinale)--and later analyzed using Hoffman, Pons, and Janer (HPJ) and Faust (f) techniques. Data were analyzed, using the Bland-Altman test to evaluate the correlation and the Mann-Whitney test to compare the medians.

RESULTS

of the analyzed samples, 46.6% were positive for intestinal parasites; Balantidium coli, accounting for 20% of contamination, Entamoeba coli (21.6) and Entamoeba histolityca (5%), Trichuris trichiura (3.3%) and Strongyloides stercoralis (2.5%) The Bland-Altman test showed significant correlation between the analyzed methods. When evaluating the averages separately, there was significant difference (p = 0.05) among the results.

CONCLUSIONS

this study proved that the HPJ technique was more effective for the detection of eggs, helminth larvae and protozoan cysts in the plants under study.

A review of current statistical methodologies for in-storage sampling and surveillance in the grains industry

Effective, statistically robust sampling and surveillance strategies form an integral component of large agricultural industries such as the grains industry. Intensive in-storage sampling is essential for pest detection, integrated pest management (IPM), to determine grain quality and to satisfy importing nation's biosecurity concerns, while surveillance over broad geographic regions ensures that biosecurity risks can be excluded, monitored, eradicated or contained within an area. In the grains industry, a number of qualitative and quantitative methodologies for surveillance and in-storage sampling have been considered. Primarily, research has focussed on developing statistical methodologies for in-storage sampling strategies concentrating on detection of pest insects within a grain bulk; however, the need for effective and statistically defensible surveillance strategies has also been recognised. Interestingly, although surveillance and in-storage sampling have typically been considered independently, many techniques and concepts are common between the two fields of research. This review aims to consider the development of statistically based in-storage sampling and surveillance strategies and to identify methods that may be useful for both surveillance and in-storage sampling. We discuss the utility of new quantitative and qualitative approaches, such as Bayesian statistics, fault trees and more traditional probabilistic methods and show how these methods may be used in both surveillance and in-storage sampling systems.