Gastric Helicobacter suis Infection Partially Protects against Neurotoxicity in A 6-OHDA Parkinson's Disease Mouse Model.

The exact etiology of Parkinson's disease (PD) remains largely unknown, but more and more research suggests the involvement of the gut microbiota. Interestingly, idiopathic PD patients were shown to have at least a 10 times higher prevalence of Helicobacter suis (H. suis) DNA in gastric biopsies compared to control patients. H. suis is a zoonotic Helicobacter species that naturally colonizes the stomach of pigs and non-human primates but can be transmitted to humans. Here, we investigated the influence of a gastric H. suis infection on PD disease progression through a 6-hydroxydopamine (6-OHDA) mouse model. Therefore, mice with either a short- or long-term H. suis infection were stereotactically injected with 6-OHDA in the left striatum and sampled one week later. Remarkably, a reduced loss of dopaminergic neurons was seen in the H. suis/6-OHDA groups compared to the control/6-OHDA groups. Correspondingly, motor function of the H. suis-infected 6-OHDA mice was superior to that in the non-infected 6-OHDA mice. Interestingly, we also observed higher expression levels of antioxidant genes in brain tissue from H. suis-infected 6-OHDA mice, as a potential explanation for the reduced 6-OHDA-induced cell loss. Our data support an unexpected neuroprotective effect of gastric H. suis on PD pathology, mediated through changes in oxidative stress.

Distinct transcriptome signatures of Helicobacter suis and Helicobacter heilmannii strains upon adherence to human gastric epithelial cells.

The porcine Helicobacter suis and canine-feline H. heilmannii are gastric Helicobacter species with zoonotic potential. However, little is known about the pathogenesis of human infections with these Helicobacter species. To gain more insight into the interactions of both zoonotic Helicobacter species with human gastric epithelial cells, we investigated bacterial genes that are differentially expressed in a H. suis and H. heilmannii strain after adhesion to the human gastric epithelial cell line MKN7. In vitro Helicobacter-MKN7 binding assays were performed to obtain bacterial RNA for sequencing analysis. H. suis and H. heilmannii bacteria attached to the gastric epithelial cells (i.e. cases) as well as unbound bacteria (i.e. controls) were isolated, after which prokaryotic RNA was purified and sequenced. Differentially expressed genes were identified using the DESeq2 package and SARTools pipeline in R. A list of 134 (83 up-regulated and 51 down-regulated) and 143 (60 up-regulated and 83 down-regulated) differentially expressed genes (padj ≤ 0.01; fold change ≥ 2) were identified for the adherent H. suis and H. heilmannii strains, respectively. According to BLASTp analyses, only 2 genes were commonly up-regulated and 4 genes commonly down-regulated in both pathogens. Differentially expressed genes of the H. suis and H. heilmannii strains belonged to multiple functional classes, indicating that adhesion of both strains to human gastric epithelial cells evokes pleiotropic adaptive responses. Our results suggest that distinct pathways are involved in human gastric colonization of H. suis and H. heilmannii. Further research is needed to elucidate the clinical significance of these findings.

Evidence that the stress hormone cortisol regulates biofilm formation differently among Flavobacterium columnare isolates.

The impact of cortisol on Flavobacterium columnare biofilm formation was explored. Firstly, the dynamics of biofilm formation by one highly (HV) and one low virulent (LV) F. columnare isolate with and without the stress hormone cortisol under microfluidic flow conditions was characterized. This to confirm that F. columnare cells could form biofilm under cortisol supplementation, and to compare the temporal and structural differences between different treatment groups. One trial revealed that in both isolates cell aggregates resembling biofilms occurred within 7-h post-inoculation. Consequently, cell clusters were sloughed away, followed by a rebuilding of bacterial cell aggregates, suggestive for a high spreading capacity. While the HV isolate revealed cell aggregates formed upstream at all time-points, for the LV isolate this was only seen upon cortisol supplementation. Secondly, the transcriptional effect of genes (gldK, gldL, gldM, gldN, sprA, sprE, sprT, and porV) belonging to the Type IX secretion system involved in gliding motility was investigated in planktonic and biofilm cells of a HV and LV isolate to which no, a low (LD) or high (HD) dose of cortisol was added. Significantly lower expression of gliding genes gldK, gldL, gldM and gldN, and of protein secretion regulator porV was seen in the LV isolate planktonic cells supplemented with a HD-cortisol. The LV isolate biofilm cells treated with the HD-cortisol showed a significant upregulation of sprT, encoding mobile surface adhesion important in bacterial colonization. This is the first evidence for the co-regulatory effect of cortisol on biofilm formation and F. columnare gliding gene expression.

A novel isolation protocol and probe-based RT-PCR for diagnosis of gastric infections with the zoonotic pathogen Helicobacter suis.

BACKGROUND: Helicobacter suis is a very fastidious microorganism associated with gastritis, gastric ulcers, and mucosa-associated lymphoid tissue lymphoma in humans. In vitro isolation of this agent from human patients has so far been unsuccessful. MATERIALS AND METHODS: A probe-based real-time PCR (RT-PCR) for the rapid detection of H. suis in gastric biopsies was developed. Secondly, a mouse-passage-based protocol was optimized for isolation of low numbers of viable H. suis bacteria. Mice were inoculated with different numbers of viable H. suis (102 -108 ) and kept for 4 weeks to allow multiplication of this pathogen. RESULTS: The probe-based real-time PCR (RT-PCR) exhibited a high degree of diagnostic specificity and analytical sensitivity, high linear correlations (r2 between 0.995 and 0.999), and high amplification efficiencies (>90%) for H. suis. No cross-reactivity was detected with human, porcine, non-human primate, and murine DNA nor with DNA from other bacteria including Helicobacter spp. and Campylobacter spp. H. suis was successfully re-isolated from the stomach of mice inoculated with at least 104 viable H. suis, using a biphasic medium (pH 5), consisting of Brucella agar with Brucella broth on top, both supplemented with vitox supplement, Campylobacter-selective supplement, amphotericin (5 µg/mL), HCl (0.05%), fetal bovine serum (20%), and linezolid (5 µg/mL). Linezolid was necessary to inhibit proliferation of contaminants, including lactobacilli. CONCLUSION: The methods described above can be implemented for detection or isolation of H. suis from human gastric biopsies.

Helicobacter and the Potential Role in Neurological Disorders: There Is More Than Helicobacter pylori.

Trillions of symbiotic microbial cells colonize our body, of which the larger part is present in the human gut. These microbes play an essential role in our health and a shift in the microbiome is linked to several diseases. Recent studies also suggest a link between changes in gut microbiota and neurological disorders. Gut microbiota can communicate with the brain via several routes, together called the microbiome-gut-brain axis: the neuronal route, the endocrine route, the metabolic route and the immunological route. Helicobacter is a genus of Gram-negative bacteria colonizing the stomach, intestine and liver. Several papers show the role of H. pylori in the development and progression of neurological disorders, while hardly anything is known about other Helicobacter species and the brain. We recently reported a high prevalence of H. suis in patients with Parkinson's disease and showed an effect of a gastric H. suis infection on the mouse brain homeostasis. Here, we discuss the potential role of H. suis in neurological disorders and how it may affect the brain via the microbiome-gut-brain axis.

In silico proteomic and phylogenetic analysis of the outer membrane protein repertoire of gastric Helicobacter species.

Helicobacter (H.) pylori is an important risk factor for gastric malignancies worldwide. Its outer membrane proteome takes an important role in colonization of the human gastric mucosa. However, in zoonotic non-H. pylori helicobacters (NHPHs) also associated with human gastric disease, the composition of the outer membrane (OM) proteome and its relative contribution to disease remain largely unknown. By means of a comprehensive survey of the diversity and distribution of predicted outer membrane proteins (OMPs) identified in all known gastric Helicobacter species with fully annotated genome sequences, we found genus- and species-specific families known or thought to be implicated in virulence. Hop adhesins, part of the Helicobacter-specific family 13 (Hop, Hor and Hom) were restricted to the gastric species H. pylori, H. cetorum and H. acinonychis. Hof proteins (family 33) were putative adhesins with predicted Occ- or MOMP-family like 18-stranded ß-barrels. They were found to be widespread amongst all gastric Helicobacter species only sporadically detected in enterohepatic Helicobacter species. These latter are other members within the genus Helicobacter, although ecologically and genetically distinct. LpxR, a lipopolysaccharide remodeling factor, was also detected in all gastric Helicobacter species but lacking as well from the enterohepatic species H. cinaedi, H. equorum and H. hepaticus. In conclusion, our systemic survey of Helicobacter OMPs points to species and infection-site specific members that are interesting candidates for future virulence and colonization studies.