Campylobacter-like organisms in chronic gastritis, peptic ulcer, and gastric carcinoma

Intracellular presence of Helicobacter pylori antigen and genes within gastric and vaginal Candida

BACKGROUND

Helicobacter pylori infections are generally acquired during childhood and affect half of the global population, but its transmission route remains unclear. It is reported that H. pylori can be internalized into Candida, but more evidence is needed for the internalization of H. pylori in human gastrointestinal Candida and vaginal Candida.

METHODS

Candida was isolated from vaginal discharge and gastric mucosa biopsies. We PCR-amplified and sequenced H. pylori-specific genes from Candida genomic DNA. Using optical and immunofluorescence microscopy, we identified and observed bacteria-like bodies (BLBs) in Candida isolates and subcultures. Intracellular H. pylori antigen were detected by immunofluorescence using Fluorescein isothiocyanate (FITC)-labeled anti-H. pylori IgG antibodies. Urease activity in H. pylori internalized by Candida was detected by inoculating with urea-based Sabouraud dextrose agar, which changed the agar color from yellow to pink, indicating urease activity.

RESULTS

A total of 59 vaginal Candida and two gastric Candida strains were isolated from vaginal discharge and gastric mucosa. Twenty-three isolates were positive for H. pylori 16S rDNA, 12 were positive for cagA and 21 were positive for ureA. The BLBs could be observed in Candida cells, which were positive for H. pylori 16S rDNA, and were viable determined by the LIVE/DEAD BacLight Bacterial Viability kit. Fluorescein isothiocyanate (FITC)-conjugated antibodies could be reacted specifically with H. pylori antigen inside Candida cells by immunofluorescence. Finally, H. pylori-positive Candida remained positive for H. pylori 16S rDNA even after ten subcultures. Urease activity of H. pylori internalized by Candida was positive.

CONCLUSION

In the form of BLBs, H. pylori can internalize into gastric Candida and even vaginal Candida, which might have great significance in its transmission and pathogenicity.

Apparent intracellular Helicobacter pylori detected by immunohistochemistry - the missing link in eradication failure

BACKGROUND

Helicobacter (H.) pylori is primarily an extracellularly living bacterium. However, seemingly intracellular occurrence can often be detected by immunohistochemical stains. Considering antimicrobial resistance, we investigated the impact of the apparent intracellular H. pylori (aiHp) on treatment failure of first-line triple therapies.

METHODS

Gastric biopsies of 814 H. pylori infected patients naïve for treatment were analyzed before and after eradication therapy by immunohistochemistry. Thereof, 373 received treatment consisting of amoxicillin, clarithromycin and PPI (AC/PPI). Availability of PCR-based clarithromycin susceptibility test results from pre-treatment gastric biopsies was a pre-condition for matching 52 aiHp to 52 non-aiHp cases within the AC/PPI-group.

RESULTS

AiHp were detected mostly in low counts predominantly in corpus, rarely in antrum biopsies (95.2% vs. 24.6%); they were found in 497 (61%) of all patients and in 192 of 373 patients (51.5%) in the AC/PPI-group. The eradication rate in aiHp vs. non-aiHp cases was 44.4% vs. 72.9% in the entire sample and 45.3% vs. 66.8% in the AC/PPI-group. Among the 104 paired patients, respective values were 46.2% vs. 78.8%; in clarithromycin susceptible cases 60.6% vs. 91.9%. Both aiHp and resistance to clarithromycin proved to be highly significant (p≤0.001) and independent predictors of eradication failure. Twelve of 13 aiHp cases with a clarithromycin sensitive strain, who failed eradication, developed resistance to the antibiotic.

CONCLUSIONS

AiHp found by immunohistochemical staining especially in corpus biopsies proved to be a risk factor for failure of first-line triple therapies; occurrence of aiHp should be considered with regard to therapy options.

Helicobacter pylori: an invading microorganism? A review

In this review we evaluate the pros and cons of Helicobacter pylori invasion of epithelial cells as part of the natural history of H. pylori infection. H. pylori is generally considered an extracellular microorganism. However, a growing body of evidence supports the controversial hypothesis that at least a subset of H. pylori microorganisms has an intracellular (intraepithelial) location. Most significant is the fact that H. pylori invades cultured epithelial cells with invasion frequencies similar to Yersinia enterocolitica and better than Shigella flexneri; furthermore, studies of invasion mechanisms suggest that H. pylori invasion of and survival within epithelial cells is not merely a passive event, but requires active participation of the microorganism. Although many studies of human gastric biopsy specimens have failed to demonstrate any intracellular H. pylori, some studies have revealed a minor fraction of H. pylori inside gastric epithelial cells, with possible linkage to peptic ulceration and epithelial cell damage. In conclusion, these data encourage further research to establish whether intracellular H. pylori does play a role in H. pylori colonization of the human stomach and in peptic ulcer pathogenesis.

Removal of mucus for ultrastructural observation of the surface of human gastric epithelium using pronase

BACKGROUND

Helicobacter pylori adhering to the human gastric epithelium causes gastric diseases such as ulcer, carcinoma and lymphoma. It is thus important to observe in detail both the surface of the epithelial cells and the H. pylori that adhered to it for the elucidation of H. pylori-induced diseases by scanning electron microscopy (SEM). Since the thick mucus layer blocks the observation of the cell surface and the bacteria, it is generally eliminated during the processing for SEM by roughly mechanical methods, but these treatments also demolish the ultrastructure of the cells. We studied the nonmechanical method for removal of mucus layer of gastric epithelium using pronase.

MATERIALS AND METHODS

To determine the optimal concentration of pronase, mucin was used as a substrate for inhibition of the viscosity. Pronase was added in 2% mucin at the concentration of 10, 50, 100, 500, 1000, 2000 or 5000 unit/ml and the flowing time of the mixture was measured. Based on the digestion experiment, biopsied specimens from 24 patients with dyspepsic symptoms were fixed in glutaraldehyde and then washed in rolling with different concentration of pronase. After the pretreatment by pronase, the specimens were treated according to the standard process for SEM.

RESULTS

We succeeded in removing the mucus layer on the surface of epithelial cells from the biopsied specimens fixed in glutaraldehyde by rinsing with 2000 unit/ml pronase for 24 hours.

CONCLUSIONS

Using our digestive method without destroying the ultrastructure, the earliest stage which H. pylori has adhered onto the human gastric epithelium can be observed for the investigation of H. pylori-induced gastric disorders by SEM.

Selective colonization by Helicobacter pylori of the deep gastric glands and intracellular canaliculi of parietal cells in the setting of chronic proton pump inhibitor use

Colonization by Helicobacter pylori of the acid-secreting tubules of gastric glands and the canaliculi of parietal cells has only rarely been reported. The presence of these organisms in such "deep" locations has only been reported in association with the more typical superficial colonization of the mucous gel layer overlying gastric epithelial cells. We report two cases of deep H. pylori infection without the presence of superficial organisms. Both patients had been using proton pump inhibitors for many years. We review the literature regarding the distribution of H. pylori within the stomach and the effect of proton pump inhibitor use on H. pylori distribution.

Prevalence of Helicobacter pylori infection in Argentina: results of a nationwide epidemiologic study. Argentinean Hp Epidemiologic Study Group

Our aim was to assess the prevalence of Helicobacter pylori (Hp) infection in Argentina, in the general population and by age groups, and to determine the value of various epidemiologic variables as predictors of Hp infection. The study comprised 754 subjects (443 women 158.7%], 311 men [41.3%]) from both genders, consecutively recruited from health centers where patients were undergoing routine medical analyses. Average age was 32 +/- 22 years. The pediatric group included subjects < or =18 years of age (n = 261). Stratification was based primarily on climatic factors and secondarily on sanitary and demographic considerations. Hp infection status was assessed through a quick serologic test. The overall Hp infection prevalence in Argentina was 35.7 +/- 3.8%. The age was statistically significant using a multiple regression test (p < 0.01). Furthermore, the socioeconomic (p < 0.05) and educational level (0 < 0.01) in the adults and the water sources (p < 0.01) in the pediatric group were all statistically significant according the multiple regression test. The overall Hp infection prevalence in Argentina was 35.7 +/- 3.8%. Age was a predictor of Hp infection status. There is evidence of low infection prevalence in children. a higher prevalence in adolescents, and a more noticeable increase at 40 years of age. Furthermore, the socioeconomic and educational level in adults and the water sources in the pediatric group explained, in part, the occurrence of Hp infection.

Helicobacter pylori infection occurs via close contact with infected individuals in early childhood

BACKGROUND

The manner in which Helicobacter pylori is transmitted is of fundamental importance when considering strategies for its control, yet, to date, the exact mode of transmission remains uncertain.

METHODS

The seroprevalence of H. pylori in a relatively isolated rural town in Japan (A-town) was examined to analyse the H. pylori infection route. The immunoglobulin G antibodies against H. pylori in 1684 subjects who had received public health examinations in A-town were determined with an enzyme-linked immunosorbent assay. The seroprevalence was compared in five areas according to the water source. The possibility and frequency of intrafamilial infection was analysed by comparing the seroprevalence among family members residing in the same home.

RESULTS

The seroprevalence of H. pylori did not differ significantly between the five areas examined. Seropositivity was significantly more common in the children whose mothers were seropositive (45.0%, 27/60) than in the children whose mothers were seronegative (10.0%, 2/20; odds ratio (OR) = 7.36, P = 0.0036, 95% confidence interval (CI) = 1.57-34.59). Seropositivity was significantly more common in the children whose older siblings were seropositive (55.0%, 22/40) than in the children whose older siblings were seronegative (23.5%, 20/85; OR = 3.97, P = 0.00051, 95% CI = 1.79-8.84). There was no significant relationship in seroprevalence between children and fathers, grandchildren and grandfathers, grandchildren and grandmothers, or within couples. Seropositivity was significantly more common in the adolescents who had attended a nursery school (44.4%, 20/45) than in the adolescents who had not attended a nursery school (25.6%, 109/426) (OR = 2.33, P = 0.0070, 95% CI = 1.24-4.36).

CONCLUSIONS

The acquisition of H. pylori infection occurs by close contact with infected individuals in early childhood, especially via contact with infected mothers and other infected children.

Effect of Helicobacter pylori infection on gastric epithelial proliferation in progression from normal mucosa to gastric carcinoma

AIM: To study the effect of Helicobacter pylori (H. pylori) infection on gastric epithelial proliferation in the progression from normal mucosa to gastric carcinoma.

METHODS: Gastric biopsy specimens from normal controls (n = 11), superficial gastritis (n = 32), atrophic gastritis with intestinal metaplasia (n = 83), dysplasia (n = 25) and gastric carcinoma (n = 10) were studied by immunohistochemical stianing of proliferating cell nuclear antigen (PCNA).

RESULTS: The gastric epithelial proliferation, expressed as PCNA labeling index (LI)%, was progressively increased in successive stages from normal mucosa to gastric carcinoma regardless of H. pylori status. There was significant difference in PCNA LI% among all groups (P < 0.01). The analysis pursuing the effect of H. pylori infection on gastric epithelial proliferation in the progression from normal mucosa to gastriccarcinoma showed that in superficial gastritis and mild atrophic gastritis groups, PCNA LI% in H. pylori positive patients were 13.14 ± 1.6 and 19.68 ± 2.22 respectively, significantly higher than 6.95 ± 0.78 and 11.34 ± 1. 89 in H. pylori negative patients (P < 0.01); but there was no such difference in other groups (P > 0.05).

CONCLUSION: H. pylori infection causes increased gastric epithelial proliferation in the stages of superficial and mild atrophic gastritis and may play a part in triggering gastric carcinogenesis.

Diagnosing Helicobacter pylori by imprint cytology: can the same biopsy specimen be used for histology?

Imprint cytology of the gastric mucosa has been found to be very simple, inexpensive, and rapid for diagnosing Helicobacter pylori infection. However, there is a fear that preparing imprint smears may damage the biopsy specimen for subsequent histologic examination. This study was planned to investigate whether this damage happens. Four antral biopsy specimens were obtained from each of the 100 patients undergoing upper gastrointestinal endoscopy. Imprint smears were made from two biopsy specimens, which were then fixed in 10% formal saline and sent for histologic study. The third and fourth biopsy specimens were directed fixed in 10% formal saline for histologic examination. Two pathologists examined the imprint smears. Agreement between the two observers was observed in 97% of cases. Beyond-chance agreement was good with a kappa index of 0.90. H. pylori organisms were seen in 82% of biopsy specimens from which imprint smears were prepared and in the same percentage of biopsy specimens that were processed directly. The pathologists could not identify the histologic sections form which imprints were made. It is concluded that imprint cytology is an excellent method of diagnosing H. pylori infection and that preparing imprint smears does not alter the quality of the tissue. The same biopsy specimen can be used for histologic studies.

Seroprevalence of Helicobacter pylori infection in medical staff in Shanghai

BACKGROUND

The epidemiology of Helicobacter pylori is still under investigation. It is postulated that the human stomach is the natural reservoir and that spread occurs by oral-oral or fecal-oral transmission. The aim of this study was to determine whether medical staff, especially endoscopy unit personnel, are at an increased risk of acquiring H. pylori infection.

METHODS

An enzyme-linked immunosorbent assay technique was used to detect circulating H. pylori IgG antibodies in 1050 medical staff from 16 hospitals in Shanghai, including 125 GI endoscopists, 45 endoscopy unit nurses, 71 gastroenterologists not doing endoscopy, 105 nurses working in gastroenterology wards, 417 internists, and 287 general nurses. This group was compared with an age-matched population obtained from the same urban area of the city.

RESULTS

The overall prevalence of H. pylori infection in total medical staff was 70.0%, compared to 44.6% in general population (P < 0.0001). Age-adjusted comparisons between subgroups of medical staff were made. The prevalence of H. pylori in GI endoscopists was 82.4%, which is significantly higher than 66.4% in internists and 65.8% in general nurses (all, P < 0.01) but not significantly different from 77.7% in endoscopy unit nurses or from 74.2% in nurses working in gastroenterology wards (all, P > 0.05). Further analysis did not show any significant difference in the prevalence of H. pylori between other subgroups. The prevalence of H. pylori infection in GI endoscopists increased with the number of years of practice.

CONCLUSIONS

Medical staff, especially endoscopy unit personnel, are at increased risk of infection with H. pylori. These findings strongly suggest the medical practice and endoscopy procedures are risk factors for H. pylori infection and support person-to-person transmission in this setting, probably from patients to medical staff.

Identification of carboxylation enzymes and characterization of a novel four-subunit pyruvate:flavodoxin oxidoreductase from Helicobacter pylori

The enzyme activities responsible for carboxylation reactions in cell extracts of the gastric pathogen Helicobacter pylori have been studied by H14CO3- fixation and spectrophotometric assays. Acetyl coenzyme A carboxylase (EC 6.4.1.2) and malic enzyme (EC 1.1.1.40) activities were detected, whereas pyruvate carboxylase (EC 6.4.1.1), phosphoenolpyruvate carboxylase (EC 4.1.3.1) and phosphoenolpyruvate carboxykinase (EC 4.1.1.49) activities were absent. However, a pyruvate-dependent, ATP-independent, and avidin-insensitive H14CO3- fixation activity, which was shown to be due to the isotope exchange reaction of pyruvate:flavodoxin oxidoreductase (EC 1.2.7.1), was present. The purified enzyme is composed of four subunits of 47, 36, 24, and 14 kDa. N-terminal sequence analysis showed that this enzyme is related to a recently recognized group of four-subunit pyruvate:ferredoxin oxidoreductases previously known only from hyperthermophiles. This enzyme from H. pylori was found to mediate the reduction of a number of artificial electron acceptors in addition to a flavodoxin isolated from H. pylori extracts, which is likely to be the in vivo electron acceptor. Indirect evidence that the enzyme is capable of in vitro reduction of the anti-H. pylori drug metronidazole was also obtained.

Effects of acid suppression on microbial flora of upper gut

Decreased acid secretion, due to therapy or disease, predisposes to increased bacterial counts in gastric juice. As bacterial numbers increase, the number of nitrate-reducing strains and the concentration of luminal nitrite usually also increase. However, there is controversy (mainly because of assay problems) about whether decreased acid increases generation of N-nitroso compounds: these may be produced by acid or by bacterial catalysis, and the relative contributions of each are still uncertain. Other potentially important factors include ascorbate secretion (can prevent nitrite conversion to nitroso compounds) and the particular spectrum of nitroso compounds produced. Nitrosation of several histamine H2-receptor antagonists has been demonstrated experimentally, but under conditions that are very unlikely to be encountered clinically. Some acid suppressant therapies have been claimed to aid eradication of Helicobacter pylori, but more work is needed to evaluate this. If ulcer treatment regimens do not also address eradication of H. pylori (when present), gastritis will progress, and the recently documented association between H. pylori and gastric carcinoma needs to be considered. Enteric flora probably also increase if acid secretion is markedly reduced: this does not appear to have nutritional consequences but probably reduces the resistance to occasional infections, of which cholera is the best documented.

Helicobacter pylori

Helicobacter pylori is an important cause of chronic active gastritis and is strongly associated with peptic ulcer disease and gastric cancer. H. pylori colonizes the surface of the gastric epithelium with production of a number of factors, resulting in inflammation and an altered mucosa. H. pylori infection occurs world-wide and the mode of transmission most likely is from human to human via the fecal-oral and/or the oral-oral route. Treatment and, in the future, prevention of this infection may result in a marked diminution of upper gastrointestinal tract disease.

Prevalence of Helicobacter pylori in southern Indian controls and patients with gastroduodenal disease

The spiral organism Helicobacter pylori has been causally implicated in the genesis of various gastroduodenal diseases. Since these diseases are common in southern India, this study was undertaken to determine the prevalence of H. pylori in the gastric mucosa of asymptomatic adults and patients with various gastroduodenal diseases. H. pylori was detected in the gastric mucosa of 25 of 30 (83.3%) normal volunteers. Prevalence rates in the disease groups were also high, and included 38 of 41 patients with duodenal ulcer (92.6%), 13/16 with gastric ulcer (81.3%), and 85/119 subjects (71.4%) with non-ulcer dyspepsia. Light microscopic examination of the gastric mucosa provided the best method of detecting H. pylori. H. pylori colonization was significantly associated with histological abnormalities, mainly chronic atrophic gastritis (147) and superficial gastritis (11), while only three of 161 H. pylori positive patients had histologically normal antral mucosa. Ultrastructural examination revealed changes in the apical complex of the gastric mucosal cells in response to bacterial adhesion, with mucus depletion and cellular damage. Bacteria were also noted disrupting the tight junctions and entering the intercellular spaces. The high prevalence of H. pylori infection may explain the high incidence of gastritis, duodenal ulceration and gastric carcinoma in this population. However, in this population, the prevalence of infection in asymptomatic individuals was nearly as high as that in duodenal ulcer, underlining the need for further study to identify the differences in host response or bacterial pathogenicity that lead to the development of ulcer in only some individuals.

Epidemiology of precancerous gastric lesions

Research over the past several decades has revealed that the major subtype of gastric cancer (intestinal gastric cancer) is an end result of a multistage transformation of the gastric mucosa over many years and that this process is mainly determined by environmental factors. Epidemiologic studies on precancerous gastric lesions, including a large population-based study of the natural history and aetiology of precancerous gastric lesions conducted in Shandong, China, are reviewed.

Imprint cytology--a cheap, rapid and effective method for diagnosing Helicobacter pylori

To compare the efficacy of imprint cytology, histology and CLO-test (for biopsy urease) in detecting Helicobacter pylori infection, antral biopsies were taken from 239 patients undergoing upper gastrointestinal endoscopy. Both imprint cytology and histology showed the presence of H. pylori in 215 (90%) patients. The sensitivity and specificity of imprint cytology vis-à-vis histology was noted to be 100%. The CLO-test was performed in 165 patients and was positive in 130 (79%) patients. The sensitivity and specificity of the CLO-test were 89% and 95%, respectively. The median time required for the CLO-test to become positive and for imprint was 60 minutes for each. The sensitivity of the CLO-test was reduced further in patients receiving colloidal bismuth subcitrate. Of the 27 patients receiving the drug the sensitivity of the CLO-test was only 9% after 4 weeks of therapy. However, the specificity was 100%. The sensitivity and specificity of imprint cytology were unaffected by the antimicrobial therapy and after 4 weeks of treatment were still 100%. It is concluded that the CLO-test has a lower sensitivity and specificity for diagnosing H. pylori infection compared to imprint cytology, which had a sensitivity and specificity equal to that of histology. Imprint cytology may be prepared as an adjunct to histology in patients in whom antral biopsies are taken as it offers a relatively quick diagnosis of H. pylori infection, is considerably cheaper than the CLO-test and does not require additional biopsy material.

Gastric cancer and Helicobacter pylori infection

Gastric adenocarcinoma can be divided into two histopathological types: intestinal and diffuse. In addition to the role of environmental factors, an association between gastric cancer and Helicobacter pylori has been suggested. A retrospective study was therefore carried out among 46 patients who had gastric cancer. As a control group, 40 patients with non-malignant disorders were selected (11 patients with peptic ulcer, 12 with chronic superficial gastritis, 17 with chronic atrophic gastritis). Twenty-six cancers were classified as intestinal type and 20 as diffuse type. H. pylori was found in 23 (88 per cent) of the intestinal type and 11 (55 per cent) of the diffuse type (P < 0.05). Patients with the intestinal-type gastric cancer had a higher prevalence of H. pylori infection than those with gastric ulcer (55 per cent) and chronic superficial gastritis (50 per cent) (P < 0.05). These findings suggest that there is a possible association between the intestinal type of gastric cancer and H. pylori infection.

Changing pattern of gastric cancer in Oxfordshire

This study compares the incidence rates of histologically confirmed gastric carcinoma in Oxfordshire in two five year periods (1960-64, 1984-88). Data were available for 215 patients in the first period, and 200 in the second. The overall incidence fell from 18/100,000 to 15/100,000 but when analysed for site, the incidence of antral tumours fell from 10 to 4.5/100,000. In contrast, there was an increase from 2.8 to 5.2/100,000 of tumours of the cardia. These changes were more pronounced in men. There was a marked association between smoking and tumours of the cardia (relative risk 4.5). Helicobacter pylori was associated with 37.5% of tumours in the 1960s series compared with 25% in the later series. The changing patterns of incidence of gastric carcinoma may, in part, be related to changes in smoking habits and perhaps a change in incidence of H pylori infection.

Cloning and genetic characterization of a Helicobacter pylori flagellin gene

Helicobacter pylori produces polar sheathed flagella, which are believed to be essential for the bacterial colonization of the human gastric mucosa. Here we report on the cloning and genetic characterization of a H. pylori gene encoding the subunit of the flagellar filament, the flagellin. Screening of a genomic library of H. pylori with an oligonucleotide probe derived from the N-terminal amino acid sequence of purified flagellin resulted in a recombinant plasmid clone carrying the flagellin-encoding gene flaA on a 9.3 kb Bg/II fragment. The nucleotide sequence of flaA revealed an open reading frame of 1530 nucleotides, encoding a protein with a predicted molecular mass of 53.2 kDa, which is similar in size with the purified flagellin protein in SDS-polyacrylamide gel electrophoresis. Sequence alignment of H. pylori flagellin (FlaA) with other bacterial flagellins demonstrates a high degree of similarity in the amino-terminal and carboxy-terminal regions, including those of the closely related genus Campylobacter (56% overall identity with Campylobacter coli flaA), but little homology in the central domain. Southern hybridizations of chromosomal DNA with flaA-specific probes did not reveal the presence of additional homologous flagellin genes in H. pylori. Sequence analysis of the flaA flanking regions and mapping of the flaA mRNA start site by a primer extension experiment indicated that transcription of the gene is under the control of a sigma 28-specific promoter sequence in H. pylori. The region upstream of the flaA promoter is subject to local DNA modification, resulting in the masking of two out of three closely linked HindIII restriction sites in the chromosome of strain 898-1. Escherichia coli strains harbouring the recombinant plasmid did not produce full-length flagellin and data obtained with FlaA fusion proteins using an E. coli plasmid expression system suggest that a distinct nucleotide sequence in the gene interferes with productive translation of this protein in E. coli.

Molecular typing of Helicobacter pylori by chromosomal and plasmid DNA organization

Diverse strains of Helicobacter pylori were examined in order to initiate a molecular epidemiological typing scheme for this agent of human gastritis. Twelve differently-sized plasmids from 1.8 to 63 kbp were identified in those strains harbouring extrachromosomal DNA. Recombinant DNA probes were cloned randomly from the chromosome of the (plasmid-free) type strain (NCTC 11637), and used to probe genomic Southern blots for restriction site variation in and around homologous loci. Genus-specific probe DNAs were obtained which grouped strains on the bases of DNA base substitution or rearrangements. On the basis of the four probes examined, all strains exhibited intraspecific chromosomal divergence, indicating that H. pylori is highly diverse genetically, but nonetheless susceptible to chromosome and plasmid molecular typing.

Mechanism of gastric mucosal damage induced by ammonia

The mechanism for Helicobacter pylori-induced gastric mucosal injury remains obscure. H. pylori has high urease activity to produce ammonia from urea in the stomach. In this study, the effects of ammonia on (a) gastric mucosal integrity, (b) gastric mucosal hemodynamics, (c) mucosal cellular viability, (d) mitochondrial respiration, and (e) energy metabolism of gastric mucosal were investigated. Ammonia (pH 10.3) at concentrations of greater than 125 mmol/L caused acute macroscopic gastric mucosal lesions in a dose-dependent manner, whereas glycine-NaOH buffer (pH 10.3) or ammonium chloride (pH 4.5) did not. The decrease in energy charge preceded the occurrence of gastric mucosal lesions, but ammonia caused no change in mucosal hemodynamics. Oxygen consumption of isolated cells and mitochondria of gastric mucosa was inhibited by ammonia dose-dependently. The present results indicate that ammonia impairs mitochondrial and cellular respiration and energy metabolism and that ammonia decreases mucosal cell viability, leading subsequently to mucosal damage.

Longitudinal study of influence of Helicobacter pylori on current risk of duodenal ulcer relapse. The Hvidovre Ulcer Project Group

Seventy-four patients with duodenal ulcer were followed up longitudinally for 2 years after initial ulcer healing. Endoscopy including biopsy of the antral mucosa was performed every 3rd month and whenever clinical symptoms of relapse occurred. The presence of Helicobacter pylori in the biopsy specimens was scored as 0 (none), 1 (sporadic occurrence), 2 (clusters), and 3 (numerous bacteria found diffusely in the mucus layer). The incidence rates of ulcer relapse per patient-month, grouped in accordance with these scores, were (with 95% confidence intervals) 0.073 (0.048-0.111), 0.083 (0.052-0.133), 0.123 (0.096-0.157), and 0.069 (0.041-0.116), respectively. No significant differences in incidence rates across H. pylori scores were observed when taking into account the observation period after healing of the first ulcer, number of ulcer recurrence (1st, 2nd, 3rd), sex, age, smoking habits, peak acid output, time of healing of the preceding ulcer, treatment of the present ulcer (cimetidine, antacids, or no treatment), or type and degree of gastritis. Thus, although H. pylori is prevalent in patients with duodenal ulcer disease, the present study indicates that H. pylori does not have a substantial note in the precipitation of active duodenal ulcer.

Use of polymerase chain reaction-amplified Helicobacter pylori urease structural genes for differentiation of isolates

Helicobacter pylori has been demonstrated as an etiologic agent of human gastritis and peptic ulcer formation. However, there is no straightforward basis to distinguish different isolates. We used the polymerase chain reaction (PCR) to amplify the urease structural subunit genes, ureA and ureB, which, when digested with appropriate restriction endonucleases, allow the differentiation of patterns on agarose gels. PCR amplification was possible with DNA rapidly extracted from H. pylori by alkaline lysis and phenol-chloroform. The 2.4-kb PCR products amplified from 22 clinical isolates and subjected to HaeII restriction endonuclease digestion produced 10 distinct patterns on agarose gels, with two patterns being shared between five and six strains. PCR amplification of the urease genes may enable the differentiation of closely related H. pylori strains by restriction digest analysis of PCR-amplified ureA and ureB genes.

15NH4+ excretion test: a new method for detection of Helicobacter pylori infection

A noninvasive test for the detection of Helicobacter pylori infection that uses [15N]urea as a tracer has been established. The principle the test is based on is the strong urease activity of H. pylori. After oral ingestion, [15N]urea is broken down into ammonia and carbon dioxide by H. pylori urease in the stomach. The ammonia is absorbed into the blood and excreted in the urine. The amount of [15N]urea, reflecting the magnitude of H. pylori infection, is evaluated by measuring the abundance and excretion rate of 15N in ammonia in the urine. Thirty-six patients were examined in our study. The 15N excretion rates in urine ammonia of patients who were H. pylori positive were significantly higher than those of H. pylori-negative patients (P less than 0.05). Twenty-three patients were H. pylori positive by Gram stain and culture. The sensitivity of the 15NH4 excretion test compared with these techniques was 96%, and no false positives were obtained. The 15NH4+ excretion rates of 13 H. pylori-negative subjects were all in the normal range (less than 0.3%). This method is a simple, precise, highly sensitive, noninvasive, nonradioactive test. It could be used for diagnosis as well as for the followup of patients receiving H. pylori eradication therapy, especially children and pregnant women. It could also be used in epidemiological investigation of H. pylori infection in a general population.

Rapid detection of Helicobacter pylori in gastric biopsy material by polymerase chain reaction

By using primers based on the sequence of a species-specific antigen of Helicobacter pylori (P. O'Toole, S.M. Logan, M. Kostrzynska. T. Wadström, and T.J. Trust, J. Bacteriol. 173:505-513, 1991), a protocol was established for detection of this microorganism in gastric biopsy samples by the polymerase chain reaction (PCR). A single primer pair was used to specifically amplify a 298-bp sequence in a rapid two-step PCR. The primers exhibited the same specificity in PCR as that which we reported for the species-specific gene probe on which they were based. The sensitivity of the method was 20 copies of the target sequence, or 70 bacterial cells, under the lysis conditions used for patient-derived material. When amplification was performed for a saturating number of cycles, visual examination of ethidium bromide-stained gels successfully detected all samples subsequently judged to be positive by Southern hybridization of the gel with a probe specific for the PCR product. The bacterium could be detected in gastric biopsy samples from patients with various gastric diseases, including samples from which the bacterium could not be cultured. Only 9 of 19 patients who tested positive by PCR of gastric biopsy material were positive when a saliva sample was analyzed. Protocols for sample handling which minimized the risk of contamination while maximizing the sensitivity of the reaction were established. The results support a role for PCR in the rapid identification of H. pylori in clinical samples.

High-affinity binding of the basement membrane proteins collagen type IV and laminin to the gastric pathogen Helicobacter pylori

The ability of 16 isolates of the human gastroduodenal pathogen Helicobacter pylori to bind 125I-radiolabelled tissue proteins was quantitated by liquid-phase assay. While capable of binding generally low levels of collagen types I and II, vitronectin, and fibronectin (average binding, 8%; highest binding, 23%), the various H. pylori isolates were good binders of the basement membrane proteins collagen type IV and laminin (average binding, 27%; highest binding, 60%). Campylobacter species tested bound lower levels of collagen type IV and laminin (average binding, 12%; highest binding, 17%). Trypsin and proteinase K treatment of H. pylori cells markedly reduced the binding of collagen type IV and laminin, as did heat treatment, suggesting that the binding of basement membrane proteins is mediated by bacterial surface proteins. Binding of both basement membrane proteins was rapid and saturable. 125I-collagen type IV binding to H. pylori 915 was inhibited by preincubation with unlabelled collagen type IV but was not inhibited by laminin or a number of other proteins. Once bound, radiolabelled collagen type IV but was not displaced by an excess of unlabelled collagen type IV, indicating that the binding interaction was of high affinity. Binding of laminin was partially reversible, and analysis in a solid-phase nonradiolabel assay showed that the interaction was of high affinity, with a Kd of 7.9 nM. This interaction was affected by salt, indicating the presence of a hydrophobic component in the ability of H. pylori to bind laminin.

Macromolecular structure and aggregation states of Helicobacter pylori urease

Urease purified from Helicobacter pylori by differential ultracentrifugation and fast pressure liquid chromatography was composed of subunits with apparent molecular weights (MrS) of 66,000 and 30,000. Electron microscopy of this purified material demonstrated that it formed disc-shaped macromolecular aggregates that were approximately 13 nm in diameter and 3 nm thick. Images of both negatively stained and shadowed preparations indicated that the discs tended to stack to form pairs and then these pairs further aggregated to form four-disc stacks. This stacking of subunits explains the heterogeneity observed previously in the molecular weight of urease preparations. In some negatively stained preparations there were also some smaller (approximately 8-nm-diameter) annular units present, which may represent individual urease units or possibly an aggregate of one of the two subunits from which urease is constructed.

Helicobacter felis gastritis in gnotobiotic rats: an animal model of Helicobacter pylori gastritis

The gastric spirillum Helicobacter felis, originally isolated from the cat stomach, colonizes the stomachs of germfree rats. Studies were designed to examine the pathological and serological responses of germfree rats inoculated orally with H. felis. At 2 weeks postinoculation, the gastric mucosa of germfree rats had lymphocytes and eosinophils scattered in small foci throughout the subglandular region of the antrum. Small numbers of lymphocytes were present in the subglandular portion of the antral mucosa that focally extended through the lamina propria towards the luminal surface. Eight weeks postinoculation, the inflammation was confined to the antrum. It was characterized by increased numbers of lymphocytes and eosinophils in the subglandular areas, with focal aggregates of lymphocytes in the submucosa. Some lymphoid aggregates extended from the submucosa through the muscularis mucosa and lamina propria to the luminal surface. H. felis was demonstrated with the Warthin-Starry stain, bacterial culture, and urease assay, particularly in the antrum. H. felis also produced a significant immunoglobulin G antibody titer at 2, 4, and 8 weeks postinoculation as well as a transitory immunoglobulin M response at 2 to 4 weeks postinoculation. Contact control rats were not infected, inferring that fecal-oral spread of H. felis did not occur.

Identification, characterization, and spatial localization of two flagellin species in Helicobacter pylori flagella

Flagellar filaments were isolated from Helicobacter pylori by shearing, and flagellar proteins were further purified by a variety of techniques, including CsCl density gradient ultracentrifugation, pH 2.0 acid disassociation-neutral pH reassociation, and differential ultracentrifugation followed by molecular sieving with a Sephacryl S-500 column or Mono Q anion-exchange column, and purified to homogeneity by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transfer to an Immobilon membrane. Two flagellin species of pI 5.2 and with apparent subunit molecular weights (Mrs) of 57,000 and 56,000 were obtained. N-terminal amino acid analysis showed that the two H. pylori flagellin species were related to each other and shared sequence similarity with the N-terminal amino acid sequence of Campylobacter coli, Bacillus, Salmonella, and Caulobacter flagellins. Analysis of the amino acid composition of the predominant 56,000-Mr flagellin species isolated from two strains showed that it was comparable to the flagellins of other species. The minor 57,000-Mr flagellin species contained a higher content of proline. Immunoelectron microscopic studies with polyclonal monospecific H. pylori antiflagellin antiserum and monoclonal antibody (MAb) 72c showed that the two different-Mr flagellin species were located in different regions of the assembled flagellar filament. The minor 57,000-Mr species was located proximal to the hook, and the major 56,000-Mr flagellin composed the remainder of the filament. Western immunoblot analysis with polyclonal rabbit antisera raised against H. pylori or Campylobacter jejuni flagellins and MAb 72c showed that the 56,000-Mr flagellin carried sequences antigenetically cross-reactive with the 57,000-Mr H. pylori flagellin and the flagellins of Campylobacter species. This antigenic cross-reactivity did not extend to the flagellins of other gram-negative bacteria. The 56,000-Mr flagellin also carried H. pylori-specific sequences recognized by two additional MAbs. The epitopes for these MAbs were not surface exposed on the assembled inner flagellar filament of H. pylori but were readily detected by immunodot blot assay of sodium dodecyl sulfate-lysed cells of H. pylori, suggesting that this serological test could be a useful addition to those currently employed in the rapid identification of this important pathogen.

Is gastroduodenitis a cause of chronic dyspepsia?

The role of Helicobacter pylori infection in causing chronic dyspepsia is in need of further clarification. More well-designed prospective studies are necessary to ascertain whether and to what extent H. pylori-related chronic inflammation in the stomach and the duodenum causes dyspeptic symptoms; whether and to what extent there is a symptom cluster characteristic for H. pylori-related gastroduodenitis; whether and to what extent H. pylori infection is demonstrable in the chronic dyspeptic population; and whether and to what extent H. pylori infection interferes with gastrin homoeostasis and acid secretion or induces motor disturbances. Well-designed prospective H. pylori-eradication studies may further contribute in unravelling its role in chronic dyspepsia, especially in patients with active polymorphonuclear gastroduodenitis and hyperacidity.

Isolation and biochemical and molecular analyses of a species-specific protein antigen from the gastric pathogen Helicobacter pylori

A protein of Mr 26,000 which was present in large quantities in extracts of cells of Helicobacter pylori was purified to homogeneity by ammonium sulfate precipitation followed by gel filtration and reversed-phase chromatography or anion-exchange chromatography. The protein appeared to be associated with the soluble fraction of the cell, and antibodies raised against the protein were reactive with whole-cell lysates of a variety of H. pylori strains in a simple immunodot blot assay. This reaction was species specific. Protein sequence determination of the amino terminus and internal cyanogen bromide fragments and amino acid composition analysis were performed. An oligonucleotide derived from these data was used to clone a fragment encoding most of the coding sequence. Expression in Escherichia coli was dependent on vector promoters. The DNA sequence of the fragment was determined. DNA probes derived from the cloned fragment hybridized to genomic DNA of all H. pylori strains tested, but not to DNAs of Helicobacter mustelae, Wolinella succinogenes, various Campylobacter species, and a panel of gram-negative enteric bacteria. The apparent uniqueness of this protein may be exploited for the development of species-specific diagnostics for this gastric pathogen.

Helicobacter pylori and progressive gastric pathology that predisposes to gastric cancer

Evidence is presented suggesting that infection by Helicobacter pylori triggers and continuously contributes to the pathophysiology of progressive gastric changes that can ultimately lead to gastric cancer. In Peru, especially in population groups of low socioeconomic status, infection by H. pylori begins earlier in life and is more prevalent and persistent than in developed countries. The infection produces a destructive lesion of the mucinous surface epithelium which probably enables other aggressive luminal factors to cause further mucosal damage. As a consequence, active chronic gastritis appears. The gastritis is of the superficial type at the beginning but may progressively change to atrophic. Chronic atrophic gastritis is found more frequently and at a younger age in dyspeptic patients with low socioeconomic status--that is, in patients having higher prevalence of persistent infection by H. pylori since earlier in life. When chronic atrophic gastritis becomes severe and extensive, hypochlorhydria ensues. Hypochlorhydria favors the appearance of bacterial overgrowth, nitrites, and N-nitroso compounds in the gastric lumen. N-nitroso compounds, because of their mutagenic-carcinogenic properties, probably induce gastric premalignant lesions like intestinal metaplasia and dysplasia of the gastric mucosa. Oral bismuth therapy apparently reverses H. pylori-associated gastric dysplasia. It is proposed that future programs designed for the control of gastric cancer would be incomplete if they do not include further evaluation of the many effects of infection by H. pylori on the gastric mucosa and of cost-effective methods to eradicate the infection.

Helicobacter pylori: controversies and an approach to management

Helicobacter pylori (formerly, Campylobacter pylori) is a gram-negative, spiral-shaped bacterium with a strong affinity for gastric-type epithelium. Convincing evidence indicates that H. pylori plays an etiologic role in the development of chronic, nonspecific gastritis, and it may play an important role in the pathogenesis of duodenal ulcer disease. An etiologic role for this organism in chronic gastric ulceration, nonulcer dyspepsia, and gastric carcinoma is not established. Whereas the diagnosis of H. pylori infection is relatively straightforward, the questions of when and how to treat the infection do not have established answers. A high rate of recrudescence follows most currently used therapeutic interventions. Until the pathogenicity of H. pylori in clinical disease is further supported and additional treatment trials have been completed, a conservative management approach is recommended.

Acridine orange fluorescence, Campylobacter pylori, and chronic gastritis

Endoscopic gastric biopsy specimens from 230 consecutive patients in a North Liverpool District were histologically studied by routine light microscopy and ultraviolet fluorescence after acridine orange staining. Eighty patients with chronic gastritis were further studied with regard to type of gastritis and its activity, presence of Campylobacter pylori (CP), and degree of colonization of the gastric mucosa. Miscellaneous gastritis, gastric ulcers, erosions, neoplasms, and histologically normal specimens were excluded from the study. The results show statistically significant correlation between chronic gastritis and CP (P = 0.01, Mann-Whitney test). The activity of gastritis correlated well with CP, but there was no statistical significance between the density of neutrophils and degree of CP colonization (P greater than 0.5, Mann-Whitney test). In a small sample of CP-positive specimens acridine orange stain was compared with Warthin-Starry, Giemsa (modified), cresyl fast violet, and haematoxylin and eosin stains. Acridine orange stain in the histologic identification of CP has been used only once before in a large study.

Effect of a Campylobacter pylori protein on acid secretion by parietal cells

The uptake of [14C]-aminopyrine by rabbit gastric epithelial cells was used as an indirect assay for acid secretion from parietal cells. Campylobacter pylori strains, isolated from the stomachs of 3 patients with chronic gastritis, duodenal ulcer, and near-normal mucosa, respectively, inhibited acid secretion as effectively as 10(-4) mol/l cimetidine. The inhibition occurred with whole organisms and with sonicates. Preliminary characterisation suggested that the inhibition was due to a nondialysable protein. The inhibitor was not toxic to gastric epithelial cells. This bacterial product may explain the hypochlorhydria seen in man acutely infected with C pylori.

Touch cytology, a useful diagnostic method for diagnosis of upper gastrointestinal tract infections

Candida albicans, Campylobacter pylori, and Giardia lamblia are microorganisms that are frequently found in the upper gastrointestinal tract. A cytological smear of biopsies obtained at endoscopy was compared with the pathologic examination of biopsies. Candida albicans was found in 55 patients, Campylobacter pylori in 54, Giardia lamblia in 31; cytology was positive in 43, 46, and 22 cases, respectively, and biopsy in 29, 43, and 22 cases. Cytology was thus the only positive test in 26 cases with Candida albicans (47% of the 55 cases), in 11 cases of Campylobacter pylori (20%), and in nine cases of Giardia lamblia (29%). We believe that the cytological smear of biopsies (touch cytology) is a quick and sensitive method for diagnosing infections of the upper gastrointestinal tract, increasing the diagnostic yield obtained by biopsy alone.

Molecular cloning and expression of Campylobacter pylori species-specific antigens in Escherichia coli K-12

A gene bank of Campylobacter pylori DNA in Escherichia coli was constructed by cloning Sau3A-cleaved DNA fragments into the bacteriophage vector lambda EMBL3. The expression of C. pylori antigens was determined by screening the gene library with adsorbed C. pylori whole-cell rabbit antisera. One recombinant clone which reacted positively (lambda CP2) was studied further. Immunoblot analysis with lambda CP2 showed a polypeptide band of 66 kilodaltons (kDa) reacting antigenically with the adsorbed antiserum. Extraction of DNA from lambda CP2 and digestion with SalI revealed a DNA insert of 17 kilobases (kb). Subcloning with SalI and the E. coli vector pUC18 showed that the DNA also encoded a 31-kDa antigen. The cloned antigens were shown by immunoblotting to have the same molecular weight in E. coli as in C. pylori and to be present in all C. pylori strains. Antiserum was raised against the cloned polypeptides and found to react only with C. pylori when analyzed by dot blotting and indirect immunofluorescence. The cloned antigens were determined to be expressed from the pUC18 lac promoter. The DNA encoding these antigens was radiolabeled with 32P and found to hybridize only to C. pylori strains. Immunoblotting with affinity-purified polyclonal antibody to the urease enzyme of C. pylori revealed that the cloned antigens may be part of the urease enzyme.

The role of Campylobacter pylori in the pathogenesis of peptic ulcer disease

Most patients with peptic ulceration have chronic gastritis, which typically involves predominantly the antrum. The association between Campylobacter pylori-associated gastritis and peptic ulceration has recently been repeatedly demonstrated. Evidence is accumulating that the bacterium plays a causal role in type-B chronic gastritis. C. pylori also colonizes the duodenum when gastric metaplasia is present. It is likely that the inflamed mucosa is more susceptible to ulcerogenic influences affecting either the stomach or duodenum.

Campylobacter pylori and ulcer disease--a causal connection?

A strong positive correlation has been demonstrated between the (antral mucosal) presence of Campylobacter pylori and active duodenal and gastric ulceration. Moreover, both duodenal and gastric ulcers heal, and remain in remission, as a consequence of therapeutic measures which eradicate C. pylori. However, the Henle-Koch postulates have not been fulfilled, because C. pylori has not been shown to produce ulcers. As for the claim that ulcer disease represents an infection with C. pylori because therapeutic eradication heals ulcers, it has been shown that antibiotics and metronidazole, as well as bismuth subcitrate, exert antiulcer actions by mechanisms which do not involve their antibacterial effects. The association between C. pylori and ulcer disease, which was noted half a century ago, remains unexplained now as it did then.

Rapid diagnosis of Campylobacter pylori by brush cytology

Campylobacter pylori (CP) was demonstrated in 67.2% of 67 patients using cytology as compared to 65.7% by histology. Brush cytology is thus found to be superior to all other methods available to date for the detection of CP. It is rapid, simple, and has a high specificity.

Campylobacter pylori and gastroduodenal ulcer disease. A prospective study in a Swedish population

In a consecutive prospective series of 208 Swedish primary peptic ulcer patients, 146 gastric, 55 duodenal and 7 in both sites, gastroduodenitis was found in 97.6% of the cases. The mucosal inflammation was associated with CP in 87% and 91% of the gastric and duodenal ulcer cases respectively. No significant correlation was found between CP colonisation and the type or severity of mucosal inflammation. Gastric metaplasia was present in only 8% of 48 bulbar ulcer cases. Ulcer healing and eradication of CP was achieved in 52% of patients treated with bismuth subnitrate in combination with erythromycin or according to the triple approach.

The efficacy of antimicrobial treatment in Campylobacter pylori-associated gastritis and duodenal ulcer

The efficacy of various antimicrobial and anti-ulcer agents on the elimination of Campylobacter pylori in duodenal ulcer patients was investigated. Ranitidine, cimetidine, pirenzepine, aluminium phosphate gel as well as combinations of H2-receptor antagonists or pirenzepine + penicillin V, ciprofloxacin, ofloxacin, phenyl-mercuryborate or rifampicin had no influence on C. pylori in vivo. Short term elimination of C. pylori was achieved in 3/15 patients treated with ranitidine + bacampicillin and in 1/5 treated with cimetidine + metronidazole. This elimination was accompanied by a significant reduction of polymorphonuclear infiltration of the antral mucosa. Development of bacterial resistance was observed in patients with additional quinolones, metronidazole and rifampicin but not in patients treated with betalactam antibiotics.