Geographic pathology of Helicobacter pylori gastritis

BACKGROUND AND AIM: Helicobacter pylori is etiologically associated with gastritis and gastric cancer. There are significant geographical differences between the clinical manifestation of H. pylori infections. The aim of this study was to compare gastric mucosal histology in relation to age among H. pylori-infected patients from different geographical areas using the same grading system. The prevalence of atrophy and intestinal metaplasia were also compared with the respective gastric cancer incidence in the different countries. METHODS: A total of 1906 patients infected with H. pylori from seven countries were evaluated. Entry criteria included H. pylori positive cases with antral and corpus biopsies between the ages of 18 and 75 years. The minimum number of cases required from a country was 100. Hematoxylin-eosin stained biopsies from antrum and corpus were scored semiquantitatively using the parameters suggested by the Sydney Classification System. Statistical evaluation was performed using Kruskal-Wallis test and Spearman's rank correlation test. RESULTS: The severity of gastric atrophy varied among the different groups with the highest scores being present in Japan. The lowest scores were found in four European countries and in Thailand. The scores for intestinal metaplasia were low in general except for Xi-an, Japan, and Shanghai. For all the countries, the presence of atrophy in the antrum correlated well (r = 0.891) with the incidence of gastric cancer. CONCLUSION: Using a standardized grading system in a large study of H. pylori-related geographic pathology, we found major differences in the overall prevalence and severity of H. pylori gastritis in relation to age. These differences mirrored the respective incidences of gastric cancer in those geographical areas.     

Prevalence of Helicobacter pylori CagA-producing strains within families

During prophylactic examination of blood sera taken from the members of 59 families by the enzyme immunoassay, antibodies to H. pylori and CagA protein were determined. As shown in this study, the children of non-infected mothers proved to be infected in 6.3% of cases and the children of infected mothers, in 72.1% of cases (p < 0.001). The children of non-infected fathers were H. pylori-positive in 71.4% and those of infected fathers, in 58.4% of cases. The CagA status was found to coincide in mothers and their children (p = 0.01), but not in fathers and their children. These data indicate that children acquire H. pylori infection from the members of their family, mainly from their mothers.     

Antibiotic resistance of Helicobacter pylori in Mazandaran, North of Iran

Background: The aim of this study was to investigate the prevalence of resistances in Helicobacter pylori against commonly used antibiotics including metronidazole, clarithromycin, amoxicillin, and tetracycline in Iranian patients. Methods: H. pylori isolates were collected from gastric biopsies from patients referred for upper gastrointestinal endoscopy at Tooba Medical Center, Sari, Iran, from 2007 to 2010. None of them had been using antibiotics for at least 8 months. H. pylori was identified based on morphological shape and positive biochemical tests for catalase, oxidase, and urease activity. Antibiotic resistance for metronidazole, clarithromycin, amoxicillin, and tetracycline was investigated by using epsilometer test. Resistance was defined by minimal inhibitory concentration (MIC) > 0.5 mg/L for amoxicillin (AMX), >4 mg/L for tetracycline (TET), >8 mg/L for metronidazole (MTZ), and >1 mg/L for clarithromycin (CLR). Results: Strains were collected from 132 patients, mean age 45.8 years, 52 (39%) were women. Patients had diverse diagnoses: gastritis 42 (31.8%), duodenal ulcer 45 (34%), gastric cancer 15 (11.3%), or gastric ulcer 30 (22.7%). The prevalences of resistance of H. pylori strains isolated from the patients were 73.4% for metronidazole, 30% for clarithromycin, 6.8% for amoxicillin, and 9% for tetracycline. Twenty‐eight (21.2%) were double resistant to MTZ‐CLR, 16 (12.1%) showed triple resistance to MTZ‐CLR‐AMX, and 8 (6%) were resistant to all four tested antibiotics (MTZ‐CLR‐AMX‐TET). No associations were detected between multiple resistant strains and clinical manifestations (p > .05). Conclusions: The prevalence of H. pylori antibiotic resistance to metronidazole and clarithromycin was high in Iran consistent with the reported low success rates for H. pylori treatment in this country.     

Helicobacter pylori enter and survive within multivesicular vacuoles of epithelial cells

Although intracellular Helicobacter pylori have been described in biopsy specimens and in cultured epithelial cells, the fate of these bacteria is unknown. Using differential interference contrast (DIC) video and immunofluorescence microscopy, we document that a proportion of cell-associated H. pylori enter large cytoplasmic vacuoles, where they remain viable and motile and can survive lethal concentrations of extracellular gentamicin. Entry into vacuoles occurs in multiple epithelial cell lines including AGS gastric adenocarcinoma, Caco-2 colon adenocarcinoma and MDCK kidney cell line, and depends on the actin cytoskeleton. Time-lapse microscopy over several hours was used to follow the movement of live H. pylori within vacuoles of a single cell. Pulsed, extracellular gentamicin treatments show that the half-life of intravacuolar bacteria is on the order of 24 h. Viable H. pylori repopulate the extracellular environment in parallel with the disappearance of intravacuolar bacteria, suggesting release from the intravacuolar niche. Using electron microscopy and live fluorescent staining with endosomal dyes, we observe that H. pylori-containing vacuoles are similar in morphology to late endosomal multivesicular bodies. VacA is not required for these events, as isogenic vacA- mutants still enter and survive within the intravacuolar niche. The exploitation of an intravacuolar niche is a new aspect of the biological life cycle of H. pylori that could explain the difficulties in eradicating this infection.     

No association between Helicobacter pylori genotypes and antibiotic resistance phenotypes within families

Background. Triple therapy combining a proton pump inhibitor with two antibiotics, e.g. clarythromycin (CLR), metronidazole (MTZ) or amoxicillin (AMX), represents the standard in Helicobacter pylori eradication regimens. Resistance to antimicrobial agents, particularly MTZ (up to 56% in Western countries) and CLR (up to 15% in southern Europe), is frequently observed and may be associated with treatment failure [ 1 ]. Recently, several studies indicated that individual H. pylori colonies from a single anatomic site may not always yield identical genotypes, or the identical patterns of susceptibility to antibiotics [ 2 - 5 ]. Representative for every single patient we analyzed 27 H. pylori antrum isolates for susceptibility to antimicrobial agents in order to test whether identical H. pylori genotypes exhibit a similar pattern of susceptibility to antibiotics. Methods. PCR, RELP, PFGE, antibiotic susceptibility testing. Results. H. pylori genotype and antibiotic susceptibility pattern in families do not segregrate. Conclusion. Molecular typing of H. pylori from family members does not predict antibiotic susceptibility pattern.     

Recombination and clonal groupings within Helicobacter pylori from different geographical regions.

A collection of 20 strains of Helicobacter pylori from several regions of the world was studied to better understand the population genetic structure and diversity of this species. Sequences of fragments from seven housekeeping genes (atpA, efp, mutY, ppa, trpC, ureI, yphC ) and two virulence-associated genes (cagA, vacA) showed high levels of synonymous sequence variation (mean percentage Ks of 10-27%) and lower levels of non-synonymous variation (mean percentage Ka of 0.2-5.6%). Cluster analysis of pairwise differences between alleles revealed the existence of two weakly clonal groupings, which included half of the strains investigated. All six strains isolated from Japanese and coastal Chinese were assigned to the 'Asian' clonal grouping, probably reflecting descent from a distinct common ancestor. The clonal groupings were not totally uniform; recombination, as measured by the homoplasy test and compatibility matrices, was extremely common within all genes tested, except cagA. The fact that clonal descent could still be discerned despite such frequent recombination possibly reflects founder effects and geographical separation and/or selection for particular alleles of these genes.     

Microevolution of Helicobacter pylori during Prolonged Infection of Single Hosts and within Families

Our understanding of basic evolutionary processes in bacteria is still very limited. For example, multiple recent dating estimates are based on a universal inter-species molecular clock rate, but that rate was calibrated using estimates of geological dates that are no longer accepted. We therefore estimated the short-term rates of mutation and recombination in Helicobacter pylori by sequencing an average of 39,300 bp in 78 gene fragments from 97 isolates. These isolates included 34 pairs of sequential samples, which were sampled at intervals of 0.25 to 10.2 years. They also included single isolates from 29 individuals (average age: 45 years) from 10 families. The accumulation of sequence diversity increased with time of separation in a clock-like manner in the sequential isolates. We used Approximate Bayesian Computation to estimate the rates of mutation, recombination, mean length of recombination tracts, and average diversity in those tracts. The estimates indicate that the short-term mutation rate is 1.4×10⁻⁶ (serial isolates) to 4.5×10⁻⁶ (family isolates) per nucleotide per year and that three times as many substitutions are introduced by recombination as by mutation. The long-term mutation rate over millennia is 5–17-fold lower, partly due to the removal of non-synonymous mutations due to purifying selection. Comparisons with the recent literature show that short-term mutation rates vary dramatically in different bacterial species and can span a range of several orders of magnitude.     

Helicobacter pylori and dyspepsia

It is clear that non-ulcer (or functional) dyspepsia is a heterogeneous syndrome that includes a subset of patients with unrecognized gastroesophageal reflux. Patient heterogeneity combined with inadequate study methodology has led to enormous confusion in interpreting the relationship between Helicobacter pylori and non-ulcer dyspepsia. The possibility that H. pylori is associated with gastroesophageal reflux disease may explain, in part, the difficulty in establishing a link between non-ulcer dyspepsia and H. pylori infection. It is unclear whether the prevalence of H. pylori is increased in non-ulcer dyspepsia over and above the background population. H. pylori does not appear to be linked to heartburn or other specific upper gastrointestinal tract symptoms. The results of eradication trials in H. pylori-infected patients with non-ulcer dyspepsia have been equivocal and generally flawed. There is no doubt that H. pylori is not a sufficient cause of non-ulcer dyspepsia, because it is well documented in the literature that dyspepsia can occur in the absence of infection and infection can occur in the absence of symptoms. At this stage, there is insufficient evidence to support the hypothesis that H. pylori is etiologically linked to non-ulcer dyspepsia, but data from well designed large randomized controlled trials of eradication therapy, are awaited with great interest.     

Childhood Hygienic Practice and Family Education Status Determine the Prevalence of Helicobacter pylori Infection in Iran

Background: Management of Helicobacter pylori , a causative agent of gastrointestinal diseases is an important health problem in most countries. The main reasons include poorly defined epidemiological status and unrecognized mode of bacterial transmission. Our objective was to investigate the prevalence of H. pylori infection in a representative population of Iran and to evaluate possible risk factors for the H. pylori infection.
Materials and methods: In this cross-sectional study, 2561 healthy individuals aged 18–65 years (mean age, 35.5 years) were selected out of 12,100,000 inhabitants of Tehran province by cluster sampling. Infection with H. pylori was evaluated by detection of anti- H. pylori IgG antibody in serum. Sociodemographic status of each subject was determined by filling up a questionnaire.
Results: Prevalence of H. pylori infection was 69% and was correlated with increasing age. The highest infection rate (79.2%) was seen in individuals 46–55 years old. No association was detected between H. pylori positivity and gender. Low education of the study subjects; low father's and mother's education; poor tooth brushing habit; crowded families in childhood; and lack of household bath, hygienic drinking water, and swage disposal facility in childhood were determined as possible risk factors.
Conclusions: The rate of prevalence of H. pylori infection was higher than developed countries. Low socioeconomic status, poor sanitary indications, and crowded families in childhood were related to high prevalence of H. pylori infection in Iran. Accordingly, fecal–oral and oral–oral routes could be considered as the main pathways of transmission of H. pylori .     

Helicobacter pylori catalase

Helicobacter pylori is the major aetiological agent of gastroduodenitis in humans. Due to the potential importance of catalase in the growth and survival of Helicobacter pylori on the surface of inflamed mucosae, we have characterized catalase from H. pylori as a prelude to further studies on the function of the enzyme in vivo. The catalase activity of H. pylori was significantly affected by the presence of blood, serum or erythrocytes in the growth medium: the greatest activity was expressed when the bacterium was grown on medium containing serum. H. pylori catalase is a tetramer with a subunit Mr of 50,000. The enzyme had a pI of 9.0-9.3, was active over a broad pH range and was stable at 56 degrees C. It was non-competitively inhibited by sodium azide, and had no detectable peroxidase activity. The Km for the purified catalase was measured as 43 +/- 3 mM-H2O2 and the V as 60 +/- 3 mmol H2O2 min-1 (mg protein)-1. The native catalase has absorption maxima at 280 nm and 405 nm with further minor shoulders or peaks at 510 nm, 535 nm and 625 nm, consistent with the presence of an iron-porphyrin prosthetic group.     

Helicobacter pylori motility

Motility is essential for Helicobacter pylori colonization. This review discusses the biochemistry, genetics and genomics of the H. pylori flagellum, and compares these features with well-characterized bacteria.     

Genomics of Helicobacter pylori

During this review period, we have definitely entered into the genomic era. The Helicobacter pylori studies reported here illustrate the use of most of the technologies currently available to globally interrogate the genome of a pathogen. Global analysis of the gene content of H. pylori strains gives insight into the extent of its genetic diversity and its in vivo evolution. Our understanding of the particularities of H. pylori as a gastric pathogen colonizing a unique niche has been improved by studies aimed at: (i) the identification of H. pylori-specific genes; (ii) the establishment of correlations between the presence of one or a group of genes (or proteins) with clinical outcome; and (iii) the analysis of global regulatory circuits or responses to the extracellular signals. The response of host cells to H. pylori infection will be developed in the chapter 'H. pylori and gastric malignancies' by Sepulveda and Coehlo. Despite our knowledge of the H. pylori genome, the function of about one third of its total proteins is still unknown. Functional genomics are straightforward approaches for the identification of new gene functions or metabolic pathways as well as for the understanding of cellular processes and the detection of new virulence factors. In silico studies combined with experimental work will undoubtedly continue to develop. To date, the expansion of proteomics with refinements in mass spectrometry technology has illustrated that through immunoproteomics and comparative studies, relevant novel antigens can be identified. Genomics not only provides invaluable information on H. pylori but also opens new perspectives for diagnostic or therapeutic applications.     

Transmission of Helicobacter pylori

Helicobacter gastroduodenitis is a serious chronic infectious disease that is responsible for widespread morbidity and mortality. An understanding of the way in which it spreads is fundamentally important when considering measures for its control. Its prevalence is highest in the developing world and in individuals with a disadvantaged socio-economic childhood. The disease is believed to be contracted during the early years of life.A faeco-oral mode of transmission is considered by many to be the most likely mode of spread, however, the organism is difficult to culture both from faeces and from the environment and unlike other enteric organisms Helicobacter does not give rise to a diarrhoeal illness that would facilitate its transmission. An orooral route of spread has also been suggested, however, Helicobacter cannot be cultured from saliva, and if it was spread orally there is no reason why childhood should be the most frequent age for its acquisition.A third possibility is that the bacterium is transmitted gastro-orally. In favor of this hypothesis, the infection is easily acquired following gastric intubation with inadequately disinfected equipment. Children have a greater tendency to vomit than adults, and tend to explore with their fingers and place foreign objects in their mouths. Initial Helicobacter infection causes a dyspeptic illness characterised by mucousy vomiting, which may provide a vehicle for transmission. Furthermore, during the acute infection the organism induces achlorhydria in the host, possibly enabling the organism to survive longer in vomited mucus in the absence of acid. This theory fits best with the epidemiological data. Those most at risk are children living in an overcrowded environment who share beds with one another and live in houses that do not possess a fixed hot water supply (thus making cleaning up of vomit more difficult). It is also commoner in institutionalized children and is associated with school catchment areas.