Failure of surface ring mutant strains of Helicobacter mustelae to persistently infect the ferret stomach

Anatomical features for an adequate choice of the experimental animal model in biomedicine: III. Ferret, goat, sheep, and horse

The anatomical characteristics of each of the many species today employed in biomedical research are very important when selecting the correct animal model(s), especially for conducting translational research. In previous papers, these features have been considered for fish (D'Angelo et al. Ann. Anat, 2016, 205:75), the most common laboratory rodents, rabbits, and pigs (Lossi et al. 2016). I here follow this line of discussion by dealing with the importance of proper knowledge of ferrets, goats, sheep, and horses' main anatomical features in translational research.

Novel urease-negative Helicobacter sp. 'H. enhydrae sp. nov.' isolated from inflamed gastric tissue of southern sea otters

A total of 31 sea otters Enhydra lutris nereis found dead or moribund (and then euthanized) were necropsied in California, USA. Stomach biopsies were collected and transected with equal portions frozen or placed in formalin and analyzed histologically and screened for Helicobacter spp. in gastric tissue. Helicobacter spp. were isolated from 9 sea otters (29%); 58% (18 of 31) animals were positive for helicobacter by PCR. The Helicobacter sp. was catalase- and oxidase-positive and urease-negative. By electron microscopy, the Helicobacter sp. had lateral and polar sheathed flagella and had a slightly curved rod morphology. 16S and 23S rRNA sequence analyses of all 'H. enhydrae' isolates had similar sequences, which clustered as a novel Helicobacter sp. closely related to H. mustelae (96-97%). The genome sequence of isolate MIT 01-6242 was assembled into a single ~1.6 Mb long contig with a 40.8% G+C content. The annotated genome contained 1699 protein-coding sequences and 43 RNAs, including 65 genes homologous to known Helicobacter spp. and Campylobacter spp. virulence factors. Histological changes in the gastric tissues extended from mild cystic degeneration of gastric glands to severe mucosal erosions and ulcers. Silver stains of infected tissues demonstrated slightly curved bacterial rods at the periphery of the gastric ulcers and on the epithelial surface of glands. The underlying mucosa and submucosa were infiltrated by low numbers of neutrophils, macrophages, and lymphocytes, with occasional lymphoid aggregates and well-defined lymphoid follicles. This is the second novel Helicobacter sp., which we have named 'H. enhydrae', isolated from inflamed stomachs of mustelids, the first being H. mustelae from a ferret.

Comparative genomics and proteomics of Helicobacter mustelae, an ulcerogenic and carcinogenic gastric pathogen

Background

Helicobacter mustelae causes gastritis, ulcers and gastric cancer in ferrets and other mustelids. H. mustelae remains the only helicobacter other than H. pylori that causes gastric ulceration and cancer in its natural host. To improve understanding of H. mustelae pathogenesis, and the ulcerogenic and carcinogenic potential of helicobacters in general, we sequenced the H. mustelae genome, and identified 425 expressed proteins in the envelope and cytosolic proteome.

Results

The H. mustelae genome lacks orthologs of major H. pylori virulence factors including CagA, VacA, BabA, SabA and OipA. However, it encodes ten autotransporter surface proteins, seven of which were detected in the expressed proteome, and which, except for the Hsr protein, are of unknown function. There are 26 putative outer membrane proteins in H. mustelae, some of which are most similar to the Hof proteins of H. pylori. Although homologs of putative virulence determinants of H. pylori (NapA, plasminogen adhesin, collagenase) and Campylobacter jejuni (CiaB, Peb4a) are present in the H. mustelae genome, it also includes a distinct complement of virulence-related genes including a haemagglutinin/haemolysin protein, and a glycosyl transferase for producing blood group A/B on its lipopolysaccharide. The most highly expressed 264 proteins in the cytosolic proteome included many corresponding proteins from H. pylori, but the rank profile in H. mustelae was distinctive. Of 27 genes shown to be essential for H. pylori colonization of the gerbil, all but three had orthologs in H. mustelae, identifying a shared set of core proteins for gastric persistence.

Conclusions

The determination of the genome sequence and expressed proteome of the ulcerogenic species H mustelae provides a comparative model for H. pylori to investigate bacterial gastric carcinogenesis in mammals, and to suggest ways whereby cag minus H. pylori strains might cause ulceration and cancer.

The genome sequence was deposited in EMBL/GenBank/DDBJ under accession number FN555004.

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.

Random mutagenesis to identify novelHelicobacter mustelaevirulence factors

Helicobacter mustelae is a gastric pathogen of ferrets, where it causes disorders similar to those caused by Helicobacter pylori in humans. The H. mustelae ferret model therefore has potential for the in vivo study of Helicobacter pathogenesis in general. In this study a library of 500 individual H. mustelae mutants was generated using an in vitro random insertion mutagenesis technique. Mutants were subsequently tested for motility and adherence, and 43 of the 500 mutants tested were found to be nonmotile in a soft agar assay. Of these 43 mutants, seven were subsequently identified as deficient in their ability to adhere to AGS cells. Insertion had taken place in different positions in the H. mustelae genome, and included mutants in or near to genes involved in motility and urease activity (e.g. the chemotaxis gene cheV and the urease accessory gene ureH). The development of a mutant library for a natural animal model of Helicobacter infection provides the opportunity to study in vivo the role of candidate Helicobacter virulence genes.

Issues to consider for preparing ferrets as research subjects in the laboratory

The domestic or European ferret (Mustela putorius furo) has been domesticated for thousands of years. Ferrets have been used for hunting and fur production, as pets, and as models in biomedical research. Despite the relatively small numbers used in the laboratory, ferrets have some unique applications including study of human influenza and severe acute respiratory syndrome (SARS)-associated corona virus. They have served as models for peptic ulcer disease, carotenoid metabolism, cystic fibrosis, and drug emesis screening, among others. Most research ferrets are males, due to estrus-related health problems in females. They may be housed conventionally and are easy to care for when their biology and behavior are understood. Due to the small number of ferret suppliers, animals are often shipped long distances, requiring air transport and intermediate handlers. It is important to minimize shipment stress, especially with weanling and pregnant animals. Additional expertise is required for success with pregnant and whelping ferrets and for rearing of neonates. The animals have specific dietary requirements, and proper nutrition is key. Successful housing requires knowledge of ferret behaviors including social behavior, eating habits, a general inquisitive nature, and a species-typical need to burrow and hide. Regular handling is necessary to maintain well-being. A ferret health care program consists of physical examination, immunization, clinical pathology, and a working knowledge of common ferret diseases. Various research methodologies have been described, from basic procedures such as blood collection to major invasive survival surgery. Ferrets have a distinct niche in biomedical research and are hardy animals that thrive well in the laboratory.

Helicobacter pylori and extragastric diseases--other Helicobacters

Reports on Helicobacter pylori and extragastric diseases have almost doubled this year compared with last year, bearing witness to the persistent scientific interest in this branch of Helicobacter-related pathology. Data belong increasingly to the area of vascular medicine, as well as hematology, dermatology, pediatrics and other fields. Unfortunately, these studies show overall controversial results, due to the impact of several confounding factors, and to the difficulty of recruiting homogeneous patient populations. Furthermore, many studies continue to be conducted on Helicobacter species other than H. pylori, focusing on animal models of gastroenterological illnesses which may retain strong similarities with human diseases. In this paper, taxonomy, detection and characterisation of Helicobacter spp. will be reviewed, together with the most important data issued this year on other Helicobacters and animal models.

Helicobacter pylori and extragastric diseases -- other helicobacters

The role of Helicobacter pylori infection is explored in more and more extragastric diseases without definite proof in most of the studies, except possibly some hematologic diseases. In cardiovascular diseases, including stroke, the presence of CagA positive strains may be involved. The possible role of helicobacters in hepatobiliary diseases goes beyond that of H. pylori to involve enterohepatic helicobacters. New Helicobacter species are regularly described and molecular methods are developed to improve their detection. Helicobacter felis remains the major species to be used in animal models of Helicobacter infection.