Helicobacter fennelliae Bacteremia: Three Case Reports and Literature Review

Proposal of Helicobacter higonensis sp. nov. isolated from a human clinical specimen, and emended description of Helicobacter valdiviensis Collado, 2014

We have previously isolated a gram-negative microaerophilic strain, PAGU2000T from a patient presenting with a fever in Kumamoto Prefecture, Japan. The present study aimed to comprehensively analyze the taxonomy of the isolated strain using a polyphasic approach. The 16S rRNA gene sequence analysis indicated that the strain was a member of enterohepatic Helicobacter. The strain PAGU2000T shared a 97.5% 16S rRNA gene nucleotide identity with Helicobacter valdiviensis, and this taxonomic position was confirmed by phylogenetic analysis of the GyrA amino acid sequences. The proposed strain PAGU2000T has a 1.482 Mbp chromosome with a DNA G + C content of 31.3 mol% and encodes 1520 predicted coding sequences. The average nucleotide identity between the strain PAGU2000T and type strain of H. valdiviensis was 70.3%, which was lower than the recommended threshold of 95% for species delineation. The strain PAGU2000T was a motile, non-spore-forming, and spiral-shaped bacterium, exhibiting catalase and oxidase activities but not urease and nitrate reduction. This study demonstrates that the isolate represents a novel species within enterohepatic Helicobacter, for which the name Helicobacter higonensis is proposed (type strain: PAGU2000T = GTC 16811T = LMG 33095T). In this study, we describe the phenotypic and morphological features of this strain and propose an emended description of some biochemical traits of H. valdiviensis.

Helicobacter fennelliae Localization to Diffuse Areas of Human Intestine, Japan

The site of enterohepatic Helicobacter colonization/infection in humans is still unknown. We report microbiologically and histopathologically confirmed H. fennelliae localization in the large intestine in an immunocompromised patient in Japan. This case contributes to better understanding of the life cycle of enterohepatic Helicobacter species.

Characterization of HcaA, a novel autotransporter protein in Helicobacter cinaedi, and its role in host cell adhesion

IMPORTANCE

Helicobacter species are classified as gastric or enterohepatic according to their habitat. Among enterohepatic Helicobacter species, which inhabit the intestine, colon, and liver, Helicobacter cinaedi has been most frequently isolated from humans. H. cinaedi often causes bacteremia and cellulitis in immunocompromised hosts. Here, we focused on the H. cinaedi autotransporter protein A (HcaA), a novel virulence factor in H. cinaedi. We discovered that HcaA contributes to cell adhesion via its Arg-Gly-Asp motif. Furthermore, in animal experiments, bacterial colonization was reduced in mice infected with HcaA-knockout strains, supporting the hypothesis that HcaA contributes to H. cinaedi adhesion to host cells. Our study provides a novel mechanism for the establishment of H. cinaedi infections and provides new insights into the role of autotransporter proteins in the establishment of Helicobacter infection.

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.

Genomic analysis of Helicobacter himalayensis sp. nov. isolated from Marmota himalayana

Background

Helicobacter himalayensis was isolated from Marmota himalayana in the Qinghai-Tibet Plateau, China, and is a new non-H. pylori species, with unclear taxonomy, phylogeny, and pathogenicity.

Results

A comparative genomic analysis was performed between the H. himalayensis type strain 80(YS1)^T and other the genomes of Helicobacter species present in the National Center for Biotechnology Information (NCBI) database to explore the molecular evolution and potential pathogenicity of H. himalayensis. H. himalayensis 80(YS1)^T formed a clade with H. cinaedi and H. hepaticus that was phylogenetically distant from H. pylori. The H. himalayensis genome showed extensive collinearity with H. hepaticus and H. cinaedi. However, it also revealed a low degree of genome collinearity with H. pylori. The genome of 80(YS1)^T comprised 1,829,936 bp, with a 39.89% GC content, a predicted genomic island, and 1769 genes. Comparatively, H. himalayensis has more genes for functions in “cell wall/membrane/envelope biogenesis” and “coenzyme transport and metabolism” sub-branches than the other compared helicobacters, and its genome contained 42 virulence factors genes, including that encoding cytolethal distending toxin (CDT).

Conclusions

We characterized the H. himalayensis 80(YS1)^T genome, its phylogenetic position, and its potential pathogenicity. However, further understanding of the pathogenesis of this potentially pathogenic bacterium is required, which might help to manage H. himalayensis-induced diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-020-07245-y.

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.

Successful treatment of recurrent Helicobacter fennelliae bacteraemia by selective digestive decontamination with kanamycin in a lung cancer patient receiving chemotherapy

INTRODUCTION

Helicobacter fennelliae is an enterohepatic Helicobacter species causing bacteraemia in immunocompromised hosts. Only a few cases of recurrent H. fennelliae bacteraemia have been reported in Japan and there are no guidelines regarding antimicrobial treatment for H. fennelliae infection.

CASE PRESENTATION

H. fennelliae bacteraemia was observed in a patient receiving platinum-based chemotherapy for lung cancer. To prevent recurrence, the patient received antibiotic therapy with cefepime, amoxicillin and doxycycline for 6 weeks, which is similar to the therapy for Helicobactercinaedi bacteraemia. Bacteraemia recurred despite the long-term antibiotic therapy. We hypothesized that the H. fennelliae bacteraemia originated from endogenous infection in the intestinal tract due to the long-term damage of the enteric mucosa by platinum-based drugs and performed selective digestive decontamination (SDD) with kanamycin. Bacteraemia did not recur after SDD.

CONCLUSION

Our observations indicate that clinicians should be aware of possible recurrent H. fennelliae bacteraemia, which could be effectively prevented by SDD with kanamycin.