New insights into Blastocystis spp.: a potential link with irritable bowel syndrome

Prevalence and Risk Factors of Human Intestinal Parasites in Roudehen, Tehran Province, Iran

BACKGROUND

Intestinal parasitic infections are among the most common infections and health problems worldwide. Due to the lack of epidemiologic information of such infections, the prevalence of, and the risk factors for, enteric parasites were investigated in residents of Roudehen, Tehran Province, Iran.

METHODS

In this cross-sectional study, 561 triple fecal samples were collected through a two-stage cluster-sampling protocol from Jun to Dec 2014. The samples were examined by formalin-ether concentration, culture, and with molecular methods.

RESULTS

The prevalence of enteric parasites was 32.7% (95% CI 27.3-38). Blastocystis sp. was the most common intestinal protozoan (28.4%; 95% CI 23.7-33.0). The formalin-ether concentration and culture methods detected Blastocystis sp., Entamoeba coli, Giardia intestinalis, Dientamoeba fragilis, Iodamoeba butschlii, Entamoeba complex cysts or trophozoite, Chilomastix mesnilii, and Enterobius vermicularis. Single-round PCR assay for Entamoeba complex were identified Entamoeba dispar and E. moshkovskii. E. histolytica was not observed in any specimen. Multivariate analysis showed a significant association of parasites with water source and close animal contact. There was no correlation between infections and gender, age, occupation, education, or travel history. Protozoan infections were more common than helminth infections.

CONCLUSION

This study revealed a high prevalence of enteric protozoan parasite infection among citizens of Rodehen. As most of the species detected are transmitted through a water-resistant cyst, public and individual education on personal hygiene should be considered to reduce transmission of intestinal parasites in the population.

Blastocystis Mitochondrial Genomes Appear to Show Multiple Independent Gains and Losses of Start and Stop Codons

Complete mitochondrion-related organelle (MRO) genomes of several subtypes (STs) of the unicellular stramenopile Blastocystis are presented. Complete conservation of gene content and synteny in gene order is observed across all MRO genomes, comprising 27 protein coding genes, 2 ribosomal RNA genes, and 16 transfer RNA (tRNA) genes. Despite the synteny, differences in the degree of overlap between genes were observed between subtypes and also between isolates within the same subtype. Other notable features include unusual base-pairing mismatches in the predicted secondary structures of some tRNAs. Intriguingly, the rps4 gene in some MRO genomes is missing a start codon and, based on phylogenetic relationships among STs, this loss has happened twice independently. One unidentified open reading frame (orf160) is present in all MRO genomes. However, with the exception of ST4 where the feature has been lost secondarily, orf160 contains variously one or two in-frame stop codons. The overall evidence suggests that both the orf160 and rps4 genes are functional in all STs, but how they are expressed remains unclear.

Prevalence and Subtype Identification of Blastocystis sp. in Healthy Individuals in the Tunis Area, Tunisia

Blastocystis sp. is currently the most common eukaryotic parasite found in humans. Despite its potential public health impact, epidemiological data regarding its prevalence and molecular subtype (ST) distribution in Maghreb are rarely reported. Therefore, the aim of this study was to determine the prevalence of the parasite in a cohort of healthy food handler Tunisian individuals and to acquire the first molecular data regarding the distribution of Blastocystis sp. STs in this country. Therefore, 524 fecal samples were collected, and 68 of them (13%) were identified as positive for the parasite by direct-light microscopy of smears. Seventeen samples of 100 negative by microscopy were also shown to be positive by real-time quantitative polymerase chain reaction. Among all the positive samples, 61 Blastocystis isolates were subtyped using partial small subunit ribosomal RNA gene analysis. ST3 was the most abundant (51%) followed by ST1 (30%), ST2 (16%), and ST4 and ST7 (both 1.6%).

Subtype analysis of Blastocystis isolates using SSU rRNA-DNA sequencing in rural and urban population in southern Turkey

Blastocystis is a common and emerging parasite often seen in many studies conducted in urban population, with scanty reports on rural communities. However, little is known about the public health significance of Blastocystis infection. A total of 28 Blastocystis isolates from 17 (17/28, 60.71%) patients living in rural area and 11 (11/28, 39.29%) patients living in urban area were screened with seven kinds of sequenced-tagged site primers for identification of subtype. PCR products were sequenced with same combination of primers using the BigDye Terminator V 3.1 cycle sequencing kit, as per the manufacturers' protocol on the 3730 DNA analyzer (Applied Biosystems, Carlsbad CA, USA). The cross-comparison of the Blastocystis sequences of samples were determined by the neighbor-joining method based on a distance matrix between sequence pairs to generate dendograms. The following subtypes were identified; subtype 1 (10/28, 35.7%), subtype 3 (7/28, 25.0%), subtype 2 (5/28, 17.8%), subtype 4 (3/28, 10.7%), subtype 5 (1/28, 3.6%), subtype 6 (1/28, 3.6%), and subtype 7 (1/28, 3.6%) in all DNA samples. The comparison of Blastocystis subtypes distribution among the patients from rural and urban area revealed subtype 5 (1/17, 5.9%), subtype 6 (1/17, 5.9%) and subtype 7 (1/17, 5.9%) from patients of rural area but not any of these subtypes in patients living urban area. This study is the first large-scale study to examine the occurrence of Blastocystis in Turkey to shed lights on the cosmopolitan distribution of Blastocystis subtypes in southern part of Turkey. Subtype 5, subtype 6 and subtype 7 were determined in only rural area. The findings of this study suggest that Blastocystis is transmitted from animal to human and possess a zoonotic potential.

On Blastocystis secreted cysteine proteases: a legumain-activated cathepsin B increases paracellular permeability of intestinal Caco-2 cell monolayers

Blastocystis spp. pathogenic potential remains unclear as these anaerobic parasitic protozoa are frequently isolated from stools of both symptomatic and asymptomatic subjects. In silico analysis of the whole genome sequence of Blastocystis subtype 7 revealed the presence of numerous proteolytic enzymes including cysteine proteases predicted to be secreted. To assess the potential impact of proteases on intestinal cells and gut function, we focused our study on two cysteine proteases, a legumain and a cathepsin B, which were previously identified in Blastocystis subtype 7 culture supernatants. Both cysteine proteases were produced as active recombinant proteins. Activation of the recombinant legumain was shown to be autocatalytic and triggered by acidic pH, whereas proteolytic activity of the recombinant cathepsin B was only recorded after co-incubation with the legumain. We then measured the diffusion of 4-kDa FITC-labelled dextran across Caco-2 cell monolayers following exposition to either Blastocystis culture supernatants or each recombinant protease. Both Blastocystis culture supernatants and recombinant activated cathepsin B induced an increase of Caco-2 cell monolayer permeability, and this effect was significantly inhibited by E-64, a specific cysteine protease inhibitor. Our results suggest that cathepsin B might play a role in pathogenesis of Blastocystis by increasing intestinal cell permeability.

Comparison of faecal microbiota in Blastocystis-positive and Blastocystis-negative irritable bowel syndrome patients

BACKGROUND

We investigated whether the carriage of Blastocystis in IBS patients was associated with differences in the faecal microbiota. Forty patients with diarrhoea-predominant IBS (26 Blastocystis-positive and 14 Blastocystis-negative) and 57 healthy controls (HC) (42 Blastocystis-positive and 15 Blastocystis-negative) submitted faecal samples for metataxonomic analysis of the 16S ribosomal RNA gene. Differences in the relative abundance of bacteria in these IBS and HC groups were evaluated from phylum to genus level.

RESULTS

Significant changes were observed in two dominant phyla in IBS patients, regardless of Blastocystis infection status, namely a rise in Firmicutes and a statistically significant reduction in relative abundance of Bacteroidetes (with a threefold increase in the Firmicutes to Bacteoridetes ratio). Significant differences at genus level in IBS subjects compared to HC were also observed for many bacterial species. However, further clinical subgroup analysis of Blastocystis-positive and Blastocystis-negative subjects, regardless of symptoms, showed no significant differences at the phylum or genus level in IBS-P compared to IBS-N.

CONCLUSIONS

Significant differences in the faecal microbiota between diarrhoea-predominant IBS patients and healthy controls were confirmed, but the carriage of Blastocystis did not significantly alter the faecal microbiota. If Blastocystis-positive patients represent a separate clinical subtype of IBS, this group is not identified by changes in the microbiota.

Prevalence, risk factors for infection and subtype distribution of the intestinal parasite Blastocystis sp. from a large-scale multi-center study in France

Background

Blastocystis sp. is the most common intestinal parasite of humans. Despite its potential public health impact, epidemiological data regarding the prevalence and molecular subtype distribution of Blastocystis sp. in Europe are rarely reported. Therefore, the first multi-center epidemiological survey performed in Europe was conducted in France to diagnose and subtype Blastocystis sp. and to identify risk factors for infection.

Methods

Stool samples from 788 patients were collected either in summer or winter in 11 hospitals throughout France together with patient data. All stool samples were tested for the presence of Blastocystis sp. by quantitative PCR targeting the SSU rDNA gene. Positive samples were sequenced to determine the distribution of the subtypes in our cohort. Statistical analyses were performed to identify potential risk factors for infection.

Results

Using quantitative PCR, the overall prevalence of Blastocystis sp. was shown to reach 18.1 %. The prevalence was significantly higher in summer (23.2 %) than in winter (13.7 %). Travellers or subjects infected with other enteric parasites were significantly more infected by Blastocystis sp. than non-travellers or subjects free of other enteric parasites, respectively. Different age-related epidemiological patterns were also highlighted from our data. The prevalence of Blastocystis sp. was not significantly higher in patients with digestive symptoms or diagnosed with chronic bowel diseases. Among symptomatic patients, Blastocystis sp. infection was significantly associated with abdominal pain. Gender, socioeconomic status, and immune status were not identified as potential risk factors associated with infection. Among a total of 141 subtyped isolates, subtype 3 was predominant (43.3 %), followed by subtype 1 and subtype 4 (20 %), subtype 2 (12.8 %), subtype 6 and subtype 7 (2.1 %). No association between ST and clinical symptoms was statistically evidenced.

Conclusions

A high prevalence of Blastocystis sp. infection was found in our French patient population. Seasonal impact on the prevalence of Blastocystis sp. was highlighted and recent travels and age were identified as main risk factors for infection. Most cases were caused by subtypes 1 to 4, with a predominance of subtype 3. Large variations in both prevalence and ST distribution between hospitals were also observed, suggesting distinct reservoirs and transmission sources of the parasite.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1776-8) contains supplementary material, which is available to authorized users.

Blastocystis Isolate B Exhibits Multiple Modes of Resistance against Antimicrobial Peptide LL-37

Blastocystis is one of the most common eukaryotic organisms found in humans and many types of animals. Several reports have identified its role in gastrointestinal disorders, although its pathogenicity is yet to be clarified. Blastocystis is transmitted via the fecal-to-oral route and colonizes the large intestines. Epithelial cells lining the intestine secrete antimicrobial peptides (AMPs), including beta-defensins and cathelicidin, as a response to infection. This study explores the effects of host colonic antimicrobial peptides, particularly LL-37, a fragment of cathelicidin, on different Blastocystis subtypes. Blastocystis is composed of several subtypes that have genetic, metabolic, and biological differences. These subtypes also have various outcomes in terms of drug treatment and immune response. In this study, Blastocystis isolates from three different subtypes were found to induce intestinal epithelial cells to secrete LL-37. We also show that among the antimicrobial peptides tested, only LL-37 has broad activity on all the subtypes. LL-37 causes membrane disruption and causes Blastocystis to change shape. Blastocystis subtype 7 (ST7), however, showed relative resistance to LL-37. An isolate, ST7 isolate B (ST7-B), from this subtype releases proteases that can degrade the peptide. It also makes the environment acidic, which causes attenuation of LL-37 activity. The Blastocystis ST7-B isolate was also observed to have a thicker surface coat, which may protect the parasite from direct killing by LL-37. This study determined the effects of LL-37 on different Blastocystis isolates and indicates that AMPs have significant roles in Blastocystis infections.

Current status of Blastocystis: A personal view

Despite Blastocystis being one of the most widespread and prevalent intestinal eukaryotes, its role in health and disease remains elusive. DNA-based detection methods have led to a recognition that the organism is much more common than previously thought, at least in some geographic regions and some groups of individuals. Molecular methods have also enabled us to start categorizing the vast genetic heterogeneity that exists among Blastocystis isolates, wherein the key to potential differences in the clinical outcome of Blastocystis carriage may lie. In this review we summarize some of the recent developments and advances in Blastocystis research, including updates on diagnostic methods, molecular epidemiology, genetic diversity, host specificity, clinical significance, taxonomy, and genomics. As we are now in the microbiome era, we also review some of the steps taken towards understanding the place of Blastocystis in the intestinal microbiota.

Pathogenic mechanisms in Blastocystis spp. - Interpreting results from in vitro and in vivo studies

Blastocystis spp. are commonly reported intestinal protists but whose clinical significance remains controversial. Infections have ranged from asymptomatic carriage to non-specific gastrointestinal symptoms and have also been linked to irritable bowel syndrome and urticaria in some patient populations. In vitro studies showed that both parasite and parasite lysates have damaging effects on intestinal epithelial cells causing apoptosis and degradation of tight junction proteins occludin and ZO1, resulting in increased intestinal permeability. Adhesion of trophic forms to the intestinal epithelium and release of cysteine proteases appear to be the major triggers leading to pathogenesis. Two putative virulence factors identified are cysteine proteases legumain and cathepsin B. Blastocystis spp. also have immuno-modulatory effects including degradation of IgA, inhibition of iNOS and upregulation of proinflammatory cytokines, IL8 and GM-CSF in intestinal epithelial cells and IL1β, IL6 and TNFα in murine macrophages. Blastocystis spp. have also been reported to dampen response to LPS in intestinal epithelial cells and monocytes. Studies in rodent models and naturally infected pigs have shown that the parasite localizes to the lumen and mucosal surface of the large intestine mostly in the caecum and colon. The parasite has been found to cause mucosal sloughing, increase in goblet cell mucin, increased intestinal permeability and to induce a pro-inflammatory cytokine response with upregulation of TNFα, IFNγ and IL12. In this review, we summarize findings from in vitro and in vivo studies that demonstrate pathogenic potential but also show considerable inter and intra subtype variation, which provides a plausible explanation on the conflicting reports on clinical significance.

Colonization with the enteric protozoa Blastocystis is associated with increased diversity of human gut bacterial microbiota

Alterations in the composition of commensal bacterial populations, a phenomenon known as dysbiosis, are linked to multiple gastrointestinal disorders, such as inflammatory bowel disease and irritable bowel syndrome, or to infections by diverse enteric pathogens. Blastocystis is one of the most common single-celled eukaryotes detected in human faecal samples. However, the clinical significance of this widespread colonization remains unclear, and its pathogenic potential is controversial. To address the issue of Blastocystis pathogenicity, we investigated the impact of colonization by this protist on the composition of the human gut microbiota. For that purpose, we conducted a cross-sectional study including 48 Blastocystis-colonized patients and 48 Blastocystis-free subjects and performed an Ion Torrent 16S rDNA gene sequencing to decipher the Blastocystis-associated gut microbiota. Here, we report a higher bacterial diversity in faecal microbiota of Blastocystis colonized patients, a higher abundance of Clostridia as well as a lower abundance of Enterobacteriaceae. Our results contribute to suggesting that Blastocystis colonization is usually associated with a healthy gut microbiota, rather than with gut dysbiosis generally observed in metabolic or infectious inflammatory diseases of the lower gastrointestinal tract.

Prevalence and Risk Factors for Intestinal Protozoan Infections with Cryptosporidium, Giardia, Blastocystis and Dientamoeba among Schoolchildren in Tripoli, Lebanon

BACKGROUND

Intestinal protozoan infections are confirmed as major causes of diarrhea, particularly in children, and represent a significant, but often neglected, threat to public health. No recent data were available in Lebanon concerning the molecular epidemiology of protozoan infections in children, a vulnerable population at high risk of infection.

METHODOLOGY AND PRINCIPAL FINDINGS

In order to improve our understanding of the epidemiology of intestinal pathogenic protozoa, a cross-sectional study was conducted in a general pediatric population including both symptomatic and asymptomatic subjects. After obtaining informed consent from the parents or legal guardians, stool samples were collected in January 2013 from 249 children in 2 schools in Tripoli, Lebanon. Information obtained from a standard questionnaire included demographic characteristics, current symptoms, socioeconomic status, source of drinking water, and personal hygiene habits. After fecal examination by both microscopy and molecular tools, the overall prevalence of parasitic infections was recorded as 85%. Blastocystis spp. presented the highest infection rate (63%), followed by Dientamoeba fragilis (60.6%), Giardia duodenalis (28.5%) and Cryptosporidium spp. (10.4%). PCR was also performed to identify species and genotypes of Cryptosporidium, subtypes of Blastocystis, and assemblages of Giardia. Statistical analysis using a logistic regression model showed that contact with family members presenting gastrointestinal disorders was the primary risk factor for transmission of these protozoa.

CONCLUSIONS

This is the first study performed in Lebanon reporting the prevalence and the clinical and molecular epidemiological data associated with intestinal protozoan infections among schoolchildren in Tripoli. A high prevalence of protozoan parasites was found, with Blastocystis spp. being the most predominant protozoans. Although only 50% of children reported digestive symptoms, asymptomatic infection was observed, and these children may act as unidentified carriers. This survey provides necessary information for designing prevention and control strategies to reduce the burden of these protozoan infections, especially in children.

Immunopathological assessments of human Blastocystis spp. in experimentally infected immunocompetent and immunosuppresed mice

Blastocystis spp., one of the most common parasites colonizing the human intestine, is an extracellular, luminal protozoan with controversial pathogenesis. The host's immune response against Blastocystis spp. infection has also not been defined yet. Therefore, this research aimed to assess the potential pathogenicity of this parasite and its ability to modulate the immune response in experimental infected immunocompetent and immunosuppresed mice. These results demonstrated that the infected immunosuppressed mice were more affected than infected immunocompetent mice. Histopathological examination of the small intestine in the infected immunosuppressed mice showed that Blastocystis spp. infiltrated all the layers. Moreover, the epithelia showed exfoliation and inflammatory cell infiltration in submucosa compared to that of the infected immunocompetent mice. As well, examination of the large intestine of the infected immunosuppressed group showed severe goblet cell hyperplasia. Blastocystis spp. infiltrated all the large intestine layers compared to that of the infected immunocompetent group. Furthermore, there was a significant upregulation of the expression of proinflammatory cytokines: interleukin 12 (IL-12) and tumor necrosis factor alpha (TNF-α) in the infected immunosuppressed mice compared to that of the infected immunocompetent ones (p ≤ 0.004 and p ≤ 0.002, respectively). However, the expression of anti-inflammatory cytokines (IL-4 and IL-10) was significantly downregulated in the infected immunosuppressed group compared to that of the infected immunocompetent group one at 10 days postinfection (p ≤ 0.002 and p ≤ 0.001, respectively). The results of this study revealed that Blastocystis spp. affected the production of pro- and anti-inflammatory cytokines in both groups of mice compared to healthy normal (naive) group. Additionally, these data showed that there was a significant upregulation (p ≤ 0.005) of the locally synthesized antibody: secretary IgA (sIgA) in the gut of the infected immunocompetent mice when compared to that of the infected immunosuppressed ones.

Molecular Characterization and Subtyping of Blastocystis Species in Irritable Bowel Syndrome Patients from North India

Blastocystis species has been extensively studied in recent few years to establish its pathogenecity. Present study was designed to identify and examine the association of Blastocystis sp. and its subtypes with Irritable Bowel Syndrome (IBS).Blastocystis sp. detected using wet-mount microscopy, trichrome staining, in-vitro culture and Polymerase Chain Reaction (PCR) assay in a cohort of IBS patients (n = 150) and healthy controls (n = 100). Isolates of Blastocystis sp.were subtyped using Sequence Tagged Site and representative samples were sequenced at SSUrRNA locus.A total of sixty five isolates of Blastocystis sp. were identified [IBS (n = 50); Controls (n = 15)] of which 91% belonged to ST3 and 9% belonged to ST1. No other subtypes could be identified. Statistically significant association was observed between Blastocystis sp. and IBS patients; however no particular subtype could be ascertained to any particular clinical type of IBS.The frequency of occurrence of Blastocystis sp. was more in IBS patients as compared to the controls and ST3 being the most prevalent subtype. The genetic polymorphism of SSU-rRNA gene amongst the different Blastocystis sp.isolates found in this study reinforces the fact that these organisms are genetically highly divergent.

Eradication of Blastocystis in humans: Really necessary for all?

Blastocystis (initially named as Blastocystis hominis) has long been known as a protist without any clinical significance. However, there is now a huge pile of case reports where Blastocystis is blamed for the symptoms and the infection described in the patients. Introduction of the presence of as many as 17 Blastocystis subtypes while many infected individuals are non-symptomatic initially brought about the correlation between the subtypes and pathogenicity; however, the outcomes of these trials were not consistent and did not explain its pathogenicity. Today, it is mostly acknowledged that Blastocystis may colonize many individuals but the infection's onset depends on the interaction between the virulence of parasites and host's immune competence. Eradication of Blastocystis is essential in some cases where it is the only infectious agent and patient is suffering from some symptoms. In such cases, metronidazole is the drug of choice but its efficacy is relatively low in some cases. Other agents used include trimethoprim-sulfamethoxazole, paromomycin, and furazolidone. Recent studies on the interactions between human health and the role of gut microbiota introduces new data which may significantly change our point of view against some protists, which we tend to see as "parasites requiring urgent eradication for cure". May the presence or absence of some Blastocystis subtypes necessary for human health, or is the absence or presence of certain Blastocystis subtypes in human gut is associated with certain diseases/infections? The answers of these questions will surely guide us to select patients requiring treatment against Blastocystis infection in future.

Prevalence and subtype distribution of Blastocystis in healthy individuals in Sharjah, United Arab Emirates

Blastocystis is estimated to be one of the most common parasites of the intestinal tract of humans, comprising multiple subtypes (ST). Meanwhile, the distribution of Blastocystis ST in many communities and countries remains unknown. In the present work, we aimed to identify the prevalence of Blastocystis and the ST distribution in human stool samples collected from healthy expatriates from different geographical regions and residing in Sharjah, United Arabian Emirates (UAE). A total of 133 samples were screened and subtyped using partial small subunit ribosomal RNA gene sequencing. Fifty-nine (44.4%) samples were identified as positive. Among these, 39 were successfully sequenced and subtyped. The ST distribution was as follows: ST3, 58.9% (23/39); ST1, 28.2% (11/39); and ST2, 7.6% (3/39). No correlation between geographic origin and infection (χ(2)=11.006; P=0.528) nor gender and infection (χ(2)=1.264; P=0.261) was observed. The data were compared with those available for other Middle Eastern and North African neighboring countries. This study is the first to provide data concerning the prevalence of Blastocystis and the frequency of various STs in the UAE, confirming the absence of ST4 and the commonness of ST1, ST2, and ST3 in this geographical region.

Mysterious chronic urticaria caused by Blastocystis spp.?

Species of the genus Blastocystis, which are single-cell, intestinal protozoan parasites of humans and animals, remain mysterious, with unclear clinical and epidemiologic significance. In recent years, many researchers have suggested a possible connection between Blastocystis spp. infection and chronic urticaria. In the present article, we review the literature and discuss the possible associations between the clinical symptomatology and pathogenicity of this organism in terms of its subtypes, morphologic forms, genetic diversity, and interactions with other intestinal microbiota.

Effect of sanitation and water treatment on intestinal protozoa infection: a systematic review and meta-analysis

BACKGROUND

Pathogenic intestinal protozoa infections are responsible for substantial mortality and morbidity, particularly in settings where people lack improved sanitation and safe drinking water. We assessed the relation between access to, and use of, sanitation facilities and water treatment and infection with intestinal protozoa.

METHODS

We did a systematic review and searched PubMed, ISI Web of Science, and Embase from inception to June 30, 2014, without restrictions on language. All publications were examined by two independent reviewers and were included if they presented data at the individual level about access or use of sanitation facilities or water treatment, in combination with individual-level data on human intestinal protozoa infections. Meta-analyses using random effects models were used to calculate overall estimates.

FINDINGS

54 studies were included and odds ratios (ORs) extracted or calculated from 2 × 2 contingency tables. The availability or use of sanitation facilities was associated with significantly lower odds of infection with Entamoeba histolytica or Entamoeba dispar (OR 0·56, 95% CI 0·42-0·74) and Giardia intestinalis (0·64, 0·51-0·81), but not for Blastocystis hominis (1·03, 0·87-1·23), and Cryptosporidium spp (0·68, 0·17-2·68). Water treatment was associated with significantly lower odds of B hominis (0·52, 0·34-0·78), E histolytica or E dispar (0·61, 0·38-0·99), G intestinalis (0·63, 0·50-0·80), and Cryptosporidium spp infections (0·83, 0·70-0·98).

INTERPRETATION

Availability and use of sanitation facilities and water treatment is associated with lower odds of intestinal protozoa infections. Interventions that focus on water and sanitation, coupled with hygiene behaviour, should be emphasised to sustain the control of intestinal protozoa infections.

FUNDING

Swiss National Science Foundation (project numbers PBBSP3-146869 and P300P3-154634), Medicor Foundation, European Research Council (614739-A_HERO).

Blastocystis specific serum immunoglobulin in patients with irritable bowel syndrome (IBS) versus healthy controls

Background

Blastocystis species are common enteric human parasites and carriage has been linked to Irritable Bowel Syndrome (IBS), particularly diarrhoea-predominant IBS. The spectrum of immune reactivity to Blastocystis proteins has been reported previously in symptomatic patients. We investigated differences in serum immunoglobulin profiles between patients with IBS, both positive and negative for Blastocystis carriage, and healthy controls (HC).

Methods

Forty diarrhoea-predominant IBS patients (26 patients positive for Blastocystis sp., 14 negative patients) and forty HC (24 positive, 16 Blastocystis-negative) were enrolled. Age, gender, ethnicity and serum immunoglobulin A (IgA) levels were recorded and faecal specimens were analysed using smear, culture and polymerase chain reaction amplification of ribosomal DNA. Sera were tested in Western blots and the reactivities compared to known targets using monoclonal antibodies Blastofluor® (Blastocystis specific antibody), MAb1D5 (cytopathicto Blastocystis cells), anti-promatrix metalloprotease-9 (anti-MMP-9) and SDS-PAGE zymograms.

Results

Levels of serum IgA were significantly lower in Blastocystis carriers (p < 0.001) but had no relationship to symptoms. Western blots demonstrated serum IgG antibodies specific for Blastocystis proteins of 17,27,37,50,60-65, 75–90, 95–105 and 150 kDa MW. Reactivity to the 27, 50 and 75-95 kDa proteins were found more frequently in the IBS group compared to the HC’s (p < 0.001) and correlation was greater for Blastocystis-positive IBS patients (p < 0.001) than for negative IBS patients (p < 0.05). MAb1D5 reacted with proteins of 27 and 100 kDa, and anti-MMP-9 with 27, 50 and 75-100 kDa proteins. Bands were seen in zymograms around 100 kDa.

Conclusions

Low serum IgA levels are associated with Blastocystis carriage. All IBS patients were more likely to demonstrate reactivity with Blastocystis proteins of 27 kDa (likely a cysteine protease), 50 and 75-95 kDa MW compared to HC. The presence of antibodies to these Blastocystis proteins in some Blastocystis-negative subjects suggests either prior exposure to Blastocystis organisms or antibody cross reactivities. The anti-proMMP-9 reaction at 50 and 75–100 kDa and the zymogram result suggest that metalloproteases may be important Blastocystis antigens.

Trial registration

Australian and New Zealand Clinical Trials registry ACTRN: 12611000918921

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1069-x) contains supplementary material, which is available to authorized users.

Blastocystis and urticaria: Examination of subtypes and morphotypes in an unusual clinical manifestation

Blastocystis is a human common enteric protist that may colonize a large variety of non-human hosts linked to symptoms and diseases such as abdominal pain, constipation, diarrhea, urticaria, flatulence and irritable bowel syndrome (IBS). Blastocystis exhibits remarkable genetic diversity and multiple subtypes (STs) within the genus with no absolute associations with clinical symptomatology. Here we analyzed fecal samples from Argentinean patients (n=270) belonging to symptomatic (urticaria and non-specific gastrointestinal symptoms, n=39) and asymptomatic control (n=28). Those patients infected with Blastocystis (n=67) were submitted for morphological analysis, DNA extraction, 18S PCR, sequencing and STs identification according to DNA barcoding. Blastocystis vacuolar forms were the predominant morphotype (75%), ameboid-like forms were evidenced in 1.5% of samples. Blastocystis ST3 was detected in 71.6% (n=48), of which 71.4%, (n=35) and 28.6% (n=14) belonged to symptomatic and asymptomatic respectively. Other subtypes identified were ST1 (14.9%), ST6 (7.5%) and ST2 (5.9%). Blastocystis 18S barcoding evidenced in non-urticaria symptomatic patients and asymptomatic control group the presence of allele 134 (ST3) (p<0.0001), while allele 34 (ST3) was detected in 85.7% (18/21) of symptomatic uricaria as compared with control group (1/21) (p<0.0001). The presence of a particular allele (a34) significantly associated with urticaria patients was detected and the clinical implications of these findings are herein discussed.

Molecular epidemiology and genetic diversity of Blastocystis infection in humans in Italy

In order to describe the molecular epidemiology of Blastocystis infection in Italy, 189 isolates, which had been collected during the years 2012-2014 from mildly symptomatic patients, or those affected by inflammatory bowel disease (IBD), irritable bowel syndrome (IBS) or chronic diarrhoea, or otherwise immunosuppressed, were subtyped by sequence analysis of the SSU rRNA gene (536 bp). Six subtypes (STs) were detected: ST1 (15·3%), ST2 (13·8%), ST3 (46·0%), ST4 (21·7%), ST6 (3·2%) and ST8 (0·5%). They clustered in distinct clades, as inferred from Bayesian inference phylogenetic and median joining network analyses. A high genetic differentiation was found at the inter-subtype level; it ranged from Jukes-Cantor (JC) distance = 0·02 (between ST1 and ST4) to JC = 0·11 (between ST6 and ST2). At the intra-ST level, a high genetic homogeneity was registered in ST4, whereas higher genetic variation was found in isolates corresponding to ST1 and ST2. Accordingly, high values of haplotype and nucleotide diversity were observed in ST1, ST2 and ST3. No association was found between patient gender and ST, whereas ST3 and ST1 were significantly more prevalent in patients aged 15-50 years. A significant occurrence of Blastocystis ST4 in patients suffering from IBS, IBD or chronic diarrhoea was observed; in addition, a slight significant association between ST1 and ST3 and IBS patients was found. Multiple correspondence analysis showed some significant contribution of different variables (subtypes, haplotypes, age) in the observed pattern of ordination of the 189 patients in the symptom categories.

Epidemiologic Study of Blastocystis Infection in an Urban Community in the Philippines

Blastocystis has been considered as the most common intestinal parasite in humans and has an augmented impact on public health. However, the prevalence of this parasite in the Philippines has not been determined. To contribute to a better understanding of the epidemiology of this infection, a cross-sectional study aimed at providing the first documented data on the prevalence and correlates, sociodemographic factors, hygiene practices, source of water supply, and dog ownership, associated with Blastocystis infection was carried out in randomly selected communities at Pateros, Metro Manila. Fecal samples from respondents were collected and cultured in diphasic agar medium for 3–7 days and examined using light microscopy. Of the 1,271 respondents, 12.98% (95% CI: 11.13–14.83) were detected positive for Blastocystis. Among the correlates of Blastocystis infection, dog ownership was found significantly associated as confirmed by multivariate analysis. Therefore, this factor should be considered in information to create awareness about Blastocystis and to prevent and control Blastocystis infection in particular and diarrheal diseases in general. Further studies using molecular approaches to distinguish subtype and to determine genetic characteristics of isolates from humans and dogs are recommended to analyze their relationship and provide more conclusive evidence of cross-transmission.

Blastocystis Isolates from Patients with Irritable Bowel Syndrome and from Asymptomatic Carriers Exhibit Similar Parasitological Loads, but Significantly Different Generation Times and Genetic Variability across Multiple Subtypes

Blastocystis spp is a common intestinal parasite of humans and animals that has been associated to the etiology of irritable bowel syndrome (IBS); however, some studies have not found this association. Furthermore, many biological features of Blastocystis are little known. The objective of present study was to assess the generation times of Blastocystis cultures, from IBS patients and from asymptomatic carriers. A total of 100 isolates were obtained from 50 IBS patients and from 50 asymptomatic carriers. Up to 50 mg of feces from each participant were cultured in Barret's and in Pavlova's media during 48 h. Initial and final parasitological load were measured by microscopy and by quantitative PCR. Amplicons were purified, sequenced and submitted to GenBank; sequences were analysed for genetic diversity and a Bayesian inference allowed identifying genetic subtypes (ST). Generation times for Blastocystis isolates in both media, based on microscopic measures and molecular assays, were calculated. The clinical symptoms of IBS patients and distribution of Blastocystis ST 1, 2 and 3 in both groups was comparable to previous reports. Interestingly, the group of cases showed scarce mean nucleotide diversity (π) as compared to the control group (0.011±0.016 and 0.118±0.177, respectively), whilst high gene flow and small genetic differentiation indexes between different ST were found. Besides, Tajima's D test showed negative values for ST1-ST3. No statistical differences regarding parasitological load between cases and controls in both media, as searched by microscopy and by qPCR, were detected except that parasites grew faster in Barret's than in Pavlova's medium. Interestingly, slow growth of isolates recovered from cases in comparison to those of controls was observed (p<0.05). We propose that generation times of Blastocystis might be easily affected by intestinal environmental changes due to IBS probably because virulent strains with slow growth may be selected, reducing their genetic variability.

The prevalence of intestinal parasites is not greater among individuals with irritable bowel syndrome: a population-based case-control study

BACKGROUND & AIMS

The parasites Dientamoeba fragilis and Blastocystis have been detected in feces from patients with irritable bowel syndrome (IBS), therefore these parasites may be involved in IBS pathogenesis. We proposed that a higher prevalence of the parasites in IBS subjects compared with asymptomatic controls would support such a mechanism. We aimed to determine the prevalence of these parasites in IBS subjects (cases) and controls and to identify risk factors associated with parasite carriage.

METHODS

We performed a population-based, case-control study of an adult population from an internet-based research institute in Denmark. In January 2010, subjects completed a questionnaire based on the Rome III criteria for IBS and answered questions on factors associated with parasite carriage. Respondents (n = 483) were asked to submit fecal samples for parasite testing; samples were analyzed from 124 cases and 204 controls.

RESULTS

A greater proportion of controls than cases carried the parasites (50% vs 36%; P = .01). D fragilis was detected in a greater proportion of fecal samples from controls than cases (35% vs 23%; P = .03), as was Blastocystis (22% of controls vs 15% of cases; P = .09), and a greater percentage of controls carried more than 1 species of parasite (16% of controls vs 8% of cases; P = .05). D fragilis infection was associated with having children 5 to 18 years old in the household and Blastocystis infection was associated with high income (≥600,000 Danish Kroner/y, approximately $100,000 US dollars/y), no animals in the household, and drinking bottled water.

CONCLUSIONS

D fragilis and Blastocystis were detected in a greater proportion of fecal samples from the asymptomatic background population in Denmark than from subjects with IBS symptoms. These findings indicate that these parasites are not likely to have a direct role in the pathogenesis of IBS. Longitudinal studies are required to understand their role in gastrointestinal health.

Prevalence and subtype analysis of Blastocystis in healthy Indian individuals

There is a growing interest in subtype (ST) analysis of the intestinal parasite Blastocystis due to its extensive genetic diversity that might reflect differences in pathogenicity. Although essential for reference, few studies are available on Blastocystis in healthy individuals. Moreover, molecular epidemiology data on Blastocystis in India still remain to emerge. In the present study we identified the prevalence and ST distribution of Blastocystis in healthy Indian individuals. A total of 220 stool samples were obtained; four of 100 samples from 100 adults were chosen randomly for construction of small subunit (SSU) rRNA gene clone libraries in order to elucidate micro-eukaryotic diversity in the human gut. From the SSU rDNA library, 64 sequences annotated to Blastocystis were used for ST analysis along with sequences obtained by direct sequencing of SSU rDNA PCR products amplified from the remaining samples and generated using primers targeting Blastocystis. Of 220 stool samples collected, 120 samples from 30 infants (aged 1week to 1year) were PCR-negative. Of the remaining 100 samples from 100 adults, 27 resulted in specific amplification. Out of these 27, four samples were suspected of mixed ST infection and so these samples were further analyzed by construction of clone libraries. Analysis of cloned sequences revealed that indeed 2 samples had mixed ST infection (ST1 and ST3) while the remaining two showed infection with two separate ST3 strains. ST3 was the most common ST present in our study group (100%) followed by ST1 (7.4%); ST1 was seen only in mixed infections. SSU rDNA clone library sequences generated by processing of pooled samples were identified as ST3. The majority of ST3 sequences exhibited allele 34 commonly found in the European population.

Low prevalence of Blastocystis sp. in active ulcerative colitis patients

Ulcerative colitis (UC) is thought to originate from a disbalance in the interplay between the gut microbiota and the innate and adaptive immune system. Apart from the bacterial microbiota, there might be other organisms, such as parasites or viruses, that could play a role in the aetiology of UC. The primary objective of this study was to compare the prevalence of Blastocystis sp. in a cohort of patients with active UC and compare that to the prevalence in healthy controls. We studied patients with active UC confirmed by endoscopy included in a randomised prospective trial on the faecal transplantation for UC. A cohort of healthy subjects who served as donors in randomised trials on faecal transplantation were controls. Healthy subjects did not have gastrointestinal symptoms and were extensively screened for infectious diseases by a screenings questionnaire, extensive serologic assessment for viruses and stool analysis. Potential parasitic infections such as Blastocystis were diagnosed with the triple faeces test (TFT). The prevalence of Blastocystis sp. were compared between groups by Chi-square testing. A total of 168 subjects were included, of whom 45 had active UC [median age 39.0 years, interquartile range (IQR) 32.5–49.0, 49 % male] and 123 were healthy subjects (median age 27 years, IQR 22.0–37.0, 54 % male). Blastocystis sp. was present in the faeces of 40/123 (32.5 %) healthy subjects and 6/45 (13.3 %) UC patients (p = 0.014). Infection with Blastocystis is significantly less frequent in UC patients as compared to healthy controls.

Draft genome sequence of the intestinal parasite Blastocystis subtype 4-isolate WR1

The intestinal protistan parasite Blastocystis is characterized by an extensive genetic variability with 17 subtypes (ST1–ST17) described to date. Only the whole genome of a human ST7 isolate was previously sequenced. Here we report the draft genome sequence of Blastocystis ST4-WR1 isolated from a laboratory rodent at Singapore.

Blastocystis is associated with decrease of fecal microbiota protective bacteria: comparative analysis between patients with irritable bowel syndrome and control subjects

Blastocystis is a protistan parasite living in the digestive tract of many animals, including humans. This highly prevalent intestinal parasite is suspected to be linked to Irritable Bowel Syndrome (IBS), a chronic functional bowel disorder. Here, we first compared the prevalence of Blastocystis among 56 IBS patients (40 IBS with constipation (IBS-C), 9 IBS with diarrhea (IBS-D), 4 mixed IBS (IBS-M) and 3 unsubtyped IBS (IBS-U) according to the Rome III criteria) and 56 control (i.e. without any diagnosed chronic or acute gastrointestinal disorder) subjects. The highest prevalence of Blastocystis spp. was observed in the IBS group, but was only statistically significant in men (36.8% in the IBS group versus 4.8% in the control group). We then conducted a meta-analysis including epidemiological studies attempting to determine whether Blastocystis carriage could be linked to IBS, and highlighted that IBS patients had a relative risk of 2.34 to be infected by Blastocystis when compared to non-IBS subjects. We also looked for Dientamoeba fragilis, which is often associated with IBS, and identified this parasite only in some IBS patients (n = 6/56). Several studies provided evidence for a major role of the gut microbiota in the pathophysiology of IBS. Thus, we investigated the possible impact of Blastocystis carriage on the enteric bacterial community through quantification of 8 major bacterial groups from the enteric flora. Our data indicated that men with IBS-C had a significant decrease in Bifidobacterium sp. when infected by Blastocystis. Interestingly, in control subjects (i.e. without any gastrointestinal disorder) positive for Blastocystis, Faecalibacterium prausnitzii, which is known for its anti-inflammatory properties, was significantly decreased in men. Our results support the hypothesis that Blastocystis might be linked to the pathophysiology of IBS-C and intestinal flora imbalance.

The microbial eukaryote Blastocystis is a prevalent and diverse member of the healthy human gut microbiota

To date, the majority of research into the human gut microbiota has focused on the bacterial fraction of the community. Inevitably, this has resulted in a poor understanding of the diversity and functionality of other intestinal microorganisms in the human gut. One such nonbacterial member is the microbial eukaryote Blastocystis, which has been implicated in the aetiology of a range of different intestinal and extra-intestinal diseases. However, prevalence data from different studies are conflicting, and crucially, there is limited information on its incidence and diversity in healthy individuals. Here, we survey the prevalence, genetic diversity and temporal stability of Blastocystis in a group of healthy adults (n = 105) using a sensitive PCR assay. Blastocystis was present in 56% of our sample set, which is much higher than previously reported from an industrialised county (Ireland). Moreover, a diversity of different subtypes (species) were detected, and Blastocystis was present in a subset of individuals sampled over a period of time between 6 and 10 years, indicating that it is capable of long-term host colonisation. These results show that Blastocystis is a common and diverse member of the healthy gut microbiota, thereby extending our knowledge of the microbial ecology of the healthy human intestine.

Blastocystis, an unrecognized parasite: an overview of pathogenesis and diagnosis

Blastocystis sp. is among the few enteric parasites with a prevalence that often exceeds 5% in the general population of industrialized countries and can reach 30-60% in developing countries. This parasite is frequently found in people who are immunocompromised (patients with human immunodeficiency virus/acquired immunodeficiency syndrome or cancer) and a higher risk of Blastocystis sp. infection has been found in people with close animal contact. Such prevalence in the human population and the zoonotic potential naturally raise questions about the impact of these parasites on public health and has increased interest in this area. Recent in vitro and in vivo studies have shed new light on the pathogenic power of this parasite, suggesting that Blastocystis sp. infection is associated with a variety of gastrointestinal disorders, may play a significant role in irritable bowel syndrome, and may be linked with cutaneous lesions (urticaria). Despite recent significant advances in the knowledge of the extensive genetic diversity of this species, the identification of extracellular proteases as virulence factors and the publication of one isolate genome, many aspects of the biology of Blastocystis sp. remain poorly investigated. In this review, we investigate several biological aspects of Blastocystis sp. (diversity and epidemiology, diagnosis tools and pathophysiology). These data pave the way for the following challenges concerning Blastocystis sp. research: deciphering key biological mechanisms and pathways of this parasite and clarification of its clinical impact in humans.

Differential regulation of proinflammatory cytokine expression by mitogen-activated protein kinases in macrophages in response to intestinal parasite infection

Blastocystis is a common enteric protistan parasite that can cause acute, as well as chronic, infection and is associated with irritable bowel syndrome (IBS). However, the pathogenic status of Blastocystis infection remains unclear. In this study, we found that Blastocystis antigens induced abundant expression of proinflammatory cytokines, including interleukin 1β (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α), in mouse intestinal explants, in mouse colitis colon, and in macrophages. Further investigation utilizing RAW264.7 murine macrophages showed that Blastocystis treatment in RAW264.7 macrophages induced the activation of ERK, JNK, and p38, the three major groups of mammalian mitogen-activated protein (MAP) kinases that play essential roles in the expression of proinflammatory cytokines. ERK inhibition in macrophages significantly suppressed both mRNA and protein expression of IL-6 and TNF-α and mRNA expression of IL-1β. On the other hand, JNK inhibition resulted in reductions in both c-Jun and ERK activation and significant suppression of all three proinflammatory cytokines at both the mRNA and protein levels. Inhibition of p38 suppressed only IL-6 protein expression with no effect on the expression of IL-1β and TNF-α. Furthermore, we found that serine proteases produced by Blastocystis play an important role in the induction of ERK activation and proinflammatory cytokine expression by macrophages. Our study thus demonstrated for the first time that Blastocystis could induce the expression of various proinflammatory cytokines via the activation of MAP kinases and that infection with Blastocystis may contribute to the pathogenesis of inflammatory intestinal diseases through the activation of inflammatory pathways in host immune cells, such as macrophages.

Location and pathogenic potential of Blastocystis in the porcine intestine

Blastocystis is an ubiquitous, enteric protozoan of humans and many other species. Human infection has been associated with gastrointestinal disease such as irritable bowel syndrome, however, this remains unproven. A relevant animal model is needed to investigate the pathogenesis/pathogenicity of Blastocystis. We concluded previously that pigs are likely natural hosts of Blastocystis with a potentially zoonotic, host-adapted subtype (ST), ST5, and may make suitable animal models. In this study, we aimed to characterise the host-agent interaction of Blastocystis and the pig, including localising Blastocystis in porcine intestine using microscopy, PCR and histopathological examination of tissues. Intestines from pigs in three different management systems, i.e., a commercial piggery, a small family farm and a research herd (where the animals were immunosuppressed) were examined. This design was used to determine if environment or immune status influences intestinal colonisation of Blastocystis as immunocompromised individuals may potentially be more susceptible to blastocystosis and development of associated clinical signs. Intestines from all 28 pigs were positive for Blastocystis with all pigs harbouring ST5. In addition, the farm pigs had mixed infections with STs 1 and/or 3. Blastocystis organisms/DNA were predominantly found in the large intestine but were also detected in the small intestine of the immunosuppressed and some of the farm pigs, suggesting that immunosuppression and/or husbandry factors may influence Blastocystis colonisation of the small intestine. No obvious pathology was observed in the histological sections. Blastocystis was present as vacuolar/granular forms and these were found within luminal material or in close proximity to epithelial cells, with no evidence of attachment or invasion. These results concur with most human studies, in which Blastocystis is predominantly found in the large intestine in the absence of significant organic pathology. Our findings also support the use of pigs as animal models and may have implications for blastocystosis diagnosis/treatment.

Communities of microbial eukaryotes in the mammalian gut within the context of environmental eukaryotic diversity

Eukaryotic microbes (protists) residing in the vertebrate gut influence host health and disease, but their diversity and distribution in healthy hosts is poorly understood. Protists found in the gut are typically considered parasites, but many are commensal and some are beneficial. Further, the hygiene hypothesis predicts that association with our co-evolved microbial symbionts may be important to overall health. It is therefore imperative that we understand the normal diversity of our eukaryotic gut microbiota to test for such effects and avoid eliminating commensal organisms. We assembled a dataset of healthy individuals from two populations, one with traditional, agrarian lifestyles and a second with modern, westernized lifestyles, and characterized the human eukaryotic microbiota via high-throughput sequencing. To place the human gut microbiota within a broader context our dataset also includes gut samples from diverse mammals and samples from other aquatic and terrestrial environments. We curated the SILVA ribosomal database to reflect current knowledge of eukaryotic taxonomy and employ it as a phylogenetic framework to compare eukaryotic diversity across environment. We show that adults from the non-western population harbor a diverse community of protists, and diversity in the human gut is comparable to that in other mammals. However, the eukaryotic microbiota of the western population appears depauperate. The distribution of symbionts found in mammals reflects both host phylogeny and diet. Eukaryotic microbiota in the gut are less diverse and more patchily distributed than bacteria. More broadly, we show that eukaryotic communities in the gut are less diverse than in aquatic and terrestrial habitats, and few taxa are shared across habitat types, and diversity patterns of eukaryotes are correlated with those observed for bacteria. These results outline the distribution and diversity of microbial eukaryotic communities in the mammalian gut and across environments.

Frequency of abnormal fecal biomarkers in irritable bowel syndrome

PRIMARY STUDY OBJECTIVE

Determine the frequency of abnormal fecal biomarker test results in patients with 13 irritable bowel syndrome (IBS)-related ICD-9 (International Statistical Classification of Diseases and Related Health Problems) codes.

STUDY DESIGN

Quantitative review of de-identified records from patients in whom IBS was a possible diagnosis.

METHODS

Records were selected for analysis if they included any of 13 IBS-related diagnostic codes and laboratory test results of fecal testing for all biomarkers of interest. Data collection was restricted to one 12-month period. Frequency distributions were calculated to identify rates of abnormal results for each biomarker within the total number of tests conducted in the eligible population.

RESULTS

Two thousand, two hundred fifty-six records were included in the study, of which 1867 (82.8%) included at least one abnormal value. Quantitative stool culture for beneficial bacteria (Lactobacillus and Bifidobacterium) indicated low growth suggestive of intestinal dysbiosis in 73.1% of records, followed by abnormally elevated eosinophil protein X (suggestive of food allergy) in 14.3%, elevated calprotectin (suggestive of inflammation) in 12.1%, detection of parasites in 7.5%, and low pancreatic elastase (suggestive of exocrine pancreatic insufficiency) in 7.1%.

CONCLUSIONS

Abnormal fecal biomarkers are prevalent in patients with diagnoses suggestive of IBS. Abnormal fecal biomarker testing, if confirmed in additional independent clinical trials, could substantially reduce the economic costs associated with diagnosis and management of IBS.

Intra-subtype variation in enteroadhesion accounts for differences in epithelial barrier disruption and is associated with metronidazole resistance in Blastocystis subtype-7

Blastocystis is an extracellular, enteric pathogen that induces intestinal disorders in a range of hosts including humans. Recent studies have identified potential parasite virulence factors in and host responses to this parasite; however, little is known about Blastocystis-host attachment, which is crucial for colonization and virulence of luminal stages. By utilizing 7 different strains of the parasite belonging to two clinically relevant subtypes ST-4 and ST-7, we investigated Blastocystis-enterocyte adhesion and its association with parasite-induced epithelial barrier disruption. We also suggest that drug resistance in ST-7 strains might result in fitness cost that manifested as impairment of parasite adhesion and, consequently, virulence. ST-7 parasites were generally highly adhesive to Caco-2 cells and preferred binding to intercellular junctions. These strains also induced disruption of ZO-1 and occludin tight junction proteins as well as increased dextran-FITC flux across epithelial monolayers. Interestingly, their adhesion was correlated with metronidazole (Mz) susceptibility. Mz resistant (Mzr) strains were found to be less pathogenic, owing to compromised adhesion. Moreover, tolerance of nitrosative stress was also reduced in the Mzr strains. In conclusion, the findings indicate that Blastocystis attaches to intestinal epithelium and leads to epithelial barrier dysfunction and that drug resistance might entail a fitness cost in parasite virulence by limiting entero-adhesiveness. This is the first study of the cellular basis for strain-to-strain variation in parasite pathogenicity. Intra- and inter-subtype variability in cytopathogenicity provides a possible explanation for the diverse clinical outcomes of Blastocystis infections.

Assessment of gastrointestinal parasites in wild chimpanzees (Pan troglodytes troglodytes) in southeast Cameroon

We tested 114 faecal samples from wild simian immunodeficiency virus (SIV)-positive (n = 43) and SIV-negative (n = 71) chimpanzees (Pan troglodytes troglodytes) in southeast Cameroon for the presence of gastrointestinal parasites by direct smear. We observed cysts from different protozoa (Entamoeba coli and Entamoeba histolytica / Entamoeba dispar, Endolimax nana, Iodamoeba butschlii, Chilomastix mesnili, Balantidium coli and Blastocystis cells) and trophozoites from Troglodytella abrassarti and Balantidium coli. Eggs from different helminths (strongylids, Ascaris lumbricoides, Abbreviata caucasica, Trichuris sp., Capillaria sp., Enterobius anthropopeci, Bertiella sp., Hymenolepis diminuta and an undetermined fluke) were also observed. Finally, we observed eggs that could not be properly identified and classified. We did not observe any differences between the SIV+ and SIV- samples except for the unidentified eggs. The studied chimpanzees were highly parasitised by strongylid (85.1% of prevalence), Troglodytella (43.8%) and Blastocystis (2.9%), and the frequency of the other parasites ranged from 0.9 to 8.8%. These high levels of parasite infections could represent an additional burden in a population where there is a high rate of the SIV virus in circulation.

Blastocystis sp. in splenic cysts: causative agent or accidental association? A unique case report

Background

Blastocystis sp. is one of the most prevalent parasites found in human stool and has been recently considered an opportunistic emerging pathogen in immunocompromised individuals. However, cases of invasive intestinal infections and skin rashes have been attributed to infection by Blastocystis sp in immunocompetent individuals, suggesting that it is an emerging parasite with pathogenic potential.

Findings

We present a case of a 22 year old female patient who complained of pain in the left hypochondrium. Ultrasonography and abdominal computed tomography scans showed two splenic cysts. The cyst fluid analysis demonstrated numerous Blastocystis sp.; PCR and DNA sequencing analyses confirmed the presence of Blastocystis subtype 3.

Conclusions

This is, to our knowledge, the first case report of the presence of Blastocystis subtype 3 in extra-intestinal organs and is strong evidence that Blastocystis sp. is potentially pathogenic and invasive. However, further studies are required to determine the pathogenicity of the parasite.

Strain-dependent induction of human enterocyte apoptosis by blastocystis disrupts epithelial barrier and ZO-1 organization in a caspase 3- and 9-dependent manner

Blastocystis is an emerging protistan parasite colonizing the human intestine. It is frequently reported to cause general intestinal symptoms of vomiting, diarrhea, and abdominal pain. We recently demonstrated that Blastocystis rearranged cytoskeletal proteins and induced intestinal epithelial barrier compromise. The effect of Blastocystis on enterocyte apoptosis is unknown, and a possible link between microbially induced enterocyte apoptosis and increased epithelial permeability has yet to be determined. The aim of this study is to assess if Blastocystis induces human enterocyte apoptosis and whether this effect influences human intestinal epithelial barrier function. Monolayers of polarized human colonic epithelial cell-line Caco-2 were incubated with Blastocystis subtype 7 and subtype 4. Assays for both early and late markers of apoptosis, phosphatidylserine externalization, and nuclear fragmentation, respectively, showed that Blastocystis ST-7, but not ST-4, significantly increased apoptosis in enterocytes, suggesting that Blastocystis exhibits host specificity and strain-to-strain variation in pathogenicity. ST-7 also activated Caco-2 caspases 3 and 9 but not 8. ST-7 induced changes in epithelial resistance, permeability, and tight junction (ZO-1) localization. Pretreatment of Caco-2 monolayers with a pan-caspase inhibitor z-VAD-fmk significantly inhibited these changes. This suggests a role for enterocyte apoptosis in Blastocystis-mediated epithelial barrier compromise in the human intestine.

Children of Senegal River Basin show the highest prevalence of Blastocystis sp. ever observed worldwide

Background

Blastocystis sp. is currently the most common intestinal protist found in human feces and considered an emerging parasite with a worldwide distribution. Because of its potential impact in public health, we reinforced the picture of Blastocystis sp. prevalence and molecular subtype distribution in Africa by performing the first survey of this parasite in Senegal.

Methods

Stool samples from 93 symptomatic presenting with various gastrointestinal disorders or asymptomatic children living in three villages of the Senegal River Basin were tested for the presence of Blastocystis sp. by non-quantitative and quantitative PCR using primer pairs targeting the SSU rDNA gene. Positive samples were subtyped to investigate the frequency of Blastocystis sp. subtypes in our cohort and the distribution of subtypes in the symptomatic and asymptomatic groups of children.

Results

By the use of molecular tools, all 93 samples were found to be positive for Blastocystis sp. indicating a striking parasite prevalence of 100%. Mixed infections by two or three subtypes were identified in eight individuals. Among a total of 103 subtyped isolates, subtype 3 was most abundant (49.5%) followed by subtype 1 (28.2%), subtype 2 (20.4%) and subtype 4 (1.9%). Subtype 3 was dominant in the symptomatic group while subtypes 1 and 2 were detected with equal frequency in both symptomatic and asymptomatic groups. The distribution of subtypes was compared with those available in other African countries and worldwide. Comparison confirmed that subtype 4 is much less frequently detected or absent in Africa while it is commonly found in Europe. Potential sources of Blastocystis sp. infection including human-to-human, zoonotic, and waterborne transmissions were also discussed.

Conclusions

The prevalence of Blastocystis sp. in our Senegalese population was the highest prevalence ever recovered worldwide for this parasite by reaching 100%. All cases were caused by subtypes 1, 2, 3 and 4 with a predominance of subtype 3. More than half of the children infected by Blastocystis sp. presented various gastrointestinal disorders. Such high prevalence of blastocystosis in developing countries makes its control a real challenge for public health authorities.

The pathogenic role of Blastocystis isolated from patients with irritable bowel syndrome and colitis from Iasi, Romania

Blastocystis is a common parasite and regarded as one of the etiologic agents of irritable bowel syndrome, colitis and chronic diarrhea. Our study was undertaken in order to identify different subtypes of Blastocystis isolated in patients with irritable bowel syndrome and colitis, as well as with chronic diarrhea and to evaluate their pathogenic potential. Seventy-three subjects (10 asymptomatic infected subjects, 49 subjects harboring Blastocystis or associated with other etiologic agents like bacteria, yeasts, protozoa, helminthes and 14 subjects with unknown etiologic agents) were investigated by in vitro parasitological and bacteriological stool samples followed by PCR subtyping of Blastocystis using STS primers, immunological markers (total serum IgA and IgE antibody levels), Helicobacter pylori antigen rapid test and fecal occult blood test. Also, among 49 subjects, there were 12 subjects harboring Blastocystis as the single etiologic agent. Subtyping proved that only three subtypes of Blastocystis were identified as following: subtype II (66.66%) in single infected subjects, subtype I (16.66%) in mixed infection with subtype II and subtype IV (8.33%) in single infected subjects. Total serum IgA and IgE antibody levels were in normal range. Subtype II was the most frequent subtype followed by subtype I and subtype IV of Blastocystis isolates in patients with irritable bowel syndrome, colitis, and chronic diarrhea as well as in asymptomatic infected group. Our results suggest that the severity of clinical manifestations depend on factors involving the host and possible parasitic density and not necessarily by isolated subtype.

Pleiotropic effects of Blastocystis spp. Subtypes 4 and 7 on ligand-specific toll-like receptor signaling and NF-κB activation in a human monocyte cell line

Blastocystis spp. is a common enteric stramenopile parasite that colonizes the colon of hosts of a diverse array of species, including humans. It has been shown to compromise intestinal epithelial cell barrier integrity and mediate the production of pro-inflammatory cytokines and chemokines. Mucosal epithelial surfaces, including the intestinal epithelium, are increasingly recognized to perform a vital surveillance role in the context of innate immunity, through the expression of pathogen recognition receptors, such as Toll-like receptors (TLRs). In this study, we use the human TLR reporter monocytic cell line, THP1-Blue, which expresses all human TLRs, to investigate effects of Blastocystis on TLR activation, more specifically the activation of TLR-2, -4 and -5. We have observed that live Blastocystis spp. parasites and whole cell lysate (WCL) alone do not activate TLRs in THP1-Blue. Live ST4-WR1 parasites inhibited LPS-mediated NF-κB activation in THP1-Blue. In contrast, ST7-B WCL and ST4-WR1 WCL induced pleiotropic modulation of ligand-specific TLR-2 and TLR-4 activation, with no significant effects on flagellin-mediated TLR-5 activation. Real time-qPCR analysis on SEAP reporter gene confirmed the augmenting effect of ST7-B on LPS-mediated NF-κB activation in THP1-Blue. Taken together, this is the first study to characterize interactions between Blastocystis spp. and host TLR activation using an in vitro reporter model.

Molecular subtyping of Blastocystis spp. using a new rDNA marker from the mitochondria-like organelle genome

Blastocystis spp. are common anaerobic intestinal protozoa found in both human and animals. They are characterized by a high genetic diversity with at least 17 subtypes (STs) that have been described on the basis of a 600 bp 'barcoding region' from the 18S rDNA gene. However, analysis of the recently sequenced genome of a Blastocystis ST7 isolate (strain B) revealed the presence of multiple variable copies of the 18S rDNA gene, with 17 completely assembled copies. Comparison of the barcoding region from these 17 copies allowed us to classify the 18S rDNA sequences into 6 clusters, each cluster containing identical sequences. Surprisingly, 4 of these clusters had the highest homology with 18S rDNA sequences from 2 other Blastocystis ST7 isolates referred as QQ98-4 and H. These results suggest that the 18S rDNA gene is not the marker of choice to discriminate between strains within STs. In the present study, we identified a single-copy subtyping rDNA marker in the genome of the mitochondria-like organelles (MLOs). Using a partial sequence of the MLO rDNA, we successfully subtyped 66 isolates from both human and animals belonging to Blastocystis ST1 to ST10. Our results also indicate that this mitochondrial marker could be useful to detect co-infections by different isolates of a same ST.

Intestinal parasitic infections in suburban government schools, Lak Hok subdistrict, Muang Pathum Thani, Thailand

OBJECTIVE

To provide baseline information of parasitic infections in 3 suburban government schools, Lakhok subdistrict of Muang Pathum Thani, Thailand.

METHODS

This study was conducted between May-June 2010 using simple direct smear and modified formalin ether and from a population of 1 253 in 3 suburban government schools.

RESULTS

Total samples of 202 registered and participated. The average of prevalence of infection from 3 schools was 13.9%, there were 13.7%, 14.3% and 13.9% in N, S and R school, respectively with no significant difference between schools (P>0.05). The infection rates did not show significant difference between genders (P>0.05). The highest rate of infection was 20.4% in Pathom 2 (8 years) students and the lowest was 4% in Pathom 1 (7 years) with statistically difference between age groups (P<0.05). The highest prevalence of pathogenic protozoa was Giardia lamblia (G. lamblia) which was found in 50% of infected cases, followed by 25% of Entamoeba histolytica (E. histolytica) and Blastocystis hominis (B. hominis). The highest prevalence of non-pathogenic protozoa was Endolimax nana (E. nana) which was found in 88.9%, followed by 11.1% of Entamoeba coli (E. coli). Mixed infections between Blastocystis hominis (B. hominis) and Endolimax nana (E. nana) were reported at 7.1%. The only helminthic infection found in this study area was hookworm, found in 1 student (3.8%). The formalin ether concentration technique showed a higher efficacy of detection (78%-100%) than the simple direct smear method (0%-50%).

CONCLUSIONS

Surveillance of Protozoan infections may need to be focused on suburban areas.

Diagnosis and subtype analysis of Blastocystis sp. in 442 patients in a hospital setting in the Netherlands

Background

Blastocystis sp. are among the most commonly observed intestinal parasites in routine clinical parasitology. Blastocystis in humans consists of at least 9 genetic subtypes. Different subtypes of Blastocystis may be associated with differences in pathogenicity and symptomatology.

Methods

Advanced microscopy on two samples and sequence-confirmed PCR on a third sample from the same individual were used for Blastocystis diagnosis and subtype analyses on routine clinical samples in a university hospital.

Results

With a combined gold standard of sequence-confirmed PCR and positive advanced microscopy, 107 out of 442 (24.2%) patients were diagnosed with Blastocystis. infection, which is a high frequency of detection in comparison to previous reports from industrialized countries. The sensitivity of microscopy and sequence-confirmed PCR was 99.1% (106/107) and 96.3% (103/107), respectively.

Among 103 typable samples, subtype 3 was most abundant (n = 43, 42%), followed by subtypes 1 and 2 (both n = 23, 22%), subtype 4 (n = 12, 12%), and single samples with subtypes 6 (1%) and subtype 7 (1%). The prevalence of Blastocystis infection was 38% in patients from the Department of Tropical Medicine and 18% in patients from other departments.

Conclusions

A high prevalence of Blastocystis infection was found with both advanced microscopy and sequence-confirmed PCR in our patient population. Most cases were caused by subtypes ST1, ST2, ST3 and ST4. A significantly higher prevalence was found among patients with a history of recent travel to tropical countries.

Blastocystis: Taxonomy, biology and virulence

The unicellular protist Blastocystis has long been an unsolved puzzle for taxonomists, microbiologists and clinicians. Over the years, the organism has been bounced on and off the different branches of the tree of life due the possession of unique phenotypic characters intermediary to different organisms. The organism is polymorphic with only few of forms such as vacuolar, granular, amoeboid, and the cyst form being commonly known. However it could exist in other forms much more frequently than the widely known forms which could be missed by the unaware observer. Certain older concepts in the life cycle of Blastocystis although has been proven wrong are still being followed in various textbooks and other trustworthy internet sources. The causal role of Blastocystis in human disease has long been a subject of controversy. It is widely believed that certain subtypes of the organism are virulent. But this is not so as other factors are also involved in the clinical outcome of the infection. In these contexts, this review intends to shed light on the past misconceptions and the recent findings on the taxonomy, biology and the virulence of this organism.

A rat model to study Blastocytis subtype 1 infections

Blastocytis sp. is the most common enteric protozoan in human, but its pathogenesis is still unclear. To study the infectious effects of Blastocytis sp. on tissue damage, we orally challenged the Sprague Dawley (SD) rats with different doses of Blastocytis subtype1 (ST1) and examined the histological changes. We found that there was no difference of disease incidence among the Blastocytis ST1-infected groups challenged with different doses of the protozoan. Histological results showed that the lamina propria was infected by Blastocytis ST1 in the vacuolar form, along with the mucus membrane slough and inflammatory cell infiltration into the lamina propria. Compared to the uninfected group, the histological scores were significantly higher in the infected groups. However, groups infected with various doses of Blastocystis ST1 showed no difference in terms of histological scores. In conclusion, this study indicates that the SD rats can be easily infected with Blastocytis ST1 even with low dose of cysts, and the histopathological effects of the infection in the intestine of the infected rats show individual differences.

Incidence, risk factors, and outcomes of Fusobacterium species bacteremia

Background

The aim of this study was to assess the epidemiology of intestinal parasitoses during a 5-year period in patients attending a tertiary-care hospital in a non-endemic setting.

Methods

In the period 2006–2010, 15,752 samples from 8,886 patients with clinically suspected parasitosis were subjected to macroscopic and microscopic examination, to parasitic antigen detection assays, and to cultures for protozoa and nematodes. Real-time PCR assays for the differentiation of Entamoeba histolytica and E. dispar and for the detection of Dientamoeba fragilis were also used.

A statistical analysis evaluating the demographic data of the patients with intestinal parasitic infections was performed.

Results

Intestinal parasitic infections were diagnosed in 1,477 patients (16.6% prevalence), mainly adults and immigrants from endemic areas for faecal-oral infections; protozoa were detected in 93.4% and helminths in 6.6% of the cases, the latter especially in immigrants. Blastocystis hominis was the most common intestinal protozoan, and G. intestinalis was the most frequently detected among pathogenic protozoa, prevalent in immigrants, males, and pediatric patients. Both single (77.9%) and mixed (22.1%) parasitic infections were observed, the latter prevalent in immigrants.

Conclusions

Despite the importance of the knowledge about the epidemiology of intestinal parasitoses in order to adopt appropriate control measures and adequate patient care all over the world, data regarding industrialized countries are rarely reported in the literature. The data presented in this study indicate that intestinal parasitic infections are frequently diagnosed in our laboratory and could make a contribution to stimulate the attention by physicians working in non-endemic areas on the importance of suspecting intestinal parasitoses.