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

Update on Novel Taxa and Revised Taxonomic Status of Bacteria Isolated from Nondomestic Animals Described in 2018 to 2021

Revisions and new additions to bacterial taxonomy can have a significant widespread impact on clinical practice, infectious disease epidemiology, veterinary microbiology laboratory operations, and wildlife conservation efforts. The expansion of genome sequencing technologies has revolutionized our knowledge of the microbiota of humans, animals, and insects. Here, we address novel taxonomy and nomenclature revisions of veterinary significance that impact bacteria isolated from nondomestic wildlife, with emphasis being placed on bacteria that are associated with disease in their hosts or were isolated from host animal species that are culturally significant, are a target of conservation efforts, or serve as reservoirs for human pathogens.

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.

Nasopulmonary mites (Acari: Halarachnidae) as potential vectors of bacterial pathogens, including Streptococcus phocae, in marine mammals

Nasopulmonary mites (NPMs) of the family Halarachnidae are obligate endoparasites that colonize the respiratory tracts of mammals. NPMs damage surface epithelium resulting in mucosal irritation, respiratory illness, and secondary infection, yet the role of NPMs in facilitating pathogen invasion or dissemination between hosts remains unclear. Using 16S rRNA massively parallel amplicon sequencing of six hypervariable regions (or “16S profiling”), we characterized the bacterial community of NPMs from 4 southern sea otters (Enhydra lutris nereis). This data was paired with detection of a priority pathogen, Streptococcus phocae, from NPMs infesting 16 southern sea otters and 9 California sea lions (Zalophus californianus) using nested conventional polymerase chain reaction (nPCR). The bacteriome of assessed NPMs was dominated by Mycoplasmataceae and Vibrionaceae, but at least 16 organisms with pathogenic potential were detected as well. Importantly, S. phocae was detected in 37% of NPM by nPCR and was also detected by 16S profiling. Detection of multiple organisms with pathogenic potential in or on NPMs suggests they may act as mechanical vectors of bacterial infection for marine mammals.

Helicobacter turcicus sp. nov., a catalase-negative new member of the Helicobacter genus, isolated from Anatolian Ground Squirrel (Spermophilus xanthoprymnus) in Turkey

Eleven Gram-negative, curved and S-shaped, oxidase activity positive, catalase activity negative bacterial isolates recovered from faeces of Anatolian ground squirrel (Spermophilus xanthoprymnus) in the city of Kayseri, Turkey, were subjected to a polyphasic taxonomic study. Results of a genus-specific PCR revealed that these isolates belonged to the genus Helicobacter . The 16S rRNA gene sequence analysis revealed that the 11 isolates had over 99 % sequence identity with each other and were most closely related to Helicobacter ganmani CMRI H02T with 97.0–97.1 % identity levels and they formed a novel phylogenetic line within the genus Helicobacter . Faydin-H64 and Faydin-H70T strains were subjected to gyrA and atpA gene and whole genome sequence analyses. These two Helicobacter strains formed separate phylogenetic clades, divergent from other known Helicobacter species. The DNA G+C content and genome size of the strain Faydin-H70T were 35.3 mol% and 1.7 Mb, respectively. Average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values between strain Faydin-H70T and its close phylogenetic neighbour H. winghamensis ATCC BAA-430T were determined as 81.7 and 34.9 %, respectively. Pairwise sequence comparison showed that it was closely related to H. ganmani CMRI H02T however it shared the highest ANI and dDDH values with H. winghamensis ATCC BAA-430T. The data obtained from the polyphasic taxonomy approach, including phenotypic characterization and whole-genome sequences, revealed that these strains represent a novel species within the genus Helicobacter , for which the name Helicobacter turcicus sp. nov., is proposed with Faydin-H70T as the type strain (=DSM 112556T=LMG 32335T).

Helicobacter cyclurae sp. Nov., Isolated From Endangered Blue Iguanas (Cyclura lewisi)

Blue iguanas (Cyclura lewisi) are endangered reptiles found only on Grand Cayman. Previously, DNA for a novel Helicobacter species GCBI1 was detected in sick and dead iguanas. In the current study, fecal and cloacal swab samples were obtained from 25 iguanas. Through molecular and microbiological techniques, a novel Helicobacter species was cultured from feces and characterized, for whom we propose the name Helicobacter cyclurae. This novel helicobacter had a prevalence of 56% by PCR and 20% by culture in samples analyzed. The type strain MIT 16-1353 was catalase, oxidase, and gamma-glutamyl transpeptidase positive. By electron microscopy, H. cyclurae has a curved rod morphology and a single sheathed polar flagellum. Phylogenetic analysis using 16S rRNA, gyrB, and hsp60 indicated that these strains were most closely related to Helicobacter sp. 12502256-12 previously isolated from lizards. H. cyclurae has a 1.91-Mb genome with a GC content of 33.37%. There were 1,969 genes with four notable virulence genes: high temperature requirement-A protein-secreted serine protease, gamma-glutamyl transpeptidase, fibronectin/fibrinogen binding protein, and neutrophil-activating protein. Whole-genome phylogeny, average nucleotide identity, and digital DNA–DNA hybridization analysis confirmed that H. cyclurae is a novel species, and the first helicobacter cultured and characterized from blue iguanas.

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 delphinicola sp. nov., isolated from common bottlenose dolphins Tursiops truncatus with gastric diseases

Gastritis and gastric ulcers are well-recognized symptoms in cetaceans, and the genus Helicobacter is considered as the main cause. In this study, we examined the gastric fluid of captive common bottlenose dolphins Tursiops truncatus with gastric diseases in order to isolate the organisms responsible for diagnosis and treatment. Four Gram-negative, rod-shaped isolates (TSBT, TSH1, TSZ, and TSH3) with tightly coiled spirals with 2-4 turns and 2-6 bipolar, sheathed flagella, were obtained from gastric fluids of common bottlenose dolphins with gastric diseases. Phylogenetic analysis, based on 16S rRNA, atpA, and 60 kDa heat-shock protein (hsp60) genes, demonstrated that these isolates form a novel lineage within the genus Helicobacter. Analyses of 16S rRNA, atpA, and hsp60 gene sequences showed that isolate TSBT was most closely related to H. cetorum MIT99-5656T (98.5% similarity), H. pylori ATCC 43504T (76.7% similarity), and H. pylori ATCC 43504T (78.0% similarity), respectively. Type strains of Helicobacter showing resistance to 2% NaCl have not been reported previously; however, these novel isolates were resistant to 2% NaCl. Culture supernatant of some isolates induced intracellular vacuolization in mammalian cultured cells. These data, together with the different morphological and biochemical characteristics of the isolates, reveal that these isolates represent a novel species for which we propose the name Helicobacter delphinicola sp. nov. with type strain TSBT (= JCM 32789T = TSD-183T). Future studies will confirm whether H. delphinicola plays a role in lesion etiopathogenesis in cetaceans.

Comparative genomics analysis to differentiate metabolic and virulence gene potential in gastric versus enterohepatic Helicobacter species

Background

The genus Helicobacter are gram-negative, microaerobic, flagellated, mucus-inhabiting bacteria associated with gastrointestinal inflammation and classified as gastric or enterohepatic Helicobacter species (EHS) according to host species and colonization niche. While there are over 30 official species, little is known about the physiology and pathogenic mechanisms of EHS, which account for most in the genus, as well as what genetic factors differentiate gastric versus EHS, given they inhabit different hosts and colonization niches. The objective of this study was to perform a whole-genus comparative analysis of over 100 gastric versus EHS genomes in order to identify genetic determinants that distinguish these Helicobacter species and provide insights about their evolution/adaptation to different hosts, colonization niches, and mechanisms of virulence.

Results

Whole-genome phylogeny organized Helicobacter species according to their presumed gastric or EHS classification. Analysis of orthologs revealed substantial heterogeneity in physiological and virulence-related genes between gastric and EHS genomes. Metabolic reconstruction predicted that unlike gastric species, EHS appear asaccharolytic and dependent on amino/organic acids to fuel metabolism. Additionally, gastric species lack de novo biosynthetic pathways for several amino acids and purines found in EHS and instead rely on environmental uptake/salvage pathways. Comparison of virulence factor genes between gastric and EHS genomes identified overlapping yet distinct profiles and included canonical cytotoxins, outer membrane proteins, secretion systems, and survival factors.

Conclusions

The major differences in predicted metabolic function suggest gastric species and EHS may have evolved for survival in the nutrient-rich stomach versus the nutrient-devoid environments, respectively. Contrasting virulence factor gene profiles indicate gastric species and EHS may utilize different pathogenic mechanisms to chronically infect hosts and cause inflammation and tissue damage. The findings from this study provide new insights into the genetic differences underlying gastric versus EHS and support the need for future experimental studies to characterize these pathogens.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5171-2) contains supplementary material, which is available to authorized users.

Other Helicobacters, gastric and gut microbiota

The current article is a review of the most important and relevant literature published in 2016 and early 2017 on non-Helicobacter pylori Helicobacter infections in humans and animals, as well as interactions between H. pylori and the microbiota of the stomach and other organs. Some putative new Helicobacter species were identified in sea otters, wild boars, dogs, and mice. Many cases of Helicobacter fennelliae and Helicobacter cinaedi infection have been reported in humans, mostly in immunocompromised patients. Mouse models have been used frequently as a model to investigate human Helicobacter infection, although some studies have investigated the pathogenesis of Helicobacters in their natural host, as was the case for Helicobacter suis infection in pigs. Our understanding of both the gastric and gut microbiome has made progress and, in addition, interactions between H. pylori and the microbiome were demonstrated to go beyond the stomach. Some new approaches of preventing Helicobacter infection or its related pathologies were investigated and, in this respect, the probiotic properties of Saccharomyces, Lactobacillus and Bifidobacterium spp. were confirmed.