Giardiasis: a pharmacotherapy review

Promising effects of 1,8 Cineole to control Giardia lamblia infection: Targeting the inflammation, oxidative stress, and infectivity

Reportedly, synthetic drugs such as metronidazole, furazolidone, tinidazole, and quinacrine are used for the treatment of giardiasis but are associated with adverse effects. In this study, we aimed to investigate the in vitro and in vivo effects of eucalyptol (ECT, 1,8 cineole) alone and in combination with metronidazole (MNZ) on Giardia lamblia. The effects of ECT on cell viability, plasma membrane permeability, and gene expression levels of adenylate cyclase (AK) and extracellular signal kinases 1 and 2 (ERK1 and ERK2) in trophozoites of G. lamblia were assessed. In vivo, the effects of ECT alone and in combination with MNZ were assessed on mice infected with G. lamblia. In addition, the gene expression of inflammatory genes (e.g., TNF-α, IL-1β, and IL-10) and antioxidant genes (catalase (CAT), superoxide dismutase 1 (SOD1), glutathione peroxidase 2 (GPX2)) was determined by real-time PCR. The IC50 values of ECT, MNZ, and ECT+MNZ on trophozoites were 30.2 µg/mL, 21.6 µg/mL, and 8.5 µg/mL, respectively. The estimated Fractional inhibitory concentration index (FICI) values for ECT and MNZ were 0.28 and 0.39, respectively. The application of ECT on G. lamblia trophozoites resulted in a dose-dependent increase in plasma membrane permeability, particularly at concentrations of ½ IC50 and IC50 (P < 0.05). The treatment of infected mice with various doses of ECT, mainly in combination with MNZ for 7 days, resulted in a significant decrease (P < 0.001) in the average number and viability of cysts. ECT, especially when combined with MNZ, caused a significant (P < 0.001) reduction in the expression of TNF-α and IL-6 genes, and an increase (P < 0.05) in the expression of IL-10 genes. ECT alone and mainly in combination with MNZ leads to a significant (P < 0.001) increase in the gene expression of CAT, SOD, and GPX genes. These findings demonstrate that the use of ECT in these doses, even for 14 days, does not have any toxic effects on the function of vital liver and kidney tissues. The study findings confirmed the promising effects of ECT against G. lamblia infection both in vitro and in vivo. Considering the possible mechanisms, ECT increases plasma membrane permeability and reduces the expression levels of infectivity-related genes. In addition, ECT suppresses inflammation and oxidative stress, controlling giardiasis in mice. More studies are needed to clarify these findings.

TATA-Binding Protein-Based Virtual Screening of FDA Drugs Identified New Anti-Giardiasis Agents

Parasitic diseases, predominantly prevalent in developing countries, are increasingly spreading to high-income nations due to shifting migration patterns. The World Health Organization (WHO) estimates approximately 300 million annual cases of giardiasis. The emergence of drug resistance and associated side effects necessitates urgent research to address this growing health concern. In this study, we evaluated over eleven thousand pharmacological compounds sourced from the FDA database to assess their impact on the TATA-binding protein (TBP) of the early diverging protist Giardia lamblia, which holds medical significance. We identified a selection of potential pharmacological compounds for combating this parasitic disease through in silico analysis, employing molecular modeling techniques such as homology modeling, molecular docking, and molecular dynamics simulations. Notably, our findings highlight compounds DB07352 and DB08399 as promising candidates for inhibiting the TBP of Giardia lamblia. Also, these compounds and DB15584 demonstrated high efficacy against trophozoites in vitro. In summary, this study identifies compounds with the potential to combat giardiasis, offering the prospect of specific therapies and providing a robust foundation for future research.

Leading Paediatric Infectious Diseases-Current Trends, Gaps, and Future Prospects in Oral Pharmacotherapeutic Interventions

Paediatric infectious diseases contribute significantly to global health challenges. Conventional therapeutic interventions are not always suitable for children, as they are regularly accompanied with long-standing disadvantages that negatively impact efficacy, thus necessitating the need for effective and child-friendly pharmacotherapeutic interventions. Recent advancements in drug delivery technologies, particularly oral formulations, have shown tremendous progress in enhancing the effectiveness of paediatric medicines. Generally, these delivery methods target, and address challenges associated with palatability, dosing accuracy, stability, bioavailability, patient compliance, and caregiver convenience, which are important factors that can influence successful treatment outcomes in children. Some of the emerging trends include moving away from creating liquid delivery systems to developing oral solid formulations, with the most explored being orodispersible tablets, multiparticulate dosage forms using film-coating technologies, and chewable drug products. Other ongoing innovations include gastro-retentive, 3D-printed, nipple-shield, milk-based, and nanoparticulate (e.g., lipid-, polymeric-based templates) drug delivery systems, possessing the potential to improve therapeutic effectiveness, age appropriateness, pharmacokinetics, and safety profiles as they relate to the paediatric population. This manuscript therefore highlights the evolving landscape of oral pharmacotherapeutic interventions for leading paediatric infectious diseases, crediting the role of innovative drug delivery technologies. By focusing on the current trends, pointing out gaps, and identifying future possibilities, this review aims to contribute towards ongoing efforts directed at improving paediatric health outcomes associated with the management of these infectious ailments through accessible and efficacious drug treatments.

Fused Enzyme Glucose-6-Phosphate Dehydrogenase::6-Phosphogluconolactonase (G6PD::6PGL) as a Potential Drug Target in Giardia lamblia, Trichomonas vaginalis, and Plasmodium falciparum

Several microaerophilic parasites such as Giardia lamblia, Trichomonas vaginalis, and Plasmodium falciparum are major disease-causing organisms and are responsible for spreading infections worldwide. Despite significant progress made in understanding the metabolism and molecular biology of microaerophilic parasites, chemotherapeutic treatment to control it has seen limited progress. A current proposed strategy for drug discovery against parasitic diseases is the identification of essential key enzymes of metabolic pathways associated with the parasite's survival. In these organisms, glucose-6-phosphate dehydrogenase::6-phosphogluconolactonase (G6PD:: 6PGL), the first enzyme of the pentose phosphate pathway (PPP), is essential for its metabolism. Since G6PD:: 6PGL provides substrates for nucleotides synthesis and NADPH as a source of reducing equivalents, it could be considered an anti-parasite drug target. This review analyzes the anaerobic energy metabolism of G. lamblia, T. vaginalis, and P. falciparum, with a focus on glucose metabolism through the pentose phosphate pathway and the significance of the fused G6PD:: 6PGL enzyme as a therapeutic target in the search for new drugs.

Analysis of Giardia lamblia Nucleolus as Drug Target: A Review

Giardia lamblia (G. lamblia) is the main causative agent of diarrhea worldwide, affecting children and adults alike; in the former, it can be lethal, and in the latter a strong cause of morbidity. Despite being considered a predominant disease in low-income and developing countries, current migratory flows have caused an increase in giardiasis cases in high-income countries. Currently, there is a wide variety of chemotherapeutic treatments to combat this parasitosis, most of which have potentially serious side effects, such as genotoxic, carcinogenic, and teratogenic. The necessity to create novel treatments and discover new therapeutic targets to fight against this illness is evident. The current review centers around the controversial nucleolus of G. lamblia, providing a historical perspective that traces its apparent absence to the present evidence supporting its existence as a subnuclear compartment in this organism. Additionally, possible examples of ncRNAs and proteins ubiquitous to the nucleolus that can be used as targets of different therapeutic strategies are discussed. Finally, some examples of drugs under research that could be effective against G. lamblia are described.

Transcriptomic analysis of albendazole resistance in human diarrheal parasite Giardia duodenalis

Benzimidazole-2-carbamates (BZ, e.g., albendazole; ALB), which bind β-tubulin to disrupt microtubule polymerization, are one of two primary compound classes used to treat giardiasis. In most parasitic nematodes and fungi, BZ-resistance is caused by β-tubulin mutations and its molecular mode of action (MOA) is well studied. In contrast, in Giardia duodenalis BZ MOA or resistance is less well understood, may involve target-specific and broader impacts including cellular damage and oxidative stress, and its underlying cause is not clearly determined. Previously, we identified acquisition of a single nucleotide polymorphism, E198K, in β-tubulin in ALB-resistant (ALB-R) G. duodenalis WB-1B relative to ALB-sensitive (ALB-S) parental controls. E198K is linked to BZ-resistance in fungi and its allelic frequency correlated with the magnitude of BZ-resistance in G. duodenalis WB-1B. Here, we undertook detailed transcriptomic comparisons of these ALB-S and ALB-R G. duodenalis WB-1B cultures. The primary transcriptional changes with ALB-R in G. duodenalis WB-1B indicated increased protein degradation and turnover, and up-regulation of tubulin, and related genes, associated with the adhesive disc and basal bodies. These findings are consistent with previous observations noting focused disintegration of the disc and associated structures in Giardia duodenalis upon ALB exposure. We also saw transcriptional changes with ALB-R in G. duodenalis WB-1B consistent with prior observations of a shift from glycolysis to arginine metabolism for ATP production and possible changes to aspects of the vesicular trafficking system that require further investigation. Finally, we saw mixed transcriptional changes associated with DNA repair and oxidative stress responses in the G. duodenalis WB-1B line. These changes may be indicative of a role for H₂O₂ degradation in ALB-R, as has been observed in other G. duodenalis cell cultures. However, they were below the transcriptional fold-change threshold (log₂FC > 1) typically employed in transcriptomic analyses and appear to be contradicted in ALB-R G. duodenalis WB-1B by down-regulation of the NAD scavenging and conversion pathways required to support these stress pathways and up-regulation of many highly oxidation sensitive iron-sulphur (FeS) cluster based metabolic enzymes.

Anaerobic energy metabolism in human microaerophile parasites

Mucosal-associated parasites, such as Giardia intestinalis, Entamoeba histolytica, and Trichomonas vaginalis, have significant clinical relevance. The pathologies associated with infection by these parasites are among those with the highest incidence of gastroenteritis (giardiasis and amoebiasis) and sexually transmitted infections (trichomoniasis). The treatment of these diseases is based on drugs that act on the anaerobic metabolism of these parasites, such as nitroimidazole and benzimidazole derivatives. One interesting feature of parasites is their ability to produce ATP under anaerobic conditions. Due to the absence of enzymes capable of producing ATP under anaerobic conditions in the vertebrate host, they have become interesting therapeutic targets. This review discusses anaerobic energy metabolism in mucosal-associated parasites, focusing on the anaerobic metabolism of pyruvate, the importance of these enzymes as therapeutic targets, and the importance of treating their infections.

The NLRP3 inflammasome recognizes alpha-2 and alpha-7.3 giardins and decreases the pathogenicity of Giardia duodenalis in mice

BACKGROUND

Giardia duodenalis is a parasitic organism that can cause giardiasis, an intestinal infection, particularly prevalent in young children, with clinical symptoms of diarrhea. We previously reported that extracellular G. duodenalis triggers intracellular nucleotide-binding oligomerization-like receptor 3 (NLRP3) inflammasome activation and regulates the host inflammatory response by secreting extracellular vesicles (EVs). However, the exact pathogen-associated molecular patterns in G. duodenalis EVs (GEVs) involved in this process and the role of the NLRP3 inflammasome in giardiasis remain to be elucidated.

METHODS

Recombinant eukaryotic expression plasmids of pcDNA3.1(+)-alpha-2 and alpha-7.3 giardins in GEVs were constructed, transfected into primary mouse peritoneal macrophages and screened by measuring the expression levels of the inflammasome target molecule caspase-1 p20. The preliminary identification of G. duodenalis alpha-2 and alpha-7.3 giardins was further verified by measuring the protein expression levels of key molecules of the NLRP3 inflammasome (NLRP3, pro-interleukin-1 beta [IL-1β], pro-caspase-1, and caspase-1 p20), the secretion levels of IL-1β, the level of apoptosis speck-like protein (ASC) oligomerization and the immunofluorescence localization of NLRP3 and ASC. The roles of the NLRP3 inflammasome in G. duodenalis pathogenicity were then evaluated using mice in which NLRP3 activation was blocked (NLRP3-blocked mice), and body weight, parasite burden in the duodenum and histopathological changes in the duodenum were monitored. In addition, we explored whether alpha-2 and alpha-7.3 giardins triggered IL-1β secretion in vivo through the NLRP3 inflammasome and determined the roles of these molecules in G. duodenalis pathogenicity in mice.

RESULTS

Alpha-2 and alpha-7.3 giardins triggered NLRP3 inflammasome activation in vitro. This led to caspase-1 p20 activation, upregulation of the protein expression levels of NLRP3, pro-IL-1β and pro-caspase-1, significant enhancement of IL-1β secretion, ASC speck formation in the cytoplasm and also induction of ASC oligomerization. Deletion of the NLRP3 inflammasome aggravated G. duodenalis pathogenicity in mice. Compared to wild-type mice gavaged with cysts, mice gavaged with cysts in NLRP3-blocked mice displayed increased trophozoite loads and severe duodenal villus damage, characterized by necrotic crypts with atrophy and branching. In vivo assays revealed that alpha-2 and alpha-7.3 giardins could induce IL-1β secretion through the NLRP3 inflammasome and that immunization with alpha-2 and alpha-7.3 giardins decreased G. duodenalis pathogenicity in mice.

CONCLUSIONS

Overall, the results of the present study revealed that alpha-2 and alpha-7.3 giardins trigger host NLRP3 inflammasome activation and decrease G. duodenalis infection ability in mice, which are promising targets for the prevention of giardiasis.

Giardia duodenalis: Flavohemoglobin is involved in drug biotransformation and resistance to albendazole

Giardia duodenalis causes giardiasis, a major diarrheal disease in humans worldwide whose treatment relies mainly on metronidazole (MTZ) and albendazole (ABZ). The emergence of ABZ resistance in this parasite has prompted studies to elucidate the molecular mechanisms underlying this phenomenon. G. duodenalis trophozoites convert ABZ into its sulfoxide (ABZSO) and sulfone (ABZSOO) forms, despite lacking canonical enzymes involved in these processes, such as cytochrome P450s (CYP450s) and flavin-containing monooxygenases (FMOs). This study aims to identify the enzyme responsible for ABZ metabolism and its role in ABZ resistance in G. duodenalis. We first determined that the iron-containing cofactor heme induces higher mRNA expression levels of flavohemoglobin (gFlHb) in Giardia trophozoites. Molecular docking analyses predict favorable interactions of gFlHb with ABZ, ABZSO and ABZSOO. Spectral analyses of recombinant gFlHb in the presence of ABZ, ABZSO and ABZSOO showed high affinities for each of these compounds with Kd values of 22.7, 19.1 and 23.8 nM respectively. ABZ and ABZSO enhanced gFlHb NADH oxidase activity (turnover number 14.5 min-1), whereas LC-MS/MS analyses of the reaction products showed that gFlHb slowly oxygenates ABZ into ABZSO at a much lower rate (turnover number 0.01 min-1). Further spectroscopic analyses showed that ABZ is indirectly oxidized to ABZSO by superoxide generated from the NADH oxidase activity of gFlHb. In a similar manner, the superoxide-generating enzyme xanthine oxidase was able to produce ABZSO in the presence of xanthine and ABZ. Interestingly, we find that gFlHb mRNA expression is lower in albendazole-resistant clones compared to those that are sensitive to this drug. Furthermore, all albendazole-resistant clones transfected to overexpress gFlHb displayed higher susceptibility to the drug than the parent clones. Collectively these findings indicate a role for gFlHb in ABZ conversion to its sulfoxide and that gFlHb down-regulation acts as a passive pharmacokinetic mechanism of resistance in this parasite.

Pre-and post-treatment evaluation of intestinal inflammation in Giardia and Blastocystis infected children: a community-based study

Giardia intestinalis and Blastocystis hominis cause frequent infections in children in developing countries. However, the role of intestinal inflammation in their pathogenesis is still poorly understood. Faecal calprotectin (FC) level is used as an indicator of intestinal inflammation and neutrophil migration in the intestinal tract. The present study aimed to evaluate intestinal inflammation by measuring FC level among children infected with either G. intestinalis or B. hominis before and after treatment. Stool samples were collected from 282 children inhabiting a rural area in Egypt and examined microscopically for intestinal parasites. FC level was estimated in a group of children infected with G. intestinalis (n = 12) or B. hominis (n = 12) before and 3 weeks after receiving nitazoxanide (200 mg twice daily for 3 days) and compared to a control group (n = 18) of parasite-free children. Cases of mixed infection were excluded. Nitazoxanide cure rate was 83% in both infections with a remarkable reduction of infection intensity in uncured children. The difference in FC levels between infected children and controls was not statistically significant. Also, the difference between the pre- and post-treatment estimations was not statistically significant. Elevated levels were observed before treatment in three children (two infected with G. intestinalis and one with B. hominis) who displayed normal post-treatment levels. Although G. intestinalis and B. hominis infections appear to cause no remarkable intestinal inflammation, they may induce abnormally elevated FC levels in a subset of children.

Probiotics in the management of Giardia duodenalis: an update on potential mechanisms and outcomes

Giardia duodenalis is a common cause of infection in children and travelers. The most frequent symptom is diarrhea in these patients. G. duodenalis trophozoites use a highly specialized adhesive disc to attach the host intestinal epithelium to induce intestinal damages. Pathological features of the small intestine following giardiasis include villous atrophy; infiltration of granulocytes, lymphocytes, and plasma cells into the lamina propria; and nodular lymphoid hyperplasia. The disturbed intestinal microbiota has been observed in patients with giardiasis. Therefore, a growing body of evidence has emphasized restoring the gut microbiome by probiotics in giardiasis. This study aimed to review the literature to find the pathologic features of giardiasis and its relationship with imbalanced microbiota. Then, benefits of probiotics in giardiasis and their potential molecular mechanisms were discussed. It has been illustrated that using probiotics (e.g., Lactobacillus and Saccharomyces) can reduce the time of gastrointestinal symptoms and repair the damages, particularly in giardiasis. Probiotics' capability in restoring the composition of commensal microbiota may lead to therapeutic outcomes. According to preclinical and clinical studies, probiotics can protect against parasite-induced mucosal damages via increasing the antioxidant capacity, suppressing oxidative products, and regulating the systemic and mucosal immune responses. In addition, they can reduce the proportion of G. duodenalis load by directly targeting the parasite. They can destroy the cellular architecture of parasites and suppress the proliferation and growth of trophozoites via the production of some factors with anti-giardial features. Further researches are required to find suitable probiotics for the prevention and treatment of giardiasis.

Risk factors for and management of metronidazole-refractory giardiasis in international travellers: A retrospective analysis

BACKGROUND

Giardia lamblia is a common cause of diarrhoea in returning travellers. Failure of the recommended first-line treatment, metronidazole, has frequently been observed. Recommendations for treatment of metronidazole-refractory giardiasis lack clarity and evidence.

METHODS

We conducted a retrospective data analysis of returned travellers with confirmed giardiasis at the Bernhard-Nocht-Clinic in Hamburg, Germany, between 2007 and 2016.

RESULTS

We identified 339 cases of giardiasis, mostly acquired in South Asia (n = 157). 308 patients received metronidazole as first-line treatment, leading to treatment failure in 93 cases. Statistical analysis suggested by far the highest risk of metronidazole treatment failure for travellers returning from South Asia (Odds Ratio 8.73). Second-line therapy consisted of various different therapy regimens. Combination therapy as second-line treatment seemed to be more effective than monotherapy. A repeat course of metronidazole proved to be futile.

CONCLUSION

This study reveals a strikingly low effectiveness of metronidazole, especially in patients returning from South Asia. Second-line treatment showed inconsistency of regimens and yielded unsatisfactory results. These findings require reconsideration of treatment strategies for giardiasis. Large prospective trials are urgently needed to assess new first-line treatment options and to help implement advice for effective, agreed second-line treatment strategies. Translational projects should be created to link the understanding of resistance mechanisms with epidemiological data and clinical outcome.

Quinacrine treatment of nitroimidazole-refractory giardiasis

Background

Limited evidence exists on efficacy and tolerability of quinacrine for nitroimidazole-refractory giardiasis.

Methods

Nitroimidazole-refractory giardiasis cases, defined as microbiologically (microscopy and/or PCR) confirmed treatment failure after 2 courses, during 2008–2020, were retrospectively identified.

Results

Of 87 patients, 54 (62%) had visited India. Quinacrine was used in 54 (62%); 51 received monotherapy and 3 combined with metronidazole. Only 3 had positive stool samples with persisting symptoms after quinacrine treatment (94% parasitological efficacy) and all were cured after a second treatment. One (1.9%) had mild adverse effects recorded.

Conclusions

Quinacrine is an effective treatment for nitroimidazole-refractory giardiasis with good tolerability.

Spatial Distribution of Common Pathogenic Human Intestinal Protozoa in Iran: A Systematic Review

Background:

Pathogenic intestinal protozoa are considered as a serious public health problem in developing countries. This study aimed to elucidate the overall prevalence and spatial distribution of three common human pathogenic intestinal protozoan infections in Iran.

Methods:

Six English and Persian databases were explored for published papers on the prevalence of Entamoeba histolytica/dispar, Giardia lamblia, and Cryptosporidium spp. in the general population of Iran from 2000 to 2015. All eligible data were collected using a pre-designed data extraction form, and the overall prevalence was estimated using a random-effects meta-analysis model. We used ArcMap for mapping the prevalence of the studied protozoa and clustering analysis.

Results:

Altogether, 118 eligible papers from 24 provinces of Iran were included and analyzed. The weighted prevalence of E. histolytica/dispar, G. lamblia, and Cryptosporidium spp. infection among Iranian general population were calculated 1.3% (95% CI 1.1–1.5%), 10.6% (95% CI 9.6–11.5%) and 2% (95% CI 1.5–2.5%), respectively.

Conclusion:

Our findings indicated human intestinal protozoan infections caused by E. histolytica/dispar, G. lamblia, and Cryptosporidium spp. have still public health importance in some parts of Iran.

The association between the lack of safe drinking water and sanitation facilities with intestinal Entamoeba spp infection risk: A systematic review and meta-analysis

Intestinal protozoa infections are responsible for considerable morbidity and mortality, especially where the exposed population suffers from a lack of drinking water and sanitation facilities. In this study, the association between the lack of safe drinking water and sanitation (toilet) facilities with intestinal Entamoeba spp infection in the children (5-11 years), adult (18-55 years), and all age (5-55 years) were assessed. For this purpose, some of the international databases such as Scopus, PubMed, Web of Science, and Embase were screened to up to 7 June 2019 in order to retrieve the related citations. Also, the pooled odds ratios (ORs) following 95% confidence intervals (CIs) were calculated using a random-effects model. Twenty-nine articles with 36 studies were included while the OR extracted or calculated by using 2 × 2 contingency tables. However, the ingestion of contaminated water insignificantly can increase the odds ratio (OR) of Entamoeba spp infection (OR 1.01, (95% confidence interval [CI] 0.58 to 1.43), no access to sanitation (toilet) facilities significantly can increase odds of Entamoeba spp infection (OR 1.18, 95% CI 1.05 to 1.32). The meta-regression analysis showed that over time, odds of intestinal Entamoeba spp infection increased in both lack of safe drinking water (Coefficient: 3.24, P-value < 0.01) and sanitation (toilet) facilities (Coefficient: 2.36, P-value < 0.05) subgroups. Considering the findings, lack of safe drinking water resulted in a further increase in intestinal Entamoeba spp infection among adult (OR: 2.76), children (OR = 0.57) and all age groups (OR: 1.50), and also lack of sanitation (toilet) facilities resulted in further increase intestinal Entamoeba spp infection in children (OR: 1.06), adult (OR: 1.26) and all age (OR: 1.16). In this context, the lack of safe drinking water and sanitation facilities (toilet) was associated with a high risk of intestinal Entamoeba spp infection. Further attempts to providing public health facilities can control the prevalence of intestinal Entamoeba spp.

Anti-Giardia Drug Discovery: Current Status and Gut Feelings

Giardia parasites are ubiquitous protozoans of global importance that impact a wide range of animals including humans. They are the most common enteric pathogen of cats and dogs in developed countries and infect ∼1 billion people worldwide. While Giardia infections can be asymptomatic, they often result in severe and chronic diseases. There is also mounting evidence that they are linked to postinfection disorders. Despite growing evidence of the widespread morbidity associated with Giardia infections, current treatment options are limited to compound classes with broad antimicrobial activity. Frontline anti-Giardia drugs are also associated with increasing drug resistance and treatment failures. To improve the health and well-being of millions, new selective anti-Giardia drugs are needed alongside improved health education initiatives. Here we discuss current treatment options together with recent advances and gaps in drug discovery. We also propose criteria to guide the discovery of new anti-Giardia compounds.

An image-based Pathogen Box screen identifies new compounds with anti-Giardia activity and highlights the importance of assay choice in phenotypic drug discovery

Giardia duodenalis, the most prevalent human intestinal parasite causes the disease, giardiasis. On an annual basis G. duodenalis infects ~1 billion people, of which ~280 million develop symptomatic disease. Giardiasis can be severe and chronic, causing malnutrition, stunted growth and poor cognitive development in children. Current treatment options rely on drugs with declining efficacy and side-effects. To improve the health and well-being of millions of people world-wide, new anti-Giardia drugs with different modes of action to currently used drugs are required. The Medicines for Malaria Venture's Pathogen Box, a collection of bio-active compounds specifically chosen to stimulate infectious disease drug discovery, represents an opportunity for the discovery of new anti-Giardia agents. While the anti-Giardia activity of Pathogen Box compounds has been reported, this work failed to identify known anti-Giardia controls within the compound set. It also reported the activity of compounds previously screened and shown to be inactive by others, suggesting data may be inaccurate. Given these concerns the anti-Giardia activity of Pathogen Box compounds was re-assessed in the current study. Data from this work identified thirteen compounds with anti-Giardia IC₅₀ values ≤2 μM. Five of these compounds were reference compounds (marketed drugs with known anti-microbial activity), or analogues of compounds with previously described anti-Giardia activity. However, eight, including MMV676358 and MMV028694, which demonstrated potent sub-μM IC₅₀s against assemblage A, B and metronidazole resistant parasites (0.3 μM and 0.9 μM respectively), may represent new leads for future drug development. Interestingly, only four of these compounds were identified in the previously reported Pathogen Box screen highlighting the importance of assay selection and design when assessing compounds for activity against infectious agents.

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13 compounds with anti-Giardia IC₅₀ values < 2 μM were identified.

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8 compounds represent new leads for drug development.

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MMV676358 and MMV028694 demonstrated the most promising acting.

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Data highlight the importance of assay selection and design in drug discovery.

Drug resistance in Giardia: Mechanisms and alternative treatments for Giardiasis

The use of chemotherapeutic drugs is the main resource against clinical giardiasis due to the lack of approved vaccines. Resistance of G. duodenalis to the most used drugs to treat giardiasis, metronidazole and albendazole, is a clinical issue of growing concern and yet unknown impact, respectively. In the search of new drugs, the completion of the Giardia genome project and the use of biochemical, molecular and bioinformatics tools allowed the identification of ligands/inhibitors for about one tenth of ≈150 potential drug targets in this parasite. Further, the synthesis of second generation nitroimidazoles and benzimidazoles along with high-throughput technologies have allowed not only to define overall mechanisms of resistance to metronidazole but to screen libraries of repurposed drugs and new pharmacophores, thereby increasing the known arsenal of anti-giardial compounds to some hundreds, with most demonstrating activity against metronidazole or albendazole-resistant Giardia. In particular, cysteine-modifying agents which include omeprazole, disulfiram, allicin and auranofin outstand due to their pleiotropic activity based on the extensive repertoire of thiol-containing proteins and the microaerophilic metabolism of this parasite. Other promising agents derived from higher organisms including phytochemicals, lactoferrin and propolis as well as probiotic bacteria/fungi have also demonstrated significant potential for therapeutic and prophylactic purposes in giardiasis. In this context the present chapter offers a comprehensive review of the current knowledge, including commonly prescribed drugs, causes of therapeutic failures, drug resistance mechanisms, strategies for the discovery of new agents and alternative drug therapies.

Ascorbic acid potentiates the Giardia duodenalis growth inhibitory activity of pure Terminalia ferdinandiana Exell compounds

Giardiasis, one of the most common causes of diarrhoeal disease, is caused by gastrointestinal protozoal parasites of the genus Giardia. Metronidazole is the most commonly used drug to treat giardiasis. However, metronidazole resistance is increasingly common, making the development of new anti-giardial drugs a high priority. A panel of 11 compounds previously identified in T. ferdinandiana fruit extracts were investigated for the ability to inhibit G. duodenalis proliferation. Eight of the 11 compounds inhibited the growth of all three G. duodenalis strains. 2,3-Dihydroxyphenyl B-D-glucopyranosiduronic acid (DPGA) was the most potent anti-giardial compound, with IC₅₀ values as low as 126 μM (38 μg/mL). Notably, DPGA inhibited a metronidazole-resistant G. duodenalis strain with similar activity as determined for the metronidazole-sensitive strains. Furthermore, the activity of DPGA was greatly potentiated when it was tested in combination with ascorbic acid, to approximately 17 μM (5 μg/mL) for the metronidazole-sensitive G. duodenalis strains and 40 μM (12 mg/mL) for the resistant strain. The T. ferdinandiana tannins (gallic acid and chebulic acid) were moderate inhibitors of G. duodenalis growth when tested in combination with ascorbic acid, although they had only low levels of activity when tested alone. All of the tested compounds (and their combinations with ascorbic acid) displayed low toxic effects and all compounds are conformed to Lipinski's rules of 5 with few violations, indicating their potential as drug leads and chemotherapies for the treatment and prevention of giardiasis.

Comparative efficacy of drugs for treating giardiasis: a systematic update of the literature and network meta-analysis of randomized clinical trials

Background

Giardiasis is the commonest intestinal protozoal infection worldwide. The current first-choice therapy is metronidazole. Recently, other drugs with potentially higher efficacy or with fewer and milder side effects have increased in popularity, but evidence is limited by a scarcity of randomized controlled trials (RCTs) comparing the many treatment options available. Network meta-analysis (NMA) is a useful tool to compare multiple treatments when there is limited or no direct evidence available.

Objectives

To compare the efficacy and side effects of all available drugs for the treatment of giardiasis.

Methods

We selected all RCTs included in systematic reviews and expert reviews of all treatments for giardiasis published until 2014, extended the systematic literature search until 2016, and identified new studies by scanning reference lists for relevant studies. We then conducted an NMA of all available treatments for giardiasis by comparing parasitological cure (efficacy) and side effects.

Results

We identified 60 RCTs from 58 reports (46 from published systematic reviews, 8 from reference lists and 4 from the updated systematic search). Data from 6714 patients, 18 treatments and 42 treatment comparisons were available. Tinidazole was associated with higher parasitological cure than metronidazole [relative risk (RR) 1.23, 95% CI 1.12-1.35] and albendazole (RR 1.35, 95% CI 1.21-1.50). Taking into consideration clinical efficacy, side effects and amount of the evidence, tinidazole was found to be the most effective drug.

Conclusions

We provide additional evidence that single-dose tinidazole is the best available treatment for giardiasis in symptomatic and asymptomatic children and adults.

In vitro and ex vivo evaluation of the anti-Giardia duodenalis activity of the supernatant of Slab51 (SivoMixx)

The effects on Giardia duodenalis of Slab51 probiotic supernatants were evaluated in vitro and ex vivo. In vitro, Slab51 (10¹ UFC) was cultured and the obtained supernatant was filtered, adjusted at pH 7, and added (100μl/ml) as such (Slab51 FS) or after heat-treatment, to G. duodenalis cultures to evaluate its effects on G. duodenalis trophozoites growth and adherence. For comparison, negative and metronidazole (20μg/ml) treated controls were used. The morphological and ultrastructural alterations of G. duodenals trophozoites following treatment with Slab51 FS supernatant were investigated by transmission electron microscopy. Ex vivo, mice duodenal portions were cultivated in standard conditions with 5x10⁵G. duodenalis trophozoites/ml, while to further five duodenal portions similarly cultured and infected, Slab51 FS 200μl was added. After 12 and 18h, samples were fixed in 10% buffered formalin and histologically processed to score Giardia infection and cell damage. Cell proliferation/apoptosis was scored by Ki67, TUNEL and Caspase–3 tests. All experiments were conducted in triplicate throughout the study. All data were statistically evaluated (P< 0.05). Results showed that Slab51 FS significantly reduced Giardia growth and adherence respect to negative controls, but its efficacy was overall lower than that of metronidazole. Moreover, the effects of Slab51 FS were significantly lowered by heat-treatment and this reduction was statistically higher at 90°C than at 56°C, indicating a heat-sensitive nature of active Slab51 FS compounds. At the ultrastructural level, Slab51 FS treated Giardia trophozoites were swelling, increased in size and showed alterations of their cellular membrane and vacuole patterns, loss of the nuclear envelope and nuclear architecture. In ex vivo trials, viable G. duodenalis trophozoites and enterocyte TUNEL+ and Caspase-3 expression were significantly reduced in intestinal sections added with Slab51 FS, while enterocyte Ki67 expression was significantly increased, confirming the anti-G. duodenalis activity of Slab51 FS observed in vitro. In conclusion, results from this study showed that the fresh culture supernatant of the commercial probiotic Slab51 has anti-G. duodenalis properties both in vitro and ex vivo in a mouse model.

Identification of a novel potassium channel (GiK) as a potential drug target in Giardia lamblia: Computational descriptions of binding sites

Background

The protozoan Giardia lamblia is the causal agent of giardiasis, one of the main diarrheal infections worldwide. Drug resistance to common antigiardial agents and incidence of treatment failures have increased in recent years. Therefore, the search for new molecular targets for drugs against Giardia infection is essential. In protozoa, ionic channels have roles in their life cycle, growth, and stress response. Thus, they are promising targets for drug design. The strategy of ligand-protein docking has demonstrated a great potential in the discovery of new targets and structure-based drug design studies.

Methods

In this work, we identify and characterize a new potassium channel, GiK, in the genome of Giardia lamblia. Characterization was performed in silico. Because its crystallographic structure remains unresolved, homology modeling was used to construct the three-dimensional model for the pore domain of GiK. The docking virtual screening approach was employed to determine whether GiK is a good target for potassium channel blockers.

Results

The GiK sequence showed 24–50% identity and 50–90% positivity with 21 different types of potassium channels. The quality assessment and validation parameters indicated the reliability of the modeled structure of GiK. We identified 110 potassium channel blockers exhibiting high affinity toward GiK. A total of 39 of these drugs bind in three specific regions.

Discussion

The GiK pore signature sequence is related to the small conductance calcium-activated potassium channels (SKCa). The predicted binding of 110 potassium blockers to GiK makes this protein an attractive target for biological testing to evaluate its role in the life cycle of Giardia lamblia and potential candidate for the design of novel antigiardial drugs.

Co-parasitism of intestinal protozoa and Schistosoma japonicum in a rural community in the Philippines

Background

Co-parasitism is a frequent occurrence in impoverished communities in the tropics resulting in a considerable disease burden. While there are extensive reports of intestinal helminthiases, including schistosomiasis japonica, the occurrence and extent of diseases caused by intestinal protozoa (IP) have yet to be investigated in depth in the Philippines. We present a detailed analysis of polyparasitism in a rural community of Northern Samar, focusing on co-infections of IP with Schistosoma japonicum.

Methods

A descriptive cross sectional study was carried out in 2015 across 18 barangays (villages) endemic for S. japonicum in Northern Samar, the Philippines to assess the burden of human schistosomiasis and IP infections. Faecal samples collected from 412 participants from the 18 barangays were included in the final molecular analysis. A multiplex quantitative PCR assay was developed and used for the detection of Blastocystis spp., Entamoeba histolytica, Cryptosporidium spp. and Giardia duodenalis in stool samples. The findings were combined with previous results of droplet digital PCR diagnosis of individuals from the same 18 barangays infected with S. japonicum determined using the same stool samples for analysis.

Results

Mean age of the study participants was 40.3 years (95% CI: 38.8–41.8) with 53% (n = 218) being males. Prevalence of S. japonicum (74.5%) and Blastocystis spp. (58.7%) was significantly higher compared to other infections, with E. histolytica having the lowest prevalence (12.1%). A majority of individuals were infected with more than one parasite with two infections being most common (n = 175, 42.5%). The prevalence of individuals with two parasites was significantly higher than all others with 27.9% (n = 115) subjects harbouring a single parasite species. Of individuals with two infections, S. japonicum and Blastocystis spp. were the most common combination (n = 110, 62.9%). Examining age within the population, 58.5% (n = 38) of school-aged children and 60.1% (n = 14) of women of child bearing age harboured at least two parasite species.

Conclusions

The study revealed that polyparasitism with IP infections and schistosomiasis japonica is highly prevalent in individuals in Northern Samar which likely contributes to the significant public health and socio-economic burden suffered by this population. More generally, the findings are of relevance when considering implementation of integrated control strategies for intestinal parasites.

Electronic supplementary material

The online version of this article (10.1186/s40249-018-0504-6) contains supplementary material, which is available to authorized users.

Efficacy of mebendazole in paediatric patients with giardiasis: A systematic review and meta-analysis

Mebendazole (MBZ), a benzimidazole compound, has received attention in treating patients with giardiasis because it has shown beneficial effects both in vitro and in vivo. The aim of this study was to assess with a systematic review and meta-analysis of randomized controlled trials (RCTs) the efficacy of MBZ compared to other antigiardial agents in children. We searched RCTs of MBZ for the treatment of Giardia infections published in PubMed and EBSCOhost. Application of inclusion and exclusion criteria, data extraction, and assessment of methodological quality were independently performed in duplicate. The primary outcome was the parasitological cure. We included 7 RCTs in the systematic review (639 patients). There was no clinical difference in the parasitological cure between MBZ and metronidazole (MTZ). The relative risk (RR) was 0.81 [95% Confidence Interval 0.61-1.09], with high heterogeneity (4 trials, I² = 81%). The prediction interval expected to cover the results of a new trial was wide enough (0.22-2.96) to support both a clinically relevant difference favouring either MBZ or MTZ. The decision to support any treatment should be based not only on efficacy but also safety and cost. Although our results suggest that MBZ may be an effective treatment option for children with Giardia infection, they should also be interpreted and translated into clinical practice with caution, as the evidence is based on a limited number of RCTs presenting high heterogeneity.

Prevalence and risk factors for intestinal parasitic infections in pregnant women residing in three districts of Bogotá, Colombia

BACKGROUND

Intestinal parasitic infections (IPI) lead to significant morbidity and mortality in pediatric and adult populations worldwide. Intestinal parasitism during pregnancy is of interest as it may affect the health of pregnant women and their offspring. This study determined the prevalence of IPI in pregnant women living in substandard conditions in three urban districts of Bogotá, Colombia. Associations between prevalence and sociodemographic factors, housing, and living conditions were also evaluated.

METHODS

In a cross-sectional and community-based study, pregnant women were recruited from three districts of Bogotá. A total of 550 participants answered a questionnaire; 331 of these also provided stool samples, with 233 providing one and 98 providing two stool samples. Questionnaire responses were associated with the presence of intestinal parasites, which was determined using a standard combined microscopy technique including direct wet mount and formol-ether concentration. Results were verified by supplementary examination of 48 stool samples by quantitative polymerase chain reaction (qPCR).

RESULTS

Among pregnant women who lived in selected poor residential areas in Bogotá, the overall prevalence of intestinal parasitism was 41% with 9% polyparasitism. Pathogenic parasites were present in 1.2% of the 331 participants including Giardia lamblia and Ascaris lumbricoides. Higher prevalence was found for parasites with debated pathogenicity, including Blastocystis hominis (25%), Endolimax nana (15%), Entamoeba coli (8%), and Iodamoeba butschlii (2%). Entamoeba histolytica/dispar complex was also detected (1.5%). When comparing a subset of stool samples using the combined microscopy technique and qPCR, the latter detected a higher 58.3% overall IPI prevalence. Higher prevalence of infections by any intestinal parasite was found in participants who had never been dewormed (p = 0.01). Higher but not statistically significant associations were found between any parasite and women living with a partner, and intestinal polyparasitism and being from a minority group and not having a water sink.

CONCLUSIONS

This first study of the prevalence of intestinal parasitism in Bogotá focused on pregnant women living in poverty, found a high prevalence of intestinal parasites of debated pathogenicity, and confirmed a low prevalence of pathogenic intestinal parasites. These results highlight the need for educational interventions to disrupt transmission routes for prevalent parasites.

Recent advances in the genomic and molecular biology of Giardia

Giardia duodenalis is the most common gastrointestinal protozoan parasite of humans and a significant contributor to the global burden of both diarrheal disease and post-infectious chronic disorders. Robust tools for analyzing gene function in this parasite have been developed and a range of genetic tools are now available. These together with public databases have provided insights on the function of different genes in Giardia. In this review we provide a current perspective on different molecular aspects of Giardia related to genomics, regulation of encystation, trophozoite transcriptional responses to physiological and xenobiotic (drug-induced) stress, and mechanisms of drug resistance. We also examine recent insights that have contributed to gain knowledge in the study of VSPs, antigenic variation, epigenetics, DNA repair and in the direct manipulation of gene function in Giardia, with a particular focus on the inducible Cre/loxP system.

Comparative effect of manuka honey on anaerobic parasitic protozoans with standard drug therapy under in vitro conditions: A preliminary study

BACKGROUND

From the past five decades, metronidazole and tinidazole have been used for treating nonresistant and resistant giardiasis and trichomoniasis. However, due to the occurrence of drug resistance to standard therapy idealizes us to explore some additional therapies which is cost-effective, easy accessibility, and natural which has least side effects. Manuka honey obtained from Leptospermum scoparium is well known for its antibacterial and wound healing properties and is thought to be a better option as an additional therapy.

OBJECTIVE

The present study was conducted to find out the effect of manuka honey on anaerobic protozoans that includes Giardia and Trichomonas under in vitro conditions in comparison to metronidazole and tinidazole.

MATERIALS AND METHODS

Axenic culture of Giardia lamblia strain Portland 1 and Trichomonas vaginalis strain 413 was used for drug sensitivity assay to tinidazole, metronidazole, and manuka honey with the highest concentration of 17.1 μg/ml, 24.7 μg/ml, and 50%v/v by using (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a tetrazole). For this, head-to-head comparison has been done and IC 50 of the standard drug as well as manuka honey was calculated.

RESULTS

The result showed that percentage inhibition on the growth of both the parasites is dependent on concentration as well as exposure time of the drug. The calculated IC 50 was found to be 5.6%v/v and 1.5%v/v for manuka honey with respect to G. lamblia and T. vaginalis.

CONCLUSION

The present study suggests that manuka honey can be used as an additional therapy for the patient with giardiasis or trichomoniasis. However, in vivo study in the near future will elucidate more about the effectiveness of honey in treating parasitic infections.

Epidemiology of intestinal parasite infections in three departments of south-central Côte d'Ivoire before the implementation of a cluster-randomised trial

Hundreds of millions of people are infected with helminths and intestinal protozoa, particularly children in low- and middle-income countries. Preventive chemotherapy is the main strategy to control helminthiases. However, rapid re-infection occurs in settings where there is a lack of clean water, sanitation and hygiene. In August and September 2014, we conducted a cross-sectional epidemiological survey in 56 communities of three departments of south-central Côte d'Ivoire. Study participants were invited to provide stool and urine samples. Stool samples were examined for helminth and intestinal protozoa infections using the Kato-Katz technique and a formalin-ether concentration method. Urine samples were subjected to a filtration method for the diagnosis of Schistosoma haematobium. Information on sociodemographic characteristics, knowledge, attitude, practices and beliefs with regard to hygiene, sanitation and intestinal parasitic diseases were collected using a questionnaire administered to household heads. Multivariable logistic regression models were employed to analyse associations between parasite infections and risk factors. Overall, 4,305 participants had complete parasitological and questionnaire data. Hookworm was the predominant helminth species (21.2%), while Ascaris lumbricoides, Trichuris trichiura, Schistosoma mansoni and S. haematobium showed prevalences below 10%. Infections with pathogenic intestinal protozoa (e.g. Entamoeba histolytica/E. dispar and Giardia intestinalis) were similarly prevalent in the three departments. Hookworm infection was associated with open defecation and participants' age and sex. Entamoeba coli infection was negatively associated with the use of tap water at home (odds ratio (OR) = 0.66; p = 0.032). Disposal of garbage in close proximity to people's home was positively associated with G. intestinalis (OR = 1.30; p = 0.015). Taken together, helminth and intestinal protozoa infections affected a considerable proportion of rural dwellers in south-central Côte d'Ivoire at the onset of a cluster-randomised intervention trial. Our results will serve as baseline to monitor the effect of a package of interventions, including preventive chemotherapy, sanitation and health education on re-infection with helminths and intestinal protozoa.

TRIAL REGISTRATION

ISRCTN53102033 (date assigned: 26 March 2014).

Nitroimidazole-refractory giardiasis: a growing problem requiring rational solutions

BACKGROUND

Giardia intestinalis is microaerophilic diarrhoea-causing protozoan common in countries with suboptimal sanitation. Standard treatment is with nitroimidazoles, but a growing number of refractory cases is being reported. Treatment failure has become increasingly prevalent in travellers who contract giardiasis in Asia. Clinicians are increasingly falling back on second-line and less well-known drugs to treat giardiasis.

AIMS

To review nitroimidazole-refractory G. intestinalis infection, examine the current efficacy of standard therapeutic agents, consider potential resistance mechanisms which could cause treatment failure and describe the practical aspects of managing this emerging clinical problem.

SOURCES

A PubMed search was conducted using combinations of the following terms: refractory, Giardia, giardiasis, resistance and treatment. Articles on the pharmacotherapy, drug resistance mechanisms and use of alternative agents in nitroimidazole-refractory giardiasis were reviewed.

CONTENT

We review the standard drugs for giardiasis, including their efficacy in initial treatment, mode of action and documented in vitro and in vivo drug resistance. We assess the efficacy of alternative drugs in nitroimidazole-refractory disease. Existing data suggest a potential advantage of combination treatment.

IMPLICATIONS

An optimal treatment strategy for refractory giardiasis has still to be determined, so there is no standard treatment regimen for nitroimidazole-refractory giardiasis. Further work on drug resistance mechanisms and the use of drug combinations in this condition is a priority.

Click Chemistry-Facilitated Structural Diversification of Nitrothiazoles, Nitrofurans, and Nitropyrroles Enhances Antimicrobial Activity against Giardia lamblia

Giardia lamblia is an important and ubiquitous cause of diarrheal disease. The primary agents in the treatment of giardiasis are nitroheterocyclic drugs, particularly the imidazoles metronidazole and tinidazole and the thiazole nitazoxanide. Although these drugs are generally effective, treatment failures occur in up to 20% of cases, and resistance has been demonstrated in vivo and in vitro Prior work had suggested that side chain modifications of the imidazole core can lead to new effective 5-nitroimidazole drugs that can combat nitro drug resistance, but the full potential of nitroheterocycles other than imidazole to yield effective new antigiardial agents has not been explored. Here, we generated derivatives of two clinically utilized nitroheterocycles, nitrothiazole and nitrofuran, as well as a third heterocycle, nitropyrrole, which is related to nitroimidazole but has not been systematically investigated as an antimicrobial drug scaffold. Click chemistry was employed to synthesize 442 novel nitroheterocyclic compounds with extensive side chain modifications. Screening of this library against representative G. lamblia strains showed a wide spectrum of in vitro activities, with many of the compounds exhibiting superior activity relative to reference drugs and several showing >100-fold increase in potency and the ability to overcome existing forms of metronidazole resistance. The majority of new compounds displayed no cytotoxicity against human cells, and several compounds were orally active against murine giardiasis in vivo These findings provide additional impetus for the systematic development of nitroheterocyclic compounds with nonimidazole cores as alternative and improved agents for the treatment of giardiasis and potentially other infectious agents.

Prokaryotic Expression of α-13 Giardin Gene and Its Intracellular Localization in Giardia lamblia

To study prokaryotic expression and subcellular localization of α-13 giardin in Giardia lamblia trophozoites, α-13 giardin gene was amplified and cloned into prokaryotic expression vector pET-28a(+). The positive recombinant plasmid was transformed into E. coli BL21(DE3) for expression by using IPTG and autoinduction expression system (ZYM-5052). The target protein was validated by SDS-PAGE and Western blotting and purified by Ni-NTA Resin. Rabbits were immunized with purified fusion proteins for preparation of polyclonal antibody; then the intracellular location of α-13 giardin was determined by fluorescence immunoassay. The results showed that the length of α-13 giardin gene was 1038 bp, encoding a polypeptide of 345 amino acids. The expressed product was a fusion protein with about 40 kDa largely present in soluble form. The target protein accounted for 21.0% of total proteins after being induced with IPTG, while it accounted for 28.8% with ZYM-5052. The anti-α13-giardin polyclonal antibody possessed good antigenic specificity as well as excellent binding activity with recombinant α-13 giardin. Immunofluorescence assays revealed that α-13 giardin was localized in the cytoplasm of G. lamblia trophozoite, suggesting that it is a cytoplasm-associated protein. The present study may lay a foundation for further functional research on α-13 giardin of G. lamblia.

A novel in vitro image-based assay identifies new drug leads for giardiasis

Giardia duodenalis is an intestinal parasite that causes giardiasis, a widespread human gastrointestinal disease. Treatment of giardiasis relies on a small arsenal of compounds that can suffer from limitations including side-effects, variable treatment efficacy and parasite drug resistance. Thus new anti-Giardia drug leads are required. The search for new compounds with anti-Giardia activity currently depends on assays that can be labour-intensive, expensive and restricted to measuring activity at a single time-point. Here we describe a new in vitro assay to assess anti-Giardia activity. This image-based assay utilizes the Perkin-Elmer Operetta^® and permits automated assessment of parasite growth at multiple time points without cell-staining. Using this new approach, we assessed the "Malaria Box" compound set for anti-Giardia activity. Three compounds with sub-μM activity (IC₅₀ 0.6-0.9 μM) were identified as potential starting points for giardiasis drug discovery.

Acute Acalculous Cholecystitis Caused by Giardia lamblia

We report a case of a 70-year-old man with acute acalculous cholecystitis caused by Giardia lamblia. Contrast-enhanced computed tomography (CT) showed distention of the gallbladder due to a pericholecystic abscess without gallstones. Magnetic resonance cholangiopancreatography and drip infusion cholecystocholangiography-CT demonstrated a stricture of the hilar bile duct and cystic duct obstruction. We conducted transpapillary bile duct brush cytology and a biopsy of the hilar bile duct stricture; numerous active trophozoites of Giardia lamblia were observed without malignant findings. We considered this bile duct lesion to be biliary giardiasis. Biliary giardiasis should be taken into consideration when diagnosing acute acalculous cholecystitis.

Lymphocytic duodenitis or microscopic enteritis and gluten-related conditions: what needs to be explored?

Microscopic enteritis (ME) is characterized by abnormal infiltration of intraepithelial lymphocytes in intestinal mucosa. It was described as duodenal lymphocytosis or lymphocytic duodenitis until the dedicated Consensus Conference of 2015. ME represents a common feature of several gluten-mediated and non-gluten related diseases; therefore, it is an umbrella term embracing several conditions. The most frequent causes of ME are gluten-related disorders (celiac disease, non-celiac gluten sensitivity, wheat allergy), Helicobacter pylori infection and drug-related damages. Less frequently, ME may be secondary to inflammatory bowel disease, some autoimmune conditions, immunoglobulin deficiencies, blood malignancies, infections and irritable bowel syndrome. Therefore, the differential diagnosis of ME may be challenging. The diagnosis of ME needs to be driven by predominant symptoms and patient history. However, it is often difficult to achieve an immediate identification of the underlying condition, and a broad variety of diagnostic tests may be required. Ultimately, long-term surveillance is needed for a final diagnosis in many cases, since a hidden or quiescent condition may be disclosed after a period of latency. In any case, strict collaboration between the clinician and the pathologist is pivotal. The treatment of ME should be personalized, depending on the underlying disease. For gluten-related conditions (celiac disease, gluten sensitivity, wheat allergy, dermatitis herpetiformis), a gluten-free diet may be proposed. For other conditions, a targeted etiologic treatment is necessary. In conclusion, ME represents a novel entity that is attracting increasing interest. The growing epidemiologic trend confirms that it will become a common condition in clinical practice.

An In Vitro Evaluation of Ozonized Organic Extra-Virgin Olive Oil on Giardia Lamblia Cysts

BACKGROUND

Giardia lamblia is a common intestinal parasite that has been reported all over the world.

OBJECTIVES

This study was conducted to evaluate the effect of ozonized organic extra-virgin olive oil on the cyst of G. lamblia.

METHODS

The olive oil was ozonized based on international standards and confirmed by the world health organization (WHO) at various times in a generator. The ozone concentration of olive oil was adjusted at 32, 64, 96, 128, 160 mg/g based on ozone absorption. Giardia lamblia cysts were isolated from heavily infected stool samples and the sucrose gradient flotation technique. Five groups of triple tubes containing Giardia cysts were exposed to olive oil with 32, 64, 96, 128, 160 ozone concentrations, and the sixth and seventh groups were exposed to non-ozonized olive oil and normal saline, respectively. The tubes were placed at room temperature, and every four hours, the mortality of the Giardia cysts was assessed.

RESULTS

The results showed that the first five groups' mortality rate of Giardia cysts reached 100% in 100 hours. An increasing concentration of ozone in olive oil leads to an increase in the mortality rate of Giardia cysts. The results showed a significant difference in the mean time of the mortality in all the groups (P ≤ 0.05). Furthermore, the higher fatality effect of ozonized organic extra-virgin olive oil (Ozonized Olive Oil = OZO) was proved in comparison with metronidazole in vitro.

CONCLUSIONS

We concluded that ozonized organic extra-virgin olive oil was a growth inhibitor of Giardia cysts, and concerning its compatibility with a biological system, it is recommended for further clinical trials.

Combination therapy in the management of giardiasis: What laboratory and clinical studies tell us, so far

Treatment failures in patients suffering from giardiasis are not uncommon feature. The most frequent approach in these cases is to treat these patients with longer repeated courses and/or higher doses of the primary therapy, or using drugs from a different class to avoid potential cross-resistance. However, a higher rate of adverse events may limit this strategy. In this context, combination therapy (CT) is emerging as a valuable option against refractory giardiasis. In the attempt to evaluate the benefits of CT, a number of experimental studies, clinical series, and randomized clinical trials (RCTs), as well as several veterinary studies have been performed, with varying results. Here, we present a critical analysis of the available information regarding CT for the treatment of Giardia infection, as well as the authors' opinion with respect to its use. RCTs of combination therapy are limited and the optimal combinations and administration strategies need yet to be clarified. Analyses of the cost-effectiveness and RCTs of CTs for Giardia infection are required to assess the role of these drugs for the control of giardiasis, mainly in the case of treatment failures linked to suspected drug tolerance are the case.

Divergent Transcriptional Responses to Physiological and Xenobiotic Stress in Giardia duodenalis

Understanding how parasites respond to stress can help to identify essential biological processes. Giardia duodenalis is a parasitic protist that infects the human gastrointestinal tract and causes 200 to 300 million cases of diarrhea annually. Metronidazole, a major antigiardial drug, is thought to cause oxidative damage within the infective trophozoite form. However, treatment efficacy is suboptimal, due partly to metronidazole-resistant infections. To elucidate conserved and stress-specific responses, we calibrated sublethal metronidazole, hydrogen peroxide, and thermal stresses to exert approximately equal pressure on trophozoite growth and compared transcriptional responses after 24 h of exposure. We identified 252 genes that were differentially transcribed in response to all three stressors, including glycolytic and DNA repair enzymes, a mitogen-activated protein (MAP) kinase, high-cysteine membrane proteins, flavin adenine dinucleotide (FAD) synthetase, and histone modification enzymes. Transcriptional responses appeared to diverge according to physiological or xenobiotic stress. Downregulation of the antioxidant system and α-giardins was observed only under metronidazole-induced stress, whereas upregulation of GARP-like transcription factors and their subordinate genes was observed in response to hydrogen peroxide and thermal stressors. Limited evidence was found in support of stress-specific response elements upstream of differentially transcribed genes; however, antisense derepression and differential regulation of RNA interference machinery suggest multiple epigenetic mechanisms of transcriptional control.

Introducing nitazoxanide as a promising alternative treatment for symptomatic to metronidazole-resistant giardiasis in clinical isolates

OBJECTIVE

To identify the frequencies (F) of ferredoxin and nitroreductase mutations on Iranian clinical isolates of Giardia lamblia in order to predict whether the nitazoxanide can be prescribed as suitable drug for symptomatic to metronidazole-resistant giardiasis.

METHODS

Forty Giardia lamblia isolates as of 38 symptomatic and two metronidazole-resistant patients were collected from Iran. DNAs were extracted and amplified by targeting ferredoxin and GlNR genes. The amplicons were directly sequenced to determine gene mutations.

RESULTS

The various amino acid substitutions (F: 20%, Haplotype diversity: 0.891, Tajima's D: -0.44013) were identified by analyzing ferredoxin gene in four symptomatic and two resistant isolates. Only two haplotypes (F: 5%, HD: 0.345; Tajima's D: 0.77815) characterized in metronidazole-resistant isolates of GlNR, however, no point mutations was found in symptomatic isolates.

CONCLUSIONS

Non-synonymous mutations of ferredoxin oxidoreductase gene reduce translational regulatory protein's binding affinity which concludes reduction of ferredoxin expression and its activity. This leads to decrease in metronidazole drug delivery into the cells. Mutations in these isolates may lead to their resistance to metronidazole. No to low synonymous mutations of GlNR demonstrates that nitazoxanide can be prescribed as promising alternative treatment for symptomatic to metronidazole-resistant giardiasis in Iranian clinical isolates.

Accuracy of Mobile Phone and Handheld Light Microscopy for the Diagnosis of Schistosomiasis and Intestinal Protozoa Infections in Côte d'Ivoire

Background

Handheld light microscopy using compact optics and mobile phones may improve the quality of health care in resource-constrained settings by enabling access to prompt and accurate diagnosis.

Methodology

Laboratory technicians were trained to operate two handheld diagnostic devices (Newton Nm1 microscope and a clip-on version of the mobile phone-based CellScope). The accuracy of these devices was compared to conventional light microscopy for the diagnosis of Schistosoma haematobium, S. mansoni, and intestinal protozoa infection in a community-based survey in rural Côte d’Ivoire. One slide of 10 ml filtered urine and a single Kato-Katz thick smear from 226 individuals were subjected to the Newton Nm1 microscope and CellScope for detection of Schistosoma eggs and compared to conventional microscopy. Additionally, 121 sodium acetate-acetic acid-formalin (SAF)-fixed stool samples were examined by the Newton Nm1 microscope and compared to conventional microscopy for the diagnosis of intestinal protozoa.

Principal Findings

The prevalence of S. haematobium, S. mansoni, Giardia intestinalis, and Entamoeba histolytica/E. dispar, as determined by conventional microscopy, was 39.8%, 5.3%, 20.7%, and 4.9%, respectively. The Newton Nm1 microscope had diagnostic sensitivities for S. mansoni and S. haematobium infection of 91.7% (95% confidence interval (CI) 59.8–99.6%) and 81.1% (95% CI 71.2–88.3%), respectively, and specificities of 99.5% (95% CI 97.0–100%) and 97.1% (95% CI 92.2–99.1%), respectively. The CellScope demonstrated sensitivities for S. mansoni and S. haematobium of 50.0% (95% CI 25.4–74.6%) and 35.6% (95% CI 25.9–46.4%), respectively, and specificities of 99.5% (95% CI 97.0–100%) and 100% (95% CI 86.7–100%), respectively. For G. intestinalis and E. histolytica/E. dispar, the Newton Nm1 microscope had sensitivity of 84.0% (95% CI 63.1–94.7%) and 83.3% (95% CI 36.5–99.1%), respectively, and 100% specificity.

Conclusions/Significance

Handheld diagnostic devices can be employed in community-based surveys in resource-constrained settings after minimal training of laboratory technicians to diagnose intestinal parasites.

Handheld light microscopes are new technologies that may be helpful in enabling better access to diagnostic testing for people living in resource-constrained settings in tropical and subtropical countries. Recent studies evaluating the accuracy of such devices have focused on their use by expert microscopists and were mainly conducted in laboratories. We evaluated the operating performance of two handheld microscopes (Newton Nm1 microscope and clip-on version of the reversed-lens CellScope) in comparison to conventional microscopy for the diagnosis of urogenital and intestinal schistosomiasis, when integrated into routine use in a community-based survey carried out in Côte d’Ivoire. Additionally, we evaluated the same microscopist’s diagnostic performance with the Newton Nm1 microscope for intestinal protozoa in a laboratory set-up. The Newton Nm1 microscope demonstrated excellent diagnostic sensitivity and specificity for schistosomiasis and intestinal protozoa. The CellScope had high specificity but only modest sensitivity for schistosomiasis diagnosis. Taken together, handheld diagnostic tools show promise to improve the quality of clinical and public health care delivered in resource-constrained settings.

Chronic spontaneous urticaria and internal parasites--a systematic review

Chronic spontaneous urticaria (CSU) is defined as persistent wheals, angioedema, or both lasting for >6 weeks due to known or unknown causes. Some epidemiological studies and case reports suggest that internal parasite infections (PI) can cause CSU. Here, we provide a systematic overview of published findings on the prevalence and relevance of PI in CSU and we discuss possible pathomechanisms. The prevalence of PI in CSU was investigated by 39 independent studies and comorbidity reportedly ranged from 0 to 75.4% (two-thirds of these studies reported infection rates of 10% or less). The prevalence of PI in adult and pediatric CSU patients ranged from 0% to 75.4% and from 0% to 37.8%, respectively. CSU patients were more often diagnosed with protozoa and had a significantly higher risk of toxocariasis seropositivity and Anisakis simplex sensitization when compared to healthy controls. Patients with chronic urticaria more frequently had seropositivity of fasciolosis, Anisakis simplex sensitization, and the presence of Blastocystis hominis allele 34 (ST3) as compared with control subjects. In 21 studies, efficacy of treatment with antiparasitic drugs ranged from 0 to 100% (35.7% of 269 CSU patients benefitted). In 9 (42.8%) of 21 studies, more than 50% of efficacy was observed. The reported rate of urticaria comorbidity in PI patients in 18 independent studies is 1-66.7%. Urticaria including CSU might be a quite common symptom of strongyloidiasis and blastocystosis. Pathogenic mechanisms in CSU due to PI may include specific IgE, Th2 cytokine skewing, eosinophils, activation of the complement, and the coagulation systems.

Synthesis, characterization and antimicrobial activity of water-soluble silver(i) complexes of metronidazole drug and selected counter-ions

A series of water-soluble silver(i) complexes of the type [Ag(MTZ)2X] [MTZ = 1-(2-hydroxyethyl)-2-methyl-5-nitro-1H-imidazole (metronidazole drug); X = NO3(-), ClO4(-), CF3COO(-), BF4(-) and CH3SO3(-)] was synthesised by the reactions of various Ag(i) salts with metronidazole (MTZ). All the complexes were characterized by ESI-MS spectrometry, solution NMR ((1)H and (13)C) and IR spectroscopy, and elemental analysis. Further evidence for the formation and molecular structure of all the complexes was provided by X-ray single-crystal crystallography. The different counter ions affect the crystal packing of the complexes and thus have an impact on the final geometries. The antimicrobial activities of the complexes against two Gram-positive strains: Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 12228, three Gram-negative strains: Pseudomonas aeruginosa ATCC 15442, Escherichia coli ATCC 25922, Proteus hauseri ATCC 13315 and yeast Candida albicans ATCC 10231 were evaluated and compared with antibacterial and antifungal properties of appropriate silver salts, metronidazole and silver sulfadiazine drugs. The newly synthesized compounds exhibited significant antibacterial activity against Gram-positive bacteria, better than the referenced silver sulfadiazine. The best active silver(i)-metronidazole complex contains a methanesulphonate counter-ion. Moreover, the complex inhibited the growth of yeast Candida albicans at a concentration 3-fold lower than that required for silver sulfadiazine. In addition, the complexes containing a tetrafluoroborate and a perchlorate as counter-ions were characterized as effective antibacterial agents against the tested Gram-negative bacteria.

A meta-analysis of the efficacy of albendazole compared with tinidazole as treatments for Giardia infections in children

Metronidazole is frequently used against Giardia infection; however, it has been associated with significant failure rates in clearing parasites from the gut; additionally, as it should be taken for 5 to 10 days, it is associated with poor compliance, probably due to side effects. Other drugs, including tinidazole (TNZ) and albendazole (ABZ) have been included in the antigiardial armamentarium. Our aim was to assess the efficacy of ABZ compared with TNZ in Giardia infections in children. A systematic review and a meta-analysis were carried out. PubMed, Medline, EMBASE, CENTRAL, and LILACS were searched electronically until February 2015. Also relevant journals and references of studies included therein were hand-searched for randomised controlled trials (RCTs). The meta-analysis was limited to RCTs evaluating the use of ABZ compared with TNZ in children with Giardia infection. The assessed outcome was parasitological efficacy. Prediction intervals (PI) were computed to better express uncertainties in the effect estimates. Five RCTs including 403 children were included. Overall, TNZ significantly outperformed ABZ without differences between subgroups defined by ABZ dosages [relative risk, (RR) 1.61 (95% CI): (1.40-1.85); P<0.0001]. The 95% prediction interval range is 1.28-2.02. There was no significant heterogeneity (I(2)=0%; Q-test of heterogeneity P=0.4507. The number-needed-to-treat, the average number of patients who need to be treated with TNZ to gain one additional good outcome as compared with ABZ was 4, 95% CI: 3-5. Our results show that TNZ outperforms ABZ in the treatment of Giardia infections in children from developing countries.

Time-Dependent Transcriptional Changes in Axenic Giardia duodenalis Trophozoites

Giardia duodenalis is the most common gastrointestinal protozoan parasite of humans and a significant contributor to the global burden of both diarrheal disease and post-infectious chronic disorders. Although G. duodenalis can be cultured axenically, significant gaps exist in our understanding of the molecular biology and metabolism of this pathogen. The present study employed RNA sequencing to characterize the mRNA transcriptome of G. duodenalis trophozoites in axenic culture, at log (48 h of growth), stationary (60 h), and declining (96 h) growth phases. Using ~400-times coverage of the transcriptome, we identified 754 differentially transcribed genes (DTGs), mainly representing two large DTG groups: 438 that were down-regulated in the declining phase relative to log and stationary phases, and 281 that were up-regulated. Differential transcription of prominent antioxidant and glycolytic enzymes implicated oxygen tension as a key factor influencing the transcriptional program of axenic trophozoites. Systematic bioinformatic characterization of numerous DTGs encoding hypothetical proteins of unknown function was achieved using structural homology searching. This powerful approach greatly informed the differential transcription analysis and revealed putative novel antioxidant-coding genes, and the presence of a near-complete two-component-like signaling system that may link cytosolic redox or metabolite sensing to the observed transcriptional changes. Motif searching applied to promoter regions of the two large DTG groups identified different putative transcription factor-binding motifs that may underpin global transcriptional regulation. This study provides new insights into the drivers and potential mediators of transcriptional variation in axenic G. duodenalis and provides context for static transcriptional studies.

Drug Development Against the Major Diarrhea-Causing Parasites of the Small Intestine, Cryptosporidium and Giardia

Diarrheal diseases are among the leading causes of morbidity and mortality in the world, particularly among young children. A limited number of infectious agents account for most of these illnesses, raising the hope that advances in the treatment and prevention of these infections can have global health impact. The two most important parasitic causes of diarrheal disease are Cryptosporidium and Giardia. Both parasites infect predominantly the small intestine and colonize the lumen and epithelial surface, but do not invade deeper mucosal layers. This review discusses the therapeutic challenges, current treatment options, and drug development efforts against cryptosporidiosis and giardiasis. The goals of drug development against Cryptosporidium and Giardia are different. For Cryptosporidium, only one moderately effective drug (nitazoxanide) is available, so novel classes of more effective drugs are a high priority. Furthermore, new genetic technology to identify potential drug targets and better assays for functional evaluation of these targets throughout the parasite life cycle are needed for advancing anticryptosporidial drug design. By comparison, for Giardia, several classes of drugs with good efficacy exist, but dosing regimens are suboptimal and emerging resistance begins to threaten clinical utility. Consequently, improvements in potency and dosing, and the ability to overcome existing and prevent new forms of drug resistance are priorities in antigiardial drug development. Current work on new drugs against both infections has revealed promising strategies and new drug leads. However, the primary challenge for further drug development is the underlying economics, as both parasitic infections are considered Neglected Diseases with low funding priority and limited commercial interest. If a new urgency in medical progress against these infections can be raised at national funding agencies or philanthropic organizations, meaningful and timely progress is possible in treating and possibly preventing cryptosporidiosis and giardiasis.