Spiral organisms: what are they? A microbiologic introduction to Helicobacter pylori

Two-tiered deep-learning-based model for histologic diagnosis of Helicobacter gastritis

AIMS

Helicobacter pylori (HP) infection is the most common cause of chronic gastritis worldwide. Due to the small size of HP and limited resolution, diagnosing HP infections is more difficult when using digital slides.

METHODS AND RESULTS

We developed a two-tier deep-learning-based model for diagnosing HP gastritis. A whole-slide model was trained on 885 whole-slide images (WSIs) with only slide-level labels (positive or negative slides). An auxiliary model was trained on 824 areas with HP in nine positive WSIs and 446 negative WSIs for localizing HP. The whole-slide model performed well, with an area under the receiver operating characteristic curve (AUC) of 0.9739 (95% confidence interval [CI], 0.9545-0.9932). The calculated sensitivity and specificity were 93.3% and 90.1%, respectively, whereas those of pathologists were 93.3% and 84.2%, respectively. Using the auxiliary model, the highlighted areas of the localization maps had an average precision of 0.5796.

CONCLUSIONS

HP gastritis can be diagnosed on haematoxylin-and-eosin-stained WSIs with human-level accuracy using a deep-learning-based model trained on slide-level labels and an auxiliary model for localizing HP and confirming the diagnosis. This two-tiered model can shorten the diagnostic process and reduce the need for special staining.

Helicobacter pylori Infection Acts Synergistically with a High-Fat Diet in the Development of a Proinflammatory and Potentially Proatherogenic Endothelial Cell Environment in an Experimental Model

Classic atherosclerosis risk factors do not explain all cases of chronic heart disease. There is significant evidence that gut microbiota may influence the development of atherosclerosis. The widespread prevalence of chronic Helicobacter pylori (H. pylori, HP) infections suggests that HP can be the source of components that stimulate local and systemic inflammatory responses. Elevated production of reactive oxygen species during HP infection leads to cholesterol oxidation, which drives atherogenesis. The aim of this study is to explore the link between persistent HP infection and a high-fat diet in the development of proinflammatory conditions that are potentially proatherogenic. An in vivo model of Caviae porcellus infected with HP and exposed to an experimental diet was investigated for the occurrence of a proinflammatory and proatherogenic endothelial environment. Vascular endothelial primary cells exposed to HP components were tested in vitro for oxidative stress, cell activation and apoptosis. The infiltration of inflammatory cells into the vascular endothelium of animals infected with HP and exposed to a high-fat diet was observed in conjunction with an increased level of inflammatory markers systemically. The arteries of such animals were the least elastic, suggesting the role of HP in arterial stiffness. Soluble HP components induced transformation of macrophages to foam cells in vitro and influenced the endothelial life span, which was correlated with Collagen I upregulation. These preliminary results support the hypothesis that HP antigens act synergistically with a high-fat diet in the development of proatherogenic conditions.

Helicobacter pylori outer membrane vesicles involvement in the infection development and Helicobacter pylori-related diseases

Helicobacter pylori - (H. pylori) play a role in the pathogenesis of gastritis, gastric and duodenal ulcers as well as gastric cancer. A possible involvement of outer membrane vesicles (OMVs) produced by H. pylori in the distribution of bacterial antigens through the gastric epithelial barrier and their role in the development of local and systemic host inflammatory and immune responses has been suggested. OMVs contain various biologically active compounds, which internalize into host cells affecting signaling pathways and promoting apoptosis of gastric epithelial and immunocompetent cells. OMVs-associated H. pylori virulence factors may strengthen or downregulate the immune responses leading to disease development. This review describes the biological importance of H. pylori OMVs and their role in the course of H. pylori infections, as well as H. pylori related local and systemic effects.

Characterization of the Gastric Microbiota in a Pediatric Population According to Helicobacter pylori Status

BACKGROUND

Helicobacter pylori colonizes the human stomach of approximately 50% of the world's population, and increases the risk of several gastric diseases. The goal of this study is to compare the gastric microbiota in pediatric patients with and without H. pylori colonization.

METHODS

We studied 51 children who underwent gastric endoscopy because of dyspeptic symptoms (18 H. pylori positive and 33 negative). Gastric biopsies were obtained for rapid urease test, culture, histology and DNA extraction. H. pylori was quantified by quantitative polymerase chain reaction and the gastric microbiome studied by V4-16S ribosomal RNA gene high-throughput sequencing.

RESULTS

Bacterial richness and diversity of H. pylori-positive specimens were lower than those of negative, and both groups were clearly separated according to beta diversity. Taxonomic analysis confirmed that H. pylori-positive subjects had a higher relative abundance of Helicobacter genus (66.3%) than H. pylori-negative subjects (0.45%). Four phyla (proteobacteria, bacteroidetes, firmicutes and actinobacteria) accounted for >97% of all reads in both groups. Within proteobacteria, gamma- and betaproteobacteria were the most abundant for H. pylori-negative patients, whereas epsilonproteobacteria was for H. pylori positive. H. pylori-positive patients were associated with low body mass index. In the group of underweight patients (body mass index, <18.5), there were 46.1% of H. pylori-positive patients compared with 24% in the nonunderweight group (P = 0.049). Patients with active superficial gastritis in H. pylori-positive patients had the lowest alpha diversity (P = 0.035).

CONCLUSIONS

We characterized the gastric microbiota for the first time in children with and without H. pylori and observed that when H. pylori is present, it tends to dominate the microbial community. In the H. pylori-negative patients, there was more relative abundance of gammaproteobacteria, betaproteobacteria, bacteroidia and clostridia classes and a higher bacterial richness and diversity.

Helicobacter pylori: the balance between a role as colonizer and pathogen

The isolation of Helicobacter pylori from the human stomach produced significant changes in how gastroenterologists, immunologists, epidemiologists, pathologists and microbiologists have approached gastro-duodenal diseases in the last half of the XX century. However, research of this organism has progressed greatly in the first decade of this century, evidence suggest that H. pylori is associated with disease only in humans older than 40 years, while, the lack of H. pylori colonization is associated with the emergence of new diseases, particularly in younger individuals. These differing effects of H. pylori colonization have created two contrasting concepts: the 'bad' and the 'good' Helicobacter. Following from renewed interest in the normal human microbiome, we need to reconsider our definitions and perhaps recognize that H. pylori might be a normal member of the human gastric microbiome in ancient humans that gradually, as results of the improvement in our environment, is disappearing.

The effect of Helicobacter pylori eradication on gastric juice and blood ammonia concentrations and on visual evoked potentials in cirrhotics

BACKGROUND

The primary source of ammonia is the gut. Ammonia can also be generated by the urease activity of Helicobacter pylori in the gastric mucosa. The aim of this study was to investigate the effect of H. pylori eradication on blood and gastric juice ammonia levels and on visual evoked potential (VEP) recordings in cirrhotic patients.

MATERIALS AND METHODS

Male patients with cirrhosis and H. pylori infection were prospectively evaluated. All patients were given triple regimen for eradication for 10 days. Gastroscopy together with gastric juice sampling for ammonia and mucosal sampling for H. pylori status was performed before and after therapy. Gastric juice and blood ammonia levels were measured and VEP recordings were obtained before and after treatment.

RESULTS

Twenty-seven patients were included in the study. Patients with overt clinical hepatic encephalopathy were excluded from the study. Twenty-four out of twenty-seven patients became H. pylori-negative after the treatment. Ammonia measurements and VEP recordings were evaluated in the 24 patients in whom eradication was successful. A slight but statistically significant decrease in blood and a considerable decrease in gastric juice ammonia levels were observed after treatment [from 44.23 micromol/l to 41.6 micromol/l compared with 3234 micromol/l to 2709 micromol/l, respectively (p <.05)] in patients in whom H. pylori was eradicated. VEP recordings were abnormal in 14 out of 24 patients before the treatment. Only four of these 14 patients with abnormal recordings showed improvement. (p > .05).

CONCLUSIONS

Helicobacter pylori eradication in cirrhotics decreases blood and gastric juice ammonia concentrations whereas it does not provide an improvement in VEP recordings.

Disinfectant activity against different morphological forms of Helicobacter pylori: first results

The pathogenic bacterium Helicobacter pylori, which has infected more than one-half of the world's human population, exists in two morphological forms; the viable helical form and the disputed viable-but-not-culturable coccoid form. Infection by the helical form proceeds through the oral-oral route, while that by the coccoid form, if possible at all, is by the faecal-oral and/or the oral-oral route. The present pilot study addresses the question of disinfectant efficacy against both forms of the bacterium.

Development of a selective medium for isolation of Helicobacter pylori from cattle and beef samples

Helicobacter pylori has been isolated from the human stomach with media containing only minimal selective agents. However, current research on the transmission and sources of infection requires more selective media due to the higher numbers of contaminants in environmental, oral, and fecal samples. The objective of this study was to develop and evaluate detection techniques that are sufficiently selective to isolate H. pylori from potential animal and food sources. Since H. pylori survives in the acidic environment of the stomach, low pH with added urea was studied as a potential selective combination. H. pylori grew fairly well on H. pylori Special Peptone plating medium supplemented with 10 mM urea at pH 4. 5, but this pH did not sufficiently inhibit the growth of contaminants. Various antibiotic combinations were then compared, and a combination consisting of 10 mg of vancomycin per liter, 5 mg of amphotericin B per liter, 10 mg of cefsulodin per liter, 62,000 IU of polymyxin B sulfate per liter, 40 mg of trimethoprim per liter, and 20 mg of sulfamethoxazole per liter proved to be highly selective but still allowed robust colonies of H. pylori to grow. This medium was highly selective for recovering H. pylori from cattle and beef samples, and it is possible that it could be used to enhance the recovery of this bacterium from human and environmental samples, which may be contaminated with large numbers of competing microorganisms.

Invasive Helicobacter-like organisms in feline gastric mucosa

BACKGROUND

Helicobacter-like organisms (HLOs) usually are present in the stomachs of cats. Although the histopathology of natural (H. felis or H. heilmannii) infections has been reported, their invasion into the lymphoid aggregates has not been described previously.

MATERIALS AND METHODS

Gastric tissues were obtained from 17 adult cats living in a natural urban environment. Biopsy sites were selected by the presence of urease on the mucosal surface stained by Genta stain and periodic acid-Schiff stain.

RESULTS

Spiral organisms morphologically similar to H. felis or to H. heilmannii were detected in all the cats, distributed predominantly over the oxyntic mucosa. Seven cats had prominent lymphoid follicles with germinal centers within the oxyntic mucosa, and in six of these seven cats, extracellular organisms were present within the lymphoid follicles. Scattered organisms also were found over sites of gastric metaplasia in the duodenum of six cats.

CONCLUSIONS

This study extends previous observations by showing that HLO infection in cats is associated with large lymphoid follicles in the stomach. In addition, HLOs were demonstrated submucosally within gastric lymphoid follicles and on patches of gastric metaplasia in the duodenum.

Paving the way for pathogens?

Indigenous intestinal microflora are known to afford protection against colonization by pathogenic microorganisms. However, the metabolic activity of at least one species of the indigenous microflora can induce expression of surface glycoconjugates, which may in turn confer susceptibility to infection.

Natural and experimental Helicobacter mustelae reinfection following successful antimicrobial eradication in ferrets

BACKGROUND

Recrudescence or reinfection may occur after eradication of Helicobacter pylori in humans.

MATERIALS AND METHODS

We used the ferret Helicobacter mustelae model to investigate the effect of prior infection and eradication on reinfection by experimental and natural routes. Two groups of ferrets with naturally acquired H. mustelae infection were treated with an eradication protocol using amoxicillin, metronidazole, and bismuth subsalicylate. The ferrets were monitored for recrudescence by repeated cultures of endoscopic gastric mucosal biopsies. The ferrets were challenged at 17 months (group I) and 6 months (group II) after eradication with a strain of H. mustelae having a distinctive restriction endonuclease analysis pattern. The eradication protocol was repeated to eliminate the infection produced by experimental challenge. The ferrets were then cohoused intermittently with naturally infected ferrets.

RESULTS

The original H. mustelae infection was successfully eliminated by the eradication protocol. No recrudescence was observed in group I for 12 months nor for 3 months in group II after eradication. All ferrets became persistently reinfected with the challenge strain. The infection from the challenge strain was eradicated successfully. No ferrets in group I and all ferrets in group II became infected through cohousing.

CONCLUSIONS

These results suggest that though prior infection with H. mustelae may confer some protection against reinfection, such protection is not universal in all circumstances; that susceptibility to reinfection by contact with infected animals varies between individuals; and that age may be a factor in this individual variability. These results are applicable to studies of reinfection after eradication of H. pylori in humans.

Nutritional requirements for growth of Helicobacter pylori

A chemically defined medium consisting of a buffered mineral base supplemented with amino acids, a purine, and thiamine supported growth of 23 clinical isolates and the type strain of Helicobacter pylori. The growth of four strains was inhibited by the presence of certain amino acids. All but one strain required alanine for growth. The amino acids leucine, valine, phenylalanine, methionine, arginine, and histidine were generally required. Isoleucine either was required or stimulated growth. Strains could be differentiated into groups on the basis of a requirement for one or more of the amino acids cysteine, serine, and proline. Only one strain however, demonstrated a requirement for all three of these amino acids.

Lymphoid follicles in the gastric mucosa of dogs. Distribution and lymphocyte phenotypes

The occurrence and distribution of lymphoid follicles within the stomachs of 36 dogs that did not have macroscopic gastric lesions are presented. The dogs ranged in age from less than 1 year to over 13 years. The number of follicles varied between the different regions of the stomach, being most numerous (15.6 follicles cm-2) and uniform in size (about 1 mm in diameter) in the fundus. The number and size of follicles in the antrum varied widely between dogs. Age-related changes in the distribution of follicles were not found following simple linear regression analysis. The phenotypes of lymphocytes in gastric lymphoid follicles of nine dogs aged from less than 1 year to 5 years were determined using monoclonal antibodies specific for canine leucocyte antigens and an indirect immunoperoxidase technique. The follicles had an organized distribution of lymphocytes subsets in that a predominantly B cell area contained some CD4+ cells and very few CD8+ cells and was adjacent to an area containing mostly T cells. Computer-assisted morphometric analysis was used to quantify the overall presence of the various lymphocyte subpopulations. Follicles in the fundus and body regions possessed similar percentages of lymphocytes averaging 42%, 22% and 3% of the area occupied by B cells, CD4+ and CD8+ cells, respectively. It is concluded that lymphoid follicles are a normal constituent of the canine gastric mucosa and possess a lymphocyte composition similar to that reported by others for solitary intestinal follicles.

Isolation and characterization of "Flexispira rappini" from laboratory mice

A bacterium with an unusual ultrastructure and possessing a fusiform protoplasmic cylinder, spiral periplasmic fibers, and bipolar tufts of sheathed flagella was identified in the intestinal mucosae of laboratory mice. The organism was cultured under microaerophilic conditions and was found to rapidly hydrolyze urea. On the basis of 16S rRNA gene sequence analysis, the organism was shown to be "Flexispira rappini." "F. rappini" is closely related to members of the genus Helicobacter and has been reported to be associated with human gastroenteritis and ovine abortion. "F. rappini" has not previously been observed in the gastrointestinal tracts of mice.