Helicobacter cinaedi bacteremia resulting from antimicrobial resistance acquired during treatment for X-linked agammaglobulinemia

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.

Helicobacter kumamotonensis sp. nov., isolated from human clinical specimens

A Gram-stain-negative, spiral bacterium (PAGU 1991^T) was isolated from the blood of a patient with diffuse large B-cell lymphoma. Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolate was very closely related to Helicobacter equorum LMG 23362^T (99.1 % similarity), originally isolated from a faecal sample from a healthy horse. PAGU 1991^T was also very closely related to PAGU 1750 in our strain library (=CCUG 41437) with 99.7 % similarity. Additional phylogenetic analyses based on the 23S rRNA gene sequence and GyrA amino acid sequence further supported the close relationship between the two human isolates (PAGU 1991^T and PAGU 1750) and the horse strain. However, a phylogenetic analysis based on 16S rRNA showed that the two human isolates formed a lineage that was distinct from the horse strain (less than 99.2 % similarity). In silico whole-genome comparisons based on digital DNA-DNA hybridization, average nucleotide identity based on blast and orthologous average nucleotide identity using usearch between the two human isolates and the type strain of H. equorum showed values of less than 52.40, 93.47, and 93.50 %, respectively, whereas those between the two human isolates were 75.8, 97.2, and 97.2 %, respectively. These data clearly demonstrated that the two human isolates formed a single species, distinct from H. equorum. Morphologically, the human isolates could be distinguished by the type of flagella; the human isolates showed a bipolar sheathed flagellum, whereas that of H. equorum was monopolar. Biochemically, the human isolate was characterized by growth at 42 °C under microaerobic conditions and nitrate reduction unability. We conclude that the two human isolates, obtained from geographically and temporally distinct sources, were a novel species, for which we propose the name Helicobacter kumamotonensis sp. nov., with the type strain PAGU 1991^T (=GTC 16810^T=CCUG 75774^T).

Helicobacter cinaedi is a human-adapted lineage in the Helicobacter cinaedi/canicola/'magdeburgensis' complex

Helicobacter cinaedi is an enterohepatic Helicobacter that causes bacteremia and other diseases in humans. While H. cinaedi-like strains are isolated from animals, including dog isolates belonging to a recently proposed H. canicola, little is known about the genetic differences between H. cinaedi and these animal isolates. Here, we sequenced 43 H. cinaedi- or H. canicola-like strains isolated from humans, hamsters, rats and dogs and collected 81 genome sequences of H. cinaedi, H. canicola and other enterohepatic Helicobacter strains from public databases. Genomic comparison of these strains identified four distinct clades (clades I–IV) in H. cinaedi/canicola/‘magderbugensis’ (HCCM) complex. Among these, clade I corresponds to H. cinaedi sensu stricto and represents a human-adapted lineage in the complex. We identified several genomic features unique to clade I. They include the accumulation of antimicrobial resistance-related mutations that reflects the human association of clade I and the larger genome size and the presence of a CRISPR-Cas system and multiple toxin-antitoxin and restriction-modification systems, both of which indicate the contribution of horizontal gene transfer to the evolution of clade I. In addition, nearly all clade I strains but only a few strains belonging to one minor clade contained a highly variable genomic region encoding a type VI secretion system (T6SS), which could play important roles in gut colonization by killing competitors or inhibiting their growth. We also developed a method to systematically search for H. cinaedi sequences in large metagenome data sets based on the results of genome comparison. Using this method, we successfully identified multiple HCCM complex-containing human faecal metagenome samples and obtained the sequence information covering almost the entire genome of each strain. Importantly, all were clade I strains, supporting our conclusion that H. cinaedi sensu stricto is a human-adapted lineage in the HCCM complex.

Infections With Enterohepatic Non-H. pylori Helicobacter Species in X-Linked Agammaglobulinemia: Clinical Cases and Review of the Literature

The genus Helicobacter is classified into two main groups according to its habitat: gastric and enterohepatic. Patients with X-linked agammaglobulinemia (XLA) appear to be associated with invasive infection with enterohepatic non-Helicobacter pylori species (NHPH), mainly H. cinaedi and H. bilis. Such infections are difficult to control and have a high potential for recurrence. The spectrum of illnesses caused by these species includes recurrent fever, bacteremia, arthritis, osteomyelitis, cellulitis, abdominal abscesses, and pyoderma gangrenosum-like ulcer. The presence of these Helicobacters is particularly difficult to diagnose and eradicate, as they are very fastidious bacteria and present resistance to several types of antibiotics. We report two clinical cases of XLA patients infected with H. bilis. These infections were chronic in these patients and could not be eradicated in one of them. We also review the cases of enterohepatic non-Helicobacter pylori species (NHPH) in patients with this inborn error of immunity.

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 cinaedi-Associated Refractory Cellulitis in Patients with X-Linked Agammaglobulinemia

X-linked agammaglobulinemia (XLA) is characterized by severe or recurrent infections, hypogammaglobulinemia, and circulating B cell deficiency. The frequent pathogens seen in patients with XLA include Streptococcus pneumoniae, Haemophilus influenzae, Pseudomonas aeruginosa, and enterovirus as well as Campylobacter and Helicobacter species. Here, we describe two patients with XLA who developed cellulitis and bacteremia caused by Helicobacter cinaedi even when administered an appropriate immunoglobulin replacement therapy. H. cinaedi may be difficult to isolate using a conventional blood culture system and could be identified by sequence analysis and mass spectrometry. H. cinaedi infection causes recurrent symptoms frequently, and patients require a long course of antibiotic treatment. Recently, the case of non-H. pylori Helicobacter (NHPH) infection such as H. cinaedi and H. bilis infection is increasing in number in patients with XLA. Systemic NHPH infection should be suspected, and extensive microbiological analysis should be performed to appropriately treat patients with XLA who present with fever and skin lesions.

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.

Other Helicobacters and gastric microbiota

This article aimed to review the literature from 2015 dealing with gastric and enterohepatic non-Helicobacter pylori Helicobacter species (NHPH). A summary of the gastric microbiota interactions with H. pylori is also presented. An extensive number of studies were published during the last year and have led to a better understanding of the pathogenesis of infections with NHPH. These infections are increasingly reported in human patients, including infections with H. cinaedi, mainly characterized by severe bacteremia. Whole-genome sequencing appears to be the most reliable technique for identification of NHPH at species level. Presence of NHPH in laboratory animals may influence the outcome of experiments, making screening and eradication desirable. Vaccination based on UreB proteins or bacterial lysate with CCR4 antagonists as well as oral glutathione supplementation may be promising strategies to dampen the pathogenic effects associated with gastric NHPH infections. Several virulent factors such as outer membrane proteins, phospholipase C-gamma 2, Bak protein, and nickel-binding proteins are associated with colonization of the gastric mucosae and development of gastritis. The development of high-throughput sequencing has led to new insights in the gastric microbiota composition and its interaction with H. pylori. Alterations in the gastric microbiota caused by the pH-increasing effect of a H. pylori infection may increase the risk for gastric cancer.