The first detection of Toxoplasma gondii DNA in environmental air samples using gelatine filters, real-time PCR and loop-mediated isothermal (LAMP) assays: qualitative and quantitative analysis

Cognitive Effects of Toxoplasma and CMV Infections: A Cross-Sectional Study of 557 Young Adults Considering Modulation by Sex and Rh Factor

One-third of humanity harbors a lifelong infection with Toxoplasma gondii, and probably about 80% are infected with human cytomegalovirus (CMV). This study aims to delineate the associations between toxoplasmosis and cognitive abilities and compare these to the associations with CMV. We evaluated the cognitive performance of 557 students, who had been examined for Toxoplasma and CMV infections, using intelligence, memory, and psychomotor tests. The results indicated cognitive impairments in seropositive individuals for both pathogens, with variations in cognitive impact related to sex and the Rh factor. Specifically, Toxoplasma infection was associated with lower IQ in men, whereas CMV was predominantly associated with worse performance by women when testing memory and reaction speeds. Analysis of the antibody concentrations indicated that certain Toxoplasma-associated cognitive detrimental effects may wane (impaired intelligence) or worsen (impaired reaction times) over time following infection. The findings imply that the cognitive impairments caused by both neurotropic pathogens are likely due to pathological changes in the brain rather than from direct manipulative action by the parasites.

Detection of chronic toxoplasmosis in the brain of mice using loop-mediated isothermal amplification (LAMP) and conventional PCR

BACKGROUND

Toxoplasma gondii is a common protozoan parasite that infects approximately one-third of the world's population. It is a disease with multiple manifestations. In immunocompetent individuals, symptoms are mild and flu-like, whereas, in immunocompromised patients, it often results in severe morbidity and mortality. Thus, studies for developing a simple, rapid diagnostic tool for early detection of Toxoplasma are emerging. Molecular diagnosis is highly accurate and helpful in congenitally infected and immunocompromised patients. The loop-mediated isothermal amplification (LAMP) technique was invented to improve nucleic acid amplification efficacy in terms of sensitivity and specificity.

AIM OF THE STUDY

The study aimed to validate a LAMP protocol for detecting Toxoplasma DNA in the brain homogenates from mice experimentally infected with Toxoplasma's ME-49 (cyst-forming type II) strain in comparison to PCR.

METHODS

In this study, the target DNA fragment was the Toxoplasma 529-bp, repeated 200-300 copies/genome. The sensitivity of both LAMP and conventional PCR techniques was estimated in brain homogenates in experimental mice at eight weeks post-infection and compared to the histopathology data.

RESULTS

The LAMP reaction showed positive results in 18 of the 26 examined samples of brain homogenates. PCR showed the characteristic 529-bp band in 15 of the 26 examined samples.

CONCLUSION

The LAMP showed a higher sensitivity over PCR in detecting Toxoplasma infection in brain homogenates of infected mice.

Perspectives on Sampling and New Generation Sequencing Methods for Low-Biomass Bioaerosols in Atmospheric Environments

Bioaerosols play essential roles in the atmospheric environment and can affect human health. With a few exceptions (e.g., farm or rainforest environments), bioaerosol samples from wide-ranging environments typically have a low biomass, including bioaerosols from indoor environments (e.g., residential homes, offices, or hospitals), outdoor environments (e.g., urban or rural air). Some specialized environments (e.g., clean rooms, the Earth's upper atmosphere, or the international space station) have an ultra-low-biomass. This review discusses the primary sources of bioaerosols and influencing factors, the recent advances in air sampling techniques and the new generation sequencing (NGS) methods used for the characterization of low-biomass bioaerosol communities, and challenges in terms of the bias introduced by different air samplers when samples are subjected to NGS analysis with a focus on ultra-low biomass. High-volume filter-based or liquid-based air samplers compatible with NGS analysis are required to improve the bioaerosol detection limits for microorganisms. A thorough understanding of the performance and outcomes of bioaerosol sampling using NGS methods and a robust protocol for aerosol sample treatment for NGS analysis are needed. Advances in NGS techniques and bioinformatic tools will contribute toward the precise high-throughput identification of the taxonomic profiles of bioaerosol communities and the determination of their functional and ecological attributes in the atmospheric environment. In particular, long-read amplicon sequencing, viability PCR, and meta-transcriptomics are promising techniques for discriminating and detecting pathogenic microorganisms that may be active and infectious in bioaerosols and, therefore, pose a threat to human health.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41745-023-00380-x.

A Novel Loop-Mediated Isothermal Amplification Assay for Rapid Detection of Yersinia pestis

Rapid detection of Yersinia pestis, the causative agent of plague, is essential during field investigations to enable prompt control measures for prevention of the spread of the disease. Affordable, efficient, reliable, and simple detection assays are extremely useful, particularly in plague-endemic regions with limited resources. We developed a loop-mediated isothermal amplification (LAMP) assay that detects Y. pestis within 30 min by simply incubating at 65°C on a dry bath heater. The assay targeted the caf1A gene that is situated on the pMT1 plasmid using six specific primers. Y. pestis presence is visually detected based on the color change in the reactions. For comparison of the assay performance, a real-time LAMP with fluorescent dye detection was conducted on a real-time PCR instrument using the same six primers. Sensitivity assessment showed that the limit of detection (LOD) was 0.2 and 0.03 pg when performed on the dry bath heater and on the real-time PCR instrument, respectively. The assay was 100% specific, having no cross-reactivity with closely related Yersinia spp. and other bacterial species. We tested the LAMP assay on field-collected fleas and showed that it successfully detected Y. pestis with identical results to that of a previously published pentaplex real-time PCR assay. These findings suggest that the relatively inexpensive and simpler LAMP assay could be used to support field investigations, yielding comparable results to more expensive and complex PCR assays.

Investigation of Toxoplasma gondii in wastewater and surface water in the Qinghai-Tibet Plateau, China using real-time PCR and multilocus genotyping

Toxoplasma gondii is a protozoan parasite, causing one of the most prevalent parasitic infections in the world. In the present study water sources of the Qinghai-Tibet Plateau (QTP), China, where the hygienic infrastructure is still developing, were investigated. A total of 214 water samples of 10 L volume, were collected from wastewater treatment plants (WWTPs), a slaughterhouse and rivers. The samples were filtered and then analysed using real-time PCR and multilocus genotyping. T. gondii DNA was found in four (1.9%) samples representing T. gondii type I; in one of them T. gondii-like oocysts were also confirmed microscopically. The approximate level of contamination of positive samples ranged between 30 and 2300 T. gondii sporozoites. The results of this study confirmed that T. gondii is present in wastewater in the greater metropolitan area of Xining and a neighbouring county. Contamination of wastewater at this level constitutes rather a moderate source of Toxoplasma infections in humans and animals. It suggests, however, a link between environmental exposure of animals, meat processing facilities and WWTPs. To our knowledge, this is the first investigation describing T. gondii detection in wastewater and environmental water samples collected from the territory of P.R. China using sensitive molecular tools.

Seroprevalence and molecular characterization of Toxoplasma gondii infecting ruminants in the North-West of Egypt

Toxoplasma gondii is a coccidian parasite known for its heavy toll on people and livestock. It can cause abortion and a variety of congenital diseases. The current study aimed to examine some seroprevalence and molecular attributes of T. gondii obtained from ruminants in the North-West of Egypt. Specimens were random selected from five different locations in Alexandria and Matrouh governorates. A total of 483 blood samples, collected from 96 mixed flocks, were screened for anti-T. gondii IgG antibodies using enzyme-linked immunosorbent assay (ELISA). The seropositive results were then confirmed using polymerase chain reaction (PCR) primers for the B1 and P30 genes. Specific PCR products were selected for sequencing and alignment against the GenBank, where phylogeny has been examined using the maximum likelihood, neighbor-joining, and maximum parsimony in MEGA6. ELISA confirmed the presence of T. gondii in 188 of the investigated samples (38.92%), indicating a higher prevalence in camels (64.51%) and sheep (43.75%) as compared to goats (27.93 %) and cattle (13.46%). PCR confirmed the presence of T. gondii-specific sequences in 159 seropositive specimens, with homology between 98.3 and 100%. The genetic distances between the investigated variants ranged from 0.1 to 0.9, and 7 single nucleotide polymorphisms (SNPs), were identified in the examined T. gondii specimens. The camel T. gondii parasite, isolated from Matrouh, showed a 100% homology with the most dangerous reference strains of T. gondii-RH in the GenBank. Our results showed that B1 and P30-specific PCR could detect T. gondii in blood samples more accurately than ELISA. In addition, the statistical analysis of our data indicated that species, age, sex, and animal location were all risk factors for toxoplasmosis. These findings are likely to boost disease control and help contain the spread of T. gondii infections.

Development of a real-time recombinase-aided amplification (RT-RAA) molecular diagnosis assay for sensitive and rapid detection of Toxoplasma gondii

Toxoplasma gondii, a protozoan intracellular parasite, is present in a wide range of hosts, including virtually all species of warm-blooded vertebrates. Toxoplasmosis spreads to humans through a variety of pathways, including contaminated food or water, and close contact with various types of domestic animals. It poses a severe threat to human health, and contributes to important economic losses, not only in cost-of-illness but also in surveillance programs. It is thus necessary to develop a rapid point-of-care field diagnostic technology to control or prevent pathogen transmission to economically important livestock animals, domestic animals, and human beings. In this study, we develop a real-time isothermal amplification method capable of detecting the T. gondii genome in swine and feline blood samples. This method can detect toxoplasma genome with a lowest detection limit of 10² copies of per reaction under optimal reaction conditions of 36 °C for 25 min. The assay displayed advantages in sensitivity and specificity in comparison to traditional real-time PCR, and can be performed in a portable instrument.

Expanding the Known Repertoire of C-Type Lectin Receptors Binding to Toxoplasma gondii Oocysts Using a Modified High-Resolution Immunofluorescence Assay

The environmental stage of the apicomplexan Toxoplasma gondii oocyst is vital to its life cycle but largely understudied. Because oocysts are excreted only by infected felids, their availability for research is limited. We report the adaptation of an agarose-based method to immobilize minute amounts of oocysts to perform immunofluorescence assays. Agarose embedding allows high-resolution confocal microscopy imaging of antibodies binding to the oocyst surface as well as unprecedented imaging of intracellular sporocyst structures with Maclura pomifera agglutinin after on-slide permeabilization of the immobilized oocysts. To identify new possible molecules binding to the oocyst surface, we used this method to screen a library of C-type lectin receptor (CLR)-human IgG constant region fusion proteins from the group of related CLRs called the Dectin-1 cluster against oocysts. In addition to CLEC7A that was previously reported to decorate T. gondii oocysts, we present experimental evidence for specific binding of three additional CLRs to the surface of this stage. We discuss how these CLRs, known to be expressed on neutrophils, dendritic cells, or macrophages, could be involved in the early immune response by the host, such as oocyst antigen uptake in the intestine. In conclusion, we present a modified immunofluorescence assay technique that allows material-saving immunofluorescence microscopy with T. gondii oocysts in a higher resolution than previously published, which allowed us to describe three additional CLRs binding specifically to the oocyst surface.

IMPORTANCE Knowledge of oocyst biology of Toxoplasma gondii is limited, not the least due to its limited availability. We describe a method that permits us to process minute amounts of oocysts for immunofluorescence microscopy without compromising their structural properties. This method allowed us to visualize internal structures of sporocysts by confocal microscopy in unprecedented quality. Moreover, the method can be used as a low- to medium-throughput method to screen for molecules interacting with oocysts, such as antibodies, or compounds causing structural damage to oocysts (i.e., disinfectants). Using this method, we screened a small library of C-type lectin receptors (CLRs) present on certain immune cells and found three CLRs able to decorate the oocyst wall of T. gondii and which were not known before to bind to oocysts. These tools will allow further study into oocyst wall composition and could also provoke experiments regarding immunological recognition of oocysts.

Seroepidemiology and Associated Risk Factors of Toxoplasma gondii in Hemodialysis Patients

PURPOSE

Immunocompromised patients may be at risk for reactivation of the toxoplasmosis infection, because of defection in cell-mediated immunity. Therefore, early diagnosis would be highly desirable in these individuals. This case-control study was designed to increase information about toxoplasmosis in hemodialysis (HD) patients in Guilan province, Iran.

METHODS

The study was performed among 150 patients and 150 controls referred to hospitals of Guilan University of Medical Sciences during 2018-2019. Questionnaire forms, including demographic and epidemiological information, were completed. Peripheral blood samples were taken for serum separation and were collected into tubes and then kept at - 20 °C until use. IgG and IgM antibodies to Toxoplasma gondii were detected by a commercial ELISA kit. Accordingly, IgG absorbance levels < 9 were considered negative, 9-11 was considered borderline, and > 11 was positive; IgM absorbance levels < 0.9 were considered negative, 0.9-1.1 was assumed to be borderline, and > 1.1 was positive.

RESULTS

Throughout the study, 72.0% of HD patients and 64.7% of the control group were positive for anti-Toxoplasma IgG antibody subsequently. 2% of HD patients and 0.7% of the control group were positive for anti-Toxoplasma IgM antibody and these difference weren't significant between control and ones with HD (P > 0.05). There was no significant difference between dialysis duration factor and the seropositivity rate. Seroprevalence of T. gondii infection did not vary significantly with age, educational level, residence and presence of a cat at home. On the contrary, seroprevalence varied significantly with gender and consumption of raw vegetables.

CONCLUSION

Because of the high percentage of positivity for Toxoplasma IgG antibodies in hemodialysis patients, we suggest a periodically screening program to carry out for monitoring and evaluating the possible dissemination of toxoplasmosis during hemodialysis.

Toxoplasma gondii in vegetables from fields and farm storage facilities in the Czech Republic

Infection with Toxoplasma gondii has usually been connected with consumption of improperly treated meat. However, contaminated water and products of plant origin have emerged as new sources of infection in the last few years. Here, 292 vegetable samples-carrot, cucumber and lettuce-obtained from nine farms in the Czech Republic were examined using triplex real time PCR targeting two specific T. gondii sequences. Irrigation water and water used for washing of vegetables were also included. Overall, a positivity rate of 9.6% was found in vegetables. The concentration varied between 1.31 × 100 and 9.00 × 102 oocysts/g of sample. A significant difference was found between the positivity of vegetables collected directly from fields and that of vegetables collected from farm storage rooms (4.4-8.6% vs 10-24.1%, respectively). All samples of irrigation water and water used to rinse vegetables were negative. Genotyping based on restriction fragment length polymorphism (RFLP) analysis using seven markers revealed the exclusive presence of genotype II.

Toxoplasmosis in Germany

BACKGROUND

With approximately 30% of the world population infected, Toxoplasma gondii is one of the most widespread pathogenic parasites in both humans and animals and a major problem for health economics in many countries.

METHODS

This review is based on the findings of individual studies, meta-analyses, and Cochrane Reviews retrieved by a selective literature survey of the Medline and Google Scholar databases.

RESULTS

Current data indicate a high rate of Toxoplasma gondii infection in Germany, ranging from 20% to 77% depending on age (95% confidence interval for 18- to 29-year-olds [17.0; 23.1]; for 70- to 79-year-olds [72.7; 80.5]). Male sex, caring for a cat, and a body mass index of 30 or more are independent risk factors for seroconversion. Postnatally acquired (food-related) infec- tion is predominant, but maternal-to-fetal transmission still plays an important role. While most infections are asymptomatic, congenital toxoplasmosis and reactivated Toxoplasma encephalitis in immunosuppressed persons (transplant recipients and others) are sources of considerable morbidity. Toxoplasma gondii infection of the retina is the most common cause of infectious uveitis in Germany. The diagnosis and treatment of this type of parasitic infection are particular to the specific organs involved in the individual patient.

CONCLUSION

Desirable steps for the near future include development of an effective treatment for the cystic stage and identifica- tion of biomarkers to assess the risk of reactivation and predict the disease course.

Dynamics of Toxoplasma gondii Oocyst Phagocytosis by Macrophages

Oocysts are the environmentally resistant stage of the protozoan parasite Toxoplasma gondii. They are responsible for foodborne infections in humans and animals worldwide. Infectious oocysts contain sporozoites that have to exit the sporocyst and oocyst walls to initiate replication of the parasite within the host tissues. Given their robustness and resistance to chemical degradation, it is still unclear how the oocyst and sporocyst walls release the sporozoites. This process called excystation is thought to occur in the small intestine as a result of the combined action of digestive agents, yet to be identified. By using an oocyst-macrophage co-culture platform, we previously demonstrated in vitro that the excystation of sporozoites and their differentiation into replicative tachyzoites could occur in absence of digestive factors, following phagocytosis by macrophages. Here, we further characterize the dynamics of the oocyst phagocytosis at the single-cell level by using optical tweezers and micropipette aspiration techniques. Our results show that the oocyst internalization kinetics can vary among a given population of macrophages, but similar processes and dynamics could be observed. Most of the cells manipulate oocysts for ~15 min before internalizing them in typically 30 min. This process mainly involves the actin cytoskeleton of the macrophages. Liberated sporozoites within macrophages then differentiate into tachyzoites within 4-6 h following oocyst-macrophage contact. Tachyzoites appear to develop better in macrophages challenged with free sporocysts or sporozoites than with whole oocysts, suggesting that opening of the oocyst wall is one of the most limiting steps for sporozoite excystation completion.

First molecular detection of Toxoplasma gondii in vegetable samples in China using qualitative, quantitative real-time PCR and multilocus genotyping

Toxoplasma gondii infection is becoming increasing problem in China but there is no data concerning contamination of vegetables intended for consumption with this parasite. The aim of the present study was to investigate fresh vegetables originated from open markets located in the Xining City, the Qinghai-Tibet Plateau (QTP), P.R. China for their contamination with T. gondii. A total of 279 fresh vegetable samples were collected and analysed using real-time PCR assay targeting B1 gene and multilocus genotyping. T. gondii DNA was found in 10 (3.6%) samples tested; eight of them represented T. gondii type I and remaining two T. gondii type II. The approximate level of contamination of positive vegetables samples, estimated based on quantitative real-time PCR (qPCR), ranged between less than one and 27000 T. gondii oocysts per sample, with majority not exceeding several oocysts per sample. The results of the study confirmed that T. gondii is present in vegetables offered in open markets in the Qinghai province, P.R. China; eating them unwashed and raw may therefore pose a threat to consumers. This is the first investigation describing T. gondii detection in fresh vegetables intended for consumption collected from the territory of P.R. China using sensitive molecular tools.

Development and comparative evaluation of different LAMP and PCR assays for coprological diagnosis of feline tritrichomonosis

The protozoan parasite Tritrichomonas foetus may cause severe diarrhea in cats all over the world. In order to evaluate the methodology in coprological molecular diagnosis of feline tritrichomonosis, we compared previously published ("old") and newly developed ("novel") loop-mediated isothermal amplification (LAMP) (targeted to the T. foetus β-tubulin and the elf1α 1 gene, respectively) as well as an old conventional and an old and novel real-time PCR (all targeted to overlapping regions of T. foetus rDNA) assays regarding their diagnostic sensitivities and specificities. Here, the novel real-time PCR yielded the best methodical performance in that a sensitivity with a detection limit of <0.1 trophozoites (corresponding to ca.<0.13 trophozoites per mg feces) and a maximal specificity for diagnosis of Tritrichomonas spp. was achieved. The other test systems exhibited either an approximately 10-times lower sensitivity (<1 trophozoite corresponding to ca.<1.3 trophozoites per mg feces) (conventional PCR and both LAMP assays) or a lower specificity (old real-time PCR). Conversely, the diagnostic performance assessed with clinical fecal samples from cats demonstrated identical sensitivities (8 of 20 samples tested were positive) for the novel PCR and both LAMP assays. Diagnostic sensitivities were significantly higher than those found for the old real-time (5 positive samples) and conventional PCR (6 positive samples), respectively. Accordingly, our data suggested the novel PCR and both LAMP assays to be well suited molecular tools for direct (i.e. without including an in vitro cultivation step) coprological diagnosis of tritrichomonosis in cats. Interestingly, relative high (novel LAMP, 7 positive samples) to at least moderate (old LAMP, 6 positive samples and 1 sample with equivocal score) diagnostic sensitivities were also achieved by testing clinical samples upon simple visual inspection of colorimetric changes during the LAMP amplification reactions. Accordingly, both LAMP assays may serve as practical molecular tools to perform epidemiological studies on feline (and bovine as well as porcine) tritrichomonosis under simple laboratory conditions.

Exposure to Toxoplasma gondii in the Roma and Non-Roma Inhabitants of Slovakia: A Cross-Sectional Seroprevalence Study

The lifestyle, health and social status of the Roma are generally below the standards characteristic for the non-Roma population. This study aimed to find out the seropositivity to Toxoplasma gondii (T. gondii) in the population of Roma living in segregated settlements and to compare it with the prevalence of antibodies in the non-Roma population from the catchment area of eastern Slovakia. The seroprevalence of antibodies to T. gondii was significantly higher in the Roma group (45.0%) than in non-Roma inhabitants (24.1%). A statistically significant difference was also recorded between the two non-Roma groups in the study, 30.4% of those from the catchment area and 19.7% from the non-catchment area were seropositive. Univariate logistic regression confirmed poverty and higher age to be significant risk factors influencing the seropositivity to T. gondii. Of the clinical symptoms analyzed in the study, only muscle and back pain were associated with seropositivity to T. gondii. The close contact of Roma with an environment contaminated by different infectious agents and the insufficient hygiene, lower level of education, poverty, lack of water and household equipment and high number of domestic animals increase the risk of infectious diseases in the Roma settlements and subsequently the spread of communicable diseases at the national or even international level.