Dietary Inulin and Trichuris suis Infection Promote Beneficial Bacteria Throughout the Porcine Gut

Getting around the roundworms: Identifying knowledge gaps and research priorities for the ascarids

The ascarids are a large group of parasitic nematodes that infect a wide range of animal species. In humans, they cause neglected diseases of poverty; many animal parasites also cause zoonotic infections in people. Control measures include hygiene and anthelmintic treatments, but they are not always appropriate or effective and this creates a continuing need to search for better ways to reduce the human, welfare and economic costs of these infections. To this end, Le Studium Institute of Advanced Studies organized a two-day conference to identify major gaps in our understanding of ascarid parasites with a view to setting research priorities that would allow for improved control. The participants identified several key areas for future focus, comprising of advances in genomic analysis and the use of model organisms, especially Caenorhabditis elegans, a more thorough appreciation of the complexity of host-parasite (and parasite-parasite) communications, a search for novel anthelmintic drugs and the development of effective vaccines. The participants agreed to try and maintain informal links in the future that could form the basis for collaborative projects, and to co-operate to organize future meetings and workshops to promote ascarid research.

Helminths' therapeutic potential to treat intestinal barrier dysfunction

The intestinal barrier is a dynamic multi-layered structure which can adapt to environmental changes within the intestinal lumen. It has the complex task of allowing nutrient absorption while limiting entry of harmful microbes and microbial antigens present in the intestinal lumen. Excessive entry of microbial antigens via microbial translocation due to 'intestinal barrier dysfunction' is hypothesised to contribute to the increasing incidence of allergic, autoimmune and metabolic diseases, a concept referred to as the 'epithelial barrier theory'. Helminths reside in the intestinal tract are in intimate contact with the mucosal surfaces and induce a range of local immunological changes which affect the layers of the intestinal barrier. Helminths are proposed to prevent, or even treat, many of the diseases implicated in the epithelial barrier theory. This review will focus on the effect of helminths on intestinal barrier function and explore whether this could explain the proposed health benefits delivered by helminths.

Modulation of the porcine intestinal microbiota in the course of Ascaris suum infection

Background

The porcine roundworm Ascaris suum impairs feed conversion and weight gain, but its effects on intestinal microbiota remain largely unexplored.

Methods

Modulation of the intestinal microbiota was assessed in pigs that were infected once with 10,000 A. suum eggs and pigs that received a trickle infection (1000 eggs/day over 10 days), compared with a non-infected control group. Six pigs each were sacrificed per group at days 21, 35 and 49 post-infection (p.i.). Faecal samples taken weekly until slaughter and ingesta samples from different intestinal compartments were subjected to next-generation sequencing of the bacterial 16S rRNA gene.

Results

The results revealed marked differences between the single- and the trickle-infected group. Single infection caused a remarkable but transient decrease in microbial diversity in the caecum, which was not observed in the trickle-infected group. However, an increase in short-chain fatty acid-producing genera in the caecum on day 21 p.i., which shifted to a decrease on day 35 p.i., was common to both groups, possibly related to changes in excretory–secretory products following the parasite’s final moult. Faecal microbial interaction networks were more similar between the single-infected and control group than the trickle-infected group. In addition, a lower degree of similarity over time indicated that A. suum trickle infection prevented microbiota stabilization.

Conclusions

These different patterns may have important implications regarding the comparability of experimental infections with natural scenarios characterized by continuous exposure, and should be confirmed by further studies.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05535-w.

Parasite-Probiotic Interactions in the Gut: Bacillus sp. and Enterococcus faecium Regulate Type-2 Inflammatory Responses and Modify the Gut Microbiota of Pigs During Helminth Infection

Dietary probiotics may enhance gut health by directly competing with pathogenic agents and through immunostimulatory effects. These properties are recognized in the context of bacterial and viral pathogens, but less is known about interactions with eukaryotic pathogens such as parasitic worms (helminths). In this study we investigated whether two probiotic mixtures (comprised of Bacillus amyloliquefaciens, B. subtilis, and Enterococcus faecium [BBE], or Lactobacillus rhamnosus LGG and Bifidobacterium animalis subspecies Lactis Bb12 [LB]) could modulate helminth infection kinetics as well as the gut microbiome and intestinal immune responses in pigs infected with the nodular worm Oesophagostomum dentatum. We observed that neither probiotic mixture influenced helminth infection levels. BBE, and to a lesser extent LB, changed the alpha- and beta-diversity indices of the colon and fecal microbiota, notably including an enrichment of fecal Bifidobacterium spp. by BBE. However, these effects were muted by concurrent O. dentatum infection. BBE (but not LB) significantly attenuated the O. dentatum-induced upregulation of genes involved in type-2 inflammation and restored normal lymphocyte ratios in the ileo-caecal lymph nodes that were altered by infection. Moreover, inflammatory cytokine release from blood mononuclear cells and intestinal lymphocytes was diminished by BBE. Collectively, our data suggest that selected probiotic mixtures can play a role in maintaining immune homeostasis during type 2-biased inflammation. In addition, potentially beneficial changes in the microbiome induced by dietary probiotics may be counteracted by helminths, highlighting the complex inter-relationships that potentially exist between probiotic bacteria and intestinal parasites.

Bacterial communities from Trichuris spp. A contribution to deciphering the role of parasitic nematodes as vector of pathogens

Microbiome taxa associated with parasitic nematodes is unknown. These invertebrate parasites could act not only as reservoirs and vectors for horizontally transferred virulence factors, but could also provide a potential pool of future emerging pathogens. Trichuris trichiura and Trichuris suis are geohelminths parasitizing the caecum of primates, including humans, and pigs, respectively. The present work is a preliminary study to evaluate the bacterial communities associated with T. trichiura and T. suis, using High Throughput Sequencing and checking the possible presence of pathogens in these nematodes, to determine whether parasitic helminths act as vectors for bacterial pathogens in human and animal hosts. Five T. trichiura adult specimens were obtained from the caecum of macaque (Macaca sylvanus) and two T. suis adults were collected from the caecum of swine (Sus scrofa domestica). The 16S rRNA gene HTS approach was employed to investigate the composition and diversity of bacterial communities in Trichuris spp., with special emphasis at its intestinal level. All samples showed a rich colonization by bacteria, included, preferently, in the phyla Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, Cyanobacteria and Verrucomicrobia. A total of 36 phyla and more than 200 families were identified in the samples. Potential pathogen bacteria were detected in these helminths related to the genera Bartonella, Mycobacterium, Rickettsia, Salmonella, Escherichia/Shigella, Aeromonas and Clostridium. The presence of pathogenic bacteria in Trichuris spp. would position these species as a new threat to humans since these nematodes could spread new diseases. This study will also contribute to the understanding of the host-microbiota relation.

The phytonutrient cinnamaldehyde limits intestinal inflammation and enteric parasite infection

Phytonutrients such as cinnamaldehyde (CA) have been studied for their effects on metabolic diseases, but their influence on mucosal inflammation and immunity to enteric infection are not well documented. Here, we show that consumption of CA in mice significantly down-regulates transcriptional pathways connected to inflammation in the small intestine, and alters T-cell populations in mesenteric lymph nodes. During infection with the enteric helminth Heligomosomoides polygyrus, CA treatment attenuated infection-induced changes in biological pathways connected to cell cycle and mitotic activity, and tended to reduce worm burdens. Mechanistically, CA did not appear to exert activity through a prebiotic effect, as CA treatment did not significantly change the composition of the gut microbiota. Instead, in vitro experiments showed that CA directly induced xenobiotic metabolizing pathways in intestinal epithelial cells and suppressed endotoxin-induced inflammatory responses in macrophages. Collectively, our results show that CA down-regulates inflammatory pathways in the intestinal mucosa and can limit the pathological response to enteric infection. These properties appear to be largely independent of the gut microbiota, and instead connected to the ability of CA to induce antioxidant pathways in intestinal cells. Our results encourage further investigation into the use of CA and related phytonutrients as functional food components to promote intestinal health in humans and animals.

Integrative biology defines novel biomarkers of resistance to strongylid infection in horses

The widespread failure of anthelmintic drugs against nematodes of veterinary interest requires novel control strategies. Selective treatment of the most susceptible individuals could reduce drug selection pressure but requires appropriate biomarkers of the intrinsic susceptibility potential. To date, this has been missing in livestock species. Here, we selected Welsh ponies with divergent intrinsic susceptibility (measured by their egg excretion levels) to cyathostomin infection and found that their divergence was sustained across a 10-year time window. Using this unique set of individuals, we monitored variations in their blood cell populations, plasma metabolites and faecal microbiota over a grazing season to isolate core differences between their respective responses under worm-free or natural infection conditions. Our analyses identified the concomitant rise in plasma phenylalanine level and faecal Prevotella abundance and the reduction in circulating monocyte counts as biomarkers of the need for drug treatment (egg excretion above 200 eggs/g). This biological signal was replicated in other independent populations. We also unravelled an immunometabolic network encompassing plasma beta-hydroxybutyrate level, short-chain fatty acid producing bacteria and circulating neutrophils that forms the discriminant baseline between susceptible and resistant individuals. Altogether our observations open new perspectives on the susceptibility of equids to strongylid infection and leave scope for both new biomarkers of infection and nutritional intervention.

Parasitic Intestinal Protists of Zoonotic Relevance Detected in Pigs by Metabarcoding and Real-Time PCR

Several parasite species are shared between humans and pigs. We explored the application of next-generation sequencing-based metabarcoding supplemented with real-time PCR to fecal DNAs from 259 samples from 116 pigs in Denmark to detect and differentiate single-celled intestinal parasites of zoonotic relevance. Enterocytozoon bieneusi, Balantioides coli, and Giardia duodenalis were observed in 34/37 (92%), 148/259 (57%), and 86/259 (33%) samples, respectively. Entamoeba polecki ST1, E. polecki ST3, and Entamoeba hartmanni were detected in 104/259 (40%), 161/259 (62%), and 8/259 (3%) samples, respectively. Metabarcoding and real-time PCR detected Cryptosporidium in 90/259 (35%) and 239/259 (92%) of the samples, respectively, with Cryptosporidium suis and Cryptosporidium scrofarum observed in nearly equal proportions. Blastocystis subtypes 1, 3, 5, and 15 were found in 72 (28%), 6 (2%), 176 (68%), and 36 (14%) of 259 samples, respectively. Iodamoeba was identified in 1/259 samples (<1%), while none of 37 tested samples was positive for Dientamoeba fragilis. Our results illustrate how metabarcoding exemplifies a 'one-fits-many' approach to detecting intestinal single-celled parasites in feces supplemented with real-time PCR for selected parasites. Using metabarcoding with pathogen-specific assays may help detect emerging and previously underdetected pathogens and further elucidate the role of micro-eukaryotic parasites in human and animal health and disease.

Emerging interactions between diet, gastrointestinal helminth infection, and the gut microbiota in livestock

Increasing evidence suggests that nutritional manipulation of the commensal gut microbiota (GM) may play a key role in maintaining animal health and production in an era of reduced antimicrobial usage. Gastrointestinal helminth infections impose a considerable burden on animal performance, and recent studies suggest that infection may substantially alter the composition and function of the GM. Here, we discuss the potential interactions between different bioactive dietary components (prebiotics, probiotics and phytonutrients) and helminth infection on the GM in livestock. A number of recent studies suggest that host diet can strongly influence the nature of the helminth-GM interaction. Nutritional manipulation of the GM may thus impact helminth infection, and conversely infection may also influence how the GM responds to dietary interventions. Moreover, a dynamic interaction exists between helminths, the GM, intestinal immune responses, and inflammation. Deciphering the mechanisms underlying the diet-GM-helminth axis will likely inform future helminth control strategies, as well as having implications for how health-promoting feed additives, such as probiotics, can play a role in sustainable animal production.

Helminth Interactions with Bacteria in the Host Gut Are Essential for Its Immunomodulatory Effect

Colonization by the benign tapeworm, Hymenolepis diminuta, has been associated with a reduction in intestinal inflammation and changes in bacterial microbiota. However, the role of microbiota in the tapeworm anti-inflammatory effect is not yet clear, and the aim of this study was to determine whether disruption of the microflora during worm colonization can affect the course of intestinal inflammation. We added a phase for disrupting the intestinal microbiota using antibiotics to the experimental design for which we previously demonstrated the protective effect of H. diminuta. We monitored the immunological markers, clinical parameters, bacterial microbiota, and histological changes in the colon of rats. After a combination of colonization, antibiotics, and colitis induction, we had four differently affected experimental groups. We observed a different course of the immune response in each group, but no protective effect was found. Rats treated with colonization and antibiotics showed a strong induction of the Th2 response as well as a significant change in microbial diversity. The microbial results also revealed differences in the richness and abundance of some bacterial taxa, influenced by various factors. Our data suggest that interactions between the tapeworm and bacteria may have a major impact on its protective effect.

Pre-clinical evaluation of the effect of co-medication with antibiotics and oral steroids in Göttingen Minipigs on the biological activity of the probiotic medicinal product TSO (Trichuris suis ova)

The probiotic medicinal product TSO (Trichuris suis ova) is administered to patients with active ulcerative colitis in an ongoing clinical phase IIb trial where the typical co-medications are steroids (prednisolone or budesonide) and antibiotics (e.g., phenoxymethylpenicillin). The present pre-clinical study evaluates the effects of these co-medications on the biological activity of TSO in Göttingen Minipigs. This translationally relevant pre-clinical model allows administration of TSO with and without oral steroids or antibiotics in a manner similar to the administration to patients, followed by quantification of the biological activity of TSO. The biological activity of TSO was not affected by oral steroids but was reduced by oral antibiotics. Fecal calprotectin, the common marker of intestinal inflammation in patients with UC, did not differ between groups.

Delivering Beneficial Microorganisms for Corals: Rotifers as Carriers of Probiotic Bacteria

The use of Beneficial Microorganisms for Corals (BMCs) to increase the resistance of corals to environmental stress has proven to be effective in laboratory trials. Because direct inoculation of BMCs in larger tanks or in the field can be challenging, a delivery mechanism is needed for efficient transmission of the BMC consortium. Packaged delivery mechanisms have been successfully used to transmit probiotics to other organisms, including humans, lobsters, and fish. Here, we tested a method for utilizing rotifers of the species Brachionus plicatilis for delivery of BMCs to corals of the species Pocillopora damicornis. Epifluorescence microscopy combined with a live/dead cell staining assay was used to evaluate the viability of the BMCs and monitor their in vivo uptake by the rotifers. The rotifers efficiently ingested BMCs, which accumulated in the digestive system and on the body surface after 10 min of interaction. Scanning electron microscopy confirmed the adherence of BMCs to the rotifer surfaces. BMC-enriched rotifers were actively ingested by P. damicornis corals, indicating that this is a promising technique for administering coral probiotics in situ. Studies to track the delivery of probiotics through carriers such as B. plicatilis, and the provision or establishment of beneficial traits in corals are the next proof-of-concept research priorities.

State-of-the-Art of the Nutritional Alternatives to the Use of Antibiotics in Humans and Monogastric Animals

Simple Summary

Antibiotic resistance represents a worldwide recognized issue affecting both human and veterinary medicine, with a particular focus being directed towards monogastric animals destined for human consumption. This scenario is the result of frequent utilization of the antibiotics either for therapeutic purposes (humans and animals) or as growth promoters (farmed animals). Therefore, the search for nutritional alternatives has progressively been the object of significant efforts by the scientific community. So far, probiotics, prebiotics and postbiotics are considered the most promising products, as they are capable of preventing or treating gastrointestinal diseases as well as restoring a eubiosis condition after antibiotic-induced dysbiosis development. This review provides an updated state-of-the-art of these nutritional alternatives in both humans and monogastric animals.

Abstract

In recent years, the indiscriminate use of antibiotics has been perpetrated across human medicine, animals destined for zootechnical productions and companion animals. Apart from increasing the resistance rate of numerous microorganisms and generating multi-drug resistance (MDR), the nonrational administration of antibiotics causes sudden changes in the structure of the intestinal microbiota such as dysbiotic phenomena that can have a great clinical significance for both humans and animals. The aim of this review is to describe the state-of-the-art of alternative therapies to the use of antibiotics and their effectiveness in humans and monogastric animals (poultry, pigs, fish, rabbits, dogs and cats). In particular, those molecules (probiotics, prebiotics and postbiotics) which have a direct function on the gastrointestinal health are herein critically analysed in the prevention or treatment of gastrointestinal diseases or dysbiosis induced by the consumption of antibiotics.

Helminth Sensing at the Intestinal Epithelial Barrier-A Taste of Things to Come

Human intestinal helminth infection affects more than 1 billion people often in the world's most deprived communities. These parasites are one of the most prevalent neglected tropical diseases worldwide bringing huge morbidities to the host population. Effective treatments and vaccines for helminths are currently limited, and therefore, it is essential to understand the molecular sensors that the intestinal epithelium utilizes in detecting helminths and how the responding factors produced act as modulators of immunity. Defining the cellular and molecular mechanisms that enable helminth detection and expulsion will be critical in identifying potential therapeutic targets to alleviate disease. However, despite decades of research, we have only recently been able to identify the tuft cell as a key helminth sensor at the epithelial barrier. In this review, we will highlight the key intestinal epithelial chemosensory roles associated with the detection of intestinal helminths, summarizing the recent advances in tuft cell initiation of protective type 2 immunity. We will discuss other potential sensory roles of epithelial subsets and introduce enteroendocrine cells as potential key sensors of the microbial alterations that a helminth infection produces, which, given their direct communication to the nervous system via the recently described neuropod, have the potential to transfer the epithelial immune interface systemically.