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

Subtype-host patterns and genetic differentiation of Blastocystis sp. in the Philippines

Blastocystis sp. is a gastrointestinal protozoan commonly encountered in humans and animals. Specificity to certain hosts may be associated with 38 known subtypes (STs) and 8 nonmammalian and avian STs (NMASTs). This can be determined by analyzing ST-host associations, ST-allele data, genetic variability analyses, and fixation index (FST) with sufficient data present. Thus, newly acquired and previously published data on Blastocystis sp. STs and NMASTs from the Philippines were compiled to determine the following: (1) ST-host associations, (2) ST-allele diversity per ST in certain hosts/sources, (3) intrasubtype diversity of certain STs found in different hosts using genetic variability analysis, and (4) comparison of similarities between specific ST populations to determine if these are the same circulating populations using FST. A total of 448 samples subtyped using both sequence-tagged site primers and the 600-bp barcoding region of the Blastocystis sp. SSU rRNA gene were analyzed in this study. Patterns of association for the Philippine samples were similar to those from neighboring Southeast Asian countries and around the world: ST1-ST4 were found in humans but ST3 was the most common, ST5 were found in pigs, and ST6 and ST7 were found in poultry. Blastocystis sp. from humans are mostly the same ST alleles (ST3 allele 34 and ST1 allele 4) while 3-5 ST alleles were found in the most common STs in pigs, macaques, and poultry. Also, ST1, ST3, ST5, and NMAST I are undergoing population expansion according to genetic variability analyses through possible addition of new alleles based on ST-allele diversity. Moreover, FST shows the same circulating population of ST1 in humans, pigs, and water indicating a possible waterborne route of cross-transmission. In contrast, ST3 found in humans possibly come from the same circulating population and is genetically distinct from those in nonhuman sources.

Irritable Bowel Syndrome Associated with Blastocystis hominis or Without Relationship to It? A Case-Control Study and Minireview

BACKGROUND

Blastocystis hominis (B. hominis) is a protozoan parasite that has a worldwide distribution. Some studies have suggested a link between B. hominis and the development of irritable bowel syndrome (IBS). The objective of this study was to determine the prevalence of B. hominis in patients with IBS compared to healthy individuals.

MATERIAL AND METHODS

A total of 65 stool samples from patients with IBS and 65 samples from healthy individuals in northern Iran were examined. The samples were tested using various methods including direct smear, formalin ether sedimentation and culture to detect the presence of B. hominis. Additionally, polymerase chain reaction (PCR) was performed on all culture-positive isolates to confirm the results and identify the genotype.

RESULTS

B. hominis was detected in 15.38% of IBS patients and 9.2% of the healthy group. The culture in RPMI1640 was found to be better than the formalin ether and direct smear methods. Positive samples were confirmed using the molecular method. No significant difference was observed in the order of B. hominis infection between the two groups.

CONCLUSIONS

The results of our study indicate that no significant difference was observed in the order of B. hominis infection between IBS patients and healthy groups. Therefore, further study is necessary to determine the potential pathogenic effects of this parasite and its role in causing IBS.

Presence of human adenovirus 36 in visceral fat tissue, viral load, and analysis of its genetic variability

It has been proposed that infection by adipogenic viruses constitutes a "low risk" factor for obesity. Here, we report the presence of adenovirus 36 (Ad36) and its viral load copy number in fat tissue of participants with obesity and normal weight; phylogenetic analysis was performed to describe their relationship and genetic variability among viral haplotypes. Adipose tissue obtained from 105 adult patients with obesity (cases) and 26 normal-weight adult participants as controls were analyzed by quantitative polymerase chain reaction (qPCR) amplifying the partial Ad36 E1a gene. The amplicons were examined by melting curves and submitted to sequencing. Then, genetic diversity and phylogenetic inferences were performed. Ad36 was identified at rates of 82% and 46% in the case and control groups, respectively (p = 1.1 × 10-4 , odds ratio = 5.28); viral load copies were also significantly different between both groups, being 25% higher in the case group. Melting curve analysis showed clear amplification among positive samples. Phylogenetic inferences and genetic diversity analyses showed that the Ad36 E1a gene exhibits low genetic variability and differentiation with strong gene flow due to an expanding process. Our results suggest that the phenomenon of infectobesity by Ad36 might not be a low-risk factor, as has been previously argued by other authors.

Identification of Blastocystis sp. in school children from a rural Mexican village: subtypes and risk factors analysis

Blastocystis sp. is a common eukaryotic microorganism that colonizes the intestinal tract of several animals, including humans, although its role as a pathogen is still unclear. In the present study, we report the prevalence and risk factors associated with Blastocystis infection in scholars from a rural community in Mexico. A cross-sectional observational study was carried out on schoolchildren aged 3 to 15 years old; fecal samples were analyzed by culture, Faust technique, and molecular analysis. In addition, a structured questionnaire was applied to identify possible risk factors. Of the 177 samples obtained, Blastocystis sp. was the microorganism that presented the highest frequency (n=78, 44%), and included the following subtypes (STs): ST1 (n=43, 56.5%), ST2 (n=18, 23.6%), and ST3 (n=15, 19.7%); Blastocystis STs were not identified in two cases. No associating factors were found between Blastocystis infection or among STs vs. symptoms. During bivariate analysis, no statistically significant risk factors were found, except for the variable of "eating sweets, snacks, and handmade food on the way home" (p=0.04). Therefore, it is plausible to conclude that schoolchildren become infected with Blastocystis sp. mainly outside their homes, perhaps by eating contaminated handmade food on their way to or from school; however, this variable should be evaluated in detail in future studies.

An update on the distribution of Blastocystis subtypes in the Americas

Blastocystis is an intestinal protist that presents worldwide distribution, colonizes animal and human hosts, and is classified into at least 34 ribosomal subtypes (STs). Herein, we conducted an update based on studies reporting Blastocystis-positive samples obtained from diverse hosts in the Americas. We described the distribution throughout the continent by assembling maps representing the distribution of STs and the most important 18S-rRNA alleles. Thirty-nine articles from the previous study, "A summary of Blastocystis subtypes in North and South America," and forty-one additional articles from March 2019 to March 2022 were considered. The most common subtype described was ST3, representing the highest percentage of positive samples. Other recently identified STs include ST12, ST13, and ST16 in humans, and ST10, ST14, and ST17 in animals. Novel subtypes have also been described in this continent. We assembled and updated the distribution of Blastocystis in the Americas. We hope this delivers new understandings and knowledge of this microorganism's prevalence and genetic diversity.

Can the genetic variability of Blastocystis sp. be associated with the climatic region of its human carriers?

Blastocystis sp. is a widespread microorganism that colonizes the intestinal tract of several animals, including human beings, while its pathogenic role in humans is still under debate. The objective of the present study was to describe the frequency of Blastocystis sp. subtypes (STs) and their genetic variation within and among samples recovered from scholars inhabiting two rural villages with tropical climates and compare this information with previously documented data from arid and temperate zones in Mexico. Blastocystis sp. positive samples and ST identification were achieved by coprological analysis screening and Polymerase Chain Reaction-sequencing, respectively. Classical population genetics indexes (nucleotide diversity (π), haplotype polymorphism (θ), gene flow (Nm), genetic differentiation (ST), and Tajima's D) were calculated by comparing the sequences here obtained (n = 42) and those from previous studies from the arid (n = 80) and temperate (n = 61) climates from Mexico. Although Blastocystis sp. was the parasite most frequently found between 33% and 26% in both communities, only STs 1-3 were found. Haplotype network inference of Blastocystis sp. STs showed different haplotype profiles among STs vs. climate zones, although no specific haplotypes were identified for any particular climatic zone. Population genetics indexes showed different values within STs and climate zones (π and θ values ranged from 0.004 to 0.147; Nm > 4 and ST from 0.006 to 0.12). Our results show that Blastocystis sp. subtypes exhibit a different genetic variability profile according to the climate zone, suggesting a balancing process between the genetic variability within the Blastocystis sp. subtype and the number of haplotypes identified in each climate.

Gut Microbiota Shifting in Irritable Bowel Syndrome: The Mysterious Role of Blastocystis sp

Irritable bowel syndrome (IBS) is a chronic disorder, which its causative agent is not completely clear; however, the interaction between microorganisms and gastrointestinal (GI) epithelial cells plays a critical role in the development of IBS and presenting symptoms. During recent decades, many studies have highlighted the high prevalence of Blastocystis sp. in patients with IBS and suggested a probable role for this protist in this disease. Recent studies have documented changes in the gut microbiota composition in patients with IBS regarding the presence of Blastocystis sp., but it is not clear that either disturbance of the gut during GI disorders is a favorable condition for Blastocystis sp. colonization or the presence of this protist may lead to alteration in the gut microbiota in IBS patients. In this review, we comprehensively gather and discuss scientific findings covering the role of Blastocystis sp. in IBS via gut microbiota shifting.

Epidemiology and subtype distribution of Blastocystis in humans: A review

Blastocystis is a commonly encountered gastrointestinal protozoan in humans and animals with uncertain pathogenicity. Despite its potential public health impact, epidemiological data regarding the prevalence and molecular subtype (ST) distribution of Blastocystis have been rarely reported. Among Blastocystis STs, ST1-ST4 are common in humans, including healthy and immunodeficient populations. According to the Chi-squared (χ²) association based on the data compiled for this cross-sectional study, the presence of ST1 is associated with asymptomatic infection, whereas the presence of ST4 is associated with symptomatic infection. However, cross-sectional studies cannot clarify the potential pathogenicity of Blastocystis, unlike in vivo and in vitro studies. Poor hygiene, poor sanitation and zoonotic transmission are possible factors associated with high Blastocystis prevalence, although this protozoan may be part of the normal healthy human gastrointestinal microbiota. This review covers the prevalence, STs and distribution of Blastocystis infection in humans. Thus, future epidemiological and subtyping studies could reveal new STs in humans as well as possible associations of STs with disease, drug resistance and related mechanisms such as protease activity. These associations with proper ST identification may facilitate the control of potential threats to host health, including the direct pathogenic effects of Blastocystis or alterations of the gastrointestinal microbiome.

Blastocystis species and Gastrointestinal Symptoms in Peruvian Adults Attended in a Public Hospital

The objective of this study was to evaluate the role of Blastocystis sp. in gastrointestinal symptoms reported by adult patients in a Peruvian hospital. A case-control 3:1 study was performed at the outpatient clinic. Direct stool examinations were done. One hundred sixty patients were included, 40 cases and 120 controls. Positivity to Blastocystis sp. was associated with dyspepsia (P <0.001), bloating (P <0.001) and abdominal pain (P = 0.03) in patients attending our hospital outpatient clinic.

Blastocystis sp. Carriage and Irritable Bowel Syndrome: Is the Association Already Established?

Simple Summary

The intestinal protist Blastocystis sp. is one of the most common intestinal parasites observed in humans, and has a worldwide distribution, being more prevalent in developing countries. Although this parasite has been described decades ago, the pathogenic potential it is still not understood completely. It has been suggested that Blastocystis sp. could be related with irritable bowel syndrome, a functional gastrointestinal disorder characterized by abdominal pain, discomfort with defecation, and changes in the frequency or form of stool. In our study, we compare a group of patients with irritable bowel syndrome with a group of healthy volunteers; no differences regarding the occurrence of Blastocystis sp. detection was found between both groups.

Abstract

Background: The aim of the present study is to describe the occurrence of Blastocystis sp. detection among asymptomatic subjects and patients with irritable bowel syndrome in order to evaluate the potential association between irritable bowel syndrome and the parasitic infection. Methods: Cross-sectional study where adult patients with irritable bowel syndrome diagnosed according to Rome IV criteria were included. A control group was formed by asymptomatic subjects older than 18 years. Exclusion criteria were: immunosuppressive condition or having received any drug with demonstrated activity against Blastocystis sp. within the last 6 months before study inclusion. Epidemiological and clinical information was collected from all included participants. Two stool samples were obtained from all participants: one sample for microscopic examination and one sample for Blastocystis sp. PCR detection. Blastocystis sp. infection was defined by the positivity of any of the diagnostic techniques. Results: Seventy-two participants were included (36 asymptomatic subjects and 36 patients with irritable bowel syndrome). Thirty-five (48.6%) were men, and median age of participants was 34 (IQR 29–49) years. The overall rate of Blastocystis sp. carriage was 27.8% (20/72). The prevalence assessed through microscopic examination was 22.2% (16/72), while the prevalence measured by PCR was 15.3% (11/72). When comparing the presence of Blastocystis sp. between asymptomatic subjects and IBS patients, we did not find any statistically significant difference (36.1% vs. 19.4% respectively, p = 0.114). Conclusions: regarding the occurrence of Blastocystis sp., no differences were found between asymptomatic participants and patients with irritable bowel disease irrespective of the diagnostic technique performed.

Prevalence and subtypes of Blastocystis among migrant workers from different working sectors in Peninsular Malaysia

Blastocystis sp. is a common enteric parasite of humans and animals associated with inadequate sanitation and poor personal hygiene. Over the years, the Malaysian thriving economy has been facilitated largely by migrant workers from developing countries, and there is concern that diseases endemic to their countries may be imported. Therefore, this study aimed to determine the current status of Blastocystis infection as well as subtypes (STs) from fecal samples among migrant workers in Selangor and Kuala Lumpur, Malaysia. Overall, almost a third of the study cohort (30.9%; n = 68/220) screened were infected with Blastocystis sp. predominantly with ST3 (54.5%; n = 12), followed by ST1 (36.4%; n = 8) and ST2 (9.1%; n = 2). Infection levels was almost similar among the different sectors; manufacturing (32.8%), domestic service (32.3%), and food service (27.3%) with common symptoms for infection included stomach and abdominal pain or discomfort and diarrhea (48.5%; n = 33). None of the socio-demographic risk factors evaluated were significant. Therefore, this study warrants continuous monitoring as well as understanding the impact of transmission among the migrant community with the local population especially those involved in food service sector.

Molecular detection and genotyping of intestinal protozoa from different biogeographical regions of Colombia

Background

Intestinal parasitic protozoa represent a serious problem of public health particularly in developing countries. Protozoa such as Blastocystis, Giardia intestinalis, Entamoeba histolytica and Cryptosporidium spp. are associated with diarrheal symptoms. In Colombia, there is little region-specific data on the frequency and circulating genotypes/species of these microorganisms. Therefore, the main objective of our study was to employ molecular detection and genotyping of G. intestinalis and Blastocystis, Cryptosporidium and Entamoeba spp. in samples from different biogeographical regions of Colombia.

Methods

We collected 649 human fecal samples from five biogeographical regions of Colombia: the Amazon, Andean, Caribbean, Orinoco and Pacific regions. Blastocystis, G. intestinalis, Cryptosporidium spp. and Entamoeba complex were detected by microscopy and conventional PCR. Molecular genotyping was conducted to identify Blastocystis subtypes (STs) (18s), G. intestinalis assemblages (triose phosphate isomerase and glutamate dehydrogenase) and Cryptosporidium species (18s). Genetic diversity indices were determined using dnasp.5.

Results

We detected G. intestinalis in 45.4% (n = 280) of samples, Blastocystis in 54.5% (n = 336) of samples, Cryptosporidium spp. in 7.3% (n = 45) of samples, Entamoeba dispar in 1.5% (n = 9) of samples, and Entamoeba moshkovskii in 0.32% (n = 2) of samples. Blastocystis STs 1–4, 8 and 9 and G. intestinalis assemblages AII, BIII, BIV, D and G were identified. The following Cryptosporidium species were identified: C. hominis, C. parvum, C. bovis, C. andersoni, C. muris, C. ubiquitum and C. felis. The Caribbean region had the highest frequency for each of the microorganisms evaluated (91.9% for G. duodenalis, 97.3% for Blastocystis, 10.8% for Cryptosporidium spp., 13.5% for E. dispar and 2.7% for E. moshkovskii). The Orinoco region had a high frequency of Blastocystis (97.2%) and the Andean region had a high frequency of G. intestinalis (69.4%). High and active transmission was apparent in several regions of the country, implying that mechanisms for prevention and control of intestinal parasitosis in different parts of the country must be improved.

Use of next-generation amplicon sequencing to study Blastocystis genetic diversity in a rural human population from Mexico

BACKGROUND

The intestinal parasite Blastocystis is found in humans and animals around the world. It is spread through the consumption of contaminated food and water and has been associated with a variety of intestinal symptoms. Blastocystis is one of the most common intestinal parasites in humans, yet its prevalence and distribution in humans in North America is not well characterized.

METHODS

Next-generation amplicon sequencing of a region of the Blastocystis SSU rRNA gene was applied to DNA extracted from fecal specimens obtained from 182 inhabitants of a rural population in Mexico to characterize Blastocystis prevalence, subtype distribution, and intra-host subtype diversity in humans.

RESULTS

Of the 182 samples tested in this study, 68.1% (124) contained one or more Blastocystis subtypes. Subtype 3 was the most common subtype observed and was found in 81.5% of the positive samples. Subtype 1, 16.9% of the positive samples, and subtype 2, 17.7% of the positive samples, were also found in this population. Mixed infections were observed in 13.7% of the positive samples. In this population, the odds of having Blastocystis increased in adulthood (> 15 years; OR: 1.72, P < 0.0001), and the odds of having subtype 1 increased in the presence of farm animals (OR: 1.51, P = 0.03). The odds of having subtype 1, subtype 2, or a mixed infection decreased in the presence of cement flooring (OR: - 1.61, P = 0.005; OR: - 1.14, P = 0.03; OR: - 1.48, P = 0.02) possibly indicating socioeconomic factors are involved in the risk of acquiring one of these subtypes.

CONCLUSIONS

These data contribute to our understanding of the epidemiology of Blastocystis infection in humans and can be used to shape future studies which aim to better characterize the transmission pathways and health outcomes of Blastocystis infections.

Molecular genotyping of Blastocystis spp. in wild mammals from Mexico

Blastocystis spp. are common intestinal parasites found worldwide in humans and a wide range of animals. They exhibit extensive genetic diversity; currently, 17 subtypes (STs) and some groups called non-mammalian and avian STs (NMASTs) have been proposed. In addition, a large variety of animals have been reported as hosts of the parasite, and new hosts and STs are still being described. In this study, Blastocystis infection of wild animals in two sylvatic areas of Mexico was surveyed. Of one hundred twenty-four fecal samples, six were positive for Blastocystis: specifically, one sample from an opossum, one sample from a bat, and four samples from different species of rodents. ST4, ST17, and nucleotide sequences similar to Blastocystis lapemi were identified based on SSU rDNA sequences. To our knowledge, this is the first report to investigate species poorly or not previously evaluated for Blastocystis infection. Mammals having different niches and geographical distribution were infected with similar genetic type of Blastocystis, so that we suggest that local water or food sources could play an important role in Blastocystis transmission and ST maintenance in wild animals. Additionally, there are STs with scarce genetic variation, suggesting that they could be highly adapted to their hosts. These data contribute to our understanding of the host range and genetic diversity of Blastocystis.

Does Irritable Bowel Syndrome Exist? Identifiable and Treatable Causes of Associated Symptoms Suggest It May Not

Significant shortcomings in irritable bowel syndrome (IBS) diagnosis and treatment may arise from IBS being an “umbrella” diagnosis that clusters several underlying identifiable and treatable causes for the same symptom presentation into one classification. This view is compatible with the emerging understanding that the pathophysiology of IBS is heterogeneous with varied disease mechanisms responsible for the central pathological features. Collectively, these converging views of the pathophysiology, assessment and management of IBS render the traditional diagnosis and treatment of IBS less relevant; in fact, they suggest that IBS is not a disease entity per se and posit the question “does IBS exist?” The aim of this narrative review is to explore identifiable and treatable causes of digestive symptoms, including lifestyle, environmental and nutritional factors, as well as underlying functional imbalances, that may be misinterpreted as being IBS.

Intestinal parasitic infections and associated factors in children of three rural schools in Colombia. A cross-sectional study

Rural children are one of the populations that are most vulnerable to gastrointestinal parasite infections. Such diseases decrease the quality of life and result in growth and cognitive delays in the long term. This cross-sectional study was conducted to determine the frequency of intestinal parasite infections among rural schoolchildren in the municipality of Apulo, Colombia. A total of 97 stool samples from children aged between 5 and 15 years were collected and examined via direct light microscopy. Microscopic examination was repeated with sediments obtained using a fecal parasite concentrator, and the Kato–Katz test was performed. Frequency of intestinal parasite infection was 100%. Endolimax nana (77.35%), Blastocystis sp. (71.1%), Giardia intestinalis (39.1%), Entamoeba coli (25.7%), and the Entamoeba histolytica/dispar/moshkovskii complex (9.2%) were the most prevalent protozoa. Trichuris trichiura was the most prevalent helminth (12.3%), followed by Enterobius vermicularis (6.15%) and Ascaris lumbricoides (5.1%). Among the analyzed associated factors, consumption of untreated water increased the risk of acquiring pathogenic intestinal parasites. Finally, because G. intestinalis was the most prevalent pathogenic protozoan, molecular analysis was conducted to establish genetic assemblages and subassemblages of Giardia through sequence-based genotyping of the glutamate dehydrogenase, triose phosphate isomerase, and beta-giardin genes. A total of 14 G. intestinalis-positive samples were genotyped, which revealed the presence of subassemblages AI (n = 1), AII (n = 7), BIII (n = 2), BIV (n = 2), and BIII/BIV (n = 1) as well as a mixed subassemblage AII + BIII (n = 1). Our results indicate that gastrointestinal parasite infections in the tested population were mainly caused by suboptimal water quality. Moreover, molecular typing of G. intestinalis suggested contamination of water by animal- and human-derived cysts.

What do we know about parasites of wildlife in high biodiversity areas with anthropogenic disturbance? The special case of Mexico

The continual rise of anthropogenic disturbance of ecosystems has been associated with an increasing incidence of emerging diseases. The largest amount of data on emerging diseases relates to bacterial and viral pathogens, but there is a lack of parasite data, especially from wildlife. Monitoring wildlife parasitic diseases should be considered a priority, especially in high biodiversity regions with strong anthropogenic impacts, like Mexico, where the wildlife/livestock/human interface is associated with increased risk of disease transmission. Mexico belongs to the top-ten megadiverse countries and is located between two biogeographic regions. This situation makes Mexico a favourable region for the spillover of animal pathogens to human beings, causing pandemics, such as the one recently caused by influenza virus A (H1N1). The current state of knowledge of Mexican wildlife parasites is scarce and focuses mainly in Neotropical fauna. Moreover, this knowledge is heterogeneous for different parasite groups, especially concerning their pathologic effects and epidemiology. The goals of this review are to compile information on Mexican wildlife parasites and to identify knowledge gaps in order to stimulate research on pending epidemiological, public health, ecological and pathological areas, and to encourage the creation of more specialized groups from the perspective of the One-Health concept.

Comprehensive Study of Phenotypic and Growth Rate Features of Blastocystis Subtypes 1-3 and 6 in Symptomatic and Asymptomatic Subjects

BACKGROUND

The present study aimed to assess the grouping of subtypes 1-3 and 6 of Blastocystis according to the size and generation time of the parasite among the symptomatic and asymptomatic subjects.

METHODS

Blastocystis subtypes 1-3 and 6 isolated from symptomatic and asymptomatic subjects and were cultivated in DMEM medium. In order to assess inter- and intra-subtype variation in size, all the isolates were measured using morphometric criteria. Generation time was calculated using approximately 1×10⁴ Blastocystis, which were cultivated in DMEM, every 24h for 4 days.

RESULTS

All subtypes had 5 to 185 μm diameter range. The smallest size was attributed to ST1, followed by ST6 and ST2. ST3 showed the most variable size and phenotypes compared with the other three subtypes. Furthermore, amoeboid forms and parasite clumping were only seen in ST3-S (symptomatic subjects). Generation time analysis showed that the number of ST1 isolated from symptomatic and asymptomatic subjects peaked higher than the other subtypes.

CONCLUSION

This is the first study discussing inter-intra-size, phenotype and generation time variations among 4 common subtypes of Blastocystis. Accordingly, ST3 was largest subtype and showed most diversities in both size and phenotype, while ST1 was smallest subtype with lowest intra-subtype variation.

Can the pyruvate: ferredoxin oxidoreductase (PFOR) gene be used as an additional marker to discriminate among Blastocystis strains or subtypes?

BACKGROUND

Blastocystis spp. are the most prevalent intestinal eukaryotes identified in humans, with at least 17 genetic subtypes (ST) based on genes coding for the small-subunit ribosomal RNA (18S). It has been argued that the 18S gene should not be the marker of choice to discriminate between STs of these strains because this marker exhibits high intra-genomic polymorphism. By contrast, pyruvate:ferredoxin oxidoreductase (PFOR) is a relevant enzyme involved in the core energy metabolism of many anaerobic microorganisms such as Blastocystis, which, in other protozoa, shows more polymorphisms than the 18S gene and thus may offer finer discrimination when trying to identify Blastocystis ST. Therefore, the objective of the present study was to assess the suitability of the PFOR gene as an additional marker to discriminate among Blastocystis strains or subtypes from symptomatic carrier children.

METHODS

Faecal samples from 192 children with gastrointestinal symptoms from the State of Mexico were submitted for coprological study. Twenty-one of these samples were positive only for Blastocystis spp.; these samples were analysed by PCR sequencing of regions of the 18S and PFOR genes. The amplicons were purified and sequenced; afterwards, both markers were assessed for genetic diversity.

RESULTS

The 18S analysis showed the following frequencies of Blastocystis subtypes: ST3 = 43%; ST1 = 38%; ST2 = 14%; and ST7 = 5%. Additionally, using subtype-specific primer sets, two samples showed mixed Blastocystis ST1 and ST2 infection. For PFOR, Bayesian inference revealed the presence of three clades (I-III); two of them grouped different ST samples, and one grouped six samples of ST3 (III). Nucleotide diversity (π) and haplotype polymorphism (θ) for the 18S analysis were similar for ST1 and ST2 (π = ~0.025 and θ = ~0.036); remarkably, ST3 showed almost 10-fold lower values. For PFOR, a similar trend was found: clade I and II had π = ~0.05 and θ = ~0.05, whereas for clade III, the values were almost 6-fold lower.

CONCLUSIONS

Although the fragment of the PFOR gene analysed in the present study did not allow discrimination between Blastocystis STs, this marker grouped the samples in three clades with strengthened support, suggesting that PFOR may be under different selective pressures and evolutionary histories than the 18S gene. Interestingly, the ST3 sequences showed lower variability with probable purifying selection in both markers, meaning that evolutionary forces drive differential processes among Blastocystis STs.

Is the genetic variability of Cathepsin B important in the pathogenesis of Blastocystis spp.?

The potential role of Blastocystis as a pathogen is controversial because it is found in both symptomatic and asymptomatic carriers. Since Cathepsin B has been identified as a main virulence factor that contributes to the pathogenesis of this parasite, the purpose of this study was to analyze the genetic polymorphisms of cathepsin B from Blastocystis from patients with irritable bowel syndrome and from asymptomatic carriers. DNA from fecal samples of both groups, which were previously genotyped by 18S sequencing, was used to amplify a fragment of the cathepsin B gene. Phylogenetic reconstructions were performed and some genetic population indexes were obtained. Amplicons of 27 samples (15 cases, 10 controls, and two commercial ATCC strains) were obtained and analyzed. Phylogenetic reconstructions using nucleotides or inferred amino acid sequences did not separate between cases or controls or among subtypes. Regarding the values of genetic variability, we found that the haplotype and nucleotide diversity indexes of cathepsin B from cases and controls were similar to the values of 18S from controls. By contrast, 18S from cases showed low variability, suggesting that the genetic variability of cathepsin B was not related to the symptomatology of Blastocystis carriers. However, since no polymorphisms related to cases or controls were found, it is logical to assume that the potential damage caused by Blastocystis in situ may be due to unclear mechanisms of Cathepsin B regulation and expression that should be studied in future studies.

Asymptomatic Intestinal Colonization with Protist Blastocystis Is Strongly Associated with Distinct Microbiome Ecological Patterns

Given the results of our study and other reports of the effects of the most common human gut protist on the diversity and composition of the bacterial microbiome, Blastocystis and, possibly, other gut protists should be studied as ecosystem engineers that drive community diversity and composition.

Blastocystis is the most prevalent protist of the human intestine, colonizing approximately 20% of the North American population and up to 100% in some nonindustrialized settings. Blastocystis is associated with gastrointestinal and systemic disease but can also be an asymptomatic colonizer in large populations. While recent findings in humans have shown bacterial microbiota changes associated with this protist, it is unknown whether these occur due to the presence of Blastocystis or as a result of inflammation. To explore this, we evaluated the fecal bacterial and eukaryotic microbiota in 156 asymptomatic adult subjects from a rural population in Xoxocotla, Mexico. Colonization with Blastocystis was strongly associated with an increase in bacterial alpha diversity and broad changes in beta diversity and with more discrete changes to the microbial eukaryome. More than 230 operational taxonomic units (OTUs), including those of dominant species Prevotella copri and Ruminococcus bromii, were differentially abundant in Blastocystis-colonized individuals. Large functional changes accompanied these observations, with differential abundances of 202 (out of 266) predicted metabolic pathways (PICRUSt), as well as lower fecal concentrations of acetate, butyrate, and propionate in colonized individuals. Fecal calprotectin was markedly decreased in association with Blastocystis colonization, suggesting that this ecological shift induces subclinical immune consequences to the asymptomatic host. This work is the first to show a direct association between the presence of Blastocystis and shifts in the gut bacterial and eukaryotic microbiome in the absence of gastrointestinal disease or inflammation. These results prompt further investigation of the role Blastocystis and other eukaryotes play within the human microbiome.

IMPORTANCE Given the results of our study and other reports of the effects of the most common human gut protist on the diversity and composition of the bacterial microbiome, Blastocystis and, possibly, other gut protists should be studied as ecosystem engineers that drive community diversity and composition.

Blastocystis subtypes and their association with Irritable Bowel Syndrome

Blastocystis spp. is a common intestinal protozoan that affects humans and animals. The role of this parasite as a pathogen is still controversial and it is suspected to be linked to Irritable Bowel Syndrome (IBS), a functional bowel disorder characterized by chronic or recurrent abdominal pain associated with altered intestinal habits. A broad search in electronic databases, libraries, portals of journals, etc. for reports on the association between the parasite and IBS without language restriction was performed. The selection was not restricted by date, but articles published in the last seven years were given preference. We investigated the evidence regarding Blastocystis and IBS coexistence as well as the implications of the parasite in pathogenesis and clinical manifestations. Only standardized parasitological tools, supplemented by epidemiological analysis, will be able to clarify whether parasite carriage could be connected to IBS and its status as a human pathogen. Although a variation in pathogenicity and virulence between subtypes has been confirmed, Blastocystis can only be considered an indicator of dysbiosis. Accurate diagnoses of this parasitic eukaryote, specifically at genotypic and phenotypic levels, as well as the complete analysis of the intestinal microbial communities, have to be included in the protocol of those patients with IBS.

Genetic Diversity and Distribution of Blastocystis Subtype 3 in Human Populations, with Special Reference to a Rural Population in Central Mexico

Blastocystis subtype 3 (ST3) is a parasitic protist found in the digestive tract of symptomatic and asymptomatic humans around the world. While this parasite exhibits a high prevalence in the human population, its true geographic distribution and global genetic diversity are still unknown. This gap in knowledge limits the understanding of the spread mechanisms, epidemiology, and impact that this parasite has on human populations. Herein, we provided new data on the geographical distribution and genetic diversity of Blastocystis ST3 from a rural human population in Mexico. To do so, we collected and targeted the SSU-rDNA region in fecal samples from this population and further compared its genetic diversity and structure with that previously observed in populations of Blastocystis ST3 from other regions of the planet. Our analyses reveled that diversity of Blastocystis ST3 showed a high haplotype diversity and genetic structure to the world level; however, they were low in the Morelos population. The haplotype network revealed a common widespread haplotype from which the others were generated recently. Finally, our results suggested a recent expansion of the diversity of Blastocystis ST3 worldwide.

Distribution of Blastocystis subtypes isolated from humans from an urban community in Rio de Janeiro, Brazil

Background

Blastocystis is a cosmopolitan protist parasite found in the human gastrointestinal tract and is highly prevalent in developing countries. Recent molecular studies have revealed extensive genetic diversity, which has been classified into different subtypes (STs) based on sequence analysis of small subunit ribosomal RNA gene. Blastocystis is one of the most common fecal parasites in Brazil, but the diversity of subtypes remains unknown in the country. This study aimed to determine the distribution of Blastocystis STs in an urban community in Duque de Caxias, Rio de Janeiro, Brazil.

Methods

A total of 64 stool samples positive for Blastocystis in Pavlova’s medium were subtyped by PCR and sequenced using primers targeting the small subunit rRNA gene, in addition to phylogenetic analysis and subtype-specific PCR using sequence-tagged-site (STS) primers.

Results

Endolimax nana (14%), Entamoeba complex (10.5%), Taenia sp. (0.6%), Trichuris trichiura (1.3%) and Enterobius vermicularis (1.3%) were detected in Blastocystis-positive samples. Of the 64 samples tested by PCR/DNA sequencing, 55 were identified as ST1 (42%), ST3 (49%), ST2 (7%) and ST4 (2%), and the presence of mixed ST (ST1 + ST3) infection was detected in nine samples (14%).

Conclusions

DNA sequencing and phylogenetic analysis of Brazilian Blastocystis isolates identified four different subtypes. To our knowledge, this study provided the first genetic characterization of Blastocystis subtypes in an urban area of Rio de Janeiro, Brazil. We also identified ST4 for the first time in Brazil. Further studies are necessary to determine the distribution of STs across human populations in Rio de Janeiro.

Clarifying the Cryptic Host Specificity of Blastocystis spp. Isolates from Alouatta palliata and A. pigra Howler Monkeys

Although the presence of cryptic host specificity has been documented in Blastocystis, differences in infection rates and high genetic polymorphism within and between populations of some subtypes (ST) have impeded the clarification of the generalist or specialist specificity of this parasite. We assessed the genetic variability and host specificity of Blastocystis spp. in wild howler monkeys from two rainforest areas in the southeastern region of Mexico. Fecal samples of 225 Alouatta palliata (59) and A. pigra (166) monkeys, belonging to 16 sylvatic sites, were analyzed for infection with Blastocystis ST using a region of the small subunit rDNA (SSUrDNA) gene as a marker. Phylogenetic and genetic diversity analyses were performed according to the geographic areas where the monkeys were found. Blastocystis ST2 was the most abundant (91.9%), followed by ST1 and ST8 with 4.6% and 3.5%, respectively; no association between Blastocystis ST and Alouatta species was observed. SSUrDNA sequences in GenBank from human and non-human primates (NHP) were used as ST references and included in population analyses. The haplotype network trees exhibited different distributions: ST1 showed a generalist profile since several haplotypes from different animals were homogeneously distributed with few mutational changes. For ST2, a major dispersion center grouped the Mexican samples, and high mutational differences were observed between NHP. Furthermore, nucleotide and haplotype diversity values, as well as migration and genetic differentiation indexes, showed contrasting values for ST1 and ST2. These data suggest that ST1 populations are only minimally differentiated, while ST2 populations in humans are highly differentiated from those of NHP. The host generalist and specialist specificities exhibited by ST1 and ST2 Blastocystis populations indicate distinct adaptation processes. Because ST1 exhibits a generalist profile, this haplotype can be considered a metapopulation; in contrast, ST2 exists as a set of local populations with preferences for either humans or NHP.

Subtypes Distribution and Frequency of Blastocystis sp. Isolated from Diarrheic and Non-diarrheic Patients

BACKGROUND

Blastocystis is one of the most common parasites, reported from both human and animals. This parasite is more prevalent in regions with low levels of hygiene, close contact with animal and unsuitable disposal systems. The aim of the study was to subtype Blastocystis sp., isolated from diarrheic and non-diarrheic patients using sequencing of 18S ribosomal DNA.

METHODS

Totally, 300 stool samples were collected from diarrheic and nondiarrheic patients referred to Imam Reza Hospital, Tehran from Apr to Aug 2015. All samples were concentrated using conventional Formalin - ether technique and recognized under light microscope. The fresh stool samples were also cultivated in clotted fetal bovine medium and examined for growing of Blastocystis every 48 h with direct smear slides for 10 d. DNA extraction was performed on all positive samples. Amplified DNA fragment of 18S rDNA was sequenced and compared with reference genes, previously deposited in Genbank database.

RESULTS

The number of diarrheic and non-diarrheic patients participated in the study was 134 (44.66%) and 166 (55.34%), respectively. Three subtypes 1, 2, 3 were identified from positive samples. Subtype 2 was the most prevalent (36.5%) followed by subtype 1 (33.3%) and subtype 3 (30.2%). There were no mixed subtypes. Furthermore, the most prevalent subtypes in diarrheic and non-diarrheic patients were subtype 2 (39.28%) and subtype 1 (37.14%), respectively.

CONCLUSION

Blastocystis sp., is one of the most prevalent unicellular parasites among diarrheic and non-diarrheic patients. Indeed, ST2 was the most prevalent subtype particularly in those samples collected from diarrheic patients.

Comparison of the genetic variability of Blastocystis subtypes between human carriers from two contrasting climatic regions of México

Blastocystis sp. is an anaerobic intestinal microorganism commonly identified in the feces of several animals, including humans. Blastocystis exhibits high genetic polymorphism and at least 17 subtypes (ST) have been identified; ST1-ST3 are frequently found in the Americas. Furthermore, in vitro assays have shown that temperature and humidity can affect the viability of Blastocystis cysts. In this study, we describe the genetic variability and genetic differentiation among and within Blastocystis STs in adults and children from the cities of Hermosillo and Morelia cities, which represent arid and humid subtropical climatic regions of México, respectively. Phylogenetic and genetic diversity was assessed by analyzing a region of the small subunit ribosomal DNA (SSU rDNA) gene as a marker. Blastocystis ST3 and ST1 were associated with children from Hermosillo and Morelia, respectively. An analysis of the nucleotide diversity (π) and haplotype polymorphism (θ) indexes showed that they were similar within each ST, but different between ST1 and ST3. Interestingly, the group of symptomatic carriers from Hermosillo showed scarce mean nucleotide diversity compared to the asymptomatic carriers (0.0039±0.0030 and 0.0329±0.0286, respectively). Furthermore, the gene flow and genetic differentiation indexes between the children and adults suggested that the Blastocystis haplotypes in the adult carriers were "highly mobile" among humans, while the haplotypes found in the children were more isolated and genetically differentiated between them.