Associations between common intestinal parasites and bacteria in humans as revealed by qPCR

Protozoan predation as a driver of diversity and virulence in bacterial biofilms

Protozoa are eukaryotic organisms that play a crucial role in nutrient cycling and maintaining balance in the food web. Predation, symbiosis and parasitism are three types of interactions between protozoa and bacteria. However, not all bacterial species are equally susceptible to protozoan predation as many are capable of defending against predation in numerous ways and may even establish either a symbiotic or parasitic life-style. Biofilm formation is one such mechanism by which bacteria can survive predation. Structural and chemical components of biofilms enhance resistance to predation compared to their planktonic counterparts. Predation on biofilms gives rise to phenotypic and genetic heterogeneity in prey that leads to trade-offs in virulence in other eukaryotes. Recent advances, using molecular and genomics techniques, allow us to generate new information about the interactions of protozoa and biofilms of prey bacteria. This review presents the current state of the field on impacts of protozoan predation on biofilms. We provide an overview of newly gathered insights into (i) molecular mechanisms of predation resistance in biofilms, (ii) phenotypic and genetic diversification of prey bacteria, and (iii) evolution of virulence as a consequence of protozoan predation on biofilms.

Commensal Intestinal Protozoa-Underestimated Members of the Gut Microbial Community

The human gastrointestinal microbiota contains a diverse consortium of microbes, including bacteria, protozoa, viruses, and fungi. Through millennia of co-evolution, the host-microbiota interactions have shaped the immune system to both tolerate and maintain the symbiotic relationship with commensal microbiota, while exerting protective responses against invading pathogens. Microbiome research is dominated by studies describing the impact of prokaryotic bacteria on gut immunity with a limited understanding of their relationship with other integral microbiota constituents. However, converging evidence shows that eukaryotic organisms, such as commensal protozoa, can play an important role in modulating intestinal immune responses as well as influencing the overall health of the host. The presence of several protozoa species has recently been shown to be a common occurrence in healthy populations worldwide, suggesting that many of these are commensals rather than invading pathogens. This review aims to discuss the most recent, conflicting findings regarding the role of intestinal protozoa in gut homeostasis, interactions between intestinal protozoa and the bacterial microbiota, as well as potential immunological consequences of protozoa colonization.

Infection with pathogenic Blastocystis ST7 is associated with decreased bacterial diversity and altered gut microbiome profiles in diarrheal patients

Background

Blastocystis is a common protistan parasite inhabiting the gastrointestinal tract of humans and animals. While there are increasing reports characterizing the associations between Blastocystis and the gut microbiome in healthy individuals, only a few studies have investigated the relationships between Blastocystis and the gut microbiota in diarrheal patients.

Methods

The effects of a specific subtype (ST7) of Blastocystis on the composition of gut microbiota in diarrheal patients were investigated using 16S ribosomal RNA (rRNA) gene sequencing and bioinformatic analyses.

Results

Compared with diarrheal patients without Blastocystis, diarrheal patients infected with Blastocystis ST7 exhibited lower bacterial diversity. Beta diversity analysis revealed significant differences in bacterial community structure between ST7-infected and Blastocystis-free patients. The proportion of Enterobacteriaceae and Escherichia-Shigella were significantly enriched in ST7-infected patients. In contrast, the abundance of Bacteroides and Parabacteroides were more prevalent in Blastocystis-free patients.

Conclusions

The results of this study revealed, for the first time, that infection with Blastocystis ST7 is associated with lower bacterial diversity and altered microbial structure in diarrheal patients. Our study on clinical diarrheal patients is also the first to reinforce the notion that ST7 is a pathogenic subtype of Blastocystis.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05435-z.

The regulatory function of Blastocystis spp. on the immune inflammatory response in the gut microbiome

Blastocystis spp. is a unicellular organism that resides in digestive tract of various vertebrates, with a worldwide distribution and a variable prevalence. For many years, Blastocystis spp. was considered a cyst of a flagellate, a fungus, or a saprophyte yeast of the digestive tract; in 1996, it is placed in the group of stramenopiles (heterokonts). Since its new classification, many questions have arisen around this protist about its role as a pathogen or non-pathogen organism. Recent evidence indicates that Blastocystis spp. participates in the immune inflammatory response in the intestinal microbiome generating an anti-inflammatory response, showing a lower concentration of fecal inflammatory markers in infected human hosts. Here, we review recent findings on the regulatory function of Blastocystis spp. in the immune inflammatory response to comprehend the purpose of Blastocystis spp. in health and disease, defining if Blastocystis spp. is really a pathogen, a commensal or even a mutualist in the human gut microbiome.

Intermittent fasting positively modulates human gut microbial diversity and ameliorates blood lipid profile

Aim

The aim was to evaluate the impact of intermittent fasting (IF) on human body mass index (BMI) and serum lipid profile thorough constructive rectification of gut microbiota.

Methods and results

Fourteen healthy women and thirty-one men were included in the study. Their blood and fecal samples were collected before and at the end of the study. Blood parameters, anthropometric values, and gut microbiology were noted to investigate the impact of intermittent fasting (IF) on human gut microbiota and physiology. Our data revealed that IF reduces the body weight and improves blood lipid profile, such as increasing high-density lipoprotein (HDL) and decreasing total cholesterol, triglycerides, and low- and very low-density lipoprotein levels. IF also decreases culturable aerobic bacterial count and increased fungal count. It was also found that the gut metagenome is altered considerably after IF. The human fecal bacterial diversity exhibited significant changes in decreased overall bacterial population, increased bacterial diversity (alpha diversity), and promoted evenness within the bacterial population at the species level. Anti-inflammatory bacteria Lactobacillus and Bifidobacterium were favorably increased, while pathogenic bacteria were decreased.

Conclusion

Collectively, these results indicated that IF could improve lipid profile and body weight in humans, and the potential mechanisms might be via regulating gut microbiota.

Significance and impact of the study

We demonstrated for the first time that IF improved body weight and blood lipid profile, indicating that IF could mitigate gut microbiota in humans.

Interplay between Intestinal Bacterial Communities and Unicellular Parasites in a Morbidly Obese Population: A Neglected Trinomial

Obesity is an epidemic causing a metabolic health crisis. Herein, the interactions between the gut prokaryotic and eukaryotic communities, metabolic comorbidities and diet were studied. Stool samples from 56 subjects, 47 with type III obesity and 9 with type II obesity and cardiovascular risk or metabolic disease, were assessed for the richness, diversity and ecology of the bacterial gut community through metagenomics, together with the study of the presence of common unicellular eukaryote parasites (Blastocystis sp., Dientamoeba fragilis and Giardia intestinalis) by qPCR. Clinical information regarding metabolic comorbidities and non-alcoholic hepatic fatty liver disease was gathered. To assess the quality of the patients’ diet, each participant filled in three dietary questionnaires. The most prevalent parasite Blastocystis sp. (46.4%), together with D. fragilis (8.9%), was found to be associated with higher mean diversity indexes regarding non-colonized subjects; the opposite of that which was observed in those with G. intestinalis (16.1%). In terms of phyla relative abundance, with Blastocystis sp. and D. fragilis, very slight differences were observed; on the contrary, G. intestinalis was related to an increase in Bacteroidetes and Proteobacteria, and a decrease in Firmicutes and Actinobacteria, presenting the lowest Firmicutes/Bacteroidetes ratio. At genus level, Blastocystis sp. and/or D. fragilis was accompanied with an increase in Lactobacillus spp., and a decrease in Akkermansia spp., Bifidobacterium spp. and Escherichia spp., while G. intestinalis was associated with an increase in Bacteroides spp., and a decrease in Faecalibacterium spp., Prevotella spp. and Lactobacillus spp., and the highest Bacteroides spp./Prevotella spp. ratio. Participants with non-alcoholic hepatic fatty liver presented a higher Firmicutes/Bacteroidetes ratio, and those with type 2 diabetes displayed a significantly lower Faecalibacterium spp./Escherichia spp. ratio, due to an overrepresentation of the genus Escherichia spp. The presence of parasites was associated with variations in the richness, diversity and distribution of taxa in bacterial communities, confirming a gain in diversity associated with Blastocystis sp. and providing different functioning of the microbiota with a potential positive effect on comorbidities such as type 2 diabetes, insulin resistance and metabolic syndrome. Future basic and clinical studies should assess the beneficial or pathogenic effect of these eukaryotes on obese subjects and focus on deciphering whether they may imply a healthier metabolic profile.

How the gut parasitome affects human health

The human gut microbiome (GM) is a complex ecosystem that includes numerous prokaryotic and eukaryotic inhabitants. The composition of GM can influence an array of host physiological functions including immune development. Accumulating evidence suggest that several members of non-bacterial microbiota, including protozoa and helminths, that were earlier considered as pathogens, could have a commensal or beneficial relationship with the host. Here we examine the most recent data from omics studies on prokaryota-meiofauna-host interaction as well as the impact of gut parasitome on gut bacterial ecology and its role as 'immunological driver' in health and disease to glimpse new therapeutic perspectives.

Stool Microbiota Diversity Analysis of Blastocystis-Positive and Blastocystis-Negative Individuals

Blastocystis is a unicellular eukaryote found in the gastrointestinal tract of both human and other animal hosts. The clinical significance of colonic Blastocystis colonization remains obscure. In this study, we used metabarcoding and bioinformatics analyses to identify differences in stool microbiota diversity between Blastocystis-positive and Blastocystis-negative individuals (n = 1285). Alpha diversity was significantly higher in Blastocystis carriers. At phylum level, Firmicutes and Bacteroidetes were enriched in carriers, while Proteobacteria were enriched in non-carriers. The genera Prevotella, Faecalibacterium, Flavonifracter, Clostridium, Succinivibrio, and Oscillibacter were enriched in carriers, whereas Escherichia, Bacteroides, Klebsiella, and Pseudomonas were enriched in non-carriers. No difference in beta diversity was observed. Individuals with Blastocystis-positive stools appear to have gut microbiomes associated with eubiosis unlike those with Blastocystis-negative stools, whose gut microbiomes are similar to those associated with dysbiosis. The role of Blastocystis as an indicator organism and potential modulator of the gut microbiota warrants further scrutiny.

Blastocystis in the faeces of children from six distant countries: prevalence, quantity, subtypes and the relation to the gut bacteriome

Background

Blastocystis is a human gut symbiont of yet undefined clinical significance. In a set of faecal samples collected from asymptomatic children of six distant populations, we first assessed the community profiles of protist 18S rDNA and then characterized Blastocystis subtypes and tested Blastocystis association with the faecal bacteriome community.

Methods

Stool samples were collected from 244 children and young persons (mean age 11.3 years, interquartile range 8.1–13.7) of six countries (Azerbaijan 51 subjects, Czechia 52, Jordan 40, Nigeria 27, Sudan 59 and Tanzania 15). The subjects showed no symptoms of infection. Amplicon profiling of the 18S rDNA was used for verification that Blastocystis was the most frequent protist, whereas specific real-time PCR showed its prevalence and quantity, and massive parallel amplicon sequencing defined the Blastocystis subtypes. The relation between Blastocystis and the stool bacteriome community was characterized using 16S rDNA profiling.

Results

Blastocystis was detected by specific PCR in 36% (88/244) stool samples and was the most often observed faecal protist. Children from Czechia and Jordan had significantly lower prevalence than children from the remaining countries. The most frequent subtype was ST3 (49%, 40/81 sequenced samples), followed by ST1 (36%) and ST2 (25%). Co-infection with two different subtypes was noted in 12% samples. The faecal bacteriome had higher richness in Blastocystis-positive samples, and Blastocystis was associated with significantly different community composition regardless of the country (p < 0.001 in constrained redundancy analysis). Several taxa differed with Blastocystis positivity or quantity: two genera of Ruminococcaceae were more abundant, while Bifidobacterium, Veillonella, Lactobacillus and several other genera were undrerrepresented.

Conclusions

Asymptomatic children frequently carry Blastocystis, and co-infection with multiple distinct subtypes is not exceptional. Prevalence and quantity of the organism clearly differ among populations. Blastocystis is linked to both faecal bacteriome diversity and its composition.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04859-3.

Impact of Metronidazole Treatment and Dientamoeba Fragilis Colonization on Gut Microbiota Diversity

OBJECTIVES

The intestinal parasite Dientamoeba fragilis is a common colonizer of children in Denmark. Metronidazole has been used to reduce gastrointestinal symptoms in children colonized with D fragilis. We aimed to identify gut microbiota changes associated with D fragilis carrier status and metronidazole treatment of D fragilis-positive children.

METHODS

The fecal microbiota of 275 fecal samples from children treated with metronidazole (n = 48) or placebo (n = 48) were characterized by ribosomal DNA sequencing. Samples collected before (T1), 2 weeks after (T2), and 8 weeks (T5) after treatment were included. Seventy fecal samples from 70 age-matched parasite-negative children served as controls.

RESULTS

The abundance of 24 bacterial genera differed significantly according to D fragilis carrier status, with Flavonifractor being remarkably more abundant in children testing negative for D fragilis. Eight bacterial genera changed significantly in abundance in children losing versus keeping D fragilis after metronidazole treatment. Of these, 7 returned to pretreatment (T1) levels at T5. Meanwhile, the abundance of Flavonifractor continued to differ at T5, whereas for Ruminococcus the abundance only remained high in children who were D fragilis-negative at T2 and T5. Increases in Hungatella, Sutterella, and Streptococcus abundances observed at T2 were specific to metronidazole exposure and hence independent of D fragilis colonization.

CONCLUSIONS

This study revealed that specific bacterial genera were associated with D fragilis colonization. Metronidazole treatment had a short-term impact on the abundance of some bacterial genera, with most of these reverting to pretreatment levels 8 weeks after completed treatment.

Gut microbiota composition in health-care facility-and community-onset diarrheic patients with Clostridioides difficile infection

The role of gut microbiota in the establishment and development of Clostridioides difficile infection (CDI) has been widely discussed. Studies showed the impact of CDI on bacterial communities and the importance of some genera and species in recovering from and preventing infection. However, most studies have overlooked important components of the intestinal ecosystem, such as eukaryotes and archaea. We investigated the bacterial, archaea, and eukaryotic intestinal microbiota of patients with health-care-facility- or community-onset (HCFO and CO, respectively) diarrhea who were positive or negative for CDI. The CDI-positive groups (CO/+, HCFO/+) showed an increase in microorganisms belonging to Bacteroidetes, Firmicutes, Proteobacteria, Ascomycota, and Opalinata compared with the CDI-negative groups (CO/-, HCFO/-). Patients with intrahospital-acquired diarrhea (HCFO/+, HCFO/-) showed a marked decrease in bacteria beneficial to the intestine, and there was evidence of increased Archaea and Candida and Malassezia species compared with the CO groups (CO/+, CO/-). Characteristic microbiota biomarkers were established for each group. Finally, correlations between bacteria and eukaryotes indicated interactions among the different kingdoms making up the intestinal ecosystem. We showed the impact of CDI on microbiota and how it varies with where the infection is acquired, being intrahospital-acquired diarrhea one of the most influential factors in the modulation of bacterial, archaea, and eukaryotic populations. We also highlight interactions between the different kingdoms of the intestinal ecosystem, which need to be evaluated to improve our understanding of CDI pathophysiology.

Intestinal Microbiota in Children With Symptomatic Dientamoeba fragilis Infection: A Case-control Study

BACKGROUND

Dientamoeba fragilis in children has been associated with gastrointestinal symptoms, like abdominal pain and diarrhea. The mechanism underlying these symptoms in children with D. fragilis remains unclear. We hypothesized that concomitant microbial alterations, which have been described in other parasitic infections, may be associated with gastrointestinal symptoms in D. fragilis.

METHODS

In this case-control study performed in 2 centers, 19 children referred to a pediatrician because of gastrointestinal symptoms and with a positive fecal PCR for D. fragilis were included as cases. We included 19 healthy children as controls and matched for age and gender, selected from an existing cohort of 63 children. A PCR for D. fragilis was performed on fecal samples of the 19 controls to assess D. fragilis carriership in this asymptomatic group. Microbiota was analyzed with the IS-pro technique, and the intestinal microbiota composition and diversity were compared between the 2 groups.

RESULTS

Microbiota of children with D. fragilis and gastrointestinal symptoms did not significantly differ in terms of composition and diversity compared with controls, both on phylum and species level. In the asymptomatic controls, a positive fecal PCR for D. fragilis was found in 16 of 19 (84.2%).

CONCLUSION

Intestinal microbiota does not seem to play a key role in the presence of clinical symptoms in children with D. fragilis. The pathogenicity of D. fragilis and pathophysiologic pathways underlying the development of gastrointestinal symptoms remains yet to be clarified.

New insights into the interactions between Blastocystis, the gut microbiota, and host immunity

The human gut microbiota is a diverse and complex ecosystem that is involved in beneficial physiological functions as well as disease pathogenesis. Blastocystis is a common protistan parasite and is increasingly recognized as an important component of the gut microbiota. The correlations between Blastocystis and other communities of intestinal microbiota have been investigated, and, to a lesser extent, the role of this parasite in maintaining the host immunological homeostasis. Despite recent studies suggesting that Blastocystis decreases the abundance of beneficial bacteria, most reports indicate that Blastocystis is a common component of the healthy gut microbiome. This review covers recent finding on the potential interactions between Blastocystis and the gut microbiota communities and its roles in regulating host immune responses.

Eukaryotic and Prokaryotic Microbiota Interactions

The nature of the relationship between the communities of microorganisms making up the microbiota in and on a host body has been increasingly explored in recent years. Microorganisms, including bacteria, archaea, viruses, parasites and fungi, have often long co-evolved with their hosts. In human, the structure and diversity of microbiota vary according to the host’s immunity, diet, environment, age, physiological and metabolic status, medical practices (e.g., antibiotic treatment), climate, season and host genetics. The recent advent of next generation sequencing (NGS) technologies enhanced observational capacities and allowed for a better understanding of the relationship between distinct microorganisms within microbiota. The interaction between the host and their microbiota has become a field of research into microorganisms with therapeutic and preventive interest for public health applications. This review aims at assessing the current knowledge on interactions between prokaryotic and eukaryotic communities. After a brief description of the metagenomic methods used in the studies were analysed, we summarise the findings of available publications describing the interaction between the bacterial communities and protozoa, helminths and fungi, either in vitro, in experimental models, or in humans. Overall, we observed the existence of a beneficial effect in situations where some microorganisms can improve the health status of the host, while the presence of other microorganisms has been associated with pathologies, resulting in an adverse effect on human health.

Relative Frequency of Blastocystis Subtypes 1, 2, and 3 in Urban and Periurban Human Populations of Arequipa, Peru

Blastocystis is one of the most common protozoa found in the human gut and are genetically diverse and widely distributed around the world. Nonspecific and inconsistent symptoms have been associated with this protozoon; thus, its clinical importance remains controversial. Our aim was to estimate the relative frequency of Blastocystis subtypes 1, 2, and 3, which are the predominant subtypes reported in South America, based on conserved regions of SSU rDNA sequences and determine the factors associated with them. A total of 116 Blastocystis-positive stool samples were processed using conventional PCR with Blastocystis-specific primers. We identified subtype 1 (10.3%), subtype 2 (7.8%), subtype 3 (25.0%), and mixed subtype infections (8.7%). However, we could not identify any Blastocystis subtypes in 48.3% of the samples; therefore, it is likely that other subtypes were present in the area. No association was found between any gastrointestinal symptom and single or mixed Blastocystis subtypes. We found a statistically significant association between Blastocystis subtype 2 and irritable bowel syndrome (OR = 17.8, 95% CI = 1.5-408.4, p = 0.039); however, the number of samples with IBS was small (n= 4). There was no association between the Blastocystis subtypes and any epidemiological variable studied. In rural populations, we only identified subtype 1, while in urban and periurban populations, we identified subtypes 1, 2, and 3.

A Study on the Prevalence and Subtype Diversity of the Intestinal Protist Blastocystis sp. in a Gut-Healthy Human Population in the Czech Republic

Blastocystis sp. is a common intestinal protist colonizing the human intestine the prevalence of which varies across non-industrialized and industrialized countries. Its role in the human gut ecosystem remains unclear due to persisting gaps in knowledge of epidemiology and factors affecting gut colonization. Here, we aimed to expand the knowledge of the epidemiology of Blastocystis sp. in the gut-healthy humans in one of the industrialized European countries, including the distribution of its subtypes, the correlation between its occurrence and several factors such as lifestyle, contact with animals, age, and sex. A total of 288 stool samples were obtained from asymptomatic individuals over the entire age-range and 136 samples from animals with which the volunteers were in frequent contact. All samples were examined in parallel by PCR and xenic in vitro culture. Blastocystis sp. was detected in samples from both human and non-human hosts. In humans, the overall prevalence was 24% and eight subtypes were found; in animals, the prevalence was 10%, and only five subtypes were detected. A higher incidence of Blastocystis sp. was observed in individuals (i) traveling outside Europe, (ii) in frequent contact with livestock, and (iii) over 50 years of age. We found no effect on gender on Blastocystis sp. colonization.

Summary

This study provides data on the prevalence and diversity of the gut protist Blastocystis sp. and its subtypes in a gut-healthy human population with emphasis on several factors such as contact with animals, lifestyle, age, and gender.

Contrasting microbiota profiles observed in children carrying either Blastocystis spp. or the commensal amoebas Entamoeba coli or Endolimax nana

Recent studies have shown how intestinal parasites can modulate gut microbiota. This observation is not surprising since the human intestinal lumen, like any other niche, is a battlefield of microbial competition, and Eukaryotes can affect bacterial populations. Intestinal pathogenic protist has been associated with reshaping the microbial community structure; however, the interactions between the colonic bacterial communities and parasites like Blastocystis spp., Entamoeba coli, and Endolimax nana have been poorly studied. In this work, we studied the distal intestinal bacterial microbiota of 49 children attending 7 public daycare centers in Medellin, Colombia, and compared the bacterial microbiota structure in the presence or absence of the protists Blastocystis spp., E. coli, and E. nana. Parasite colonization was associated with an increase in bacterial richness. Moreover, Blastocystis spp. presented a positive relationship with Prevotella, since this bacterium was selectively enriched in children carrying it. Remarkably, the E. coli colonized children showed a microbial profile that was closer to uninfected controls, although some bacterial taxa displayed to be enriched. This is the case for Akkermansia, which showed to be favored in E. coli colonized individuals, while notably reduced in the Blastocystis spp. parasitized group.

Blastocystis, urticaria, and skin disorders: review of the current evidences

Blastocystis is one of the most common intestinal protozoan parasites worldwide, which is linked to cutaneous lesions and urticaria. In a setting of systematic review, the data on the association of Blastocystis infection with cutaneous lesions were searched in order to summarize the main clinical symptoms, diagnostic methods, treatment, and outcome of the patients. The search identified 28 eligible articles, including 12 cross-sectional studies and 16 case reports/case series (including 23 cases). A diverse spectrum of skin symptoms, mainly urticaria, rash, and itching, was reported from the studies. Of the 23 infected cases with the skin symptoms, gastrointestinal symptoms were reported from the 16 cases, whereas 7 cases with urticaria had asymptomatic infection. The most frequent subtypes were ST1, ST2, and ST3, respectively. Metronidazole, paromomycin, and tinidazole were the most prescribed drugs in patients with single Blastocystis infection. Notably, urticaria and other cutaneous symptoms of all treated patients were resolved after treatment. In conclusion, this study indicates that Blastocystis infection can be a neglected cause of urticaria and skin disorders. Since the treatment of Blastocystis infection is simple, screening and treatment of this infection should be considered in patients with urticaria and other skin disorders.

Dientamoeba fragilis in children: a systematic review on diagnostic considerations and efficacy of treatment

Introduction: The presence of D. fragilis in feces is characterized by an asymptomatic carrier ship to a spectrum of gastrointestinal symptoms. However, a causal relationship remains to be elucidated. In this systematic review, we aimed to evaluate the relationship between the eradication of D. fragilis and symptoms to establish the strength of evidence that D. fragilis in symptomatic children warrants antibiotic treatment.Areas covered: This systematic review covers a challenge in daily clinical practice. Is it necessary to test for D. fragilis in children with gastrointestinal symptoms and does a positive fecal PCR test warrant treatment?Expert opinion: Testing for D. fragilis seems justified in a selection of children with persistent unexplained chronic abdominal pain and diarrhea. Treatment of D. fragilis should be withhold until other causes like celiac disease have been excluded. Both microscopic and Real Time-PCR methods (or a combination of the two) can be used for diagnosis. Paromomycin or clioquinol are antibiotics of choice based on their small spectrum of activity, fewer side effects, and better eradication rates than metronidazole. Future randomized studies, with strict inclusion criteria, appropriate diagnostic testing, and doses of antibiotics based on bodyweight are warranted.

Helminths, polyparasitism, and the gut microbiome in the Philippines

Polyparasitism, involving soil-transmitted helminths. and Schistosoma blood flukes, is common in low to middle income countries. These helminths impact on the gut environment and can cause changes to the gut microbiome composition. Here we examined the gut microbiome in individuals with polyparasitism from two human cohorts in the Philippines utilising DNA sequencing-based profiling. Multiple helminth species infections were high with 70.3% of study participants harbouring at least two parasite species, and 16% harbouring at least five species. Increased numbers of helminth co-infections, in particular with the gut-resident soil-transmitted helminths, were significantly associated with increased bacterial diversity; however no significant parasite-gut microbiome associations were evident for individuals infected only with Schistosoma japonicum. In general, a healthy gut is associated with high bacterial diversity, which in these human cohorts may be the result of helminth-mediated immune modulation, or due to changes in the gut environment caused by these parasitic helminths.

Exploring Micro-Eukaryotic Diversity in the Gut: Co-occurrence of Blastocystis Subtypes and Other Protists in Zoo Animals

Blastocystis is a genetically diverse microbial eukaryote thriving in the gut of humans and other animals. While Blastocystis has been linked with gastrointestinal disorders, its pathogenicity remains controversial. Previous reports have suggested that one out of six humans could be carrying Blastocystis in their gut, while the numbers could be even higher in animals. Most studies on Blastocystis are either exclusively targeting the organism itself and/or the associated prokaryotic microbiome, while co-occurrence of other microbial eukaryotes has been mainly ignored. Herein, we aimed to explore presence and genetic diversity of Blastocystis along with the commonly occurring eukaryotes Cryptosporidium, Eimeria, Entamoeba and Giardia in the gut of asymptomatic animals from two conservation parks in the United Kingdom. Building upon a previous study, a total of 231 fecal samples were collected from 38 vertebrates, which included 12 carnivorous and 26 non-carnivorous species. None of the animals examined herein showed gastrointestinal symptoms. The barcoding region of the small subunit ribosomal RNA was used for subtyping of Blastocystis. Overall, 47% of animal species were positive for Blastocystis. Twenty six percent of samples carried more than one subtypes, including the newly identified hosts Scottish wildcat, bongo and lynx. Fifty three percent of samples carried at least another microbial eukaryote. Herewith, we discuss potential implications of these findings and the increasingly blurred definition of microbial parasites.

Blastocystis Colonization Is Associated with Increased Diversity and Altered Gut Bacterial Communities in Healthy Malian Children

Blastocystis is the most common protozoan colonizing the gut of vertebrates. It modulates the human digestive microbiota in the absence of inflammation and gastrointestinal disease. Although it has been associated with human diseases, including inflammatory bowel disease, its pathogenicity remains controversial. This study aimed to assess the influence of Blastocystis on the gut bacterial communities in healthy children. We conducted a cross-sectional study on 147 Blastocystis-colonized and 149 Blastocystis-noncolonized Malian children, with Blastocystis colonization assessed by real-time PCR and gut microbial communities characterized via 16S rRNA gene (Illumina MiSeq) sequencing and bioinformatics analysis. The gut microbiota diversity was higher in Blastocystis-colonized compared to Blastocystis-noncolonized children. The phyla Firmicutes, Elusimicrobia, Lentisphaerae, and Euryarchaeota were higher in Blastocystis-colonized children, whereas Actinobacteria, Proteobacteria, unassigned bacteria, and Deinococcus-Thermus were higher in Blastocystis-noncolonized children. Moreover, Faecalibacterium prausnitzii (family Ruminococcaceae) and Roseburia sp. (family Lachnospiraceae) abundance was higher in Blastocystis-colonized children. We conclude that Blastocystis colonization is significantly associated with a higher diversity of the gut bacterial communities in healthy children, while it is not associated with the presence of potentially pathogenic bacteria in the human gut.

High prevalence of Pentatrichomonas hominis infection in gastrointestinal cancer patients

BACKGROUND

Pentatrichomonas hominis is a flagellated protozoan that inhabits the large intestine of humans. Although several protozoans have been proposed to have a role in cancer progression, little is known about the epidemiology of P. hominis infection in cancer patients.

METHODS

To determine the prevalence of P. hominis in patients with digestive system malignancies, we collected 195 and 142 fecal samples from gastrointestinal cancer patients and residents without any complaints related to the digestive system, respectively. Each sample was detected for the presence of P. hominis by nested PCR amplifying the internal transcribed spacer (ITS) region and partial 18S rRNA gene.

RESULTS

A significantly higher prevalence of P. hominis was found in cancer patients than that in the control population (41.54 vs 9.15%, χ2 = 42.84, df = 1, P < 0.001), resulting in a 6.75-fold risk of gastrointestinal cancers (OR: 6.75, 95% CI: 3.55-12.83, P < 0.001). The highest prevalence of P. hominis infection was detected in small intestine cancer patients (60%, OR: 14.88, 95% CI: 0.82-4.58, P = 0.009) followed by liver (57.14%, χ2 = 10.82, df = 1, P = 0.001) and stomach cancer patients (45.1%, χ2 = 31.95, df = 1, P < 0.001). In addition, phylogenetic analysis provided some evidence supporting that human P. hominis infection might derive from animal sources.

CONCLUSIONS

To our knowledge, this study is the first report presenting the high association between P. hominis and gastrointestinal cancers. Nevertheless, whether there is any possible pathological role of P. hominis infection in cancer patients needs to be further elucidated.

Diversity profiling of xenic cultures of Dientamoeba fragilis following systematic antibiotic treatment and prospects for genome sequencing

The presence of bacterial DNA in Dientamoeba fragilis DNA extracts from culture poses a substantial challenge to sequencing the D. fragilis genome. However, elimination of bacteria from D. fragilis cultures has proven difficult in the past, presumably due to its dependence on some unknown prokaryote/s. This study explored options for removal of bacteria from D. fragilis cultures and for the generation of genome sequence data from D. fragilis. DNA was extracted from human faecal samples and xenic D. fragilis cultures. Extracts were subjected to 16S ribosomal DNA bacterial diversity profiling. Xenic D. fragilis cultures were then subject to antibiotic treatment regimens that systematically removed bacterial species depending on their membrane structure (Gram-positive or Gram-negative) and aerobic requirements. The impact of these treatments on cultures was assessed by 16S amplicon sequencing. Prior to antibiotic treatment, the cultures were dominated by Gram-negative bacteria. Addition of meropenem to cultures eliminated anaerobic Gram-negative bacteria, but it also led to protozoan death after 5 days incubation. The seeding of meropenem resistant Klebsiella pneumoniae strain KPC-2 into cultures before treatment by meropenem prevented death of D. fragilis cells beyond this 5 day period, suggesting that one or more species of Gram-negative bacteria may be an essential nutritional requirement for D. fragilis. Gram-positive cells were completely eliminated using vancomycin without affecting trophozoite growth. Finally, this study shows that genome sequencing of D. fragilis is feasible following bacterial elimination from cultures as the result of the major advances occurring in bioinformatics. We provide evidence on this fact by successfully sequencing the D. fragilis 28S large ribosomal DNA subunit gene using culture-derived DNA.

Population-level analysis of Blastocystis subtype prevalence and variation in the human gut microbiota

OBJECTIVE

Human gut microbiome studies are mainly bacteria- and archaea-oriented, overlooking the presence of single-cell eukaryotes such as Blastocystis, an enteric stramenopiles with worldwide distribution. Here, we surveyed the prevalence and subtype variation of Blastocystis in faecal samples collected as part of the Flemish Gut Flora Project (FGFP), a Western population cohort. We assessed potential links between Blastocystis subtypes and identified microbiota-host covariates and quantified microbiota differentiation relative to subtype abundances.

DESIGN

We profiled stool samples from 616 healthy individuals from the FGFP cohort as well as 107 patients with IBD using amplicon sequencing targeting the V4 variable region of the 16S rRNA and 18S rRNA genes. We evaluated associations of Blastocystis, and their subtypes, with host parameters, diversity and composition of bacterial and archaeal communities.

RESULTS

Blastocystis prevalence in the non-clinical population cohort was 30% compared with 4% among Flemish patients with IBD. Within the FGFP cohort, out of 69 previously identified gut microbiota covariates, only age was associated with Blastocystis subtype carrier status. In contrast, a strong association between microbiota community composition and Blastocystis subtypes was observed, with effect sizes larger than that of host covariates. Microbial richness and diversity were linked to both Blastocystis prevalence and subtype variation. All Blastocystis subtypes detected in this cohort were found to be less prevalent in Bacteroides enterotyped samples. Interestingly, Blastocystis subtypes 3 and 4 were inversely correlated with Akkermansia, suggesting differential associations of subtypes with host health.

CONCLUSIONS

These results emphasise the role of Blastocystis as a common constituent of the healthy gut microbiota. We show its prevalence is reduced in patients with active IBD and demonstrate that subtype characterisation is essential for assessing the relationship between Blastocystis, microbiota profile and host health. These findings have direct clinical applications, especially in donor selection for faecal transplantation.

Interactions Between Parasites and the Bacterial Microbiota of Chickens

Except for the important role coccidia have as predisposing factors of necrotic enteritis, the role parasites play in the dynamics of a healthy microbiota of chickens is not well explored. This review describes the interactions of relevant intestinal parasites of chickens with bacteria. Infection with Eimeria spp. favor the growth of Clostridium perfringens and suppress the growth of many other bacteria by increasing viscosity and passage time of the ingesta, and by causing lesions to the intestinal mucosa that improve the availability of nutrients for C. perfringens. Conversely, there are indications that bacteria influence the course of disease after infections with Eimeria spp. Not much is known about intestinal cryptosporidiosis in chickens, but results in mice show that the intestinal microbiota induces some resistance against infection with Cryptosporidium parvum and that the innate immune response triggered by infections with cryptosporidia might have an effect on other intestinal microbes. Histomonas meleagridis depend on bacteria in vitro, and in vivo it will cause lesions in chickens only in the presence of bacteria. Blastocystis spp. are very common in chickens, but there is no information about interactions with bacteria. In humans, there is evidence of the correlation of the detection of Blastocystis and changes in the intestinal microbiota. There are indications of interactions between Ascaridia galli and various bacteria in chickens and Ascaridia spp. of mammals are known to produce various types of antimicrobial molecules. However, often the underlying mechanisms of these interactions between parasites and bacteria remain unknown and only correlations but not causation can be established.

Interactions between a pathogenic Blastocystis subtype and gut microbiota: in vitro and in vivo studies

BACKGROUND

Blastocystis is a common gut eukaryote detected in humans and animals. It has been associated with gastrointestinal disease in the past although recent metagenomic studies also suggest that it is a member of normal microbiota. This study investigates interactions between pathogenic human isolates belonging to Blastocystis subtype 7 (ST7) and bacterial representatives of the gut microbiota.

RESULTS

Generally, Blastocystis ST7 exerts a positive effect on the viability of representative gut bacteria except on Bifidobacterium longum. Gene expression analysis and flow cytometry indicate that the bacterium may be undergoing oxidative stress in the presence of Blastocystis. In vitro assays demonstrate that Blastocystis-induced host responses are able to decrease Bifidobacterium counts. Mice infected with Blastocystis also reveal a decrease in beneficial bacteria Bifidobacterium and Lactobacillus.

CONCLUSIONS

This study shows that particular isolates of Blastocystis ST7 cause changes in microbiota populations and potentially lead to an imbalance of the gut microbiota. This study suggests that certain isolates of Blastocystis exert their pathogenic effects through disruption of the gut microbiota and provides a counterpoint to the increasing reports indicating the commensal nature of this ubiquitous parasite.

Cross-Domain and Viral Interactions in the Microbiome

The importance of the microbiome to human health is increasingly recognized and has become a major focus of recent research. However, much of the work has focused on a few aspects, particularly the bacterial component of the microbiome, most frequently in the gastrointestinal tract. Yet humans and other animals can be colonized by a wide array of organisms spanning all domains of life, including bacteria and archaea, unicellular eukaryotes such as fungi, multicellular eukaryotes such as helminths, and viruses. As they share the same host niches, they can compete with, synergize with, and antagonize each other, with potential impacts on their host. Here, we discuss these major groups making up the human microbiome, with a focus on how they interact with each other and their multicellular host.

Development and evaluation of molecular tools for detecting and differentiating intestinal amoebae in healthy individuals

Amoebae are single-celled parasites frequently colonizing human gut. However, few molecular tools are available for accurate identification. Here, we evaluated a panel of polymerase chain reactions (PCRs) targeting Entamoeba histolytica, Entamoeba dispar, Entamoeba coli, Entamoeba hartmanni, Entamoeba polecki, Endolimax nana and Iodamoeba bütschlii. Thirty-six faecal samples (18 containing at least one amoeba species by microscopy and 18 microscopy negative for amoebae) were tested. Real-time PCRs were used for detection and differentiation of E. histolytica and E. dispar. Conventional PCR with Sanger sequencing were applied for detection and differentiation of E. coli, E. hartmanni, E. polecki, E. nana and I. bütschlii. All microscopy results were confirmed by DNA-based methods. However, more samples were positive for single and mixed amoebic species by DNA-based assays than by microscopy (22 vs 18 and 7 vs 1, respectively). DNA sequencing allowed identification of E. coli subtypes (ST1 and ST2), showed low intra-specific variation within E. hartmanni, identified two phylogenetically distinct groups within E. nana, and identified Iodamoeba at the ribosomal lineage level. Taking into account the high intra-genetic diversity within some of the species at the small subunit (SSU) rRNA gene level, amplification of SSU rRNA genes with subsequent sequencing represents a useful method for detecting, differentiating and subtyping intestinal amoebae.

Altered Gut Microbiota Composition in Subjects Infected With Clonorchis sinensis

Clonorchiasis is an infectious disease caused by helminths of Clonorchis sinensis (C. sinensis). The adult parasite mainly inhabits the bile duct and gall bladder, and results in various complications to the hepatobiliary system. The amount of bile secreted into the intestine is reduced in cases of C. sinensis infection, which may alter the pH of the gut and decrease the amount of surfactant protein D released from the gallbladder. However, the impact of parasitic infection on the human gut microbiome remains unclear. To this end, we examined the gut microbiota composition in 47 modified Kato–Katz thick smear-positive (egg-positive) volunteers and 42 healthy controls from five rural communities. Subjects were grouped into four sub-populations based on age and infection status. High-throughput 16S rRNA gene sequencing revealed significant changes in alpha diversity between EP1 and EN1. The beta diversity showed alterations between C. sinensis-infected subjects and healthy controls. In C. sinensis infected patients, we found the significant reduction of certain taxa, such as Bacteroides and anti-inflammatory Bifidobacterium (P < 0.05). Bacteroides, a predominant gut bacteria in healthy populations, was negatively correlated with the number of C. sinensis eggs per gram (EPG, r = −0.37, P adjust < 0.01 in 20–60 years old group; r = −0.64, P adjust = 0.04 in the 60+ years old group). What’s more, the reduction in the abundance of Bifidobacterium, a common probiotic, was decreased particularly in the 60 + years old group (r = −0.50, P = 0.04). The abundance of Dorea, a potentially pro-inflammatory microbe, was higher in infected subjects than in healthy individuals (P < 0.05). Variovorax was a unique bacteria that was only detected in infected subjects. These results clearly demonstrate the significant influence of C. sinensis infection on the human gut microbiota and provided new insights into the control, prevention, diagnosis, and clinical study of clonorchiasis through the human gut microbiota.

Evaluating rodent experimental models for studies of Blastocystis ST1

Blastocystis is a common inhabitant of the human gut, colonizing at least one billion people at a prevalence ranging from <10% to 100% in healthy human populations globally. The majority of carriers remain asymptomatic, suggesting that Blastocystis is largely a commensal, though Blastocystis has also been implicated in disease in some people. However, there are no in vivo model systems in which to experimentally test the impact of Blastocystis on mammalian hosts and the gut ecosystem and determine which factors underlie these variable clinical outcomes. We evaluated a rat model for sustaining of a human-derived Blastocystis ST1 and assess colonization success and longevity. Because of the broad host range of Blastocystis, we compared the rat with three other rodent species to establish the reproducibility of our method. Blastocystis was introduced by esophageal gavage and colonization success evaluated by Blastocystis culture. Culture was also used to determine that all animals were negative prior to colonization and negative controls remain Blastocystis-free. In this study, Blastocystis ST1 established in 100% of the outbred rats (Rattus norvegicus) and gerbils (Meriones unguiculatus) challenged. Rats were colonized asymptomatically for more than one year, but Blastocystis ST1 was not transmitted between rats. Mus musculus strain CD1 and Mastomys coucha were not susceptible to Blastocystis ST1. Thus, rats appear to be a suitable in vivo model for studies of Blastocystis ST1, as do gerbils though testing was less extensive. This work lays the foundation for experimental work on the role of Blastocystis in health and disease.

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.

Characteristics of the bacterial microbiome in association with common intestinal parasites in irritable bowel syndrome

Objective

A low prevalence of intestinal parasites has been identified in individuals with irritable bowel syndrome (IBS), but potential associations with alterations in the bacterial microbiome remain largely unexplored. We aimed to investigate the relationship between parasites and bacteria in individuals with IBS in order to identify potential trans-kingdom microbial characteristics.

Design

Stool samples were collected from the Danish background population classified into IBS (n = 119), unspecific gastrointestinal (GI) symptoms (n = 114), and asymptomatic controls (n = 186) based on the Rome III criteria for IBS. Bacterial (16S) and eukaryotic (18S) ribosomal DNA was sequenced, and 18S data were merged with data from conventional parasite laboratory tests. The bacterial microbiome was analyzed according to symptom group and parasite colonization status.

Results

Bacterial richness and diversity were similar for IBS and controls but higher in those with unspecific GI symptoms. A higher abundance of Bacteroides and a lower abundance of Faecalibacterium were detected in individuals with IBS and unspecific GI symptoms compared with controls. Principal component analyses indicated differences in bacterial composition related to parasite colonization rather than symptom group. Parasites were detected at the lowest frequency in the IBS group (39%) and in samples dominated by Bacteroides. Higher bacterial richness and diversity were found in parasite-positive samples from controls and those with unspecific GI symptoms but not in individuals with IBS.

Conclusion

Parasite colonization, rather than bacterial composition, differed between individuals with IBS and healthy controls. Parasite colonization was associated to a rich and diverse bacterial microbiome; however, this association was altered in IBS.

The relation between Blastocystis and the intestinal microbiota in Swedish travellers

Background

Blastocystis sp. is a unicellular eukaryote that is commonly found in the human intestine. Its ability to cause disease is debated and a subject for ongoing research. In this study, faecal samples from 35 Swedish university students were examined through shotgun metagenomics before and after travel to the Indian peninsula or Central Africa. We aimed at assessing the impact of travel on Blastocystis carriage and seek associations between Blastocystis and the bacterial microbiota.

Results

We found a prevalence of Blastocystis of 16/35 (46%) before travel and 15/35 (43%) after travel. The two most commonly Blastocystis subtypes (STs) found were ST3 and ST4, accounting for 20 of the 31 samples positive for Blastocystis. No mixed subtype carriage was detected. All ten individuals with a typable ST before and after travel maintained their initial ST. The composition of the gut bacterial community was not significantly different between Blastocystis-carriers and non-carriers. Interestingly, the presence of Blastocystis was accompanied with higher abundances of the bacterial genera Sporolactobacillus and Candidatus Carsonella. Blastocystis carriage was positively associated with high bacterial genus richness, and negatively correlated to the Bacteroides-driven enterotype. These associations were both largely dependent on ST4 – a subtype commonly described from Europe – while the globally prevalent ST3 did not show such significant relationships.

Conclusions

The high rate of Blastocystis subtype persistence found during travel indicates that long-term carriage of Blastocystis is common. The associations between Blastocystis and the bacterial microbiota found in this study could imply a link between Blastocystis and a healthy microbiota as well as with diets high in vegetables. Whether the associations between Blastocystis and the microbiota are resulting from the presence of Blastocystis, or are a prerequisite for colonization with Blastocystis, are interesting questions for further studies.

Electronic supplementary material

The online version of this article (10.1186/s12866-017-1139-7) contains supplementary material, which is available to authorized users.

Large-scale comparative metagenomics of Blastocystis, a common member of the human gut microbiome

The influence of unicellular eukaryotic microorganisms on human gut health and disease is still largely unexplored. Blastocystis spp. commonly colonize the gut, but its clinical significance and ecological role are currently unsettled. We have developed a high-sensitivity bioinformatic pipeline to detect Blastocystis subtypes (STs) from shotgun metagenomics, and applied it to 12 large data sets, comprising 1689 subjects of different geographic origin, disease status and lifestyle. We confirmed and extended previous observations on the high prevalence the microrganism in the population (14.9%), its non-random and ST-specific distribution, and its ability to cause persistent (asymptomatic) colonization. These findings, along with the higher prevalence observed in non-westernized individuals, the lack of positive association with any of the disease considered, and decreased presence in individuals with dysbiosis associated with colorectal cancer and Crohn's disease, strongly suggest that Blastocystis is a component of the healthy gut microbiome. Further, we found an inverse association between body mass index and Blastocystis, and strong co-occurrence with archaeal organisms (Methanobrevibacter smithii) and several bacterial species. The association of specific microbial community structures with Blastocystis was confirmed by the high predictability (up to 0.91 area under the curve) of the microorganism colonization based on the species-level composition of the microbiome. Finally, we reconstructed and functionally profiled 43 new draft Blastocystis genomes and discovered a higher intra subtype variability of ST1 and ST2 compared with ST3 and ST4. Altogether, we provide an in-depth epidemiologic, ecological, and genomic analysis of Blastocystis, and show how metagenomics can be crucial to advance population genomics of human parasites.