Helicobacter baculiformis sp. nov., isolated from feline stomach mucosa

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.

Methylation-Independent Chemotaxis Systems Are the Norm for Gastric-Colonizing Helicobacter Species

Many bacteria and archaea rely on chemotaxis signal transduction systems for optimal fitness. These complex, multiprotein signaling systems have core components found in all chemotactic microbes, as well as variable proteins found in only some species. We do not yet understand why these variations exist or whether there are specific niches that favor particular chemotaxis signaling organization. One variation is in the presence/absence of the chemotaxis methylation adaptation enzymes CheB and CheR. Genes for CheB and CheR are missing in the gastric pathogen Helicobacter pylori but present in related Helicobacter that colonize the liver or intestine. In this work, we asked whether there was a general pattern of CheB/CheR across multiple Helicobacter species. Helicobacter spp. all possess chemotactic behavior, based on the presence of genes for core signaling proteins CheA, CheW, and chemoreceptors. Genes for the CheB and CheR proteins, in contrast, were variably present. Niche mapping supported the idea that these genes were present in enterohepatic Helicobacter species and absent in gastric ones. We then analyzed whether there were differences between gastric and enterohepatic species in the CheB/CheR chemoreceptor target methylation sites. Indeed, these sites were less conserved in gastric species that lack CheB/CheR. Lastly, we determined that cheB and cheR could serve as markers to indicate whether an unknown Helicobacter species was of enterohepatic or gastric origin. Overall, these findings suggest the interesting idea that methylation-based adaptation is not required in specific environments, particularly the stomach. IMPORTANCE Chemotaxis signal transduction systems are common in the archaeal and bacterial world, but not all systems contain the same components. The rationale for this system variation remains unknown. In this report, comparative genomics analysis showed that the presence/absence of CheR and CheB is one main variation within the Helicobacter genus, and it is strongly associated with the niche of Helicobacter species: gastric Helicobacter species, which infect animal stomachs, have lost their CheB and CheR, while enterohepatic Helicobacter species, which infect the liver and intestine, retain them. This study not only provides an example that a chemotaxis system variant is associated with particular niches but also proposes that CheB and CheR are new markers distinguishing gastric from enterohepatic Helicobacter species.

Gastric Helicobacter species associated with dogs, cats and pigs: significance for public and animal health

This article focuses on the pathogenic significance of Helicobacter species naturally colonizing the stomach of dogs, cats and pigs. These gastric "non-Helicobacter (H.) pylori Helicobacter species" (NHPH) are less well-known than the human adapted H. pylori. Helicobacter suis has been associated with gastritis and decreased daily weight gain in pigs. Several studies also attribute a role to this pathogen in the development of hyperkeratosis and ulceration of the non-glandular stratified squamous epithelium of the pars oesophagea of the porcine stomach. The stomach of dogs and cats can be colonized by several Helicobacter species but their pathogenic significance for these animals is probably low. Helicobacter suis as well as several canine and feline gastric Helicobacter species may also infect humans, resulting in gastritis, peptic and duodenal ulcers, and low-grade mucosa-associated lymphoid tissue lymphoma. These agents may be transmitted to humans most likely through direct or indirect contact with dogs, cats and pigs. Additional possible transmission routes include consumption of water and, for H. suis, also consumption of contaminated pork. It has been described that standard H. pylori eradication therapy is usually also effective to eradicate the NHPH in human patients, although acquired antimicrobial resistance may occasionally occur and porcine H. suis strains are intrinsically less susceptible to aminopenicillins than non-human primate H. suis strains and other gastric Helicobacter species. Virulence factors of H. suis and the canine and feline gastric Helicobacter species include urease activity, motility, chemotaxis, adhesins and gamma-glutamyl transpeptidase. These NHPH, however, lack orthologs of cytotoxin-associated gene pathogenicity island and vacuolating cytotoxin A, which are major virulence factors in H. pylori. It can be concluded that besides H. pylori, gastric Helicobacter species associated with dogs, cats and pigs are also clinically relevant in humans. Although recent research has provided better insights regarding pathogenic mechanisms and treatment strategies, a lot remains to be investigated, including true prevalence rates, exact modes of transmission and molecular pathways underlying disease development and progression.

Helicobacter spp. in the Stomach of Cats: Successful Colonization and Absence of Relevant Histopathological Alterations Reveals High Adaptation to the Host Gastric Niche

In addition to Helicobacter pylori, many non-Helicobacter pylori Helicobacters (NHPH) are able to cause gastric disease in humans. Cats are a natural reservoir for many of these species. Accordingly, living in close and intimate contact with animals has been identified as a risk factor, and an important zoonotic significance has therefore been attributed to NHPH. To determine the prevalence and associated gastric histopathological changes of Helicobacter species, the gastric mucosa of 71 cats were evaluated. Only four presented normal histopathological mucosa with the absence of spiral-shaped organisms. Normal gastric mucosa and the presence of spiral-shaped bacteria were observed in 13 cats. The remaining animals presented histopathological changes representative of gastritis. Helicobacter species were detected in 53 cats (74.6%) by at least one detection method. None of the animals were positive for H. pylori or for H. ailurogastricus. Helicobacter heilmannii organisms were identified in 20 animals, predominantly in the body gastric region. Helicobacter salomonis was the second most prevalent species (57.1%), although it was mainly found in association with other NHPH. Helicobacter felis and H. bizzozeronii were less frequently detected. The great majority of the Helicobacter spp. PCR-positive animals presented normal features regarding fibrosis/mucosal atrophy, neutrophils, eosinophils, or other inflammatory cells and lymphofollicular hyperplasia. Given the controversy and the strong evidence of absence of significant histopathological alterations associated with the presence of Helicobacter spp. in cats, it is possible to hypothesize that these bacteria may be able to adapt to the feline gastric microenvironment or even to comprise part of the gastric microbiome of this animal species. Thus, prudency must be taken when prescribing an antibiotic therapy based solely on the presence of these bacteria in the feline stomach.

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.

Helicobacter labacensis sp. nov., Helicobacter mehlei sp. nov., and Helicobacter vulpis sp. nov., isolated from gastric mucosa of red foxes (Vulpes vulpes)

Six Helicobacter-like isolates were recovered from 15 gastric mucosa samples of red foxes (Vulpes vulpes) shot by hunters in the surroundings of Ljubljana, Slovenia. Gram-negative, tightly coiled, intensely motile, 7-15 µm long and ≤1 µm wide bacteria grew on the biphasic blood agar plates. By using a genus-specific polymerase chain reaction (PCR), all isolates were confirmed as Helicobacter sp. and subsequently subjected to whole-genome sequencing (WGS). Five isolates showed a genome-wide average nucleotide identity (ANI) value of <95 % to the previously described Helicobacter species and one isolate was classified as Helicobacter felis. In the five unidentified isolates, the 16S rRNA gene sequence similarity to the type strains of all Helicobacter species ranged from 98.6 to 98.9 %. Their taxonomic status was established using a polyphasic taxonomic approach comprising the core genome-based phylogeny, morphological and phenotypic characteristics, including an analysis of matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) mass spectra. Phylogeny revealed the existence of three novel and well-supported clusters, with Helicobacter bizzozeronii and Helicobacter baculiformis being the most closely related species. The isolates also differed from the previously described species in their MALDI-TOF profiles and some biochemical characteristics. In conclusion, the data presented herein indicate that the obtained isolates, excluding H. felis isolate, represent three novel Helicobacter species, for which the names Helicobacter labacensis sp. nov., Helicobacter mehlei sp. nov., and Helicobacter vulpis sp. nov. are proposed, with isolates L9^T (=DSM 108823^T=CRBIP 111719^T), L15^T (=DSM 108730^T=CCUG 72910^T) and L2^T (=DSM 108727^T=CCUG 72909^T) as type strains, respectively.

Helicobacter pylori-induced gastric pathology: insights from in vivo and ex vivo models

Gastric colonization with Helicobacter pylori induces diverse human pathological conditions, including superficial gastritis, peptic ulcer disease, mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric adenocarcinoma and its precursors. The treatment of these conditions often relies on the eradication of H. pylori, an intervention that is increasingly difficult to achieve and that does not prevent disease progression in some contexts. There is, therefore, a pressing need to develop new experimental models of H. pylori-associated gastric pathology to support novel drug development in this field. Here, we review the current status of in vivo and ex vivo models of gastric H. pylori colonization, and of Helicobacter-induced gastric pathology, focusing on models of gastric pathology induced by H. pylori, Helicobacter felis and Helicobacter suis in rodents and large animals. We also discuss the more recent development of gastric organoid cultures from murine and human gastric tissue, as well as from human pluripotent stem cells, and the outcomes of H. pylori infection in these systems.

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.

Divergence between the Highly Virulent Zoonotic Pathogen Helicobacter heilmannii and Its Closest Relative, the Low-Virulence "Helicobacter ailurogastricus" sp. nov

Helicobacter heilmannii naturally colonizes the stomachs of dogs and cats and has been associated with gastric disorders in humans. Nine feline Helicobacter strains, classified as H. heilmannii based on ureAB and 16S rRNA gene sequences, were divided into a highly virulent and a low-virulence group. The genomes of these strains were sequenced to investigate their phylogenetic relationships, to define their gene content and diversity, and to determine if the differences in pathogenicity were associated with the presence or absence of potential virulence genes. The capacities of these helicobacters to bind to the gastric mucosa were investigated as well. Our analyses revealed that the low-virulence strains do not belong to the species H. heilmannii but to a novel, closely related species for which we propose the name Helicobacter ailurogastricus. Several homologs of H. pylori virulence factors, such as IceA1, HrgA, and jhp0562-like glycosyltransferase, are present in H. heilmannii but absent in H. ailurogastricus. Both species contain a VacA-like autotransporter, for which the passenger domain is remarkably larger in H. ailurogastricus than in H. heilmannii. In addition, H. ailurogastricus shows clear differences in binding to the gastric mucosa compared to H. heilmannii. These findings highlight the low-virulence character of this novel Helicobacter species.

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.

Helicobacter himalayensis sp. nov. isolated from gastric mucosa of Marmota himalayana

A Gram-stain-negative, microaerophilic strain, 80(YS1)T, with a spiral-shaped morphology and 1-2 sheathed flagella at each end of the cells was isolated from the gastric mucosa of Marmota himalayana, the animal reservoir of Yersinia pestis in China, on the Qinghai-Tibet Plateau. The strain grew at 30, 35 and 42 °C, but not at 25 °C. Growth was in the form of a thinly spreading film on brain heart infusion agar containing 8 % sheep blood under microaerobic conditions. The strain did not hydrolyse urea or hippurate, and did not grow on media containing 1 % glycine. It reduced nitrate to nitrite, and was catalase- and alkaline-phosphatase-positive, susceptible to nalidixic acid and resistant to cefalotin. It was positive for genus-specific PCR for the genus Helicobacter, but could not be classified to any recognized species according biochemical tests results. Therefore, a phylogenetic study based on 16S rRNA, 23S rRNA, 60 kDa heat-shock protein (hsp60) and gyrase subunit B (gyrB) genes was conducted. The 16S rRNA gene sequence (1468 bp) analysis showed that strain 80(YS1)T was most closely related to Helicobacter marmotae (96.7 % similarity). The 23S rRNA gene sequence (2879 bp) analysis showed that the strain was most closely related to Helicobacter canis (96 % similarity). The complete gyrB gene sequence (2325 bp) analysis showed that it was related phylogenetically to Helicobacter cinaedi (79.4 % similarity) and H. marmotae (79.1 % similarity). Analysis of the partial sequence of the hsp60 gene of strain 80(YS1)T showed closest similarity to the sequences of Helicobacter equorum (82 %) and H. cinaedi (81 %), respectively. However, there was no hsp60 sequence of H. marmotae available for analysis. The data of morphological, biochemical and phylogenetic characteristics all supported that this strain represents a novel species. The name Helicobacter himalayensis sp. nov. is proposed for this novel species with the type strain 80(YS1)T ( = CGMCC 1.12864T = DSM 28742T).

Development of new PCR primers by comparative genomics for the detection of Helicobacter suis in gastric biopsy specimens

BACKGROUND

Although the infection rate of Helicobacter suis is significantly lower than that of Helicobacter pylori, the H. suis infection is associated with a high rate of gastric mucosa-associated lymphoid tissue (MALT) lymphoma. In addition, in vitro cultivation of H. suis remains difficult, and some H. suis-infected patients show negative results on the urea breath test (UBT).

MATERIALS AND METHODS

Female C57BL/6J mice were orally inoculated with mouse gastric mucosal homogenates containing H. suis strains TKY or SNTW101 isolated from a cynomolgus monkey or a patient suffering from nodular gastritis, respectively. The high-purity chromosomal DNA samples of H. suis strains TKY and SNTW101 were prepared from the infected mouse gastric mucosa. The SOLiD sequencing of two H. suis genomes enabled comparative genomics of 20 Helicobacter and 11 Campylobacter strains for the identification of the H. suis-specific nucleotide sequences.

RESULTS

Oral inoculation with mouse gastric mucosal homogenates containing H. suis strains TKY and SNTW101 induced gastric MALT lymphoma and the formation of gastric lymphoid follicles, respectively, in C57BL/6J mice. Two conserved nucleotide sequences among six H. suis strains were identified and were used to design diagnostic PCR primers for the detection of H. suis.

CONCLUSIONS

There was a strong association between the H. suis infection and gastric diseases in the C57BL/6 mouse model. PCR diagnosis using an H. suis-specific primer pair is a valuable method for detecting H. suis in gastric biopsy specimens.

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.

Helicobacter heilmannii sp. nov., isolated from feline gastric mucosa

Three gram-negative, microaerophilic bacteria, strains ASB1(T), ASB2 and ASB3, with a corkscrew-like morphology isolated from the gastric mucosa of cats were studied using a polyphasic taxonomic approach. The isolates grew on biphasic culture plates under microaerobic conditions at 37 °C and exhibited urease, oxidase and catalase activities. They were also able to grow in colonies on dry agar plates. Based on 16S rRNA gene sequence analysis, ASB1(T), ASB2 and ASB3 were identified as members of the genus Helicobacter and showed 98 to 99 % sequence similarity to strains of Helicobacter felis, Helicobacter bizzozeronii, 'Candidatus Helicobacter heilmannii', Helicobacter cynogastricus, Helicobacter baculiformis and Helicobacter salomonis, six related Helicobacter species previously detected in feline or canine gastric mucosa. Sequencing of the partial hsp60 gene demonstrated that ASB1(T), ASB2 and ASB3 constitute a separate taxon among the feline and canine Helicobacter species. The urease gene sequences of ASB1(T), ASB2 and ASB3 showed approximately 91 % similarity to those of 'Candidatus Helicobacter heilmannii'. Protein profiling, the absence of alkaline phosphatase activity and several other biochemical characteristics also allowed strains ASB1(T), ASB2 and ASB3 to be differentiated from other Helicobacter species of feline or canine gastric origin. The results of this polyphasic taxonomic study show that the cultured isolates constitute a new taxon corresponding to 'Candidatus Helicobacter heilmannii', which was previously demonstrated in the stomach of humans, wild felidae, cats and dogs. The name Helicobacter heilmannii sp. nov. is proposed for these isolates; the type strain is ASB1(T) (=DSM 24751 (T) =LMG 26292(T)) [corrected].

Characterization of multiple Helicobacter bizzozeronii isolates from a Finnish patient with severe dyspeptic symptoms and chronic active gastritis

BACKGROUND

Helicobacter pylori is the primary cause of gastritis and peptic ulceration in humans. In a minority of patients with upper gastrointestinal symptoms, long tightly coiled spiral bacteria, provisionally named "Helicobacter heilmannii," are observed in gastric biopsies. These bacteria are extremely fastidious and only one previous study has succeeded in obtaining an isolate in vitro.

MATERIALS AND METHODS

We used two different selective media to isolate "H. heilmannii" from the gastric mucosa of a Finnish patient presenting with severe dyspeptic symptoms. The isolates were characterized by testing for urease and catalase activity, by using light and electron microscopy, and by sequencing of the partial 16S rRNA and ureAB genes. Single-enzyme amplified fragment length polymorphism (sAFLP) was used to analyze the genetic diversity among the isolates.

RESULTS

We obtained 15 isolates from different gastric biopsies prior and three after unsuccessful treatment of the patient. The isolates were identified as Helicobacter bizzozeronii. Eradication therapy was unsuccessful most probably due to high level of resistance to metronidazole. Persistent colonization by the same H. bizzozeronii clone was confirmed by sAFLP, however, small differences between the profiles suggested long-term colonization of the patient.

CONCLUSIONS

Helicobacter bizzozeronii remains the only "H. heilmannii" species isolated from human gastric mucosa although it has been an infrequent observation among "H. heilmannii"-infected patients in PCR-based screening studies. The relevance of H. bizzozeronii and other potentially zoonotic gastric Helicobacter spp. in human disease remains to be determined.

Gastric helicobacters in domestic animals and nonhuman primates and their significance for human health

Helicobacters other than Helicobacter pylori have been associated with gastritis, gastric ulcers, and gastric mucosa-associated lymphoid tissue lymphoma in humans. These very fastidious microorganisms with a typical large spiral-shaped morphology were provisionally designated "H. heilmannii," but in fact they comprise at least five different Helicobacter species, all of which are known to colonize the gastric mucosa of animals. H. suis, which has been isolated from the stomachs of pigs, is the most prevalent gastric non-H. pylori Helicobacter species in humans. Other gastric non-H. pylori helicobacters colonizing the human stomach are H. felis, H. salomonis, H. bizzozeronii, and the still-uncultivable "Candidatus Helicobacter heilmannii." These microorganisms are often detected in the stomachs of dogs and cats. "Candidatus Helicobacter bovis" is highly prevalent in the abomasums of cattle but has only occasionally been detected in the stomachs of humans. There are clear indications that gastric non-H. pylori Helicobacter infections in humans originate from animals, and it is likely that transmission to humans occurs through direct contact. Little is known about the virulence factors of these microorganisms. The recent successes with in vitro isolation of non-H. pylori helicobacters from domestic animals open new perspectives for studying these microorganisms and their interactions with the host.

Non-Helicobacter pylori helicobacters detected in the stomach of humans comprise several naturally occurring Helicobacter species in animals

Besides the well-known gastric pathogen Helicobacter pylori, other Helicobacter species with a spiral morphology have been detected in a minority of human patients who have undergone gastroscopy. The very fastidious nature of these non-Helicobacter pylori helicobacters (NHPH) makes their in vitro isolation difficult. These organisms have been designated 'Helicobacter heilmannii'. However, sequencing of several genes detected in NHPH-infected tissues has shown that the 'H. heilmannii' group comprises at least five different Helicobacter species, all of them known to colonize the stomach of animals. Recent investigations have indicated that Helicobacter suis is the most prevalent NHPH species in human. This species has only recently been isolated in vitro from porcine stomach mucosa. Other NHPH that colonize the human stomach are Helicobacter felis, Helicobacter bizzozeronii, Helicobacter salomonis and 'Candidatus Helicobacter heilmannii'. In numerous case reports of human gastric NHPH infections, no substantial information is available about the species status of the infecting strain, making it difficult to link the species with certain pathologies. This review aims to clarify the complex nomenclature of NHPH species associated with human gastric disease and their possible animal origin. It is proposed to use the term 'gastric NHPH' to designate gastric spirals that are morphologically different from H. pylori when no identification is available at the species level. Species designations should be reserved for those situations in which the species is defined.

Protective immunization with homologous and heterologous antigens against Helicobacter suis challenge in a mouse model

Helicobacter (H.) suis colonizes the stomach of more than 60% of slaughter pigs and is also of zoonotic importance. Recently, this bacterium was isolated in vitro, enabling the use of pure cultures for research purposes. In this study, mice were immunized intranasally or subcutaneously with whole bacterial cell lysate of H. suis or the closely related species H. bizzozeronii and H. cynogastricus, and subsequently challenged with H. suis. Control groups consisted of non-immunized and non-challenged mice (negative control group), as well as of sham-immunized mice that were inoculated with H. suis (positive control group). Urease tests on stomach tissue samples at 7 weeks after challenge infection were negative in all negative control mice, all intranasally immunized mice except one, and in all and 3 out of 5 animals of the H. cynogastricus and H. suis subcutaneously immunized groups, respectively. H. suis DNA was detected by PCR in the stomach of all positive control animals and all subcutaneously immunized/challenged animals. All negative control animals and some intranasally immunized/challenged mice were PCR-negative. In conclusion, immunization using antigens derived from the same or closely related bacterial species suppressed gastric colonization with H. suis, but complete protection was only achieved in a minority of animals following intranasal immunization.

Extragastric manifestations of Helicobacter pylori infection: other Helicobacters

The finding that Helicobacter pylori is the main cause of gastritis and peptic ulcer disease has opened a new era in the gastrointestinal world. Today there is evidence that H. pylori may also play a role in different nongastric diseases, opening the new "extragastric manifestations of H. pylori infection" field. Concerning this, several studies have been published in the last year. The most convincing data arise from those investigating idiopathic thrombocytopenic purpura and sideropenic anemia, while there is also an increasing evidence for a possible association with atherosclerotic disease. Furthermore, 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. In particular, several species have been studied for a potential role in different liver and intestinal diseases with interesting findings.

Isolation and characterization of Helicobacter suis sp. nov. from pig stomachs

A new cultivation method was successfully applied for the in vitro isolation of a hitherto uncultured spiral Helicobacter species associated with ulceration of the non-glandular stomach and gastritis in pigs and formerly described as 'Candidatus Helicobacter suis'. Three isolates, HS1(T), HS2 and HS3, were subcultured from the stomach mucosa of three pigs after slaughter and were analysed using a polyphasic taxonomic approach. The novel isolates grew on biphasic culture plates or very moist agar bases in microaerobic conditions and exhibited urease, oxidase and catalase activities. Sequencing of the 16S rRNA gene, the 23S rRNA gene, the partial hsp60 gene and partial ureAB genes confirmed that the strains present in the gastric mucosa of pigs constituted a separate taxon, corresponding to 'Helicobacter heilmannii' type 1 strains as detected in the gastric mucosa of humans and other primates. For all genes sequenced, the highest sequence similarities were obtained with Helicobacter felis, Helicobacter bizzozeronii and Helicobacter salomonis, Helicobacter species isolated from the gastric mucosa of dogs and cats, which have also been detected in the human gastric mucosa and which are commonly referred to as 'Helicobacter heilmannii' type 2. SDS-PAGE of whole-cell proteins of strains HS1(T), HS2 and HS3 differentiated them from other Helicobacter species of gastric origin. The results of the polyphasic taxonomic analysis confirmed that the novel isolates constitute a novel taxon corresponding to 'Helicobacter heilmannii' type 1 strains from humans and to 'Candidatus H. suis' from pigs. The name Helicobacter suis sp. nov. is proposed for the novel isolates with the type strain HS1(T) (=LMG 23995(T)=DSM 19735(T)).