Detection of Toxoplasma gondii oocysts in water sample concentrates by real-time PCR

Molecular evidence of Toxoplasma gondii from the tissue and blood of naturally infected sheep

Toxoplasmosis is a cosmopolitan zoonotic infection that has significant effects on public health and causes economic losses in the livestock industry. The current study was designed to detect the Toxoplasma parasite in sheep blood samples and tissue samples of slaughtered sheep at the Sulaimani abattoir using molecular technique. A total of 300 peripheral sheep blood samples were randomly collected from 20 small ruminant flocks at 4 locations in the Sulaymaniyah province, northern Iraq. Also, 150 meat samples from thigh muscle, heart, and diaphragm were collected from slaughtered sheep. All collected blood samples were subjected to polymerase chain reaction (PCR) amplification to confirm Toxoplasma infection; in addition, meat samples were also analyzed for Toxoplasma by PCR following the digestion process. Of the 300 amplified blood samples, 94 were considered positive for Toxoplasma gondii, with a prevalence rate of 31.3%. The overall prevalence of Toxoplasma among meat samples was 34%. The diaphragm reported a higher infection rate (46%) than the heart (32%), while the femoral muscle reported an infection rate of 24%. Aged animals (older than 24 months) presented a higher infection rate (32.8%) than younger animals (28.9%). Contact with or consumption of uncooked meat from infected sheep increases the chance of parasite transmission to humans.

Comparative Evaluation of Re 529-Bp Sequence and B1 Gene in the Detection of Toxoplasma gondii Through PCR in Water Samples of Denizli, Turkey

Purpose

While Toxoplasma gondii (T. gondii) infection is asymptomatic in immunocompetent individuals, it is a life-threatening protozoan in immunocompromised individuals. Its water-borne transmission to humans poses a serious public health concern. Polymerase Chain Reaction (PCR) has a considerable potential for the sensitive and specific detection of T. gondii oocysts in waters.

Methods

Comparative evaluation of RE 529-bp sequence and B1 gene to detect T. gondii tachyzoites and oocysts via PCR in agricultural irrigation water taken from downtown Denizli, Turkey and water samples collected from neighborhood fountains was performed for the first time in Turkish context.

Results

Based on real-time PCR targeting the B1 genetic markers and RE 529-bp sequence, T. gondii DNA was identified in 6 (16.7%) out of 48 samples collected from agricultural irrigation water. Besides, our PCR analysis did not establish any presence of T. gondii in drinking water samples.

Conclusion

T. gondii showed lower sensitivity in B1-based PCR than in PCR targeting RE 529-bp sequence.

Detection of Toxoplasma gondii oocysts on organic and conventionally grown produce

Toxoplasma gondii infection can result in toxoplasmosis and potential psychological effects. Research commonly focuses on infection through contact with cat fecal matter or consumption of contaminated meat. However, T. gondii oocysts can persist in the environment for years and may be present in soils and on soil-grown produce. Rates of oocyst DNA recovery from produce were high, with 18% of vegetable samples testing positive for T. gondii via PCR test and melt curve analysis. Radishes had significantly higher oocyst counts than arugula, collard greens, kale, lettuce, and spinach. There were no significant differences in oocyst detection rates between samples taken from organic farmer's markets and conventional grocery stores. This study demonstrates that these oocysts can transfer to produce grown both conventionally and using organic techniques.

Prevalence, genotypes and risk factors for Toxoplasma gondii contamination in marine bivalve shellfish in offshore waters in eastern China

We conducted a large-scale epidemiological investigation to detect the prevalence of Toxoplasma gondii in four marine bivalve shellfish species collected from six representative coastal regions of Weihai, eastern China. Between January 2018 and December 2018, 14,535 marine bivalve shellfish pooled into 2907 samples were randomly collected and examined for T. gondii DNA by a nested PCR assay targeting B1 gene. The results showed that 2.8% (82) of the 2907 pooled samples were tested positive for T. gondii DNA. Two T. gondii genotype (ToxoDB Genotype #9 and ToxoDB Genotype #1) were identified PCR-restriction fragment length polymorphism analysis. Factors that were found significantly associated with the presence of T. gondii DNA in marine bivalve shellfish included the source of samples (being wild) (odds ratio [OR], 3.34; 95% confidence interval [CI], 2.00-5.84; p < 0.01), surface runoff near the sampling site (OR, 2.64; 95% CI, 1.47-4.72; p < 0.01), and presence of cats near the sampling site (OR, 1.77; 95% CI, 1.02-3.07; p = 0.04). Moreover, the prevalence of T. gondii DNA in marine bivalve shellfish correlated with temperature (Pearson's correlation: R = 0.75, p = 0.0049) and precipitation (R = 0.87, p = 0.00021). These findings provide new insights into the presence of T. gondii DNA in marine bivalve shellfish and highlight the impact of human activity on marine pollution by such an important terrestrial pathogen pollutant.

Molecular Methods for the Detection of Toxoplasma gondii Oocysts in Fresh Produce: An Extensive Review

Human infection with the important zoonotic foodborne pathogen Toxoplasma gondii has been associated with unwashed raw fresh produce consumption. The lack of a standardised detection method limits the estimation of fresh produce as an infection source. To support method development and standardisation, an extensive literature review and a multi-attribute assessment were performed to analyse the key aspects of published methods for the detection of T. gondii oocyst contamination in fresh produce. Seventy-seven published studies were included, with 14 focusing on fresh produce. Information gathered from expert laboratories via an online questionnaire were also included. Our findings show that procedures for oocyst recovery from fresh produce mostly involved sample washing and pelleting of the washing eluate by centrifugation, although washing procedures and buffers varied. DNA extraction procedures including mechanical or thermal shocks were identified as necessary steps to break the robust oocyst wall. The most suitable DNA detection protocols rely on qPCR, mostly targeting the B1 gene or the 529 bp repetitive element. When reported, validation data for the different detection methods were not comparable and none of the methods were supported by an interlaboratory comparative study. The results of this review will pave the way for an ongoing development of a widely applicable standard operating procedure.

Determination of the viability of Toxoplasma gondii oocysts by PCR real-time after treatment with propidium monoazide

This study aimed to investigate a methodology for discriminating viable and non-viable T. gondii oocysts in water. Analyses included two steps: (i) microscopic investigation with vital dyes; (ii) molecular investigation, using a real time PCR (qPCR), after parasite treatment (or not) with propidium monoazide (PMA). The method was called qPCR-PMA. Oocyst aliquots were incubated (15 min) at 25 ºC or 100 ºC and analyzed by microscopy, after trypan blue and neutral red staining. Microscopic investigation determined viable and non-viable oocysts. For the molecular investigation, both aliquots of oocysts were treated with PMA. Non-viable oocysts, after PMA treatment, exhibited an inhibition of DNA amplification by qPCR. Although analyses were carried out with oocysts treated experimentally, these results suggest that qPCR-PMA can be a useful strategy to distinguish viable and non-viable T. gondii oocysts in water safety testing, showing if water is safe to drink.

A rapid and sensitive method to detect Toxoplasma gondii oocysts in soil samples

Documenting the extent of soil contamination by Toxoplasma gondii oocysts is a key issue to prevent the worldwide infection caused by this protozoan. Our aim was to improve the practicability and sensitivity of a low-cost method to detect T. gondii DNA in soil samples developed a few years ago. Various parameters of the reference protocol were modified to determine their effect on the detection of T. gondii DNA in soil samples ("natural soil" and "sand") spiked with oocysts. We tested i) filtration using stomacher bags, ii) Tween 80, Tween 20, SDS and Triton X100 as dispersion solutions, iii) sucrose solution, zinc chloride solution, Optiprep and Percoll as density gradients, iv) freeze/thaw versus mechanical grinding as lysis methods, and v) Qiagen versus Fastprep as extraction kits The optimized protocol is quicker and easier to use than the previous one, and includes the following items: 0.1% Tween80/PBS for dispersion, sucrose solution for flotation, mechanical grinding, and FastDNA spin kit for extraction. It accurately detects T. gondii DNA in both fresh and frozen soil samples and displays a detection limit below 1 oocyst/g of fresh soil.

Comparison of PCR assays to detect Toxoplasma gondii oocysts in green-lipped mussels (Perna canaliculus)

Toxoplasma gondii is recognised as an important pathogen in the marine environment, with oocysts carried to coastal waters in overland runoff. Currently, there are no standardised methods to detect T. gondii directly in seawater to assess the extent of marine ecosystem contamination, but filter-feeding shellfish may serve as biosentinels. A variety of PCR-based methods have been used to confirm presence of T. gondii DNA in marine shellfish; however, systematic investigations comparing molecular methods are scarce. The primary objective of this study was to evaluate analytical sensitivity and specificity of two nested-PCR (nPCR) assays targeting dhps and B1 genes and two real-time (qPCR) assays targeting the B1 gene and a 529-bp repetitive element (rep529), for detection of T. gondii. These assays were subsequently validated for T. gondii detection in green-lipped mussel (Perna canaliculus) haemolymph using oocyst spiking experiments. All assays could reliably detect 50 oocysts spiked into mussel haemolymph. The lowest limit of detection was 5 oocysts using qPCR assays, with the rep529 primers performing best, with good correlation between oocyst concentrations and Cq values, and acceptable efficiency. Assay specificity was evaluated by testing DNA from closely related protozoans, Hammondia hammondi, Neospora caninum, and Sarcocystis spp. Both nPCR assays were specific to T. gondii. Both qPCR assays cross-reacted with Sarcocystis spp. DNA, and the rep529 primers also cross-reacted with N. caninum DNA. These studies suggest that the rep529 qPCR assay may be preferable for future mussel studies, but direct sequencing is required for definitive confirmation of T. gondii DNA detection.

Comparison of sensitivity of two primer sets for the detection of Toxoplasma gondii DNA in wildlife

Toxoplasma gondii, a coccidian parasite known to infect almost all warm-blooded animals, is the cause of one of the most common zoonotic parasitic diseases. The aim of the study is to determine whether the 529 bp fragment or the TGR1E gene is more useful target for PCR identification of T. gondii, for common use. The brains of 221 carnivores and omnivores collected between 2013 and 2015 from north-eastern Poland were examined for the presence of this parasite. The DNA was extracted and then amplified using specific primers. Positive results were obtained in 24% of brain samples using the TGR1E target and 19% using the 529 bp sequence. The results demonstrate that both TGR1E and 529 bp repeat element are suitable for detecting T. gondii DNA in wildlife animals, and the combination of two methods is necessary to obtain reliable results.

Bacterial Degraders of Coexisting Dichloromethane, Benzene, and Toluene, Identified by Stable-Isotope Probing

Most bioremediation studies on volatile organic compounds (VOCs) have focused on a single contaminant or its derived compounds and degraders have been identified under single contaminant conditions. Bioremediation of multiple contaminants remains a challenging issue. To identify a bacterial consortium that degrades multiple VOCs (dichloromethane (DCM), benzene, and toluene), we applied DNA-stable isotope probing. For individual tests, we combined a ¹³C-labeled VOC with other two unlabeled VOCs, and prepared three unlabeled VOCs as a reference. Over 11 days, DNA was periodically extracted from the consortia, and the bacterial community was evaluated by next-generation sequencing of bacterial 16S rRNA gene amplicons. Density gradient fractions of the DNA extracts were amplified by universal bacterial primers for the 16S rRNA gene sequences, and the amplicons were analyzed by terminal restriction fragment length polymorphism (T-RFLP) using restriction enzymes: HhaI and MspI. The T-RFLP fragments were identified by 16S rRNA gene cloning and sequencing. Under all test conditions, the consortia were dominated by Rhodanobacter, Bradyrhizobium/Afipia, Rhizobium, and Hyphomicrobium. DNA derived from Hyphomicrobium and Propioniferax shifted toward heavier fractions under the condition added with ¹³C-DCM and ¹³C-benzene, respectively, compared with the reference, but no shifts were induced by ¹³C-toluene addition. This implies that Hyphomicrobium and Propioniferax were the main DCM and benzene degraders, respectively, under the coexisting condition. The known benzene degrader Pseudomonas sp. was present but not actively involved in the degradation.

Evaluating the presence of Toxoplasma gondii in peripheral blood of patients with diverse forms of uveitis

The purpose of this study was to evaluate the presence of Toxoplasmosis gondii in samples of peripheral blood from patients with varying etiologies of uveitis. Whole blood from patients with different forms of uveitis was tested for the presence of T. gondii using real-time PCR targeting the well-characterized 529 bp fragment. Extracted DNA was both frozen. Thirty-one patients were included in the current study and grouped as follows: acute toxoplasmosis (n = 10); toxoplasmic retinal scars (n = 9); non-infectious etiologies of uveitis (n = 6); and IgG negative for toxoplasmosis (n = 6). In total, only two patients were shown to have circulating T. gondii in peripheral blood; both of these patients were IgG positive for toxoplasmosis, were receiving immunosuppressive therapy for autoimmune uveitis, and had no clinical features of toxoplasmosis. T. gondii was identified in peripheral blood of some immunosuppressed patients. No other patients, including those with acute toxoplasmosis, had circulating parasites in peripheral blood.

Molecular detection of Toxoplasma gondii in water samples from Scotland and a comparison between the 529bp real-time PCR and ITS1 nested PCR

Waterborne transmission of Toxoplasma gondii is a potential public health risk and there are currently no agreed optimised methods for the recovery, processing and detection of T. gondii oocysts in water samples. In this study modified methods of T. gondii oocyst recovery and DNA extraction were applied to 1427 samples collected from 147 public water supplies throughout Scotland. T. gondii DNA was detected, using real time PCR (qPCR) targeting the 529bp repeat element, in 8.79% of interpretable samples (124 out of 1411 samples). The samples which were positive for T. gondii DNA originated from a third of the sampled water sources. The samples which were positive by qPCR and some of the negative samples were reanalysed using ITS1 nested PCR (nPCR) and results compared. The 529bp qPCR was the more sensitive technique and a full analysis of assay performance, by Bayesian analysis using a Markov Chain Monte Carlo method, was completed which demonstrated the efficacy of this method for the detection of T. gondii in water samples.

Physical lysis only (PLO) methods suitable as rapid sample pretreatment for qPCR assay

Quantitative PCR (qPCR) enables rapid and sensitive gene quantification and is widely used in genomics, such as biological, medical, environmental, and food sciences. However, sample pretreatment requires the use of conventional DNA extraction kits which are time-consuming and labor intensive. In this study, we investigated four physical lysis only (PLO) methods which are rapid and could serve as alternatives to conventional DNA extraction kits. These PLO methods are bead mill, heating, sonication, and freeze-thaw. Using ethidium bromide-based assay, their performance was evaluated and compared. The effects of cell debris and its removal were also investigated. Bead mill method without cell debris removal appeared to yield the best qPCR results among the four PLO methods. In addition, bead mill method also performed better than conventional DNA extraction kits. It is probably due to the substantial loss of DNA material during the extensive purification of the conventional DNA extraction kits. The bead mill method has been demonstrated to successfully quantify 10(2) to 10(7) copies of the PAH-RHDα gene of Pseudomonas putida.

Molecules to modeling: Toxoplasma gondii oocysts at the human-animal-environment interface

Environmental transmission of extremely resistant Toxoplasma gondii oocysts has resulted in infection of diverse species around the world, leading to severe disease and deaths in human and animal populations. This review explores T. gondii oocyst shedding, survival, and transmission, emphasizing the importance of linking laboratory and landscape from molecular characterization of oocysts to watershed-level models of oocyst loading and transport in terrestrial and aquatic systems. Building on discipline-specific studies, a One Health approach incorporating tools and perspectives from diverse fields and stakeholders has contributed to an advanced understanding of T. gondii and is addressing transmission at the rapidly changing human-animal-environment interface.

The impact of the waterborne transmission of Toxoplasma gondii and analysis efforts for water detection: an overview and update

The ubiquitous protozoa Toxoplasma gondii is now the subject of renewed interest, due to the spread of oocysts via water causing waterborne outbreaks of toxoplasmosis in different parts of the world. This overview discusses the different methods for detection of Toxoplasma in drinking and environmental water. It includes a combination of conventional and molecular tools for effective oocyst recovery and detection in water sources as well as factors hindering the detection of this parasite and shedding light on a promising new molecular assay for the diagnosis of Toxoplasma in environmental samples. Hopefully, this attempt will facilitate future approaches for better recovery, concentration, and detection of Toxoplasma oocysts in environmental waters.

Detection of multiple waterborne pathogens using microsequencing arrays

AIMS

A microarray was developed to simultaneously detect Cryptosporidium parvum, Cryptosporidium hominis, Enterococcus faecium, Bacillus anthracis and Francisella tularensis in water.

METHODS AND RESULTS

A DNA microarray was designed to contain probes that specifically detected C. parvum, C. hominis, Ent. faecium, B. anthracis and F. tularensis. The microarray was then evaluated with samples containing target and nontarget DNA from near-neighbour micro-organisms, and tap water spiked with multiple organisms. Results demonstrated that the microarray consistently detected Ent. faecium, B. anthracis, F. tularensis and C. parvum when present in samples. Cryptosporidium hominis was only consistently detected through the use of shared probes between C. hominis and C. parvum.

CONCLUSIONS

This study successfully developed and tested a microarray-based assay that can specifically detect faecal indicator bacteria and human pathogens in tap water.

SIGNIFICANCE AND IMPACT OF THE STUDY

The use of indicator organisms has become a practical solution for monitoring for water quality. However, they do not always correlate well with the presence of many microbial pathogens, thus necessitating direct monitoring for most pathogens. This microarray can be used to simultaneously detect multiple organisms in a single sample. More importantly, it can provide occurrence information that may be used in assessing potential exposure risks to waterborne pathogens.

Loop-mediated isothermal amplification (LAMP): early detection of Toxoplasma gondii infection in mice

Background

Toxoplasmosis is a widespread zoonotic parasitic disease that occurs in both animals and humans. Traditional molecular assays are often difficult to perform, especially for the early diagnosis of Toxoplasma gondii infections. Here, we established a novel loop-mediated isothermal amplification targeting the 529 bp repeat element (529 bp-LAMP) to detect T. gondii DNA in blood samples of experimental mice infected with tachyzoites of the RH strain.

Findings

The assay was performed with Bst DNA polymerase at 65°C for 1 h. The detection limit of the 529 bp-LAMP assay was as low as 0.6 fg of T. gondii DNA. The sensitivity of this assay was 100 and 1000 fold higher than that of the LAMP targeting B1 gene (B1-LAMP) and nested PCR targeting 529 bp repeat element (529 bp-nested PCR), respectively. The specificity of the 529 bp-LAMP assay was determined using the DNA samples of Trypanosoma evansi, Plasmodium falciparum, Paragonimus westermani, Schistosoma japonicum, Fasciola hepatica and Angiostrongylus cantonensis. No cross-reactivity with the DNA of any parasites was found. The assay was able to detect T. gondii DNA in all mouse blood samples at one day post infection (dpi).

Conclusions

We report the following findings: (i) The detection limit of the 529 bp-LAMP assay is 0.6 fg of T. gondii DNA; (ii) The assay does not involve any cross-reactivity with the DNA of other parasites; (iii) This is the first report on the application of the LAMP assay for early diagnosis of toxoplasmosis in blood samples from experimentally infected mice. Due to its simplicity, sensitivity and cost-effectiveness for common use, we suggest that this assay should be used as an early diagnostic tool for health control of toxoplasmosis.

Investigation of Toxoplasma gondii presence in farmed shellfish by nested-PCR and real-time PCR fluorescent amplicon generation assay (FLAG)

To evaluate the presence of Toxoplasma gondii in edible farmed shellfish, 1734 shellfish specimens i.e., 109 Crassostrea gigas (6 pools), 660 Mytilus galloprovincialis (22 pools), 804 Tapes decussatus (28 pools) and 161 Tapes philippinarum (6 pools), were collected from the Varano Lagoon (Apulia, Italy). Shellfish from 62 pools were subjected to two molecular techniques: a nested-PCR assay, and a fluorescent amplicon generation (FLAG) real-time PCR assay, both based on the multi-copy B1 target, were performed. One pooled sample of gills from C. gigas and one pooled sample of haemolymphs from T. decussatus were assessed as positive for T. gondii DNA by both techniques. The results demonstrated the presence of T. gondii in edible farmed C. gigas and T. decussatus and indicate that there may be a considerable health threat involved in eating contaminated raw shellfish.

Determining UV inactivation of Toxoplasma gondii oocysts by using cell culture and a mouse bioassay

The effect of UV exposure on Toxoplasma gondii oocysts has not been completely defined for use in water disinfection. This study evaluated UV-irradiated oocysts by three assays: a SCID mouse bioassay, an in vitro T. gondii oocyst plaque (TOP) assay, and a quantitative reverse transcriptase real-time PCR (RT-qPCR) assay. The results from the animal bioassay show that 1- and 3-log(10) inactivation is achieved with 4 mJ/cm(2) UV and 10 mJ/cm(2) low-pressure UV, respectively. TOP assay results, but not RT-qPCR results, correlate well with bioassay results. In conclusion, a 3-log(10) inactivation of T. gondii oocysts is achieved by 10-mJ/cm(2) low-pressure UV, and the in vitro TOP assay is a promising alternative to the mouse bioassay.