The transmission of Helicobacter pylori via exposure to common sources outweighs the person-to-person contact among spouses in developing countries

Biofilm Formation by Helicobacter pylori and Its Involvement for Antibiotic Resistance

Bacterial biofilms are communities of microorganisms attached to a surface. Biofilm formation is critical not only for environmental survival but also for successful infection. Helicobacter pylori is one of the most common causes of bacterial infection in humans. Some studies demonstrated that this microorganism has biofilm forming ability in the environment and on human gastric mucosa epithelium as well as on in vitro abiotic surfaces. In the environment, H. pylori could be embedded in drinking water biofilms through water distribution system in developed and developing countries so that the drinking water may serve as a reservoir for H. pylori infection. In the human stomach, H. pylori forms biofilms on the surface of gastric mucosa, suggesting one possible explanation for eradication therapy failure. Finally, based on the results of in vitro analyses, H. pylori biofilm formation can decrease susceptibility to antibiotics and H. pylori antibiotic resistance mutations are more frequently generated in biofilms than in planktonic cells. These observations indicated that H. pylori biofilm formation may play an important role in preventing and controlling H. pylori infections. Therefore, investigation of H. pylori biofilm formation could be effective in elucidating the detailed mechanisms of infection and colonization by this microorganism.

First degree relatives and familial aggregation of gastric cancer: who to choose for control in case-control studies?

Gastric carcinogenesis is a multifactorial process involving host gene and environmental interactions. Diverse case-control studies using different types of controls addressed the familial aggregation role for gastric cancer development. Our aim is to discuss the advantages and expected bias according to the different type of eligible controls. A PubMed search of papers on a query on first degree relatives of gastric cancer patients was conducted. The retrieved studies were evaluated regarding quality based on STROBE checklist. Data concerning risk of premalignant lesions and Helicobacter pylori infection was retrieved as the type of controls used on each study. Nine case-control studies were selected. A variety of controls were used ranging from general population to dyspeptic patients and spouses of the cases. We have observed that, independently of the type of control, the risk for the prevalence of premalignant lesions and H. pylori infection was higher for the cases. However, all of the evaluated case-control studies were average quality studies (mean 28 out of 45), with a small number of cases and controls (range from 39 to 300). Furthermore, concerning gene-environment interaction, each of the discussed type of control (general population, dyspeptic, spouse and neighbor) has potential advantages and disadvantages. The current data suggests that selection of any type of the aforementioned controls is feasible and seems to be mainly related to the feasibility of recruitment more than the genetic or environmental backgrounds. General population and dyspeptic patients would be equally appropriate for studies on familial aggregation of gastric cancer. Nevertheless, high-quality cohort studies are needed to validate this assumption.

The transmission of Helicobacter pylori: the effects of analysis method and study population on inference

Although much is known about the virulence of Helicobacter pylori, the transmission pathways for this bacterium are still unresolved. Transmission has been addressed through: (1) prevalence within families; (2) detection in fecal/oral environments; (3) detection in the abiotic/biotic environment; and (4) direct inference from strain similarity. Here, we review the molecular and biochemical methods used and discuss the relative merits of each. Furthermore, as there are differences between developing and developed nations, we discuss the results obtained from transmission studies in light of the study population. We conclude that H. pylori is probably transmitted person-to-person, facilitated by fecal-oral transmission during episodes of diarrhea or gastro-oral contact during periods of vomiting. The persistence of H. pylori in abiotic and biotic environments remains unproven but possible reactivation from viable, non-culturable coccoid forms should be further investigated. Finally, we speculate on the effect of host-pathogen interactions in confounding the inference of transmission.

Development of two PCR-based techniques for detecting helical and coccoid forms of Helicobacter pylori

The primary mode of transmission of Helicobacter pylori, a human pathogen carried by more than half the population worldwide, is still unresolved. Some epidemiological data suggest water as a possible transmission route. H. pylori in the environment transforms into a nonculturable, coccoid form, which frequently results in the failure to detect this bacterium in environmental samples by conventional culture techniques. To overcome limitations associated with culturing, molecular approaches based on DNA amplification by PCR have been developed and used for the detection of H. pylori in clinical and environmental samples. Our results showed the glmM gene as the most promising target for detection of H. pylori by PCR amplification. Under optimal amplification conditions, glmM-specific primers generated PCR-amplified products that were specific for H. pylori and some other Helicobacter species. Genome sequence analysis revealed the existence of a conserved region linked to a hypervariable region upstream of the 16S rRNA gene of H. pylori. Selective PCR primer sets targeting this sequence were evaluated for the specific detection of H. pylori. One primer set, Cluster2 and B1J99, were shown to be highly specific for H. pylori strains and did not produce any PCR products when other Helicobacter species and other bacterial species were analyzed. In tests with 32 strains of H. pylori, 6 strains of other Helicobacter species, 8 strains of Campylobacter jejuni, and 21 strains belonging to different genera, the primers for glmM were selective for the Helicobacter genus and the primers containing the region flanking the 16S rRNA gene were selective for H. pylori species only. The combination of two sensitive PCR-based methods, one targeting the glmM gene and the other targeting a hypervariable flanking region upstream of the 16S rRNA gene, are complementary to each other. Whereas the glmM-specific primers provide a rapid, sensitive presumptive assay for the presence of H. pylori and closely related Helicobacter spp., the primers for sequences flanking the 16S rRNA gene can confirm the presence of H. pylori and locate the potential source of this bacterium.

Detection of Helicobacter pylori DNA in drinking water biofilms: implications for transmission in early life

AIMS

To provide evidence of water quality as a risk factor for acquisition of Helicobacter pylori in early life, and to identify evidence for its presence within pots used to store drinking water.

METHODS AND RESULTS

A prospective cohort study of 65 infants was conducted in the rural village of Keneba, The Gambia. Age of H. pylori colonization was determined and water pot biofilms were tested for H. pylori by sequencing of amplified DNA. Use of supplemental water was a strong risk factor for H. pylori colonization in infants (OR 4.71, 95% CI 1.17-22.5). DNA with 95% homology to the 16S rRNA gene of H. pylori was isolated from biofilms of water pots.

CONCLUSIONS

Drinking water may be a reservoir for H. pylori in areas of the developing world where water quality is poor. Early introduction of water, particularly if stored in, or collected from contaminated sources, may be associated with an increased rate of H. pylori colonization.