Helicobacter equorum sp. nov., a urease-negative Helicobacter species isolated from horse faeces

Phylogenetic analysis of pathogenic genes in Helicobacter species

BACKGROUND

Helicobacter bacteria are associated with gastrointestinal diseases, especially Helicobacter pylori (H. pylori). With the isolation of many non-Helicobacter pylori Helicobacters (NHPH) from the liver, intestines, and gallbladder of natural animal reservoirs, NHPH have been potential zoonotic pathogens, but their infection and pathogenic mechanisms are still unclear.

AIM

To explore the phylogenetic relationship of Helicobacter species based on their pathogenic genes.

METHODS

The present study collected the genomic sequences of 50 strains in genus Helicobacter, including 12 strains of H. pylori and 38 strains of NHPH. Based on 16S rRNA gene and several pathogenic genes (flagella, urease, and virulence factors), MAGA software (Version 11.0) was used to align their sequences and construct phylogenetic trees.

RESULTS

The phylogenetic tree of 16S rRNA gene showed that gastric Helicobacter (GH) and enterohepatic Helicobacter species (EHS) were clustered into two large branches, respectively. All of the GH's hosts were mammals, while the hosts of EHS were many wild poultry and mammals. Based on the flagella motility-related genes (flaA, flaB, fliP, fliQ, fliR, fliG, fliM, and fliN), the phylogenetic trees were divided into two major branches (GH and EHS). Similarly, the phylogenetic trees of lipopolysaccharide (LPS) biosynthesis-related genes (lptA, waaC, and waaF) presented two major branches (GH and EHS), too. The urease genes existed in all of the 12 strains of H. pylori, 13 strains of gastric NHPH, and 4 strains of EHS (H. hepaticus, H. muridarum, H. bilis, and H. anseris). However, no significant phylogenetic patterns of GH and EHS were observed in the seven urease genes (ureA, ureB, ureE, ureF, ureG, ureH, and ureI).

CONCLUSION

The phylogenetic relationship of Helicobacter species' pathogenic genes is dominated distinctly by the special colonization areas including gastric and enterohepatic niches.

A Tripartite Efflux System Affects Flagellum Stability in Helicobacter pylori

Helicobacter pylori uses a cluster of polar, sheathed flagella for swimming motility. A search for homologs of H. pylori proteins that were conserved in Helicobacter species that possess flagellar sheaths but were underrepresented in Helicobacter species with unsheathed flagella identified several candidate proteins. Four of the identified proteins are predicted to form part of a tripartite efflux system that includes two transmembrane domains of an ABC transporter (HP1487 and HP1486), a periplasmic membrane fusion protein (HP1488), and a TolC-like outer membrane efflux protein (HP1489). Deleting hp1486/hp1487 and hp1489 homologs in H. pylori B128 resulted in reductions in motility and the number of flagella per cell. Cryo-electron tomography studies of intact motors of the Δhp1489 and Δhp1486/hp1487 mutants revealed many of the cells contained a potential flagellum disassembly product consisting of decorated L and P rings, which has been reported in other bacteria. Aberrant motors lacking specific components, including a cage-like structure that surrounds the motor, were also observed in the Δhp1489 mutant. These findings suggest a role for the H. pylori HP1486-HP1489 tripartite efflux system in flagellum stability. Three independent variants of the Δhp1486/hp1487 mutant with enhanced motility were isolated. All three motile variants had the same frameshift mutation in fliL, suggesting a role for FliL in flagellum disassembly.

Determinación de Helicobacter spp. en mucosa gástrica glandular de mulas a través de la prueba de la actividad de la ureasa e histopatología

La información sobre la presentación y los factores predisponentes del síndrome de úlcera gástrica en mulas (SUGM) es escasa en comparación con el síndrome de úlcera gástrica en equinos (SUGE) y asnales. Debido a la naturaleza multifactorial de este síndrome, la helicobacteriosis ha sido estudiada en otras especies. El objetivo fue establecer la presencia de Helicobacter spp. en mucosa gástrica de mulas a través de la prueba rápida de la ureasa (PRU) y de análisis histopatológico. Menos del 27% de las muestras reaccionaron a la PRU, con tiempos prolongados de reacción, y al Agar Urea (prueba de oro), con menor porcentaje de positividad. La histopatología reveló procesos inflamatorios crónicos, sin presencia de bacterias curvoespiraladas. Las PRU no fueron conclusivas en la determinación de Helicobacter spp., comportamiento similar reportado en equinos. Se requieren exámenes diagnósticos específicos y procedimientos complementarios que explore regiones del estómago en consideración del número de muestras representativas.

Helicobacters and cancer, not only gastric cancer?

The Helicobacter genus actually comprises 46 validly published species divided into two main clades: gastric and enterohepatic Helicobacters. These bacteria colonize alternative sites of the digestive system in animals and humans, and contribute to inflammation and cancers. In humans, Helicobacter infection is mainly related to H. pylori, a gastric pathogen infecting more than half of the world's population, leading to chronic inflammation of the gastric mucosa that can evolve into two types of gastric cancers: gastric adenocarcinomas and gastric MALT lymphoma. In addition, H. pylori but also non-H. pylori Helicobacter infection has been associated with many extra-gastric malignancies. This review focuses on H. pylori and its role in gastric cancers and extra-gastric diseases, as well as malignancies induced by non-H. pylori Helicobacters. Their different virulence factors and their involvement in carcinogenesis is discussed. This review highlights the importance of both gastric and enterohepatic Helicobacters in gastrointestinal and liver cancers.

Enterohepatic Helicobacter species - clinical importance, host range, and zoonotic potential

The genus Helicobacter defined just over 30 years ago, is a highly diverse and fast-growing group of bacteria that are able to persistently colonize a wide range of animals. The members of this genus are subdivided into two groups with different ecological niches, associated pathologies, and phylogenetic relationships: the gastric Helicobacter (GH) and the enterohepatic Helicobacter (EHH) species. Although GH have been mostly studied, EHH species have become increasingly important as emerging human pathogens and potential zoonotic agents in the last years. This group of bacteria has been associated with the development of several diseases in humans from acute pathologies like gastroenteritis to chronic pathologies that include inflammatory bowel disease, and liver and gallbladder diseases. However, their reservoirs, as well as their routes of transmission, have not been well established yet. Therefore, this review summarizes the current knowledge of taxonomy, epidemiology, and clinical role of the EHH group.

The combination of nutraceuticals and functional feeds as additives modulates gut microbiota and blood markers associated with immune response and health in weanling piglets

This study aimed to evaluate the effects of a combination of feed additives with complementary functional properties on the intestinal microbiota, homocysteine, and vitamins E and B status as well as systemic immune response of weanling piglets. At weaning, 32 litters were assigned to one of the following dietary treatments (DT): 1) conventional diet (CTRL); 2) CTRL diet supplemented with antibiotics (ATB); 3) a cocktail of feed additives containing cranberry extract, encapsulated carvacrol, yeast-derived products, and extra vitamins A, D, E, and B complex (CKTL); or 4) CKTL diet with bovine colostrum in replacement of plasma proteins (CKTL + COL). Within each litter, the piglets with lowest and highest birth weights (LBW and HBW, respectively) and two piglets of medium birth weight (MBW) were identified. The MBW piglets were euthanized at 42 d of age in order to characterize the ileal and colonic microbiota. Blood samples were also collected at weaning and at 42 d of age from LBW and HBW piglets to measure insulin-like growth factor-1 (IGF-1), cysteine, homocysteine, and vitamins E, B₆, and B₁₂, and to characterize the leukocyte populations. At 42 d of age, cytokine production by stimulated peripheral blood mononuclear cells was also measured. In a second experiment, piglets were reared under commercial conditions to evaluate the effects of the DT on the growth performance. At the indicator species analysis, the highest indicator value (IV) for Succinivibrio dextrinosolvens was found in the CKTL group, whereas the highest IV for Lactobacillus reuteri and Faecalibacterium prausnitzii was evidenced in the CKTL + COL group (P < 0.05). Compared with the other DT, CTRL piglets had higher concentrations of homocysteine, whereas the CKTL and CKTL + COL supplementations increased the concentrations of vitamins E and B₁₂ (P < 0.05). DT had no effect on IGF-1 concentration and on blood leukocytes populations; however, compared with HBW piglets, LBW animals had lower values of IGF-1, whereas the percentages of γδ T lymphocytes and T helper were decreased and increased, respectively (P < 0.05). CKTL + COL also improved the growth performance of piglets reared under commercial conditions (P < 0.05). This study highlights the impact of birth weight on piglet systemic immune defenses and the potential of weaning diet supplemented with feed additives and bovine colostrum to modulate the homocysteine metabolism and the intestinal microbiota.

Whole-Genome Sequencing and Bioinformatics as Pertinent Tools to Support Helicobacteracae Taxonomy, Based on Three Strains Suspected to Belong to Novel Helicobacter Species

The present study describes three putative novel species received at the French National Reference Center for Campylobacters & Helicobacters (CNRCH). The CNRCH 2005/566H strain was isolated in 2005 from the feces of a patient with a hepatocellular carcinoma and gastroenteritis. Strain 48519 was isolated in 2017 from the blood of a male patient suffering from a bacteremia. Strain Cn23e was isolated from a gastric biopsy from a dog suffering from chronic gastritis. Biochemical and growth characteristics and electron microscopy for these three strains were studied. Their genomes were also sequenced. gyrA based phylogeny built with 72 nucleotide sequences placed CNRCH 2005/566H among the unsheathed enterohepatic helicobacters, close to Helicobacter valdiviensis; strain 48519 among the sheathed enterohepatic helicobacters, close to Helicobacter cinaedi; and strain Cn23e among gastric helicobacters, close to Helicobacter felis. 16S rRNA gene phylogeny showed similar results, but with weak discriminant strength. Average nucleotide identity and in silico DNA–DNA hybridization analyses revealed that CNRCH 2005/566H and 48519 strains belong to new putative species, but confirmed that Cn23e corresponds to H. felis. Cn23e was able to infect C57BL6 mice and to induce gastric inflammation. The genomics data, together with their different morphological and biochemical characteristics, revealed that these two strains represent novel Helicobacter species. We propose the following names: ‘Helicobacter burdigaliensis,’ with the type strain CNRCH 2005/566H ( =CECT 8850 =CIP 111660), and ‘Helicobacter labetoulli,’ with the type strain 48519 ( =CCUG 73475 =CIP 1111659). This study highlights that the diversity of the Helicobacteraceae family remains to be fully explored.

Equine glandular gastric disease: prevalence, impact and management strategies

Equine glandular gastric disease (EGGD) is an increasingly recognized disease of the glandular mucosa of the equine stomach. Diagnosis is confirmed by gastric endoscopy and scored based upon one of several different endoscopic scoring systems. Prevalence appears to be variable, depending upon breed and discipline. Primary identified risk factors include exercise frequency, and stress; therefore, management strategies are focused on reducing exercise and stress. Limiting grain intake and increasing pasture turnout may also be helpful preventative measures. Pharmacologic treatment consists primarily of an approved omeprazole product with or without misoprostol or sucralfate. Further research into the pathophysiology of EGGD may allow for identification of other targeted treatments.

Minimal standards for describing new species belonging to the families Campylobacteraceae and Helicobacteraceae: Campylobacter, Arcobacter, Helicobacter and Wolinella spp

Ongoing changes in taxonomic methods, and in the rapid development of the taxonomic structure of species assigned to the Epsilonproteobacteria have lead the International Committee of Systematic Bacteriology Subcommittee on the Taxonomy of Campylobacter and Related Bacteria to discuss significant updates to previous minimal standards for describing new species of Campylobacteraceae and Helicobacteraceae. This paper is the result of these discussions and proposes minimum requirements for the description of new species belonging to the families Campylobacteraceae and Helicobacteraceae, thus including species in Campylobacter, Arcobacter, Helicobacter, and Wolinella. The core underlying principle remains the use of appropriate phenotypic and genotypic methods to characterise strains sufficiently so as to effectively and unambiguously determine their taxonomic position in these families, and provide adequate means by which the new taxon can be distinguished from extant species and subspecies. This polyphasic taxonomic approach demands the use of appropriate reference data for comparison to ensure the novelty of proposed new taxa, and the recommended study of at least five strains to enable species diversity to be assessed. Methodological approaches for phenotypic and genotypic (including whole-genome sequence comparisons) characterisation are recommended.

First demonstration of equid gammaherpesviruses within the gastric mucosal epithelium of horses

Horses commonly develop gastric mucosal ulcers, similar to humans, a condition known as equine gastric ulcer syndrome (EGUS) that can lead to poor performance and lost training time and care expenses. Unlike humans, however, an infectious bacterial cause of ulcers has not been conclusively identified. Herpesviruses, while well-established causative agents of diseases such as cold sores, genital lesions, and certain types of cancer, have also been implicated in the development of a subset of gastric ulcers in humans. The presence of equid herpesviruses in the gastrointestinal tract and their potential contribution to EGUS has not been evaluated. Here, we provide the first evidence of equid gammaherpesviruses 2 and 5 (EHV-2 and -5) within the epithelium of the gastric mucosa of horses. These viruses were initially detected by a nested PCR screen of gastric tissue samples obtained from client- and university-owned horses with and without ulcers; however, no association with EGUS was found in this limited sample set. We then validated a highly sensitive in situ hybridization (ISH) assay and used this assay to characterize the distribution of these viruses in necropsy gastric tissue samples from five racehorses. Analyses revealed frequent EHV-2 and EHV-5 co-infections within the gastric mucosal epithelium, regardless of the ulcer status. These results are the first to demonstrate the presence of equid gammaherpesviruses in the gastric mucosa of horses and warrants further investigation to determine the contribution of these viruses to the development of EGUS and/or other gastrointestinal diseases.

The GyrA encoded gene: A pertinent marker for the phylogenetic revision of Helicobacter genus

Phylogeny of Epsilonproteobacteria is based on sequencing of the 16S rRNA gene. However, this gene is not sufficiently discriminatory in Helicobacter species and alternative markers would be useful. In this study, the 16S rRNA, gyrA, hsp60, gyrB, and ureA-ureB gene sequences, as well as GyrA, HSP60 and GyrB protein sequences were analyzed as tools to support Helicobacter species phylogeny: 72 Helicobacter strains, belonging to 41 species of which 36 are validated species, were included. Results of the phylogenetic reconstructions of the GyrA gene encoded protein (approximately 730 residues) indicated the most stable trees to bootstrap resampling with a good separation of Helicobacter taxa, especially between gastric and enterohepatic species. Moreover, the GyrA tree revealed high similarity with that of the gyrB and ureA-ureB genes (restricted to urease-positive Helicobacter species). However, some differences in clustering were observed when compared to the hsp60 and 23S rRNA gene trees. Altogether, these revised phylogenies (except the 16S rRNA gene for enterohepatic Helicobacters) enabled reliable clustering of Helicobacter cinaedi and 'Flexispira' strains, determined a reliable position for Helicobacter mustelae (except the hsp60 gene) and for novel Helicobacter species proposed such as 'Helicobacter sanguini', 'Helicobacter apodemus' or 'Helicobacter winghamensis', and suggest that Helicobacter species MIT 09-6949 and MIT 05-5293 isolated from rodents constitute novel species. Although they are not commonly used to study the phylogeny of Epsilonproteobacteria, protein sequences and, in particular, the GyrA protein sequence may constitute pertinent phylogenetic markers for Helicobacter genus.

Sepsis Due to a Novel Urease-Positive Helicobacter Species in a Young Man

We report the first case of sepsis with enterocolitis that was caused by a novel urease-positive Helicobacter species in a young man. The isolate was characterized via 16S rRNA gene sequencing and their biochemical properties, and the patient was successfully treated with short-term antimicrobial therapy; no recurrence was observed.

Description of Helicobacter valdiviensis sp. nov., an Epsilonproteobacteria isolated from wild bird faecal samples

Two Gram-stain-negative, gently curved rod-shaped isolates (WBE14T and WBE19), recovered from wild bird faecal samples in the city of Valdivia (Southern Chile) were subjected to a polyphasic taxonomic study. Results of a genus-specific PCR indicated that these isolates belonged to the genus Helicobacter . This was further confirmed by a phylogenetic analyses based on the 16S rRNA, 60 kDa heat-shock protein (cpn60) and gyrase subunit B (gyrB) genes, where both strains formed a novel phylogenetic line within this genus. The 16S rRNA gene sequence similarity of strain WBE14T to the type strains of all other species of the genus Helicobacter examined ranged from 89.4 to 97.0 %; Helicobacter brantae and Helicobacter pametensis were the most closely related species. However, on the basis of the protein-coding genes Helicobacter pullorum and Helicobacter canadensis are the most closely related species. These data, together with their different morphological and biochemical characteristics, revealed that these strains represent a novel species, for which the name Helicobacter valdiviensis sp. nov. is proposed, with the type strain WBE14T ( = CECT 8410T = LMG 27920T).

Differentiation of non-pylori Helicobacter species based on PCR-restriction fragment length polymorphism of the 23S rRNA gene

Phenotypic identification of non-pylori Helicobacter species has always been problematic and time-consuming in comparison with many other bacteria. We developed a rapid two-step identification assay based on PCR-restriction fragment length polymorphism (PCR-RFLP) analysis of the 23S rRNA gene for differentiating between non-pylori Helicobacter species. A new genus-specific primer pair based on all available complete and partial 23S rRNA sequences of Helicobacter species was designed. In silico restriction analysis of variable regions of the 23S rRNA gene suggested SmaI and HindIII endonucleases would provide a good level of differentiation. Analysis of the obtained 23S rRNA RFLP patterns divided all Helicobacter study strains into three species groups (groups A-C) and 12 unique restriction patterns. Wolinella succinogenes also gave a unique pattern. Our proposed PCR-RFLP method was found to be as a valuable tool for routine identification of non-pylori Helicobacter species from human or animal samples.

Refractory chronic pleurisy caused by Helicobacter equorum-like bacterium in a patient with X-linked agammaglobulinemia

We describe a 35-year-old man with X-linked agammaglobulinemia who had refractory chronic pleurisy caused by a Helicobacter equorum-like bacterium. Broad-range bacterial PCR targeting the 16S and 23S rRNA genes and in situ hybridization targeting the 16S rRNA gene of H. equorum confirmed the presence of this pathogen in a human for the first time.

Acute in vivo interactions of Helicobacter equorum with its equine host

REASONS FOR PERFORMING STUDY

A novel urease-negative Helicobacter species has been isolated from faecal samples of clinically healthy horses, but no information is available about the main sites of colonisation in the equine gastrointestinal tract nor is the pathogenic potential of this microorganism known. An experimental infection in horses was therefore carried out.

METHODS

Four horses were infected with H. equorum strain CCUG 52199T and subjected to euthanasia at 10 (n = 2) and 30 days (n = 2) post inoculation. A fifth animal was inoculated with phosphate buffered saline and used as control. Gastrointestinal samples were examined histologically and bacteriologically. These samples, as well as faecal material collected at regular intervals, were also subjected to PCR analysis.

RESULTS

All horses remained clinically healthy and no specific macroscopic lesions were identified, nor were there any microscopic changes. H. equorum-DNA was detected in the faeces during the whole experiment in all infected animals but not in the negative control. Sites of colonisation were caecum, colon and rectum.

CONCLUSIONS

H. equorum is able to colonise the equine lower bowel and is excreted in faeces without apparent pathology. No association between the presence of the organism and gastrointestinal disease was demonstrated.

Helicobacter equorum: prevalence and significance for horses and humans

Helicobacter equorum colonizes the caecum, colon and rectum of horses. The agent is highly prevalent in <6-month-old foals. In adult horses, the prevalence of H. equorum seems to be rather low, but these animals may harbour low, subdetectable numbers of this microorganism in their intestines. So far, no association could be made between the presence of H. equorum and clinical disease or intestinal lesions in adult horses. Further research is necessary to elucidate the pathogenic potential of this bacterial species towards young foals. Helicobacter equorum DNA was not detected in human faeces, indicating that this microorganism does not commonly spread from horses towards humans.

Immunogenicity and pathogenicity of Helicobacter infections of veterinary animals

The initial discovery that the human stomach is commonly infected by the bacterium Helicobacter pylori subsequently resulted in the identification of a whole new family of pathogenic bacteria. In less than 25 years, the Helicobacter genus has grown from obscurity to number at least 38 different species with many more awaiting classifications. These bacteria, many of which are either direct or opportunistic pathogens, are present in virtually every mammalian species examined, and have also now been identified in a number of birds. The pathogenesis associated with these infections is predominantly the result of a chronic inflammatory response mounted by the host against the infection. This is typically a Th1-driven response which can result in a range of conditions from hepatitis, through gallstones to cancer. In some cases the inflammatory response to these infections is normally well managed by the host and disease only results when there is a breakdown or misbalance in the immunoregulatory process, which for example can result in inflammatory bowel disease in experimental models. Understanding the disease association and pathogenic mechanisms of the different Helicobacter infections is clearly of potential significance not only from an animal welfare point of view but also from the growing realisation of how commonly transmission of Helicobacter occurs between different mammals, including pathogenic zoonotic infections of humans.

Extragastric manifestations of Helicobacter pylori infection -- other Helicobacters

Today there is evidence that Helicobacter pylori has a critical role in different extragastric diseases. The discovery of a number of other novel Helicobacter species has stimulated the research in different extragastric diseases, in which an infectious hypothesis is plausible. Enterohepatic Helicobacter species have been hypothesized to play a role in different disorders, including hepatocellular carcinoma, gallstones formation and cholangiocellular carcinoma, as well as enteric diseases and inflammatory bowel diseases. Concerning the extragastric manifestations of H. pylori infection, idiopathic thrombocytopenic purpura, and sideropenic anemia represent, based on the current data, the diseases in which the pathogenic link appears to be strongest. There is also an increasing evidence for a possible association of H. pylori with cardiovascular disease.

Detection of Helicobacter-like DNA in the gastric mucosa of Thoroughbred horses

AIMS

To assess the presence of Helicobacter DNA in the gastric mucosa Thoroughbred horses.

METHODS AND RESULTS

Squamous and glandular mucosa samples were collected from 20 Thoroughbreds. None of these horses had shown any clinical symptoms of gastrointestinal disease. Necropsy tissues were analysed using histopathological techniques and a Helicobacter genus-specific PCR assay followed by sequencing of the amplicons. Seven horses were diagnosed with gastric ulceration, five with gastritis and six with both pathologies. Only two horses had a healthy gastric mucosa. Helicobacter-like DNA was detected in two out of seven horses with gastric ulcers, three out of five horses with gastritis, five out of six horses with both pathologies and one horse with normal gastric mucosa. The sequences of 1195 and 1237 bp fragments of the 16S rRNA gene shared 99% identity with the Helicobacter pylori 16S rRNA gene. However, all the samples were negative when tested with H. pylori-specific PCR assays targeting the cagA and glmM genes.

CONCLUSIONS

The Helicobacter genus might colonize the gastric mucosa of horses.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report of Helicobacter-like DNA in the gastric mucosa of horses and the pathogenic potential of these organisms requires further investigation.