Isolation and characterization of Helicobacter suis from human stomach

Helicobacter suis, a bacterial species naturally hosted by pigs, can colonize the human stomach in the context of gastric diseases such as gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Because H. suis has been successfully isolated from pigs, but not from humans, evidence linking human H. suis infection to gastric diseases has remained incomplete. In this study, we successfully in vitro cultured H. suis directly from human stomachs. Unlike Helicobacter pylori, the viability of H. suis decreases significantly on neutral pH; therefore, we achieved this using a low-pH medium for transport of gastric biopsies. Ultimately, we isolated H. suis from three patients with gastric diseases, including gastric MALT lymphoma. Successful eradication of H. suis yielded significant improvements in endoscopic and histopathological findings. Oral infection of mice with H. suis clinical isolates elicited gastric and systemic inflammatory responses; in addition, progression of gastric mucosal metaplasia was observed 4 mo postinfection. Because H. suis could be isolated from the stomachs of infected mice, our findings satisfied Koch's postulates. Although further prospective clinical studies are needed, H. suis, like H. pylori, is likely a gastric pathogen in humans. Furthermore, comparative genomic analysis of H. suis using complete genomes of clinical isolates revealed that the genome of each H. suis isolate contained highly plastic genomic regions encoding putative strain-specific virulence factors, including type IV secretion system-associated genes, and that H. suis isolates from humans and pigs were genetically very similar, suggesting possible pig-to-human transmission.

Specific and Accurate Detection of the Citrus Greening Pathogen Candidatus liberibacter spp. Using Conventional PCR on Citrus Leaf Tissue Samples

Citrus greening, also known as huanglongbing, is a destructive citrus disease ravaging citrus farms globally. This disease causes asymmetrical yellow leaf mottling, vein yellowing, defoliation, root decay, and ultimately, the death of the citrus plant. When infected, the citrus plants have stunted growth and produce flowers out of season. These flowers rarely yield fruit, and those that do yield small, bitter, irregularly shaped citrus fruit that are not desirable. This disease is spread by the Asian citrus psyllid, Diaphorina citri, and by the grafting of infected citrus tissue. The pathogen has a long and variable incubation period within the citrus plant-sometimes years, before symptoms appear. Attempts to culture this pathogen in vitro have been unsuccessful, possibly due to the low and uneven concentration of the pathogen within infected citrus tissue, or because it is difficult to replicate the environmental conditions conducive to growth of the pathogen. It is very difficult to identify the disease before it has spread, due to its long incubation period and researchers' inability to culture the pathogen. As a result, the disease only becomes apparent after suddenly destroying a citrus farmer's entire yield. Presented here is a method for the accurate and specific detection of the citrus greening pathogen, Candidatus liberibacter spp. using a genomic DNA extraction kit and PCR. This method is simple, efficient, cost effective, and adaptable for quantitative analysis. This method can be adapted for use on any citrus tissue; however, it is potentially limited by the amount of pathogen present in the tissue. Nevertheless, this method will allow citrus farmers to identify infected citrus plants earlier, and curb the spread of this destructive disease before it can further spread.

Helicobacter heilmannii sensu lato: An overview of the infection in humans

Helicobacter heilmannii sensu lato (H. heilmannii s.l.) is a group of gastric non-Helicobacter pylori Helicobacter species that are morphologically indistinguishable from each other. H. heilmannii s.l. infect the stomach of several animals and may have zoonotic potential. Although the prevalence of these infections in humans is low, they are associated with gastric pathology, including mucosa-associated lymphoid tissue lymphoma, making them a significant health issue. Here, the taxonomy, epidemiology, microbiology, diagnosis, and treatment of these infections will be reviewed. The gastric pathology associated with H. heilmannii s.l. infections in humans will also be addressed. Finally, the features of the complete bacterial genomes available and studies on species-specific pathogenesis will be reviewed. The understanding of the mechanisms that underlie gastric disease development mediated by the different bacterial species that constitute H. heilmannii s.l. is essential for developing strategies for prevention and treatment of these infections.

Genome sequence of Helicobacter suis supports its role in gastric pathology

Helicobacter (H.) suis has been associated with chronic gastritis and ulcers of the pars oesophagea in pigs, and with gastritis, peptic ulcer disease and gastric mucosa-associated lymphoid tissue lymphoma in humans. In order to obtain better insight into the genes involved in pathogenicity and in the specific adaptation to the gastric environment of H. suis, a genome analysis was performed of two H. suis strains isolated from the gastric mucosa of swine. Homologs of the vast majority of genes shown to be important for gastric colonization of the human pathogen H. pylori were detected in the H. suis genome. H. suis encodes several putative outer membrane proteins, of which two similar to the H. pylori adhesins HpaA and HorB. H. suis harbours an almost complete comB type IV secretion system and members of the type IV secretion system 3, but lacks most of the genes present in the cag pathogenicity island of H. pylori. Homologs of genes encoding the H. pylori neutrophil-activating protein and γ-glutamyl transpeptidase were identified in H. suis. H. suis also possesses several other presumptive virulence-associated genes, including homologs for mviN, the H. pylori flavodoxin gene, and a homolog of the H. pylori vacuolating cytotoxin A gene. It was concluded that although genes coding for some important virulence factors in H. pylori, such as the cytotoxin-associated protein (CagA), are not detected in the H. suis genome, homologs of other genes associated with colonization and virulence of H. pylori and other bacteria are present.

Clinical significance of Helicobacter species other than Helicobacter pylori

The cultivation of Helicobacter pylori and the recognition of its clinical significance have served to stimulate interest in bacteria associated with the gastrointestinal and hepatobiliary tracts. Many novel Helicobacter species have been identified and are increasingly recognized in association with human disease, most of which is likely acquired as a zoonosis. Because their identification can be difficult by use of routine methods available in the clinical laboratory, awareness of methods for diagnosis and treatment of these Helicobacter species is important, particularly in the evaluation of immunocompromised patients.

Cellular immune responses in Helicobacter heilmannii infection: evaluation of the role of the host and the bacterium

We evaluated some aspects of the immune response to Helicobacter heilmannii in two mouse strains. Gastritis that was more severe in infected C57BL/6 mice. A proliferative response to H. pylori antigens was observed in splenocytes from H. heilmannii-positive and -negative mice, similar in the positive- and negative-BALB/c mice, but lower in the positive- than in the negative-C57BL/6 animals. A decrease in B cells and an increase in CD4+ cells after stimulation with type I H. pylori antigen and an increase in CD8+ cells after stimulation with type I and II antigens was observed in infected C57BL/6 mice. Conversely, the percentage of CD4+, CD8+, and B cells was similar in positive- and negative-BALB/c mice. These results demonstrated that the immune response is similar in H. heilmannii and H. pylori infection and strengthened the importance of host and bacterial virulence markers in the immune response to gastric Helicobacter infections.

Comparison of gastritis and gastric epithelial proliferation in Helicobacter heilmannii-infected nude and BALB/c mice

Gastric mucosal hypertrophy/nodular hyperplasia occurs as a consequence of Helicobacter infection in mice and humans. The pathogenesis of this hyperplastic response is not understood. To determine the role of host cellular immunity in gastric mucosal hypertrophy/hyperplasia, 6-8-week-old female euthymic BALB/c (n = 30) or NIH athymic nude (n = 40) mice were inoculated with H. heilmannii. Equal numbers of uninoculated mice of each strain served as controls. Mice from each group were euthanatized at 0.5, 6, 12, and 18 months postinoculation (PI). Lymphoplasmacytic gastritis and lymphoid follicle development were less severe in nude mice than in euthymic mice at <6 months PI. The prevalence of gastritis at 0.5, 6, 12, and 18 months PI was 0%, 17%, 67%, and 88%, respectively, in infected nude mice and 33%, 83%, 71%, and 100%, respectively, in infected BALB/c mice. CD4+ T cells in infected nude mice were evident at > or =6 months PI but were less numerous than in infected BALB/c mice at comparable time intervals. However, numbers of CD4+ T cells increased substantially throughout the experiment in infected BALB/c mice. The prevalence of nodular mucosal hyperplasia at 0.5, 6, 12, and 18 months PI was 0%, 0%, 33%, and 20%, respectively, in infected nude mice and 0%, 33%, 80%, and 80%, respectively, in infected BALB/c mice. Nodular hyperplasia occurred in association with the appearance of chronic lymphoplasmacytic inflammation and CD4+ T cells at 12 and 18 months PI in nude mice. H. heilmannii-associated gastritis and mucosal remodeling is reduced in immunodeficient mouse strains lacking normal CD4+ T cell numbers as compared with the response in immunocompetent mice. Additionally, CD4 immunocompetence is an integral aspect of the mucosal hypertrophy/nodular hyperplasia in experimental H. heilmannii-associated disease of mice.

Gastrospirillum hominis and Helicobacter pylori infection in Thai individuals: comparison of histopathological changes of gastric mucosa

The presence of Helicobacter pylori (H. pylori) in the stomach is closely associated with histological signs of chronic active gastritis and peptic ulcer. Another spiral organism named Gastrospirillum hominis (G. hominis) has led to further interest in the bacterial pathogenesis of gastritis. Due to the low prevalence of G. hominis, it is difficult to evaluate its biological behavior. Recently 16 cases of G. hominis-associated gastritis were found in 257 Thai individuals, which made it possible to study the biological characteristics of G. hominis and its relationship with gastric mucosal inflammation. The results showed that H. pylori and G. hominis could be easily observed in the lower third of the mucous layer and in the mucosa of the gastric pits by means of toluidine blue staining. Both bacteria immunostained positive. Helicobacter pylori were usually in the shape of curved bacillary while G. hominis often appeared in spiral configuration. In 257 cases of Thai subjects, 169 cases were found to be H. pylori positive, the detection rate was 65.7%, and 16 cases were G. hominis positive, with a 6.2% detection rate. In G. hominis infection, 43.6% of cases had normal gastric mucosa. Superficial, erosive and atrophic gastritis cases were 13.2, 10.9 and 12.5%, respectively. Mucosal inflammation was usually severe in H. pylori, but neutrophil polymorph infiltration was often mild and focal in G. hominis infection. Although no G. hominis infection with carcinoma was shown in our cases, the occurrence of mucosal atrophy, metaplasia and dysplasia was higher in both bacterial infections compared with H. pylori- and G. hominis-negative cases. It is suggested that G. hominis may be partly responsible for the mucosal inflammation and some malignant-associated lesions.

Gastrospirillum hominis and human chronic gastritis

Gastrospirillum hominis, a new spiral bacterium, was found in the gastric mucosa of two patients with antral chronic gastritis. These 2 cases originated from a series of 2781 consecutive gastric biopsies observed over a period of five years, with a prevalence of 0.072%. Dogs and cats may be responsible for transmission to humans but in our experience no contact with pets was documented. Detection of these organisms might provide new insight into the pathogenesis of human gastritis.

Spiral bacteria in the human stomach: the gastric helicobacters

During the past decade, Helicobacter pylori has become recognized as one of the most common human pathogens, colonizing the gastric mucosa of almost all persons exposed to poor hygienic conditions from childhood. It also is often found, albeit with a lower frequency, in groups of high socioeconomic status. H. pylori causes chronic active gastritis and is a major factor in the pathogenesis of duodenal ulcers and, to a lesser extent, gastric ulcers. In addition, the presence of this bacterium is now recognized as a risk factor for gastric adenocarcinoma and lymphoma. Nevertheless, most infections appear without clinical consequences. In this second decade of intensive research, it is important to understand why H. pylori is sometimes a dangerous pathogen, and to determine how it can be eradicated in those at highest risk for severe disease.