Methods and basic concepts for microbiota assessment

Unveiling the gastric microbiota: implications for gastric carcinogenesis, immune responses, and clinical prospects

High-throughput sequencing has ushered in a paradigm shift in gastric microbiota, breaking the stereotype that the stomach is hostile to microorganisms beyond H. pylori. Recent attention directed toward the composition and functionality of this 'community' has shed light on its potential relevance in cancer. The microbial composition in the stomach of health displays host specificity which changes throughout a person's lifespan and is subject to both external and internal factors. Distinctive alterations in gastric microbiome signature are discernible at different stages of gastric precancerous lesions and malignancy. The robust microbes that dominate in gastric malignant tissue are intricately implicated in gastric cancer susceptibility, carcinogenesis, and the modulation of immunosurveillance and immune escape. These revelations offer fresh avenues for utilizing gastric microbiota as predictive biomarkers in clinical settings. Furthermore, inter-individual microbiota variations partially account for differential responses to cancer immunotherapy. In this review, we summarize current literature on the influence of the gastric microbiota on gastric carcinogenesis, anti-tumor immunity and immunotherapy, providing insights into potential clinical applications.

Human immunodeficiency virus and oral microbiota: mutual influence on the establishment of a viral gingival reservoir in individuals under antiretroviral therapy

The role of the oral microbiota in the overall health and in systemic diseases has gained more importance in the recent years, mainly due to the systemic effects that are mediated by the chronic inflammation caused by oral diseases, such as periodontitis, through the microbial communities of the mouth. The chronic infection by the human immunodeficiency virus (HIV) interacts at the tissue level (e.g. gut, genital tract, brain) to create reservoirs; the modulation of the gut microbiota by HIV infection is a good example of these interactions. The purpose of the present review is to assess the state of knowledge on the oral microbiota (microbiome, mycobiome and virome) of HIV-infected patients in comparison to that of HIV-negative individuals and to discuss the reciprocal influence of HIV infection and oral microbiota in patients with periodontitis on the potential establishment of a viral gingival reservoir. The influence of different clinical and biological parameters are reviewed including age, immune and viral status, potent antiretroviral therapies, smoking, infection of the airway and viral coinfections, all factors that can modulate the oral microbiota during HIV infection. The analysis of the literature proposed in this review indicates that the comparisons of the available studies are difficult due to their great heterogeneity. However, some important findings emerge: (i) the oral microbiota is less influenced than that of the gut during HIV infection, although some recurrent changes in the microbiome are identified in many studies; (ii) severe immunosuppression is correlated with altered microbiota and potent antiretroviral therapies correct partially these modifications; (iii) periodontitis constitutes a major factor of dysbiosis, which is exacerbated in HIV-infected patients; its pathogenesis can be described as a reciprocal reinforcement of the two conditions, where the local dysbiosis present in the periodontal pocket leads to inflammation, bacterial translocation and destruction of the supporting tissues, which in turn enhances an inflammatory environment that perpetuates the periodontitis cycle. With the objective of curing viral reservoirs of HIV-infected patients in the future years, it appears important to develop further researches aimed at defining whether the inflamed gingiva can serve of viral reservoir in HIV-infected patients with periodontitis.

Equine fecal microbiota response to short term antibiotic administration

Though generally safe, research continues to demonstrate negative side effects of antibiotic administration on the gastrointestinal (GIT) microbiota across species. In horses, antibiotic associated diarrhea (AAD) is a life-threatening condition linked to the GIT microbiota. This study tested the hypothesis that short term antibiotic administration to healthy horses would negatively impact the fecal microbiota as measured by their ability to digest nutrients and through fecal shedding of disease-associated-bacteria. Twenty-four horses were assigned to one of four treatment groups: control (CO); potassium penicillin/gentamicin sulfate (KPG); ceftiofur crystalline free acid (EX); trimethoprim/sulfamethoxazole (SMZ); and treated for 4 days. Fecal samples were collected before treatment began (S0), the day after treatment conclusion (S5), and at 10, 14, 21, and 28 days after initiating treatment. Horses had highly individualized responses to antibiotic administration. All horses receiving antibiotics experienced significantly softer stool compared to controls. Lactobacillus spp. were dramatically reduced in all antibiotic treated S5 samples. Horses receiving antibiotics were significantly more likely to test positive for C. difficile or C. perfringens on fecal qPCR. In conclusion, response to antibiotic administration displays high inter-individual variability, but shows changes to the functions of fecal microbiota that may depend on the antibiotic used.

Investigating the modulatory effects of Moringa oleifera on the gut microbiota of chicken model through metagenomic approach

Introduction

This study aimed to assess the effects of supplementing chicken feed with Moringa oleifera leaf powder, a phytobiotic, on the gastrointestinal microbiota. The objective was to examine the microbial changes induced by the supplementation.

Methods

A total of 40, one-day-old chickens were fed their basal diet for 42 days and then divided into two groups: SG1 (basal diet) and SG2 (basal diet + 10 g/kg Moringa oleifera leaf powder). Metagenomics analysis was conducted to analyze operational taxonomic units (OTUs), species annotation, and biodiversity. Additionally, 16S rRNA sequencing was performed for molecular characterization of isolated gut bacteria, identified as Enterococcus faecium. The isolated bacteria were tested for essential metabolites, demonstrating antibacterial, antioxidant, and anticancer activities.

Results and discussion

The analysis revealed variations in the microbial composition between the control group (SG1) and the M. oleifera-treated group (SG2). SG2 showed a 47% increase in Bacteroides and a 30% decrease in Firmicutes, Proteobacteria, Actinobacteria, and Tenericutes compared to SG1. TM7 bacteria were observed exclusively in the M. oleifera-treated group. These findings suggest that Moringa oleifera leaf powder acts as a modulator that enhances chicken gut microbiota, promoting the colonization of beneficial bacteria. PICRUSt analysis supported these findings, showing increased carbohydrate and lipid metabolism in the M.oleifera-treated gut microbiota.

Conclusion

This study indicates that supplementing chicken feed with Moringa oleifera leaf powder as a phytobiotic enhances the gut microbiota in chicken models, potentially improving overall health. The observed changes in bacterial composition, increased presence of Bacteroides, and exclusive presence of TM7 bacteria suggest a positive modulation of microbial balance. The essential metabolites from isolated Enterococcus faecium bacteria further support the potential benefits of Moringa oleifera supplementation.

Polycystic Ovary Syndrome and Gut Microbiota: Phenotype Matters

Abnormalities in gut microbiota diversity are considered important mechanisms in metabolic disorders in polycystic ovarian syndrome (PCOS). However, the data on the association of these disorders with the PCOS phenotype remain controversial. The objectives of this study were to estimate the alpha diversity of the gut microbiota of healthy women and PCOS patients depending on phenotype. The study participants (184 premenopausal women: 63 with PCOS, 121 without PCOS) were recruited during the annual employment assessment in the Irkutsk Region and the Buryat Republic (Russia) in 2016-2019. For PCOS diagnosis, we used the Rotterdam (2003) criteria and definitions of PCOS phenotypes. Five indexes of alpha diversity (ASV, Shannon, Simpson, Chao, and ACE) were estimated for the gut microbiota in all participants using amplicon metasequencing. As a result, two out of five alpha diversity indexes showed a statistical difference between the non-PCOS and PCOS groups. We did not find a significant difference in the alpha diversity of gut microbiota in the subgroups of women with hyperandrogenic PCOS phenotypes vs non-androgenic phenotype D and the group of women with the presence of only one of the PCOS criteria. Nevertheless, "classic" PCOS phenotypes demonstrated the most significant decrease in alpha diversity compared with healthy women without any signs of PCOS.

Canine chronic enteropathy—Current state-of-the-art and emerging concepts

Over the last decade, chronic inflammatory enteropathies (CIE) in dogs have received great attention in the basic and clinical research arena. The 2010 ACVIM Consensus Statement, including guidelines for the diagnostic criteria for canine and feline CIE, was an important milestone to a more standardized approach to patients suspected of a CIE diagnosis. Great strides have been made since understanding the pathogenesis and classification of CIE in dogs, and novel diagnostic and treatment options have evolved. New concepts in the microbiome-host-interaction, metabolic pathways, crosstalk within the mucosal immune system, and extension to the gut-brain axis have emerged. Novel diagnostics have been developed, the clinical utility of which remains to be critically evaluated in the next coming years. New directions are also expected to lead to a larger spectrum of treatment options tailored to the individual patient. This review offers insights into emerging concepts and future directions proposed for further CIE research in dogs for the next decade to come.

Prevalence of bacteriuria in cats with neurogenic bladder

Urinary tract infections are defined as the adherence, multiplication, and persistence of an infectious agent within the urogenital system, causing an associated inflammatory response and clinical signs; instead, the presence of bacteria in urine as determined by positive bacterial culture (PUC) from a properly collected urine specimen, in the absence of clinical signs, is defined subclinical bacteriuria. Limited information on the prevalence of PUC in spinal cord injury cats affected by neurogenic bladder (NB) is available. On contrary, in NB dogs and humans the prevalence of bacteriuria is well documented. Moreover, while in humans information about bacteriemia associated with NB is already available, this aspect has never been studied in NB cats. The aim of this prospective study was to determine the prevalence of PUC in cats with NB, compared to animals affected by chronic kidney disease (CKD) and healthy cats. Furthermore, the prevalence of bacteriemia in cats with NB was evaluated. Fifty-one cats met the inclusion criteria: 12 cats were affected by NB, 22 had CKD and 17 were healthy. The prevalence of PUC was 58.33% and 18% in NB and CKD cat populations, respectively. All blood cultures were negative. The incomplete bladder emptying and the decreased resistance in the bladder wall could be considered predisposing elements to PUC in the NB feline population. The results of this study highlight, for the first time, an high prevalence of PUC in cats affected by NB, which was not found to be associated with bacteriemia.

Clinical evaluation and microbiota analysis in 9 dogs with antibiotic-responsive enteropathy: A prospective comparison study

Background

Antibiotic‐responsive enteropathy (ARE) is diagnosed by excluding other causes of diarrhea and when there is a short‐term response to administration of antibiotics.

Objectives

To characterize the gut microbiota and clinical trend of dogs with suspected ARE and to evaluate the variation in microbiota before (T0), after 30 days (T30) of tylosin treatment, and 30 days after discontinuation of treatment (T60). A further objective was to evaluate whether changes in gut microbiota are related to relapses of diarrhea when the therapy is tapered.

Animals

Study sample (group A) was composed of 15 dogs with chronic diarrhea, group B was composed of 15 healthy dogs. Group A was given tylosin for 30 days.

Methods

A multicentric prospective study. Clinical Indexes, fecal score, and samples for microbiota analysis were collected at T0, T30, and T60 in group A and T0 and T30 in group B. The gut microbiota was analyzed via 16S ribosomal RNA gene. Qiime2 version 2020.2 was used to perform bioinformatic analyses, and Alpha‐ and Beta‐diversity were computed.

Results

Diarrhea recurred after T30 in 9 of 14 dogs, which were classified as affected by ARE. At T0, a difference was noted in the beta‐diversity between groups (Bray Curtis metric P = .006). A T0‐T30 difference in alpha‐diversity was noted in group A (Shannon index P = .001, Faith PD P = .007).

Conclusions and Clinical Importance

Although tylosin influences the microbiota of dogs with ARE, we failed to find any specific characteristic in the microbiota of dogs with ARE.

A systematic review of the factors influencing microbial colonization of the preterm infant gut

Prematurity coupled with the necessary clinical management of preterm (PT) infants introduces multiple factors that can interfere with microbial colonization. This study aimed to review the perinatal, physiological, pharmacological, dietary, and environmental factors associated with gut microbiota of PT infants. A total of 587 articles were retrieved from a search of multiple databases. Sixty studies were included in the review after removing duplicates and articles that did not meet the inclusion criteria. Review of this literature revealed that evidence converged on the effect of postnatal age, mode of delivery, use of antibiotics, and consumption of human milk in the composition of gut microbiota of PT infants. Less evidence was found for associations with race, sex, use of different fortifiers, macronutrients, and other medications. Future studies with rich metadata are needed to further explore the impact of the PT exposome on the development of the microbiota in this high-risk population.

Species-Level Gut Microbiota Analysis after Antibiotic-Induced Dysbiosis in Horses

All current studies have used Illumina short-read sequencing to characterize the equine intestinal microbiota. Long-read sequencing can classify bacteria at the species level. The objectives of this study were to characterize the gut microbiota of horses at the species level before and after trimethoprim sulfadiazine (TMS) administration and to compare results with Illumina sequencing. Nine horses received TMS (30 mg/kg) orally for 5 days twice a day to induce dysbiosis. Illumina sequencing of the V4 region or full-length PacBio sequencing of the 16S rRNA gene was performed in fecal samples collected before and after antibiotic administration. The relative abundance and alpha diversity were compared between the two technologies. PacBio failed to classify the equine intestinal microbiota at the species level but confirmed Bacteroidetes as the most abundant bacteria in the feces of the studied horses, followed by Firmicutes and Fibrobacteres. An unknown species of the Bacteroidales order was highly abundant (13%) and deserves further investigation. In conclusion, PacBio was not suitable to classify the equine microbiota species but detected greater richness and less unclassified bacteria. Further efforts in improving current databanks to be used in equine studies are necessary.

Analysis of the gut microbiome in dogs and cats

The gut microbiome is an important immune and metabolic organ. Intestinal bacteria produce various metabolites that influence the health of the intestine and other organ systems, including kidney, brain, and heart. Changes in the microbiome in diseased states are termed dysbiosis. The concept of dysbiosis is constantly evolving and includes changes in microbiome diversity and/or structure and functional changes (eg, altered production of bacterial metabolites). Molecular tools are now the standard for microbiome analysis. Sequencing of microbial genes provides information about the bacteria present and their functional potential but lacks standardization and analytical validation of methods and consistency in the reporting of results. This makes it difficult to compare results across studies or for individual clinical patients. The Dysbiosis Index (DI) is a validated quantitative PCR assay for canine fecal samples that measures the abundance of seven important bacterial taxa and summarizes the results as one single number. Reference intervals are established for dogs, and the DI can be used to assess the microbiome in clinical patients over time and in response to therapy (eg, fecal microbiota transplantation). In situ hybridization or immunohistochemistry allows the identification of mucosa‐adherent and intracellular bacteria in animals with intestinal disease, especially granulomatous colitis. Future directions include the measurement of bacterial metabolites in feces or serum as markers for the appropriate function of the microbiome. This article summarizes different approaches to the analysis of gut microbiota and how they might be applicable to research studies and clinical practice in dogs and cats.

Gut Health in Veterinary Medicine: A Bibliometric Analysis of the Literature

Gut health is a recent relevant research topic in veterinary medicine and it has been shown to be associated with better zootechnical performances and animal welfare. A bibliometric analysis was performed to explore publication trends, dynamics and possible knowledge gaps in this field in the last twenty years (2000-2020). The database Web of Science was searched and the results were analyzed by the R package Bibliometrix. A total of 1696 documents were retrieved in the evaluated period, showing a constant annual growth in the number of publications of 22.4%. These articles focused mainly on pigs (34.8%), poultry (chicken, duck, turkey and quail-33.9%) and aquaculture (fishes, crustaceans and frog-15.0%) while a scarce number was found on felines, cows, horses, rodents, goats and sheep. China was the most productive country (24.7%) followed by the USA (17.2%) and Canada (5.7%). Keyword's analysis showed that the main research lines aimed to explore animal nutrition, prevention of inflammatory diseases and microbiota composition. This study shows a comprehensive bibliometric analysis of the evolution of veterinary gut health research that will help to drive future investigations on this topic.

How Can Nutrition Help with Gastrointestinal Tract-Based Issues?

Many horses are fed differently than their wild ancestors. They often have limited access to pasture and are fed conserved forage and concentrates rich in starch and sugars, in only 2 meals per day. Feeding practices in contrast to natural feeding behavior can lead to gastrointestinal issues. Standard nutritional evaluation is warranted because of its important role in prevention and in treatment and management of diseases. When medical and nutritional treatments are combined, success rates are higher. New techniques to characterize equine microbiota have been used, allowing for microbiota manipulation to prevent and treat intestinal diseases.

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.

Impact of Changes in Gastrointestinal Microbiota in Canine and Feline Digestive Diseases

The intestinal microbiome is an important immune and metabolic organ in health and disease. Recent molecular and metabolomic approaches have provided a better characterization of different types of dysbiosis, including mucosa-adherent bacteria and functional changes in the microbiome. This article summarizes recent advances in assessment of dysbiosis, the importance of the bile acid-converting Clostridium hiranonis as an important beneficial bacterium in the canine gut, and different therapeutic approaches to dysbiosis.

PCR and RT-PCR in the Diagnosis of Laboratory Animal Infections and in Health Monitoring

Molecular diagnostics (PCR and RT-PCR) have become commonplace in laboratory animal research and diagnostics, augmenting or replacing serological and microbiologic methods. This overview will discuss the uses of molecular diagnostics in the diagnosis of pathogenic infections of laboratory animals and in monitoring the microbial status of laboratory animals and their environment. The article will focus primarily on laboratory rodents, although PCR can be used on samples from any laboratory animal species.

Cross-talk between airway and gut microbiome links to IgE responses to house dust mites in childhood airway allergies

A connection between airway and gut microbiota related to allergen exposure in childhood allergies was not well addressed. We aimed to identify the microbiota alterations in the airway and gut related to mite-specific IgE responses in young children with airway allergies. This study enrolled 60 children, including 38 mite-sensitized children (20 rhinitis and 18 asthma), and 22 non-mite-sensitized healthy controls. Microbiome composition analysis of the throat swab and stool samples was performed using bacterial 16S rRNA sequencing. An integrative analysis of the airway and stool microbial profiling associated with IgE reactions in childhood allergic rhinitis and asthma was examined. The Chao1 and Shannon indices in the airway were significantly lower than those in the stool. Additionally, an inverse association of the airway microbial diversity with house dust mite (HDM) sensitization and allergic airway diseases was noted. Fecal IgE levels were positively correlated with the serum Dermatophagoides pteronyssinus- and Dermatophagoides farinae-specific IgE levels. Airway Leptotrichia spp. related to asthma were strongly correlated with fecal Dorea and Ruminococcus spp., which were inversely associated with fecal IgE levels and risk of allergic rhinitis. Moreover, four airway genera, Campylobacter, Selenomonas, Tannerella, and Atopobium, were negatively correlated with both serum mite-specific and fecal IgE levels. Among them, the airway Selenomonas and Atopobium spp. were positively correlated with stool Blautia and Dorea spp. related to asthma and allergic rhinitis, respectively. In conclusion, airway microbial dysbiosis in response to HDM and its cross-talk with the gut microbial community is related to allergic airway diseases in early childhood.

Probiotic Strains and Intervention Total Doses for Modulating Obesity-Related Microbiota Dysbiosis: A Systematic Review and Meta-analysis

Obesity is a growing health threat worldwide. Administration of probiotics in obesity has also parallelly increased but without any protocolization. We conducted a systematic review exploring the administration pattern of probiotic strains and effective doses for obesity-related disorders according to their capacity of positively modulating key biomarkers and microbiota dysbiosis. Manuscripts targeting probiotic strains and doses administered for obesity-related disorders in clinical studies were sought. MEDLINE, Scopus, Web of Science, and Cochrane Library databases were searched using keywords during the last fifteen years up to April 2020. Two independent reviewers screened titles, abstracts, and then full-text papers against inclusion criteria according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. From 549 interventional reports identified, we filtered 171 eligible studies, from which 24 full-text assays were used for calculating intervention total doses (ITD) of specific species and strains administered. Nine of these reports were excluded in the second-step because no specific data on gut microbiota modulation was found. Six clinical trials (CT) and 9 animal clinical studies were retained for analysis of complete outcome prioritized (body mass index (BMI), adiposity parameters, glucose, and plasma lipid biomarkers, and gut hormones). Lactobacillus spp. administered were double compared to Bifidobacterium spp.; Lactobacillus as single or multispecies formulations whereas most Bifidobacteria only through multispecies supplementations. Differential factors were estimated from obese populations' vs. obesity-induced animals: ITD ratio of 2 × 106 CFU and patterns of administrations of 11.3 weeks to 5.5 weeks, respectively. Estimation of overall probiotics impact from selected CT was performed through a random-effects model to pool effect sizes. Comparisons showed a positive association between the probiotics group vs. placebo on the reduction of BMI, total cholesterol, leptin, and adiponectin. Moreover, negative estimation appeared for glucose (FPG) and CRP. While clinical trials including data for positive modulatory microbiota capacities suggested that high doses of common single and multispecies of Lactobacillus and Bifidobacterium ameliorated key obesity-related parameters, the major limitation was the high variability between studies and lack of standardized protocols. Efforts in solving this problem and searching for next-generation probiotics for obesity-related diseases would highly improve the rational use of probiotics.

Gut dysbiosis in Spondyloarthritis: Cause or effect?

Spondyloarthritis (SpA) is a group of chronic, inflammatory rheumatic diseases mainly affecting the axial skeleton. Although the pathogenesis of the disease remains elusive, alterations of intestinal microbial composition have been demonstrated in patients with SpA and associated with intestinal and systemic immune alterations. Substantial data have been published in recent years in ethnically different patient populations, demonstrating in a consolidated way the presence of alterations in the composition of the microbial flora in patients with SpA. It is not currently possible to establish whether these alterations are intrinsically inherent in the disease, for example, the effect of particular genes that confer susceptibility to the disease itself, or are a consequence of a more systemic inflammatory process that also involves the intestine. However, data deriving from animal models and studies on relatives of patients with SpA strongly suggest that these alterations might precede the onset of the disease. In this review, we will try to critically analyze studies on dysbiosis in SpA and animal models of SpA, analyzing their functional consequences and the impact of biotechnological therapies on intestinal bacterial composition.

Celiac Disease and the Microbiome

Growing evidence supports the hypothesis that changes in both the composition and function of the intestinal microbiome are associated with a number of chronic inflammatory diseases including celiac disease (CD). One of the major advances in the field of microbiome studies over the last few decades has been the development of culture-independent approaches to identify and quantify the components of the human microbiota. The study of nucleic acids DNA and RNA found in feces or other biological samples bypasses the need for tissue cultures and also allows the characterization of non-cultivable microbes. Current evidence on the composition of the intestinal microbiome and its role as a causative trigger for CD is highly heterogeneous and sometimes contradictory. This review is aimed at summarizing both pre-clinical (basic science data) and clinical (cross-sectional and prospective studies) evidence addressing the relationship between the intestinal microbiome and CD.