Specific, sensitive, and rapid diagnosis of active toxoplasmosis by a loop-mediated isothermal amplification method using blood samples from patients

Trend in serological and molecular diagnostic methods for Toxoplasma gondii infection

BACKGROUND

Toxoplasma gondii, an intracellular parasite, is a significant cause of zoonotic disease, with an estimated one-third of the world's human population believed to be infected. T. gondii is transmitted to humans through the consumption of contaminated water, soil, vegetables, fruits, shellfish or undercooked meat, and can also be passed from human to human through vertical transmission, transplants and blood transfusion. While T. gondii infection typically manifests mild symptoms such as colds among immunocompetent individuals, it can prove lethal for those with weakened immune systems.

METHODS

To summarize the diagnostic methods for Toxoplasma gondii infection, we performed a literature search on PubMed from 1948 to 2023 using the keywords "T. gondii serological diagnosis" or "T. gondii molecular diagnosis".

RESULTS

Rapid and accurate diagnosis of T. gondii infection is imperative. Although a diagnostic kit is currently commercially available, there are a number of disadvantages to the validation principles applied to each diagnostic kit. Consequently, multiple diagnostic methods are concurrently employed to offset these limitations. Serological methods for diagnosing T. gondii infection include the Dye Test (DT), Agglutination Test (AT), Modified Agglutination Test (MAT), Latex Agglutination Test (LAT), Enzyme-Linked Immunosorbent Assay (ELISA), and Western Blot. Meanwhile, molecular methods such as polymerase chain reaction (PCR), nested PCR, real-time PCR, loop-mediated isothermal amplification (LAMP), multiplex PCR, and PCR-restriction fragment length polymorphism (PCR-RFLP) are also utilized. Each of these methods possess its own set of advantages and disadvantages.

CONCLUSIONS

By summarizing the advantages and disadvantages of different diagnostic techniques, it is hoped that the epidemiology, prevention, and control of toxoplasmosis will be improved in the future through the use of appropriate technologies.

Development of a LAMP method with lateral flow DNA chromatography to diagnose toxoplasmosis in immunocompromised patients

BACKGROUND

Rapid and accurate diagnosis of toxoplasmosis is critical, particularly for immunocompromised patients. Several molecular methods could have value for toxoplasmosis diagnosis, but often require sophisticated and expensive equipment, and as such are impractical for use in resource-limited countries. Our study aimed to develop a new rapid diagnostic test for toxoplasmosis that can be used in developed countries as well as low- or middle-income countries.

METHODS

Common primers for conventional loop-mediated isothermal amplification (LAMP) and the new LAMP DNA chromatography method were designed based on a 529-bp repeat present in Toxoplasma gondii genomic DNA. A total of 91 clinical samples from 44 patients suspected of having toxoplasmosis who were treated at several hospitals across Japan were tested using the new LAMP DNA chromatography method, conventional LAMP, and nested PCR and the sensitivity and specificity of the methods was compared.

RESULTS

The LAMP DNA chromatography method showed better sensitivity and specificity (68.2% and 100%, respectively) compared with the nested PCR (45.4% and 100%, respectively) and conventional LAMP (63.6% and 100%, respectively) methods for diagnosis of toxoplasmosis in immunocompromised patients. LAMP DNA chromatography also has better sensitivity and specificity (75% and 100%, respectively) than nested PCR (50.0% and 93.5%, respectively) and conventional LAMP (62.5% and 100%, respectively) to diagnose toxoplasma encephalitis using CSF samples.

CONCLUSION

We developed a LAMP DNA chromatography method to detect T. gondii DNA in clinical samples. This method also successfully detected T. gondii DNA in CSF from patients with toxoplasma encephalitis. This newly developed method can be a valuable rapid diagnostic test for toxoplasmosis in a range of settings, including resource-limited areas like those in low- or middle-income countries.

One-pot, one-step, label-free miRNA detection method based on the structural transition of dumbbell probe

In this study, we present a one-pot, one-step, label-free miRNA detection method through a structural transition of a specially designed dumbbell-shape probe, initiating a rolling circle transition (RCT). In principle, target miRNA binds to right loop of the dumbbell probe (DP), which allows structural change of the DP to circular form, exposing a sequence complementary to the T7 promoter (T7p) previously hidden within the stem. This exposure allows T7 RNA polymerase to initiate RCT, producing a repetitive Mango aptamer sequence. TO1-biotin, fluorescent dye, binds to the aptamer, inducing a detectable enhancement of fluorescence intensity. Without miR-141, the DP stays closed, RCT is prevented, and the fluorescence intensity remains low. By employing this novel strategy, target miRNA was successfully identified with a detection of 73 pM and a dynamic linear range of 0-10 nM. Additionally, the method developed enables one-pot, one-step, and label-free detection of miRNA, demonstrating potential for point-of-care testing (POCT) applications. Furthermore, the practical application of the designed technique was demonstrated by reliably detecting the target miRNA in the human serum sample. We also believe that the conceived approach could be widely used to detect not only miRNAs but also diverse biomolecules by simply replacing the detection probe.

Molecular detection of toxoplasmosis in wild rats using loop-mediated isothermal amplification assay

Background and Aim

Toxoplasmosis is caused by the parasite Toxoplasma gondii. Cats are the only known hosts that excrete resistant oocysts. Wild rats serve as crucial reservoirs and intermediate hosts for T. gondii's survival and dissemination. Consuming soil and water containing oocysts can lead to illness. This study aimed to estimate the prevalence of toxoplasmosis in wild rats through molecular detection as an indicator of environmental contamination in Surabaya.

Materials and Methods

One hundred rats were collected from the three areas (housing, dense settlements, and traditional markets) and distributed into the five zones: West, East, Central, North, and South of Surabaya. Brain tissue samples were extracted using a Geneaid™ (New Taipei City, Taiwan) DNA isolation kit and analyzed through the loop-mediated isothermal amplification (LAMP) method.

Results

The study analyzed brain tissue from 100 wild rats, consisting of 77 Rattus tanezumi and 33 Rattus norvegicus, displaying 30% LAMP positivity. The study revealed that 30% (30/100) of wild rats tested were infected with T. gondii. The molecular prevalence rate in male rats was 32.35% (22/68), compared to females with 25% (8/32). 41.9% of the housing population, 33.3% of traditional markets, and 22.6% of dense settlements had the highest molecular prevalence. The high positive molecular rate at the trapping site can be attributed to cats and dense populations.

Conclusion

Thirty percentage wild rats were tested positive for toxoplasmosis in Surabaya, East Java, Indonesia using LAMP method. Implementing strict control and monitoring is crucial in preventing the transmission of diseases from wild rats to humans. It is necessary to carry out further research related to genetic analysis of T. gondii to determine the type of T. gondii that infects animals and humans in Surabaya through bioassay and molecular test.

Comparison of B1 and RE 529 gene targets by real time PCR and LAMP assay for diagnosis of toxoplasmosis in pregnant females

PURPOSE

The aim of this study is to accurately diagnose the presence of toxoplasmosis in pregnant women. In this study we evaluated two gene targets B1 and RE-529 using two different molecular methods i.e., real-time PCR and LAMP.

PROCEDURE

A total of 150 blood samples were collected from pregnant women attending the PGIMER outpatient clinic. The serum and Buffy layer were extracted and various serological (ELISA) and molecular tests (qPCR and LAMP) targeting B1 and RE-529 were carried out.

FINDING

Out of 150 patients, 32 were seropositive. Amongst which for the RE-529 gene, 18 were LAMP positive and 16 were qPCR positive, while for the B1 gene, 14 were LAMP positive and 13 were qPCR positive.

CONCLUSIONS

Molecular methods were more sensitive than serological tests to diagnose congenital toxoplasmosis in antenatal females. Few seronegative patients were reported positive using molecular methods. In addition, LAMP targeting the RE-529 gene is more sensitive than qPCR, and LAMP targets the B1 gene.

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.

Rapid and Visual Detection of Toxoplasma gondii in Blood Samples from Pet Cats and Dogs by Loop-Mediated Isothermal Amplification

Background: Toxoplasma gondii is an obligate intracellular parasite that invades nearly all nucleated cells of a broad spectrum of vertebrate hosts, and which may cause serious disease in immunocompromised patients, as well as in the immunologically incompetent fetus. This study aimed to establish a loop-mediated isothermal amplification (LAMP) technique to rapidly detect T. gondii in the blood infection by targeting the 529 bp repeat element of T. gondii. Methods: A turbidity monitoring system, together with visual reagent, was used to test the amplification result of the LAMP assay. In addition, the specificity and sensitivity of the LAMP assay were measured. Results: The results suggest that the successfully established LAMP assay profile can detect the DNA of T. gondii at 67°C within 40 min. The limit of detection of the LAMP assay was 10¹ copies/μL. No cross reaction occurred with Plasmodium vivax, Toxocara cati, Clonorchis sinensi, Spirometra mansoni or Cryptosporidium parvum. We validated the developed LAMP assay by detecting T. gondii in DNA extracted from 353 blood samples collected from domestic cats and dogs. The percentages of positive results in detecting these blood samples by LAMP and conventional PCR were 5.38% and 2.83%, respectively. Conclusions: Our findings show that the developed LAMP assay offers higher analytical sensitivity than conventional PCR and good analytical specificity, minimizes aerosol contamination, and can be applied to on-site rapid detection of T. gondii.

Clinical validation of visual LAMP and qLAMP assays for the rapid detection of Toxoplasma gondii

Humans are exposed to Toxoplasma gondii infection as pet cats gradually become family members and represent an increasing public health risk worldwide. Toxoplasmosis diagnosis constitutes an important measure for disease prevention and control. In this study, real-time fluorescence quantitative loop-mediated isothermal amplification (qLAMP) and visual LAMP detection technologies were established to conduct tests of T. gondii based on the membrane DNA extraction method, and the optimal detection mix was determined by adding the protective reagent trehalose and screening the concentrations of Mg²⁺ and dNTPs. Paraffin and lyophilization were used to reduce and even remove aerosol pollution, constructing a detailed anti-contamination protocol. Based on the positive standard plasmid DNA, the LODs of qLAMP and visual LAMP were 92 copies/μL and 92 copies/μL, and the standard curve of qLAMP was Y=2.9503X+20.8992 with R^{2 =} 0.99. The applicability of the qLAMP and visual LAMP assays in disease diagnosis was assessed by evaluating 200 clinical cat faeces samples. The assays showed good diagnostic consistency, with kappa values of 1.0 and 0.99 compared with TaqMan qPCR, respectively. Compared with TaqMan qPCR, the diagnostic specificity/sensitivity of qLAMP and visual LAMP were 100%/100% and 100%/80%, respectively. The qLAMP and visual LAMP assays reported here are rapid and simple tests without extensive sample preparation and have a short turnaround time within 60 min, making them suitable for point-of-care testing.

Seroprevalence and Genetic Characterization of Toxoplasma gondii among Children with Neurodevelopmental Disorders in Egypt

Toxoplasma gondii is a parasite with a special predilection for the central nervous system. Toxoplasmosis's contribution to the triggering of many neurodevelopmental disorders was established. This study aimed to detect the seroprevalence and genotypes of T. gondii strains in children with neurodevelopmental disorders. The study included 180 children with neurodevelopmental disorders and 180 children in the control group. Assessment of seropositivity of Toxoplasma IgM and IgG antibodies in patients and controls was carried out. Genetic characterization of T. gondii was obtained by nested polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) technique targeting dense granule gene (GRA6). Our results showed that the overall seroprevalence of T. gondii antibodies in the patient and controls was 35.6% and 11.7%, respectively. Nested PCR showed positivity in 11.1% of the patient group for T. gondii DNA. T. gondii seropositivity rate was significantly high in patients with hydrocephalus and also in patients with epilepsy. Positive nested PCR was significantly high in children with hydrocephalus only. Genotyping using nested PCR-RFLP showed genotype I (80%) followed by atypical strains (20%) with no association with any specific clinical presentation. In conclusion, among toxoplasmosis-positive children with neurodevelopmental disorders, analysis of T. gondii GRA6 locus revealed the predominance of type I genotype followed by atypical strains.

RPA/CRISPR/Cas12a-Based On-Site and Rapid Nucleic Acid Detection of Toxoplasma gondii in the Environment

Toxoplasma gondii is an opportunistic pathogen widely distributed within the world, poses a huge threat to human health, and causes significant economic losses to the livestock industry. Herein, we developed a portable one-pot detection of T. gondii by combining recombinase polymerase amplification (RPA) and a clustered regularly interspaced short palindromic repeats (CRISPR)/Cas12a system. A glass microfiber filter device used for the first step can efficiently extract T. gondii from low-concentration samples. The lyophilized RPA reagents and Cas12a/crRNA reagents are prestored in one Eppendorf tube, and both reactions can be performed on a low-cost thermal controller (∼37 °C), avoiding the drawbacks of the step-by-step addition of components. The developed RPA/CRISPR/Cas12a system exhibits a high selectivity toward the B1 gene amplicon of T. gondii over other parasites with a limit of detection of 3.3 copies/μL. The visual signal readout can be easily realized by a fluorometer or lateral-flow strip. A portable suitcase containing the minimum equipment and lyophilized reagents was adopted for the rapid determination of T. gondii in heavily polluted landfill leachate. This system presents rapidness, robustness and on-site features for the detection of nucleic acids of the parasite, making it a promising tool for field applications in remote areas.

Molecular diagnosis of toxoplasmosis: recent advances and a look to the future

INTRODUCTION

Toxoplasmosis is a globally distributed parasitic infection that can be particularly severe when opportunistic or congenital. Its diagnosis requires accurate and rapid techniques that rely mainly on serology and molecular methods.

AREAS COVERED

The aim of this review was to discuss the positioning of the molecular diagnosis of toxoplasmosis according to the different clinical situations possibly resulting from infection with T. gondii, and to detail recent developments in this technique. The English and French literature were searched with the following keywords: 'Toxoplasmosis', "Molecular diagnosis" and 'PCR'.

EXPERT OPINION

Molecular techniques have revolutionized the diagnosis of toxoplasmosis, and practices have considerably evolved over the past decades. However, there is still a high degree of inter-laboratory heterogeneity which impairs comparisons between results and studies. Efforts to standardize practices are underway.

Optimization of a Loop-Mediated Isothermal Amplification Assay as a Point-of-Care Tool for the Detection of Wuchereria bancrofti in Human Blood in Tana River Delta, Kenya

INTRODUCTION

Accurate detection of filarial parasites in humans and vectors is essential for the implementation and evaluation of Global and National Programs to eliminate lymphatic filariasis. Immunological methods to detect infection are available; however, cross-reactivity issues have been reported in most of them. Nucleic acid-based molecular assays offer high levels of specificity and sensitivity and can be used to detect the infections.

METHODS

In this study, we evaluated loop-mediated isothermal amplification (LAMP) tests to amplify Wuchereria bancrofti DNA in patients' blood. The amplicons were tested by both pH-sensitive dyes for enhanced visual detection and agarose gel electrophoresis. A closed-tube LAMP assay was also evaluated. Cohen's Kappa statistics was used for statistical analysis of the assays. 125 patients consented for blood sampling which were used for clinical analysis of LAMP assays with the PCR method used as the "gold standard."

RESULTS

The sensitivity of the evaluated Wuchereria bancrofti LAMP was 92.3%, with a specificity of 97.3% and kappa statistics value of 0.84, which is in a strong agreement.

CONCLUSION

In this study, LAMP assays coupled with fluorescence dye detection have been found to be suitable for diagnosis and monitoring of Wuchereria bancrofti infections in the Kenyan population.

One-Day Molecular Detection of Salmonella and Campylobacter in Chicken Meat: A Pilot Study

Salmonella and Campylobacter ssp. are bacterial pathogens responsible for most foodborne infections in EU countries. Poultry serves as a reservoir for these pathogens, and its important role in the meat industry makes it essential to develop a rapid detection assay able to provide results in one day. Indeed, the rapid identification of foodborne pathogens is an important instrument for the monitoring and prevention of epidemic outbreaks. To date, Salmonella and Campylobacter screening is mainly conducted through molecular methods (PCR or real-time PCR) performed after 18–24 h long enrichments. In this study, we evaluated short enrichments (0, 2, 4, and 6 h) combined with a colorimetric loop-mediated isothermal AMPlification (LAMP) or real-time PCR to detect Salmonella and Campylobacter in poultry meat contaminated at different concentration levels (10¹, 10³, and 10⁵ CFU/g). Our results show that real-time PCR allows the detection of Salmonella and Campylobacter, even after shorter enrichment times than prescribed by ISO references; particularly, it detected Salmonella down to 10¹ CFU/g since T0 and Campylobacter from 10³ CFU/g since T0. Detection with LAMP was comparable to real-time PCR without the requirement of a thermal cycler and with shorter execution times. These characteristics make colorimetric LAMP a valid alternative when one-day results are needed, improving the timely identification of positive meat batches, even in the absence of specialized instrumentation.

Detection of Toxoplasma gondii bradyzoite genes in the peripheral blood mononuclear cells among patients with toxoplasmic chorioretinitis

BACKGROUND

Toxoplasmic chorioretinitis may occur as a result of acquired toxoplasmosis or reactivated congenital toxoplasmosis. In this study, Toxoplasma gondii bradyzoite genes along with the B1 gene were evaluated to detect T. gondii DNA in serum and peripheral blood mononuclear cells (PBMCs) of patients with toxoplasmic chorioretinitis.

METHODS

Blood samples were collected from 10 patients (7 cases of active chorioretinal lesions and 3 cases of old chorioretinal scars). The genomic DNA was extracted from the patients' serum and PBMCs and a polymerase chain reaction (PCR) assay was performed using bradyzoite genes along with B1. The subjects were also evaluated in terms of the T. gondii antibodies.

RESULTS

The PCR results were positive in four of seven patients (57.1%) with active ocular toxoplasmosis lesions. In three patients (42.8%), the PCR results were positive for MAG-1 and SAG-4 and in one patient (14.3%) the PCR results were only positive for the B1 gene. The PCR results were positive only in the PBMCs, whereas they were negative in the serum samples. Two patients with positive PCR results showed high Toxoplasma immunoglobulin G (IgG) antibody titres. However, none of the patients showed positive Toxoplasma IgM antibodies.

CONCLUSIONS

The PBMCs are suitable for evaluating toxoplasmic chorioretinitis. The present results showed that PCR with bradyzoite genes is useful in the diagnosis of toxoplasmic chorioretinitis in PBMCs.

The Loop-Mediated Isothermal Amplification Technique in Periodontal Diagnostics: A Systematic Review

The course of periodontal disease is affected by many factors; however, the most significant are the dysbiotic microflora, showing different pathogenicity levels. Rapid colonization in the subgingival environment can radically change the clinical state of the periodontium. This systematic review aims to present an innovative technique of loop-mediated isothermal amplification for rapid panel identification of bacteria in periodontal diseases. The decisive advantage of the loop-mediated isothermal amplification (LAMP) technique in relation to molecular methods based on the identification of nucleic acids (such as polymerase chain reaction (PCR or qPCR) is the ability to determine more pathogens simultaneously, as well as with higher sensitivity. In comparison with classical microbiological seeding techniques, the use of the LAMP method shortens a few days waiting time to a few minutes, reducing the time necessary to identify the species and determine the number of microorganisms. The LAMP technology requires only a small hardware base; hence it is possible to use it in outpatient settings. The developed technique provides the possibility of almost immediate assessment of periodontal status and, above all, risk assessment of complications during the treatment (uncontrolled spread of inflammation), which can certainly be of key importance in clinical work.

Development and validation of a one-step reverse transcription loop-mediated isothermal amplification (RT-LAMP) for rapid detection of ZIKV in patient samples from Brazil

We have previously developed and validated a one-step assay based on reverse transcription loop-mediated isothermal amplification (RT-LAMP) for rapid detection of the Zika virus (ZIKV) from mosquito samples. Patient diagnosis of ZIKV is currently carried out in centralized laboratories using the reverse transcription-quantitative polymerase chain reaction (RT-qPCR), which, while the gold standard molecular method, has several drawbacks for use in remote and low-resource settings, such as high cost and the need of specialized equipment. Point-of-care (POC) diagnostic platforms have the potential to overcome these limitations, especially in low-resource countries where ZIKV is endemic. With this in mind, here we optimized and validated our RT-LAMP assay for rapid detection of ZIKV from patient samples. We found that the assay detected ZIKV from diverse sample types (serum, urine, saliva, and semen) in as little as 20 min, without RNA extraction. The RT-LAMP assay was highly specific and up to 100 times more sensitive than RT-qPCR. We then validated the assay using 100 patient serum samples collected from suspected cases of arbovirus infection in the state of Pernambuco, which was at the epicenter of the last Zika epidemic. Analysis of the results, in comparison to RT-qPCR, found that the ZIKV RT-LAMP assay provided sensitivity of 100%, specificity of 93.75%, and an overall accuracy of 95.00%. Taken together, the RT-LAMP assay provides a straightforward and inexpensive alternative for the diagnosis of ZIKV from patients and has the potential to increase diagnostic capacity in ZIKV-affected areas, particularly in low and middle-income countries.

Loop-mediated isothermal amplification (LAMP) assay for detection of sesame phyllody phytoplasmas in Vietnam

Phloem-limiting phytoplasmas are known to be causal agents of phyllody, which is recognized by the abnormal development of floral structures resulting in serious yield losses in sesame plants. Currently, identification of the various groups of phytoplasmas that cause sesame phyllody (SP) is conducted by nested PCR, RFLP, and multiplex real-time qPCR assays. However, these methods require intensive labor and are costly and time-consuming so can only be undertaken in well-equipped labs. Here, diagnostic loop-mediated isothermal amplification (LAMP)-based assays allowing rapid detection of specific groups of phytoplasmas within 30 min were developed based on detection of the 16S rRNA sequence of phytoplasmas. Universal 16S rRNA phytoplasma primers and seven primer sets of different 16Sr group phytoplasmas (16SrI, 16SrII, 16SrIII, 16SrIV, 16SrV, 16SrX, 16SrXI) and universal plant cytochrome oxidase (cox) gene primers were used to detect 16S rRNA group phytoplasma sequences and the cox gene in sesame plants. The LAMP assays were carried out using a real-time fluorometer with amplification plots and annealing curves visualized directly. Results demonstrated that the 16SrI and 16SrII group phytoplasmas were causal agents of sesame phyllody in Vietnam. LAMP-based assays for in-field detection of sesame phyllody-causing phytoplasmas revealed advantages and potential applicability in comparison with conventional approaches. To the best of our knowledge, this is the first assessment of multiple phytoplasma infection associated with sesame phyllody disease in Vietnam using LAMP-based assays.

A loop-mediated isothermal amplification (LAMP) assay for detection of Toxoplasma gondii infection in women with spontaneous abortion

The present study aimed to use the loop-mediated isothermal amplification (LAMP) technique in comparison with serological tests to determine the rate of T. gondii infection in women suffering from spontaneous abortion (SA). A total of 140 women suffering from their first SA were included in this study. The collected aborted fetal remains and blood samples from each patient were examined in sterilized conditions using the LAMP technique and ELISA. Of the 140 women, 80 (57.1%) tested seropositive for anti-Toxoplasma antibodies by ELISA, 72 (51.4%) women tested seropositive for the IgG antibody, 8 (5.7%) tested seropositive for the IgM antibody. Among the eight women who'd had their first SA who tested seropositive for IgM antibody by ELISA, only five cases (62.5%) reported positively to the LAMP test. The difference in the frequency distribution of the LAMP results for measuring the Toxoplasma infection in pregnant women under study was statistically significant (P < 0.001) from the results of the serological test (ELISA). Although there was a significant difference between age and positivity in the LAMP test (P = 0.017), no significant difference was observed between positivity in the LAMP test and other variables. The findings of the present investigation suggest that LAMP is a preferred method for determining Toxoplasma infection in pregnant women suffering from SA compared with other routine serological tests. Even in a field with limited facilities and equipment, this technique can be effective and efficient in accurately and specifically diagnosing Toxoplasma infections in women at high risk of SA.

Majid R. A Review on the Prevalence of Toxoplasma gondii in Humans and Animals Reported in Malaysia from 2008-2018

Toxoplasmosis is a disease caused by the protozoan parasite Toxoplasma gondii (T. gondii). Human toxoplasmosis seroprevalence in Malaysia has increased since it was first reported in 1973 as shown in previous reviews of 1991 and 2007. However, over a decade since the last review, comprehensive data on toxoplasmosis in Malaysia is lacking. This work aimed at reviewing articles on toxoplasmosis research in Malaysia in order to identify the research gaps, create public awareness, and efforts made so far and proffer management options on the disease. The present review examines the available published research articles from 2008 to 2018 related to toxoplasmosis research conducted in Malaysia. The articles reviewed were retrieved from nine credible databases such as Web of Science, Google Scholar, ScienceDirect, PubMed, Scopus, Springer, Wiley online library, Ovid, and Cochrane using the keywords; Malaysia, toxoplasmosis, Toxoplasma gondii, toxoplasma encephalitis, seroprevalence, human immunodeficiency virus (HIV) patients, pregnant women, genotype strain, anti-toxoplasma antibodies, felines, and vaccine. The data highlighted seropositive cases from healthy community members in Pangkor Island (59.7%) and among migrant workers (57.4%) at alarming rates, as well as 42.5% in pregnant women. Data on animal seroprevalence were limited and there was no information on cats as the definitive host. Genetic characterization of Toxoplasma gondii from HIV patients; pregnant women, and domestic cats is lacking. This present review on toxoplasmosis is beneficial to researchers, health workers, animal health professionals, and policymakers. Therefore, attention is required to educate and enlighten health workers and the general public about the risk factors associated with T. gondii infection in Malaysia.

Challenging TaqMan probe-based real-time PCR and loop-mediated isothermal amplification (LAMP): the two sensitive molecular techniques for the detection of toxoplasmosis, a potentially dangerous opportunistic infection in immunocompromised patients

Due to defects and drawbacks of most conventional diagnostic methods including serology for the diagnosis of toxoplasmosis as a dangerous opportunistic infection in immunocompromised individuals, the accurate, rapid, and sensitive detection of infection in such patients is essential. In this study, the TaqMan probe-based real-time PCR and, a relatively new nucleic acid amplification method, the loop-mediated isothermal amplification (LAMP) technique was compared based on the repetitive elements (RE) sequence to detect Toxoplasma gondii (T. gondii) DNA in blood samples of immunocompromised individuals. During this study, 119 blood samples from immunocompromised cancer patients with renal failure, undergoing dialysis were studied. After DNA extraction from blood samples using the salt extraction method, the molecular techniques of TaqMan probe-based real-time PCR and LAMP were used to investigate the contamination of the samples with T. gondii, based on the 529 bp (RE) sequence of T. gondii. The analytical sensitivity of LAMP and real-time PCR was evaluated by duplicating the five-step serial dilutions of T. gondii tachyzoites from 0.25 to 5×10⁵ spiked tachyzoites per milliliter of the Toxoplasma seronegative blood sample. The extracted DNA from other parasites and human chromosomal DNA were used to determine the specificity of the molecular methods. The obtained results were analyzed using Kappa statistical test and SPSS22 software. Out of 119 studied samples, 7 (5.8%) and 5 (4.2%) samples were positive for Toxoplasma by TaqMan probe-based real-time PCR and LAMP, respectively. The limits of detection of TaqMan probe-based real-time PCR and RE-LAMP in negative serum samples were one and five tachyzoites (CT 38), respectively. Both real-time PCR and LAMP methods were 100% specific for Toxoplasma detection. Positive results were obtained only with T. gondii DNA, while other DNA samples were negative. The TaqMan probe-based real-time PCR based on the RE sequence showed higher sensitivity to T. gondii DNA detection in blood samples of cancer patients and serial dilutions of parasitic tachyzoites. The results show that TaqMan probe-based real-time PRC is a sensitive and specific method for the detection of toxoplasmosis in immunocompromised individuals, as well as the LAMP assay, which can be used as a suitable alternative diagnostic method for the detection of toxoplasmosis in such patients, without need the for any expensive equipment.

Development of a LAMP method for detecting the N75S mutant in SDHI-resistant Corynespora cassiicola

The replacement of asparagine with serine at codon 75 of the sdhC gene (N75S) confers succinate dehydrogenase inhibitor resistance in Corynespora cassiicola, which caused by consecutive fungicide application. To rapidly detect the mutation of N75S, a method based on loop-mediated isothermal amplification (LAMP) was developed in this study. The optimal primer set among the six primer sets designed could clearly identify N75S from the wild-type genotype. The detection threshold of the optimized LAMP mixture (10 μL) was 8.8 fg of target DNA at 63 °C within 60 min. This method specifically showed a color change and ladder-like band only when DNA extracted from isolates containing the N75S mutation was added. The results of stability tests suggested a satisfactory repeatability of this method. Additionally, the assay could positively distinguish N75S mutants from crude DNA isolated from conidia and mycelia of C. cassiicola. Given the high efficiency, sensitivity, specificity, repeatability and simplicity of operation, the LAMP method established here could be useful to evaluate the shift in the sensitivity of C. cassiicola to SDHIs and will provide significant data for the management of Corynespora leaf spot.

Validation of Loop-Mediated Isothermal Amplification (LAMP) Field Tool for Rapid and Sensitive Diagnosis of Contagious Agalactia in Small Ruminants

Simple Summary

Contagious agalactia (CA) is an infectious disease of small ruminants endemic in the Mediterranean countries, causing significant socioeconomic impacts predominantly on small-scale farmers who still subsist on marginal lands. Mycoplasma agalactiae is historically considered the principal etiological agent of CA, especially in sheep. Clinical signs are characterised by mastitis, arthritis, keratoconjunctivitis and occasionally, abortion. Rapid, accurate and cost-effective field tests are urgently needed for effective control of M. agalactiae mastitis. Our study illustrated the validation of a Loop-Mediated Isothermal Amplification (LAMP) test for the detection of M. agalactiae in dairy sheep in order to confirm its application as a diagnostic tool in the field level.

Abstract

Contagious agalactia (CA), an infectious disease of small ruminants, caused by Mycoplasma agalactiae, is responsible for severe losses to dairy sheep production with substantial socioeconomic impacts on small-scale farmers. The diagnosis of CA is still problematic, time-consuming and requires well-equipped labs for confirmation of outbreaks. Therefore, rapid, accurate and cost-effective diagnostic tests are urgently needed. This work aims to validate a novel Loop-Mediated Isothermal Amplification (LAMP) test, based on the p40 target gene, for the detection of M. agalactiae in dairy sheep in order to confirm its potential practical use as a rapid and cheap field test. The LAMP system proposed in this study consists of a portable device composed of real-time fluorometer with the automatic interpretation of results displayed in a tablet. A total of 110 milk samples (90 positives and 20 negatives) were analysed to optimise the analysis procedure and to investigate the efficacy and robustness of the LAMP method. All samples were analysed using LAMP and conventional real-time PCR to compare the diagnostic sensitivity of the methods. The sensitivity of the LAMP was 10-fold higher than that of real-time PCR, with a detection limit up to 10³ CFU/ml. The LAMP assay was able to detect M. agalactiae in 81 of 90 (90%, 95%CI 0.84–0.96) positive milk samples compared to 69 (77%, 95%CI 0.59–0.95) positive samples detected by real-time PCR; no positive signal occurred for any of the negative milk samples in either test. Therefore, the LAMP assay was found to be more sensitive than real-time PCR, low-cost, easy to perform, fast and not affected by contamination, indicating its potential as an effective diagnostic tool in the field level for the diagnosis of CA.

Loop mediated isothermal amplification (LAMP) of Toxoplasma DNA from dried blood spots

INTRODUCTION

The cosmopolitan protozoan Toxoplasma gondii is a major parasite of warm-blooded animals including man. Early and accurate diagnosis is a must for proper treatment that prevents life threatening sequels. Loop-mediated isothermal amplification (LAMP) is a novel technique that can amplify DNA with high sensitivity and specificity under isothermal conditions.

AIM OF THE STUDY

To validate a LAMP-specific protocol for detection of Toxoplasma DNA using dried blood spots (DBS) from mice experimentally infected with the cystogenic Toxoplasma ME-49 strain.

METHODS

In this study, the target DNA fragment was the Toxoplasma 529-bp repeat element that exists in 200-300 copies per T. gondii genome. The sensitivity of both LAMP and conventional PCR techniques was estimated in DBS samples from experimental mice at 1-week and 8-weeks post-infection.

RESULTS

Out of 20 blood samples gathered on Whatman filter paper from mice at 1-week post-infection, 18 and 16 were positive by LAMP and conventional PCR, respectively. Neither techniques detected parasite DNA in blood at 8th week of infection.

CONCLUSION

Dried blood spots are easy source of material for molecular studies. LAMP assay proved higher sensitivity than the conventional PCR in detecting parasitemia in early infection with the cystogenic Toxoplasma strain.

Comparison of the RE-529 sequence and B1 gene for Toxoplasma gondii detection in blood samples of the at-risk seropositive cases using uracil DNA glycosylase supplemented loop-mediated isothermal amplification (UDG-LAMP) assay

Diagnosis of toxoplasmosis is an important issue, especially in at-risk patients. The molecular methods showed a promising future for such diagnosis; however, the method itself and the target sequence to be detected is an important part of accurate detection of the infection. The aim of the present study was to evaluate the RE-529 sequence and B1 gene for Toxoplasma gondii detection in blood samples of the at-risk seropositive cases using uracil DNA glycosylase supplemented loop-mediated isothermal amplification (UDG-LAMP) assay. In this study, 110 T. gondii seropositive at-risk individuals (pregnant women and immunocompromised patients) and 110 seronegative controls were enrolled. The two most studied sequences (RE-529 and B1) were used and compared for accurate and reliable detection of T. gondii in blood samples using UDG-LAMP assay and compared with real-time PCR method. The detection limit, accuracy, and reliability of UDG-LAMP for the parasite's DNA were also studied. Among 110 studied cases, 39 (35.45%) and 36 (32.7%) were positive for T. gondii DNA with the RE-LAMP and B1-LAMP, respectively. The seronegative cases remained negative for T. gondii DNA with the studied genes, however, there were few false negatives compared with real-time PCR method. The detection limit of the UDG-LAMP for both DNA targets was 0.16 tachyzoite's DNA per reaction tube. Based on the results of this study, the RE-529 sequence has a better detection rate compared to the B1 gene for toxoplasmosis among at-risk people. UDG-LAMP is a highly sensitive, accurate, and reliable method with no false-positive results for the diagnosis of T. gondii infection in blood specimens, however few cases may be missed.

Serological and molecular rapid diagnostic tests for Toxoplasma infection in humans and animals

Infection by Toxoplasma gondii is prevalent worldwide. The parasite can infect a broad spectrum of vertebrate hosts, but infection of fetuses and immunocompromised patients is of particular concern. Easy-to-perform, robust, and highly sensitive and specific methods to detect Toxoplasma infection are important for the treatment and management of patients. Rapid diagnostic methods that do not sacrifice the accuracy of the assay and give reproducible results in a short time are highly desirable. In this context, rapid diagnostic tests (RDTs), especially with point-of-care (POC) features, are promising diagnostic methods in clinical microbiology laboratories, especially in areas with minimal laboratory facilities. More advanced methods using microfluidics and sensor technology will be the future trend. In this review, we discuss serological and molecular-based rapid diagnostic tests for detecting Toxoplasma infection in humans as well as animals.

Serological and molecular screening of umbilical cord blood for Toxoplasma gondii infection

BACKGROUND

Human umbilical cord blood has proven to be a successful alternate source of hematopoietic stem cells for pediatric patients with major hematologic disorders. Toxoplasma gondii is a global opportunistic protozoan which cause fatal complications in immunocompromised individuals.

AIM

Our goal is to study the prevalence of toxoplasmosis in umbilical cord blood (UCB) and to assess the sensitivity of ELISA and PCR for Toxoplasma infection screening.

MATERIAL AND METHODS

One hundred cord blood samples were collected immediately after delivery. Anti-Toxoplasma IgG and IgM antibodies were determined using ELISA method; Toxoplasma DNA was detected using nested PCR technique. Total nucleated cells (TNC) and HB were also determined. Demographic data and risk factors data related to the transmission of toxoplasmosis, were collected from mothers.

RESULTS

Among 100 cord blood samples, 36 (36%) were positive for anti-Toxoplasma IgG antibodies and 6 (6%) were positive for anti-Toxoplasma IgM antibodies. The nested PCR showed 11 (11%) samples containing Toxoplasma DNA from which, 6 (55%) samples were IgM positive. There was no significant association between the risk of Toxoplasma transmission and cord blood positivity for toxoplasmosis.

CONCLUSION

Owing to the prevalence of toxoplasmosis, its rapid progression and its fatal outcome in immunocompromised patients, cord blood screening for toxoplasmosis with nested PCR should be incorporated into cord blood bank screening protocols.

LAMP detection of the genetic element 'Mona' associated with DMI resistance in Monilinia fructicola

BACKGROUND

The increasing use of demethylation inhibitor (DMI) fungicides for the control of peach brown rot has resulted in resistance in Monilinia fructicola. Resistance in the southeastern USA is caused by overexpression of the MfCYP51 gene due to the presence of a 65-bp inserted element 'Mona' located in the upstream regulatory region of MfCYP51. A rapid diagnostic assay would be useful to detect the presence and monitor further spread of this resistance mechanism.

RESULTS

A loop-mediated isothermal amplification (LAMP) method was developed for rapid detection of 'Mona'-based DMI resistance. The assay was optimized for specificity and sensitivity, and was shown to detect the presence of 10 fg of purified target DNA per reaction within 85 min. Only DNA isolated from DMI-resistant isolates containing 'Mona' resulted in a fluorescent signal after LAMP assay amplification. DNA from sensitive isolates from China and the USA and six other common fungal species of peach did not yield a signal. The method also positively identified 'Mona' from crude DNA extracts (using Lyse and Go reagents heated to 100 °C for 10 min) obtained from the mycelium and conidia of symptomatic fruit.

CONCLUSION

Considering its specificity, stability and repeatability, the LAMP assay could be a valuable tool for rapid on-site diagnosis of M. fructicola isolates resistant to DMI fungicides in the southeastern USA. © 2018 Society of Chemical Industry.

Serological and Molecular Diagnosis of Toxoplasma gondii Infections in Thalassemia Patients

BACKGROUND

This study aimed to the serological and molecular diagnosis of Toxoplasma gondii infections and related risk factors in patients with thalassemia major and healthy controls.

METHODS

This case-control study was performed in Shahrekord University of Medical Sciences, Shahrekord, west of Iran from Jan 2014 to Jan 2015. Overall, 235 patients with thalassemia major and 235 healthy controls were enrolled. Assessment of anti-Toxoplasma antibodies in sera samples was performed using commercial ELISA kits. In order to the molecular investigate of T. gondii in blood samples, a relatively new molecular assay, LAMP technique based on Toxoplasma SAG1 gene was conducted for the first time. The specificity of LAMP outer primers for the T. gondii detection was confirmed by sequencing the purified PCR product.

RESULTS

51.9% of thalassemia patients and 34.8% of healthy controls were positive for anti-Toxoplasma IgG antibodies, which the difference was statistically significant (P<0.01). In terms of anti-Toxoplasma IgM antibody, 3.4% of thalassemia patients and 2.1% of healthy individuals were positive, which the difference was not statistically significant (P=1). Based on SAG1-LAMP, 9.78% of the thalassemia patients and 5.95% of healthy controls were positive for T. gondii DNA, which the difference was not statistically significant (P≤0.230).

CONCLUSION

Thalassemia patients, probably due to repeated blood transfusion and consequently, immune deficiency, are at risk of transmitting Toxoplasma infection more than healthy people. Therefore, screening of Toxoplasma infection in blood transfusion centers may be effective in the prevention of toxoplasmosis in these patients.

Real-time loop-mediated isothermal amplification for rapid detection of Enterocytozoon hepatopenaei

Background

Enterocytozoon hepatopenaei (EHP) is a newly emerged microsporidian parasite that causes retarded shrimp growth in many countries. But there are no effective approaches to control this disease to date. The EHP could be an immune risk factor for increased dissemination of other diseases. Further, EHP infection involves the absence of obvious clinical signs and it is difficult to identify the pathogen through visual examination, increasing the risk of disease dissemination. It is urgent and necessary to develop a specific, rapid and sensitive EHP-infected shrimp diagnostic method to detect this parasite. In the present study, we developed and evaluated a rapid real-time loop-mediated isothermal amplification (real-time LAMP) for detection of EHP.

Methods

A rapid and efficient real-time LAMP method for the detection of EHP has been developed. Newly emerged EHP pathogens in China were collected and used as the sample, and three sets of specificity and sensitivity primers were designed. Three other aquatic pathogens were used as templates to test the specificity of the real-time LAMP assay. Also, we compared the real-time LAMP with the conventional LAMP by the serial dilutions of EHP DNA and their amplification curves. Application of real-time LAMP was carried out with clinical samples.

Results

Positive products were amplified only from EHP, but not from other tested species, EHP was detected from the clinical samples, suggesting a high specificity of this method. The final results of this assay were available within less than 45 min, and the initial amplification curve was observed at about 6 min. We found that the amplification with an exponential of sixfold dilutions of EHP DNA demonstrated a specific positive signal by the real-time LAMP, but not for the LAMP amplicons from the visual inspection. The real-time LAMP amplification curves demonstrated a higher slope than the conventional LAMP.

Discussion

In this study, pathogen virulence impacts have been increased in aquaculture and continuous observation was predominantly focused on EHP. The present study confirmed that the real-time LAMP assay is a promising and convenient method for the rapid identification of EHP in less time and cost. Its application greatly aids in the detection, surveillance, and prevention of EHP.

Development of a LAMP Method for Detecting SDHI Fungicide Resistance in Botrytis cinerea

Resistance to succinate dehydrogenase inhibitors (SDHI) in Botrytis cinerea is associated with point mutations in the target gene succinate dehydrogenase subunit B (SdhB). The substitution from histidine to arginine at codon 272 (H272R) is currently the predominant mutation in SDHI-resistant populations in B. cinerea worldwide. In order to monitor the development of resistance to SDHI, a rapid, simple, and efficient method with high specificity to the H272R point mutation was developed based on loop-mediated isothermal amplification (LAMP). To specifically detect the H272R mutation, a set of four primers was designed based on the sequence of SdhB, and the LAMP reaction was optimized. When SYBR Green I was added after reaction, only samples with the H272R mutation showed the color change (from brown to fluorescent yellow), indicating that this set of primers could successfully discriminate the H272R genotype from other genotypes. Specificity and accuracy tests showed that this LAMP assay had high specificity and accuracy. Moreover, the LAMP method was further simplified with fungal mycelia and conidia as the amplification template which could be prepared within 5 min. Due to the low cost, simplicity, high efficiency, and specificity, the developed LAMP assay may contribute to the monitoring of resistance development to SDHI in B. cinerea, especially in field and high-throughput experiments.

Isothermal PCR for Feasible Molecular Diagnosis of Primary Toxoplasmosis in Women Recently Experienced Spontaneous Abortion

AIM:

The current study aimed to assess the practicability of a simple loop-mediated isothermal amplification (LAMP) about real-time quantitative PCR to diagnose primary toxoplasmosis among high-risk pregnant women.

METHODS:

Cloned Toxoplasma samples were used to calculate the analytical sensitivity while specificity was assessed using pooled DNA samples extracted from other parasitic stages.

RESULTS:

Both techniques showed 100% sensitivity and specificity and then applied to detect recent Toxoplasma infection in peripheral blood of 77 IgG negative women out of a total 139 women lately experienced spontaneous abortion. The 2 techniques obtained positive results in 8 samples confirming primary toxoplasmosis.

CONCLUSION:

Generally, LAMP assay is a simple, cost-effective molecular technique can be completed in less than half an hour to diagnose primary Toxoplasma infection. The technique can be applied in a minimally equipped laboratory by ordinary workers to screen the vulnerable groups. Further analysis using larger samples with the quantitative approach is recommended to confirm the sensitivity of this emergent molecular technique.

Visual loop-mediated isothermal amplification (LAMP) for the rapid diagnosis of Enterocytozoon hepatopenaei (EHP) infection

The emerging microsporidian parasite Enterocytozoon hepatopenaei (EHP), the causative agent of hepatopancreatic microsporidiosis, has been widely reported in shrimp-farming countries. EHP infection can be detected by light microscopy observation of spores (1.7 × 1 μm) in stained hepatopancreas (HP) tissue smears, HP tissue sections, and fecal samples. EHP can also be detected by polymerase chain reaction (PCR) targeting the small subunit (SSU) ribosomal RNA (rRNA) gene or the spore wall protein gene (SWP). In this study, a rapid, sensitive, specific, and closed tube visual loop-mediated isothermal amplification (LAMP) protocol combined with FTA cards was developed for the diagnosis of EHP. LAMP primers were designed based on the SSU rRNA gene of EHP. The target sequence of EHP was amplified at constant temperature of 65 °C for 45 min and amplified LAMP products were visually detected in a closed tube system by using SYBR™ green I dye. Detection limit of this LAMP protocol was ten copies. Field and clinical applicability of this assay was evaluated using 162 field samples including 106 HP tissue samples and 56 fecal samples collected from shrimp farms. Out of 162 samples, EHP could be detected in 62 samples (47 HP samples and 15 fecal samples). When compared with SWP-PCR as the gold standard, this EHP LAMP assay had 95.31% sensitivity, 98.98% specificity, and a kappa value of 0.948. This simple, closed tube, clinically evaluated visual LAMP assay has great potential for diagnosing EHP at the farm level, particularly under low-resource circumstances.

Closed tube loop-mediated isothermal amplification assay for rapid detection of hepatitis B virus in human blood

Recently, many studies have demonstrated the significant advantages of loop-mediated isothermal amplification (LAMP) based methods over serological tests and PCR for rapid detection of microbial pathogens. Here, a rapid LAMP assay was developed to detect the hepatitis B virus (HBV) from DNA, and particularly, blood samples from infected patients using a commercially available master mix and portable real-time fluorometer. The final optimized fluorescence-based LAMP assay provided significant amplification time of less than 15 minutes compared with over 1 hour for PCR and an opened tube LAMP system described previously. Results indicated that fluorescence-based LAMP assay was more sensitive than PCR as a rapid, sensitive, efficient, and highly reliable approach for rapid detection of HBV.

Disodium cromoglycate may act as a novel adjuvant for UV-attenuated Toxoplasma gondii vaccine in mouse model

We have proven the beneficial effects during acute Toxoplasma gondii infection when mast cells were inhibited by disodium cromoglycate (DSCG). Here we investigated the adjuvant effect of DSCG on the protective efficacy of UV-attenuated T. gondii (UV-Tg) vaccine. Mice were infected with 10²Tg alone or infected with 10²Tg plus DSCG (Tg + DSCG), immunized with 10⁵ UV-Tg and challenged with 10²Tg (UV-Tg + Tg) or immunized with 10⁵ UV-Tg plus DSCG and challenged with 10²Tg (UV-Tg + DSCG + Tg). Compared to Tg group, Tg + DSCG, UV-Tg + Tg, and UV-Tg + DSCG + Tg showed significantly prolonged survival times, decreased parasite burdens, reduced liver histopathologies, and increased levels of Th1 and Th2 cytokines and IL-17 in the livers and spleens by using quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR). Compared to UV-Tg + Tg, UV-Tg + DSCG + Tg had significantly longer survival time, lower tissue parasite burden and histopathological score, and higher levels of Th1 and Th2 cytokines and IL-17 in the livers or spleens. Our data suggest that DSCG may play an adjuvant role in the immunization induced by UV-attenuated T. gondii in mice, by promoting cellular immune response against T. gondii challenge.

Advances in serological, imaging techniques and molecular diagnosis of Toxoplasma gondii infection

BACKGROUND

Toxoplasmosis is worldwide distributed zoonotic infection disease with medical importance in immunocompromised patients, pregnant women and congenitally infected newborns. Having basic information on the traditional and new developed methods is essential for general physicians and infectious disease specialists for choosing a suitable diagnostic approach for rapid and accurate diagnosis of the disease and, consequently, timely and effective treatment.

METHODS

We conducted English literature searches in PubMed from 1989 to 2016 using relevant keywords and summarized the recent advances in diagnosis of toxoplasmosis.

RESULTS

Enzyme-linked immunosorbent assay (ELISA) was most used method in past century. Recently advanced ELISA-based methods including chemiluminescence assays (CLIA), enzyme-linked fluorescence assay (ELFA), immunochromatographic test (ICT), serum IgG avidity test and immunosorbent agglutination assays (ISAGA) have shown high sensitivity and specificity. Recent studies using recombinant or chimeric antigens and multiepitope peptides method demonstrated very promising results to development of new strategies capable of discriminating recently acquired infections from chronic infection. Real-time PCR and loop-mediated isothermal amplification (LAMP) are two recently developed PCR-based methods with high sensitivity and specificity and could be useful to early diagnosis of infection. Computed tomography, magnetic resonance imaging, nuclear imaging and ultrasonography could be useful, although their results might be not specific alone.

CONCLUSION

This review provides a summary of recent developed methods and also attempts to improve their sensitivity for diagnosis of toxoplasmosis. Serology, molecular and imaging technologies each has their own advantages and limitations which can certainly achieve definitive diagnosis of toxoplasmosis by combining these diagnostic techniques.

Molecular diagnosis of toxoplasmosis in immunocompromised patients

PURPOSE OF REVIEW

Toxoplasmosis in immunocompromised patients is associated with a high mortality rate. Molecular techniques are important tools to diagnose acute disease in immunocompromised patients, but there are various methods with variable efficiency. Some of them have been validated for the diagnosis of congenital toxoplasmosis, but the impact of their use has not been evaluated in immunocompromised patients.

RECENT FINDINGS

Toxoplasmosis is of increasing importance in non-HIV immunocompromised patients. In addition, the picture of disease shows greater severity in South America, both in immunocompetent study participants and in congenitally infected infants. These epidemiological differences could influence the sensitivity of diagnostic methods. This review analyzes recent data on molecular diagnosis and compares them with older ones, in light of progress gained in molecular techniques and of recent epidemiological findings. Most recent studies were conducted in South America and used PCR targeting the B1 gene. PCR on blood could allow diagnosing a significant proportion of patients with ocular toxoplasmosis in Brazil.

SUMMARY

Quantitative PCR methods with specific probes should be used to improve sensitivity and warrant specificity. Performance of quantitative PCR targeting the repeated 529 bp sequence for the diagnosis of toxoplasmosis in immunocompromised patients needs evaluation in field studies in South America and in western countries.

Loop-Mediated Isothermal Amplification-Lateral-Flow Dipstick (LAMP-LFD) to detect Toxoplasma gondii oocyst in ready-to-eat salad

The apicomplexan parasite Toxoplasma gondii is the causative agent of toxoplasmosis, a foodborne zoonosis with a global distribution and estimated to cause up to 20% of the total foodborne disease burden in Europe. Association between T. gondii infection and the consumption of unwashed raw fruits and vegetables contaminated with oocysts has been reported and the increasing habit to eat pre-washed ready-to-eat salads poses a new potential risk for consumers. It is therefore important to trace the occurrence of potential contamination with this parasite to guarantee the safety of ready-to-eat vegetables. Detection of T. gondii in vegetables by molecular techniques has been achieved but low sensitivity (PCR) or expensive equipments (qPCR) limit routine applicability. Here, we describe the development and validation of a sensitive and robust method relying on a LAMP assay, targeting the 529 bp locus, to detect T. gondii oocysts down to 25 oocysts/50 g in ready-to-eat baby lettuce. The LAMP has been also adapted for a faster visualization of the result by a lateral flow dipstick chromatographic detection method.

Development of a loop-mediated isothermal amplification technique and comparison with quantitative real-time PCR for the rapid visual detection of canine neosporosis

Background

Dogs are the definitive hosts of Neospora caninum and play an important role in the transmission of the parasite. Despite the high sensitivity of existing molecular tools such as quantitative real-time PCR (qPCR), these techniques are not suitable for use in many countries because of equipment costs and difficulties in implementing them for field diagnostics. Therefore, we developed a simplified technique, loop-mediated isothermal amplification (LAMP), for the rapid visual detection of N. caninum.

Methods

LAMP specificity was evaluated using a panel containing DNA from a range of different organisms. Sensitivity was evaluated by preparing 10-fold serial dilutions of N. caninum tachyzoites and comparing the results with those obtained using qPCR. Assessment of the LAMP results was determined by recognition of a colour change after amplification. The usefulness of the LAMP assay in the field was tested on 396 blood and 115 faecal samples from dogs, and one placenta from a heifer collected in Lopburi, Nakhon Pathom, Sa Kaeo, and Ratchaburi provinces, Thailand.

Results

Specificity of the LAMP technique was shown by its inability to amplify DNA from non-target pathogens or healthy dogs. The detection limit was the equivalent of one genome for both LAMP and qPCR. LAMP and qPCR detected positive N. caninum infection in 15 of 396 (3.8%) blood samples; LAMP detected 9/115 (7.8%) positive faecal samples, while qPCR detected 5/115 (4.3%) positive faecal samples. The placental tissue was shown to be positive by both techniques. Agreement between LAMP and qPCR was perfect in blood samples (kappa value, 1.00) and substantial in faecal samples (kappa value, 0.697).

Conclusions

This is the first known LAMP assay developed for the amplification of N. caninum. The technique effectively and rapidly detected the parasite with high sensitivity and specificity and was cost-effective. This assay could be used in the field to confirm the diagnosis of canine or bovine neosporosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2330-2) contains supplementary material, which is available to authorized users.

Recombinase polymerase amplification (RPA) combined with lateral flow (LF) strip for detection of Toxoplasma gondii in the environment

Toxoplasma gondii infects all warm-blooded vertebrates, resulting in a great threat to human health and significant economic loss to the livestock industry. Ingestion of infectious oocysts of T. gondii from the environment is the major source of transmission. Detection of T. gondii oocysts by existing methods is laborious, time-consuming and expensive. The objective of the present study was to develop a recombinase polymerase amplification (RPA) method combined with a lateral flow (LF) strip for detection of T. gondii oocysts in the soil and water. The DNA of T. gondii oocysts was amplified by a pair of specific primers based on the T. gondii B1 gene over 15min at a constant temperature ranging from 30°C to 45°C using RPA. The amplification product was visualized by the lateral flow (LF) strip within 5min using the specific probe added to the RPA reaction system. The sensitivity of the established assay was 10 times higher than that of nested PCR with a lower detection limit of 0.1 oocyst per reaction, and there was no cross-reactivity with other closely related protozoan species. Fifty environmental samples were further assessed for the detection validity of the LF-RPA assay (B1-LF-RPA) and compared with nested PCR based on the B1 gene sequence. The B1-LF-RPA and nested PCR both showed that 5 out of the 50 environmental samples were positive. The B1-LF-RPA method was also proven to be sufficiently tolerant of existing inhibitors in the environment. In addition, the advantages of simple operation, speediness and cost-effectiveness make B1-LF-RPA a promising molecular detection tool for T. gondii.

Loop-mediated isothermal amplification (LAMP): A novel rapid detection platform for pathogens

Foodborne bacterial infections and diseases have been considered to be a major threat for public health in the worldwide. Increased incidence of human diseases caused by foodborne pathogens have been correlated with growing world population and mobility. Loop-mediated isothermal amplification (LAMP) has been regarded as an innovative gene amplification technology and emerged as an alternative to PCR-based methodologies in both clinical laboratory and food safety testing. Nowadays, LAMP has been applied to detection and identification on pathogens from microbial diseases, as it showed significant advantage in high sensitivity, specificity and rapidity. The high sensitivity of LAMP enables detection of the pathogens in sample materials even without time consuming sample preparation. An overview of LAMP mainly containing the development history, reaction principle and its application to four kind of foodborne pathogens detection are presented in this paper. As concluded, with the advantages of rapidity, simplicity, sensitivity, specificity and robustness, LAMP is capable of applications for clinical diagnosis as well as surveillance of infection diseases. Moreover, the main purpose of this paper is to provide theoretical basis for the clinical application of LAMP technology.

Improvement and Evaluation of Loop-Mediated Isothermal Amplification for Rapid Detection of Toxoplasma gondii Infection in Human Blood Samples

Loop-mediated isothermal amplification (LAMP), an attractive DNA amplification method, was developed as a valuable tool for the rapid detection of Toxoplasma gondii. In this study, species-specific LAMP primers were designed by targeting the AF146527 sequence, which was a conserved sequence of 200- to 300-fold repetitive 529 bp fragment of T.gondii. LAMP reaction system was optimized so that it could detect the minimal DNA sample such as a single tachyzoite or 10 copies of recombinant plasmid. No cross-reactivity was found when using DNA from other parasites as templates. Subsequently, a total of 200 human blood samples were directly investigated by two diagnostic methods, LAMP and conventional PCR. Fourteen of 200 (7%) samples were positive for Toxoplasma by LAMP (the primers developed in this study), whereas only 5 of 200 (2.5%) were proved positive by conventional PCR. The procedure of the LAMP assay was very simple, as the reaction would be carried out in a single tube under isothermal conditions at 64°C and the result would be read out with 1 h (as early as 35 min with loop primers). Thus, this method has the advantages of rapid amplification, simple operation, and easy detection and would be useful for rapid and reliable clinical diagnosis of acute toxoplasmosis, especially in developing countries.

Deciphering the Draft Genome of Toxoplasma gondii RH Strain

Toxoplasmosis is a widespread parasitic infection by Toxoplasma gondii, a parasite with at least three distinct clonal lineages. This article reports the whole genome sequencing and de novo assembly of T. gondii RH (type I representative strain), as well as genome-wide comparison across major T. gondii lineages. Genomic DNA was extracted from tachyzoites of T. gondii RH strain and its identity was verified by PCR and LAMP. Subsequently, whole genome sequencing was performed, followed by sequence filtering, genome assembly, gene annotation assignments, clustering of gene orthologs and phylogenetic tree construction. Genome comparison was done with the already archived genomes of T. gondii. From this study, the genome size of T. gondii RH strain was found to be 69.35Mb, with a mean GC content of 52%. The genome shares high similarity to the archived genomes of T. gondii GT1, ME49 and VEG strains. Nevertheless, 111 genes were found to be unique to T. gondii RH strain. Importantly, unique genes annotated to functions that are potentially critical for T. gondii virulence were found, which may explain the unique phenotypes of this particular strain. This report complements the genomic archive of T. gondii. Data obtained from this study contribute to better understanding of T. gondii and serve as a reference for future studies on this parasite.

Detection of Toxoplasma gondii in Diabetic Patients Using the Nested PCR Assay via RE and B1 Genes

BACKGROUND

Toxoplasma gondii is an obligate intracellular protozoan parasite that exists worldwide. Various techniques have been developed for T. gondii detection.

OBJECTIVES

The aim of this study was the detection of T. gondii in diabetic patients with RE and B1 genes and the comparison of these two genes for diagnosis using the nested-PCR assay method.

PATIENTS AND METHODS

DNA samples from 205 diabetic patients who had been referred to the diabetes center of Ali Asghar hospital in Zahedan, Iran, were collected and analyzed using the nested-PCR assay method. Toxoplasma antibody data gathered using the enzyme-linked immunosorbent assay (ELISA) method from a previous study was used to group patients. The data were analyzed using SPSS 18. The chi-square test was used for comparison.

RESULTS

Of the diabetic patients selected, the following results were obtained: 53 (IgG+, IgM+); 20 (IgG-, IgM+); 72 (IgG+, IgM-); and 60 (IgG-, IgM-). The nested-PCR detected the following: in the acute group, 21/53 (39.63%), 30/53 (56.60%) (IgM+, IgG+); in the chronic group, 40/72 (55.56%), 51/72 (70.83%), (IgG+, IgM-); in the false positive group, 18/20 (90%), 17/20 (85%) (IgM+, IgG-); and sero-negative samples of 38/60 (63.33%) and 60/ 41 (77.35%) for RE and B1 genes, respectively. The prevalence of toxoplasmosis showed positive in patients with diabetes in the B1 gene 139 (67.8%) and RE gene 117 (57.1%).

CONCLUSIONS

Our study demonstrated that the B1 gene, more so than the RE gene, showed positive samples and can be used to detect toxoplasmosis, although the B1 gene, in comparison to the RE gene, did not show any superiority of molecular diagnosing capability. Results also showed that toxoplasma molecular detection methods can be used instead of routine serological detection methods in a clinical laboratory testing.

Loop-Mediated Isothermal Amplification Assay for Identification of Five Human Plasmodium Species in Malaysia

The lack of rapid, affordable, and accurate diagnostic tests represents the primary hurdle affecting malaria surveillance in resource- and expertise-limited areas. Loop-mediated isothermal amplification (LAMP) is a sensitive, rapid, and cheap diagnostic method. Five species-specific LAMP assays were developed based on 18S rRNA gene. Sensitivity and specificity of LAMP results were calculated as compared with microscopic examination and nested polymerase chain reaction. LAMP reactions were highly sensitive with the detection limit of one copy for Plasmodium vivax, Plasmodium falciparum, and Plasmodium malariae and 10 copies for Plasmodium knowlesi and Plasmodium ovale. LAMP positively detected all human malaria species in all positive samples (N = 134; sensitivity = 100%) within 35 minutes. All negative samples were not amplified by LAMP (N = 67; specificity = 100%). LAMP successfully detected two samples with very low parasitemia. LAMP may offer a rapid, simple, and reliable test for the diagnosis of malaria in areas where malaria is prevalent.

Evaluation of Loop-Mediated Isothermal Amplification Assay for the Detection of Pneumocystis jirovecii in Immunocompromised Patients

Pneumocystis pneumonia (PCP) is one of the common opportunistic infection among HIV and non-HIV immunocompromised patients. The lack of a rapid and specific diagnostic test necessitates a more reliable laboratory diagnostic test for PCP. In the present study, the loop-mediated isothermal amplification (LAMP) assay was evaluated for the detection of Pneumocystis jirovecii. 185 clinical respiratory samples, including both BALF and IS, were subjected to GMS staining, nested PCR, and LAMP assay. Of 185 respiratory samples, 12/185 (6.5%), 41/185 (22.2%), and 49/185 (26.5%) samples were positive by GMS staining, nested PCR, and LAMP assay, respectively. As compared to nested PCR, additional 8 samples were positive by LAMP assay and found to be statistically significant (p < 0.05) with the detection limit of 1 pg. Thus, the LAMP assay may serve as a better diagnostic tool for the detection of P. jirovecii with high sensitivity and specificity, less turn-around time, operational simplicity, single-step amplification, and immediate visual detection.

The use of loop-mediated isothermal amplification improves Toxoplasma gondii detection in wildlife

Toxoplasma gondii is among the most widespread parasites worldwide. Wildlife is recognized as an important reservoir and source of infection of T. gondii. The goal of the present work was to assess the performance of loop-mediated isothermal amplification (LAMP) as a diagnostic tool for T. gondii infection in the skeletal muscle and central nervous system (CNS) of free-ranging ungulates and carnivores. Fifty-seven wild animals were tested for the presence of T. gondii DNA by polymerase chain reaction (PCR) and LAMP. The use of LAMP amplification improved sensitivity in T. gondii molecular detection compared with conventional PCR on skeletal muscle (χ2 = 5.8, P < 0.05), having a lower minimum detection limit (0.1 tachyzoite) than PCR (1 tachyzoite). No significant differences existed between the detection capacities of both assays when performed on CNS. LAMP is a valid tool to improve the diagnosis of T. gondii infection in wild game meat. The technique provides a sensitive yet specific method that can be applicable to both field surveys and large-scale testing of wildlife samples.

Colorimetric Detection of Dengue by Single Tube Reverse-Transcription-Loop-Mediated Isothermal Amplification

Dengue is usually diagnosed by isolation of the virus, serology or molecular diagnostic methods. Several commercial kits for the diagnosis of dengue are existing, but concerns have arisen regarding to the affordability and performance characteristics of these kits. Hence, the loop-mediated isothermal amplification (LAMP) is potentially ideal to be used especially in resource limited environments. Serum was collected from healthy donors and patients diagnosed with dengue infection. RNA extracted from the serum samples were tested by reverse-transcription-LAMP assay developed based on 3′-NCR gene sequences for DENV 1–4. Results were interpreted by a turbidity meter in real time or visually at the end of the assay. Sensitivity and specificity of RT-LAMP results were calculated and compared to qRT-PCR and ELISA. RT-LAMP is highly sensitive with the detection limit of 10 RNA copies for all serotypes. Dengue virus RNA was detected in all positive samples using RT-LAMP and none of the negative samples within 30–45 minutes. With continuing efforts in the optimization of this assay, RT-LAMP may provide a simple and reliable test for detecting DENV in areas where dengue is prevalent.

Diagnosis of toxoplasmosis and typing of Toxoplasma gondii

Toxoplasmosis, caused by the obligate intracellular protozoan Toxoplasma gondii, is an important zoonosis with medical and veterinary importance worldwide. The disease is mainly contracted by ingesting undercooked or raw meat containing viable tissue cysts, or by ingesting food or water contaminated with oocysts. The diagnosis and genetic characterization of T. gondii infection is crucial for the surveillance, prevention and control of toxoplasmosis. Traditional approaches for the diagnosis of toxoplasmosis include etiological, immunological and imaging techniques. Diagnosis of toxoplasmosis has been improved by the emergence of molecular technologies to amplify parasite nucleic acids. Among these, polymerase chain reaction (PCR)-based molecular techniques have been useful for the genetic characterization of T. gondii. Serotyping methods based on polymorphic polypeptides have the potential to become the choice for typing T. gondii in humans and animals. In this review, we summarize conventional non-DNA-based diagnostic methods, and the DNA-based molecular techniques for the diagnosis and genetic characterization of T. gondii. These techniques have provided foundations for further development of more effective and accurate detection of T. gondii infection. These advances will contribute to an improved understanding of the epidemiology, prevention and control of toxoplasmosis.