High-resolution melt curve analysis: A real-time based multipurpose approach for diagnosis and epidemiological investigations of parasitic infections

Detecting Dirofilaria immitis: Current Practices and Novel Diagnostic Methods

The nematode Dirofilaria immitis is responsible for a vector-borne disease affecting canines and humans worldwide, known as cardiopulmonary dirofilariasis. An accurate and early diagnosis is of the utmost importance for effective disease management. While traditional microscopy-based methods remain invaluable, they have inherent limitations. Serological tests, in particular ELISA and immunochromatographic tests, are employed due to their capacity to detect D. immitis antigens, offering ease of use and diagnostic accuracy. The advent of molecular methods has the potential to enhance routine diagnostic approaches, with polymerase chain reaction (PCR) and real-time PCR (qPCR) becoming the most prevalent techniques. Despite not yet being integrated into routine diagnostics, which are predominantly based on the Knott's test and serological methods, these techniques offer significant benefits in the context of scientific research. This article proceeds to examine the potential of advanced techniques, such as high-resolution melting qPCR (HRM-qPCR), loop-mediated isothermal amplification (LAMP), droplet digital PCR (ddPCR), and microRNA (miRNA) detection, which are capable of enhanced sensitivity and early detection. The following work provides an in-depth analysis of the various diagnostic methods, emphasising the necessity of the continuous improvement and adaptation of these tools to effectively combat D. immitis. The findings underscore the importance of integrating these advanced methods into routine practice to improve detection rates and outcomes for infected animals.

Advances in genotypic antimicrobialresistance testing: a comprehensive review

Antimicrobial resistance (AMR) represents a substantial threat to global public health, complicating the treatment of common infections and leading to prolonged illness and escalated healthcare expenses. To effectively combat AMR, timely and accurate detection is crucial for AMR surveillance and individual-based therapy. Phenotypic antibiotic resistance testing (AST) has long been considered the gold standard in clinical applications, serving as the foundation for clinical AMR diagnosis and optimized therapy. It has significantly contributed to ensuring patients' health and the development of novel antimicrobials. Despite advancements in automated culture-based AST technologies, inherent limitations impede the widespread use of phenotypic AST in AMR surveillance. Genotypic AST technologies offer a promising alternative option, exhibiting advantages of rapidity, high sensitivity, and specificity. With the continuous advancement and expanding applications of genotypic AST technologies, such as microfluidics, mass spectrometry, and high-resolution melting curve analysis, new vigor has been injected into the development and clinical implementation of genotypic AST technologies. In this narrative review, we discuss the principles, applications, and advancements of emerging genotypic AST methods in clinical settings. The comprehensive review aims to highlight the significant scientific potential of emerging genotypic AST technologies in clinical AMR diagnosis, providing insights to enhance existing methods and explore novel approaches.

Assemblage characterization of Giardia duodenalis in South Khorasan province, eastern Iran, using HRM real-time PCR method

BACKGROUND

Giardia duodenalis is a common parasitic protozoan causing gastrointestinal illness in humans worldwide. The genetic diversity of G. duodenalis is reflected through the identification of different assemblages. In this study, we aimed to determine the assemblages of G. duodenalis in eastern Iran using nested-PCR and high-resolution melting (HRM) real-time PCR methods.

METHODS

A total of 58 positive G. duodenalis, which were isolated from 1800 subjects, referred to medical center laboratories in South Khorasan province, eastern Iran, from April 2020 to March 2022, were included in this study. DNA was extracted and HRM real-time PCR was performed for assemblage characterization.

RESULTS

HRM real-time PCR successfully characterized all samples. Accordingly, out of 58 positive samples, 53 (91.36%) and 5 (8.62%) were identified as assemblage A and B, respectively.

CONCLUSIONS

Our findings showed that HRM real-time PCR was able to characterize the assemblages of G. duodenalis. In addition, our results suggest high prevalence of assemblage A in eastern region of Iran.

Toward waterborne protozoa detection using sensing technologies

Drought and limited sufficient water resources will be the main challenges for humankind during the coming years. The lack of water resources for washing, bathing, and drinking increases the use of contaminated water and the risk of waterborne diseases. A considerable number of waterborne outbreaks are due to protozoan parasites that may remain active/alive in harsh environmental conditions. Therefore, a regular monitoring program of water resources using sensitive techniques is needed to decrease the risk of waterborne outbreaks. Wellorganized point-of-care (POC) systems with enough sensitivity and specificity is the holy grail of research for monitoring platforms. In this review, we comprehensively gathered and discussed rapid, selective, and easy-to-use biosensor and nanobiosensor technologies, developed for the early detection of common waterborne protozoa.

High-resolution melting analysis identifies reservoir hosts of zoonotic Leishmania parasites in Tunisia

BACKGROUND

Leishmaniasis is endemic in Tunisia and presents with different clinical forms, caused by the species Leishmania infantum, Leishmania major, and Leishmania tropica. The life cycle of Leishmania is complex and involves several phlebotomine sand fly vectors and mammalian reservoir hosts. The aim of this work is the development and evaluation of a high-resolution melting PCR (PCR-HRM) tool to detect and identify Leishmania parasites in wild and domestic hosts, constituting confirmed (dogs and Meriones rodents) or potential (hedgehogs) reservoirs in Tunisia.

METHODS

Using in vitro-cultured Leishmania isolates, PCR-HRM reactions were developed targeting the 7SL RNA and HSP70 genes. Animals were captured or sampled in El Kef Governorate, North West Tunisia. DNA was extracted from the liver, spleen, kidney, and heart from hedgehogs (Atelerix algirus) (n = 3) and rodents (Meriones shawi) (n = 7) and from whole blood of dogs (n = 12) that did not present any symptoms of canine leishmaniasis. In total, 52 DNA samples were processed by PCR-HRM using both pairs of primers.

RESULTS

The results showed melting curves enabling discrimination of the three Leishmania species present in Tunisia, and were further confirmed by Sanger sequencing. Application of PCR-HRM assays on reservoir host samples showed that overall among the examined samples, 45 were positive, while seven were negative, with no Leishmania infection. Meriones shawi were found infected with L. major, while dogs were infected with L. infantum. However, co-infections with L. major/L. infantum species were detected in four Meriones specimens and in all tested hedgehogs. In addition, multiple infections with the three Leishmania species were found in one hedgehog specimen. Sequence analyses of PCR-HRM products corroborated the Leishmania species found in analyzed samples.

CONCLUSIONS

The results of PCR-HRM assays applied to field specimens further support the possibility of hedgehogs as reservoir hosts of Leishmania. In addition, we showed their usefulness in the diagnosis of canine leishmaniasis, specifically in asymptomatic dogs, which will ensure a better evaluation of infection extent, thus improving elaboration of control programs. This PCR-HRM method is a robust and reliable tool for molecular detection and identification of Leishmania and can be easily implemented in epidemiological surveys in endemic regions.

Development of HRM real-time PCR for assemblage characterization of Giardia lamblia

A total of 90 stool samples were collected from dogs, referred to a dog shelter and a veterinary clinic. In addition, 395 stool samples obtained from pet dog owners and shelter keepers, as well as individuals referred to a medical laboratory as controls, were collected in Shahryar district, Tehran, Iran. Stool samples were parasitologically examined and the positive G. lamblia isolates were tested with Nested-PCR/sequencing for the tpi, gdh, and bg genes, and HRM real-time PCR. Microscopical examination revealed 20 (22.2%) and 34 (8.6%) Giardia-positive samples from dogs and humans, respectively. Regarding HRM real-time PCR, the prevalence of assemblages A and B in humans was 55.8% and 14.7%, respectively. In addition, 14.7% of samples were mix assemblages. HRM real-time PCR detected most of microscopically-positive samples in comparison to PCR/sequencing in both humans and dogs. The high prevalence of assemblages A and B in dogs signified the importance of a same source for infection between dogs and humans.

A genotyping assay to determine geographic origin and transmission potential of Plasmodium falciparum malaria cases

As countries work towards malaria elimination, it is important to monitor imported cases to prevent reestablishment of local transmission. The Plasmodium falciparum Pfs47 gene has strong geographic population structure, because only those parasites with Pfs47 haplotypes compatible with the mosquito vector species in a given continent are efficiently transmitted. Analysis of 4,971 world-wide Pfs47 sequences identified two SNPs (at 707 and 725 bp) as sufficient to establish the likely continent of origin of P. falciparum isolates. Pfs47 sequences from Africa, Asia, and the New World presented more that 99% frequency of distinct combinations of the SNPs 707 and 725 genotypes. Interestingly, Papua New Guinea Pfs47 sequences have the highest diversity in SNPs 707 and 725. Accurate and reproducible High-Resolution Melting (HRM) assays were developed to genotype Pfs47 SNPs 707 and 725 in laboratory and field samples, to assess the geographic origin and risk of local transmission of imported P. falciparum malaria cases.

Species-level identification of trypanosomes infecting Australian wildlife by High-Resolution Melting - Real Time Quantitative Polymerase Chain Reaction (HRM-qPCR)

Conventional nested PCR and Sanger sequencing methods are currently the gold standards for detecting trypanosomes in wildlife. However, these techniques are time-consuming and can often overlook mixed infections. True trypanosome prevalence can thus be underrepresented. Here, we designed an 18S rDNA-based real-time quantitative PCR (qPCR) assay coupled with High-Resolution Melting Analysis (HRMA) to detect and discriminate three Trypanosoma species (T. copemani, T. noyesi, and T. vegrandis) commonly infecting Australian marsupials. A total of 68 genetically characterised samples from blood and tissue were used to validate the High-Resolution Melting - Real Time Quantitative Polymerase Chain Reaction (HRM-qPCR) assay. A further 87 marsupial samples consisting of blood, tissue and in vitro cultures derived from wildlife blood samples, were screened for the first time using this assay, and species identity confirmed using conventional PCR and Sanger sequencing. All three Trypanosoma species were successfully detected in pure cultures using the HRM-qPCR assay, and in samples containing mixed trypanosome infections. Of the 87 marsupial samples screened using the HRM-qPCR assay, 93.1% were positive for trypanosomes, and 8.0% contained more than one trypanosome species. In addition to the three targeted Trypanosoma species, this assay was also able to detect and identify other native and exotic trypanosomes. The turnaround time for this assay, from sample preparation to obtaining results, was less than 2 h, with a detection limit of 10 copies of the amplicon in a reaction for each of the targeted trypanosome species. This more rapid and sensitive diagnostic tool provides a high throughput platform for the detection, identification and quantification of trypanosome infections. It will also improve understanding of host diversity and parasite relationships and facilitate conservation management decisions.

Human intestinal parasitic infection: a narrative review on global prevalence and epidemiological insights on preventive, therapeutic and diagnostic strategies for future perspectives

INTRODUCTION

Intestinal parasitic infection (IPI) is a global health concern among socioeconomically deprived communities in many developing countries. Many preventative strategies have been deployed to control IPI, however, there is a lack in standards on the techniques used to diagnose and monitor the prevalence of IPI.

AREAS COVERED

The present article will review the diseases associated with IPI and discuss the current IPI control strategies such as the water, sanitation, and hygiene (WASH) interventions, community-led total sanitation (CLTS) approach, and regular anthelminthic treatments. For the first time, this review will also evaluate all currently practised diagnostic techniques for the detection of intestinal parasites and provide insights on future IPI control strategies.

EXPERT OPINION

Advanced and improved diagnostic methods such as qPCR coupled with a high-resolution melting curve, aptamers, biosensors, and detection of extracellular vesicles can be used for detection of IPI. Vaccination against intestinal parasites can be made available to increase antibodies to interfere with the blood-feeding process by the parasites, which subsequently reduces the reproductive rates of the parasites. These methods collectively can serve as future management strategies for intestinal parasitic infections.