Outer membrane biogenesis in Escherichia coli, Neisseria meningitidis, and Helicobacter pylori: paradigm deviations in H. pylori

The bacterial pathogen Helicobacter pylori is capable of colonizing the gastric mucosa of the human stomach using a variety of factors associated with or secreted from its outer membrane (OM). Lipopolysaccharide (LPS) and numerous OM proteins have been shown to be involved in adhesion and immune stimulation/evasion. Many of these factors are essential for colonization and/or pathogenesis in a variety of animal models. Despite this wide array of potential targets present on the bacterial surface, the ability of H. pylori to vary its OM profile limits the effectiveness of vaccines or therapeutics that target any single one of these components. However, it has become evident that the proteins comprising the complexes that transport the majority of these molecules to the OM are highly conserved and often essential. The field of membrane biogenesis has progressed remarkably in the last few years, and the possibility now exists for targeting the mechanisms by which β-barrel proteins, lipoproteins, and LPS are transported to the OM, resulting in loss of bacterial fitness and significant altering of membrane permeability. In this review, the OM transport machinery for LPS, lipoproteins, and outer membrane proteins (OMPs) are discussed. While the principal investigations of these transport mechanisms have been conducted in Escherichia coli and Neisseria meningitidis, here these systems will be presented in the genetic context of ε proteobacteria. Bioinformatic analysis reveals that minimalist genomes, such as that of Helicobacter pylori, offer insight into the smallest number of components required for these essential pathways to function. Interestingly, in the majority of ε proteobacteria, while the inner and OM associated apparatus of LPS, lipoprotein, and OMP transport pathways appear to all be intact, most of the components associated with the periplasmic compartment are either missing or are almost unrecognizable when compared to their E. coli counterparts. Eventual targeting of these pathways would have the net effect of severely limiting the delivery/transport of components to the OM and preventing the bacterium's ability to infect its human host.

Mechanism of H. pylori intracellular entry: an in vitro study

The majority of Helicobacter pylori reside on gastric epithelial cell surfaces and in the overlying mucus, but a small fraction of H. pylori enter host epithelial and immune cells. To explore the role of the nudA invasin in host cell entry, a ΔnudA deletion derivative of strain J99 was constructed and transformants were verified by PCR and by fluorescence in situ hybridization. AGS cells were inoculated with either wild type (WT) strain J99 or its ΔnudA mutant to determine the fraction of bacteria that were bound to the cells and were present inside these cells using the gentamicin protection assay. We observed no significant difference between either the density of H. pylori bound to AGS cell membranes or the density of intracellular H. pylori. To further explore this finding, separate chambers of each culture were fixed in glutaraldehyde for transmission electron microscopy (TEM) and immunogold TEM. This addition to the “classical” gentamicin assay demonstrated that there were significantly more intracellular, and fewer membrane-bound, H. pylori in WT-infected AGS cells than in ΔnudA allele infected cells. Thus, the sum of intracellular and membrane-bound H. pylori was similar in the two groups. Since no other similar TEM study has been performed, it is at present unknown whether our observations can be reproduced by others Taken together however, our observations suggest that the “classical” gentamicin protection assay is not sufficiently sensitive to analyze H. pylori cell entry and that the addition of TEM to the test demonstrates that nudA plays a role in H. pylori entry into AGS cells in vitro. In addition, deletion of the invasin gene appears to limit H. pylori to the AGS cell surface, where it may be partly protected against gentamicin. In contrast, this specific environment may render H. pylori more vulnerable to host defense and therapeutic intervention, and less prone to trigger normal immune, carcinogenic, and other developmental response pathways.

Helicobacter pylori in Iran: A systematic review on the association of genotypes and gastroduodenal diseases

BACKGROUND

Helicobacter pylori (H. pylori) infection is known as a major etiologic factor for a variety of gastroduodenal diseases. In Iran, with a high rate of H. pylori infection close to 90%, numerous studies have revealed many aspects of interaction between the bacterium, mucosal surface and induction of disease outcome. The organism is genetically diverse and several virulence factors are attributed to the more virulent strains. The well-characterized virulence factors of H. pylori are cytotoxin associated gene A and vacuolating cytotoxin gene A. The distribution pattern of H. pylori genotypes and its association with disease status varies geographically. The present review focused on the virulence factors and genotyping of H. pylori in relation to gastroduodenal disorders in different regions of Iran.

METHODS

In total, 398 studies were reported on different aspects related to H. pylori in our electronic search from 1995-2011. H. pylori infection and its virulence factors in association with disease status were investigated in 159 reports. Looking specifically at the gastrointestinal tract disorders, the most relevant reports including 37 papers were selected.

RESULTS

We found no correlation of cagA genotype and disease status in the majority of studies, whereas vacA was demonstrated as a useful marker in predicting the disease outcome. The results of reports on other virulence factors of H. pylori such as blood group antigen-binding adhesion gene A, the induced by contact with epithelium gene A, the outer inflammatory protein A, the duodenal ulcer promoting gene A, and Helicobacter outer membrane gene and their relation with disease status were contradictory.

CONCLUSIONS

Although different markers of H. pylori were emphasized as useful when predicting disease outcomes in some studies, the inconsistent researches and the scarcity of data made any conclusion or even comparison impossible. Considering the gap of information observed during our search relating to genotyping and other aspects of H. pylori infection, further investigations are suggested.

Imprint cytology: a simple, cost effectiveness analysis for diagnosing Helicobacter pylori, in west of Iran

BACKGROUND

This study was to determine the sensitivity, specificity, positive predictive value (PPV), negative predictive values (NPV) and agreement between two methods of the stained gastric imprint cytology smears and stained gastric specimen biopsy mucosal methods for detection of H. pylori.

METHODS

Air-dried imprint smears of gastric biopsies from 330 patients were stained by the Grunwald-Giemsa method in the endoscopy suite and examined for H. pylori, providing results within minutes. The grade of H pylori infection was documented. The same biopsy was processed and stained with H&E and Grunwald-Giemsa stains, and reviewed by two different pathologists blind to the imprint cytology results.

RESULTS

Ninety-four of the 238 patients were male with a mean age of 46 (±16.4) years. Based on histology, the H. pylori prevalence was very high at 77.87% and according to cytology H.Pylori prevalence was high at 75.45% in this region our country. The sensitivity and specificity of imprint cytology in the detection of H. pylori were 96.88% and 90.12%, respectively. The PPV and NPV were 96.88% and 90.12%, respectively. The agreement between two diagnostic methods was 95.26% which confirms reliability of imprint cytology method for ion of H.pylori detection.

CONCLUSION

Gastric imprint smears stained with Grunwald-Giemsa method is a rapid and cost effective method in addition to histology for detecting H. pylori in patients undergoing upper gastrointestinal endoscopy and biopsy. It does not require any additional biopsy.

Helicobacter Pylori DNA in Liver Tissues From Chronic Hepatitis C Egyptian Patients

Background

Hepatitis C virus (HCV) is considered the most common etiology of chronic liver disease in Egypt, which may progress to cirrhosis and hepatocellular carcinoma (HCC). Previous studies have documented an association between Helicobacter pylori (H. pylori) infection and liver cirrhosis with or without HCC. This study aimed to investigate the presence of H. pylori DNA in the liver tissue of Egyptian patients with chronic hepatitis C (CHC).

Methods

Fifty-two CHC Egyptian patients were enrolled in this study. Plasma anti-H. pylori IgG was assessed with ELISA. Liver biopsies were tested for presence of Helicobacter DNA using genus specific nested polymerase chain reaction (PCR) and species was identified by sequencing.

Results

Anti-H. pylori IgG was detected in 31/52 (59.6%) CHC patients while Helicobacter DNA was detected in 6 (11.5%) patients, all were H. Pylori by sequencing. Helicobacter DNA was more frequent in patients with high stage liver fibrosis (33.3%) than in those with low stage fibrosis (2.7%) (P = 0.006). There was no association between the presence of H. pylori DNA in the liver and age, gender of patients, liver function tests, AFP levels or viral load.

Conclusions

These data confirm the presence of H. pylori DNA in liver of some CHC Egyptian patients and suggest an association of this bacterium with progression of liver fibrosis.

Relation between ABO blood groups and Helicobacter pylori infection in symptomatic patients

Epidemiological studies have demonstrated higher frequencies of the O blood group and the nonsecretor phenotype of ABH antigens among patients suffering from peptic ulcers. Since Helicobacter pylori has been established as the main etiological factor in this disease, controversies about the associations of the ABO and Lewis blood group phenotypes and secretor and nonsecretor phenotypes in relation to susceptibility towards infection by this bacillus have been presented. The aim of this study was to verify the frequencies of ABO and Rhesus (Rh) blood groups in H. pylori seropositive symptomatic patients. The study included (n = 1108) patients with dyspepsia symptoms referred from an outpatient clinic in Erbil city for investigation. Age, sex, and residency were recorded as a routine laboratory framework. Patients underwent SD Bioline (Standard Diagnostics Inc, Kyonggi-do, South Korea) and enzyme-linked immunosorbent assay serologic tests for H. pylori. ABO blood group phenotypes were determined by a standard hemagglutination test. Results showed that 64.8% of patients (n = 718/1108) were seropositive for H. pylori infection, and (35.2%) (n = 390/1108) were seronegative. Of the seropositive patients, 40.8% (n = 293/718) were male and 59.2% (n = 425/718) were female; while of the seronegative patients, 46.7% (n = 182/390) were male and 53.3% (n = 208/390) were female. The mean age for seropositives and seronegatives was (38.0 ± 14.6) years and (37.6 ± 15.7) years respectively. The frequency of the ABO and Rh-positive (Rh+) blood groups among seropositive patients was (A = 32.0%, B = 19.5%, AB = 6.7%, O = 41.8%, and Rh+ = 92.5%) and was (A = 32.3%, B = 28.2%, AB = 8.0%, O = 31.5%, and Rh+ = 92.5%) in seronegatives. The results of this study suggest that ABO blood groups, age, and gender influence seropositivity for H. pylori infection.

Helicobacter pylori bab genes during chronic colonization

Helicobacter pylori BabA adhesin metastability could yield variants with potential for periodic activation and deactivation of their mediated adherence. babA/B or babB/A chimeras could play an important role in translational regulation. We investigated the frequency of different bab gene profiles in paired isolates from antrum and corpus recovered from patients with chronic gastritis. Isolates from 174 biopsies from 34 patients were included, and bab genes at the three common chromosomal loci were investigated. Inter-micro-niche variation was found in 1/4 patients, counting duplicate copies of babA or babB, babB/A or babA/B chimeras, opposite location of babA and babB or babC and babB, and absence of babB ATG translational codon. Truncated BabA was identified in 2/34 patients without inter-micro-niche variation. Isolates from 12/34 patients harbored babA/B or babB/A chimeras -either in one, several or all micro-niches indicating that chimera formation is a common mechanism to control BabA expression. To note, babA gene was absent in 11/34 patients, and in this population, babA/B chimeras which lack expression predominated over babB/A, able to exhibit Le(b) binding phenotype.

Prevention of Gastric Cancer: When is Treatment of Helicobacter Pylori Warranted?

Chronic gastritis induced by Helicobacter pylori (H. pylori) is the strongest known risk factor for adenocarcinoma of the distal stomach, yet the effects of bacterial eradication on carcinogenesis remain unclear. H. pylori isolates possess substantial genotypic diversity, which engenders differential host inflammatory responses that influence clinical outcome. H. pylori strains that possess the cag pathogenicity island and secrete a functional cytotoxin induce more severe gastric injury and further augment the risk for developing distal gastric cancer. Carcinogenesis is also influenced by host genetic diversity, particularly involving immune response genes such as interleukin-1ß and tumor necrosis factor-α. Human trials and anima studies have indicated that eradication of H. pylori prior to the development of atrophic gastritis offers the best chance for prevention of gastric cancer. However, although the timing of intervention influences the magnitude of suppression of premalignant and neoplastic lesions, bacterial eradication, even in longstanding infections, is of clear benefit to the host. It is important to gain insight into the pathogenesis of H. pylori-induced gastritis and adenocarcinoma not only to develop more effective treatments for gastric cancer, but also because it might serve as a paradigm for the role of chronic inflammation in the genesis of other malignancies that arise within the gastrointestinal tract.

Genetic Polymorphisms of Molecules Associated with Innate Immune Responses, TRL2 and MBL2 Genes in Japanese Subjects with Functional Dyspepsia

Inflammatory changes in the gastric mucosa are commonly observed in Japanese patients with functional dyspepsia (FD). However, detailed data regarding the possible association between the genetic factors of inflammation related molecules and FD are not available. Toll like receptor 2 (TLR2) and mannan-binding lectin (MBL) protein play important roles in the innate immune activation. We aimed to clarify the association between common polymorphisms of TLR2 and MBL2 genes with FD in Japanese subjects. TLR2 −196 to −174 del and MBL2 codon54 G/A polymorphisms were genotyped in 111 FD patients according to Rome III criteria and 106 asymptomatic controls. Non-significant correlation was found between TLR2 and MBL2 polymorphisms with FD. However, in Helicobacter pylori (H. pylori) positives, we found significant inverse association between TLR2 −196 to −174 del carrier and FD among H. pylori positive subjects (Adjusted odds ratio (OR) = 0.48, 95% confidence interval (CI) = 0.23–0.996, p = 0.0488). We also found significant inverse association between the same genotype with postprandial distress syndrome (PDS) among H. pylori positive subjects (Adjusted OR = 0.22, 95% CI = 0.07–0.69, p = 0.0099). Our data suggest that TLR2 −196 to −174 del carriers’s status but not MBL2 codon54 G/A is inversely related to the risk with FD in H. pylori-infected subjects.

H. pylori-Eradication Therapy Increases RUNX3 Expression in the Glandular Epithelial Cells in Enlarged-Fold Gastritis

Helicobacter pylori (HP)-eradication therapy increases Runt domain transcription factor 3 (RUNX3) expression in the glandular epithelial cells in enlarged-fold gastritis. The aim of this study is to evaluate expression of the RUNX3 protein, the product of a gastric tumor suppression gene, and mutagenic oxidative stress in human gastric mucosal specimens obtained from patients with HP-induced enlarged-fold gastritis. Methods. RUNX3 expression was immunohistochemically scored and the degree of the mucosal oxidative stress was directly measured by the chemiluminescense (ChL) assay in the biopsy specimens. Results. RUNX3 expression was detected in the gastric epithelial cells. HP-eradication significantly increased RUNX3 expression in the glandular epithelium of the corpus, however, no change was observed in those of the antrum. A fourfold higher mucosal ChL value was observed in the corpus as compared with that in the antrum. HP-eradication significantly decreased the mucosal ChL values in both portions of the stomach to nearly undetectable levels. Conclusion. The glandular epithelium is exposed to a high level of carcinogenic oxidative stress and shows low levels of expression of the tumor suppressive molecule, RUNX3; however, this expression was restored after HP-eradication, suggesting the high risk of carcinogenesis associated with HP-induced enlarged-fold gastritis of the corpus.

Helicobacter pylori: prevalence and relationship with abdominal pain in school children in Makkah City, western Saudi Arabia

BACKGROUND/AIM

The published data on Helicobacter pylori (H. pylori) prevalence and its relationship with abdominal pain in Saudi Arabia is scarce. This study was carried out to determine the prevalence of H. pylori and its relationship with chronic recurrent abdominal pain (RAP) among school students in Makkah City, Saudi Arabia.

MATERIALS AND METHODS

Three hundred and fourteen school students, 103 at the intermediate level (grades 7-9) aged 12-15 years and 211 at the secondary level (grades 10-12) aged 15-18 years were tested for H. pylori. Urea breath test (UBT) was used for this purpose. Children with chronic RAP were identified as per the Apley criteria.

RESULTS

Overall, the UBT was positive in 86/314 (27.4%) students. It was positive in 45/103 (43.7%) intermediate school students and 41/211 (19.4%) secondary students. Out of the 55 students with chronic RAP, 40 (73%) were positive for H. pylori. Further, 62.9% and 82.1% were positive among the intermediate and secondary school students with RAP, respectively. The overall and specific odds ratios of RAP were 12.35 [95% confidence interval (C.I.) 6.30-24.22] and 10.40 (95% C.I. 1.75-11.73) for the intermediate school students and 22.69 (95% C.I. 7.99-64.44) for the secondary school students.

CONCLUSION

The prevalence of H. pylori among the school children in Makkah, Saudi Arabia, is relatively low compared with developing countries. The prevalence was found to be higher among the younger age group. Further, there was a significant relation between H. pylori infection and RAP among the school students.

A study of Helicobacter pylori-associated gastritis patterns in Iraq and their association with strain virulence

BACKGROUND/AIM

Helicobacter pylori (H. pylori) infection causes peptic ulceration and gastric adenocarcinoma. In Iraq, gastric cancer is rare. We investigated whether infected adults had the antral-predominant pattern of H. pylori-associated gastritis, which does not predispose to cancer.

MATERIALS AND METHODS

We evaluated histopathological changes by the Sydney scoring system in gastric biopsies taken from 30 H. pylori-infected adults and studied the correlation of these changes with the virulence factors. The Mann-Whitney test was used for the comparison of histopathological data. The presence or absence of each pathological index was evaluated with respect to the possession of virulence factors by the infecting H. pylori strain using the chi(2) test.

RESULTS

Gastric lymphocyte infiltration was more prominent in the antrum (P = 0.01). Neutrophil infiltration was mild and gastric mucosal atrophy was rare. No relationship was found between virulence factors and histopathological changes.

CONCLUSIONS

The mild pathology and antral-predominant gastritis help explain the low cancer rate in Iraq.

In-vitro antimicrobial activity of selected honeys on clinical isolates of Helicobacter pylori

BACKGROUND

Helicobacter pylori is a gram-negative bacterium incriminated in gastroduodenal ulcers, and mucosa-associated lymphoid tissue lymphoma imposing a major burden on health care systems worldwide. Honeys have been shown to have in vitro activity against microorganisms and suitable for use in ulcers, infected wounds and burns.

OBJECTIVE

The study was aimed at evaluating the antimicrobial potential of honeys (Manuka™, Capillano®, Eco- and Mountain) at different concentrations (10%v/v, 20%v/v, 50%v/v and 75%v/v) against clinical isolates of H. pylori.

METHODS

H. pylori was isolated from gastric biopsies of patients with gastroduodenal pathologies following standard microbiological procedures. Antimicrobial susceptibility of the isolates to different honey varieties was determined by the disk diffusion assay. Also, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the most potent honey was determined by the agar dilution method. Data were analysed using the Fisher exact test and statistical significance considered at p<0.05.

RESULTS

All the four honey varieties exhibited antibacterial activity. The strongest inhibitory activity (82.22%) was demonstrated by Mountain honey at 75%v/v, followed by Capillano® and Manuka™ honeys (75.56%), and Eco-honey (73.36%) at the same concentration. However, no statistically significant difference (p>0.05) was noted between the honeys at different concentrations. The MIC and MBC concentrations of Mountain honey were in the range 0.117 - 0.938ì/mL and 0.366 - 2.965ìg/mL respectively. The antimicrobial potential of these honeys at different concentrations were highly comparable to clarithromycin, the positive control.

CONCLUSION

These honeys may contain compounds with therapeutic potential against our local isolates of H. pylori.

The antibacterial activity of honey on helicobacter pylori

OBJECTIVE

This project aimed to assess the antibacterial potential of various brands of honey sold in Muscat area on some isolates of H. pylori and to determine if there is any synergy between honey and amoxycillin or clarithromycin used in the treatment of H. pylori gastritis and duodenal ulcer.

METHODS

Eight samples of commercial honey were used in the experiment after they were checked for purity by sub-culturing on blood agar and incubating for 48 hours at 37°c. Honey samples showing gross contamination were discarded. Purified culture isolates of H. pylori from our laboratory stock cultures were swabbed on chocolate plate using 1x 10(4) cfu/ml. One hundred microlitres (100μl) of various honey samples were placed on each plate which was subsequently incubated microaerophilically at 37ºc for 3 days. The presence or absence of growth inhibition zones on each plate was noted and an average zone size of each honey was taken. Honey samples with high zone sizes were further diluted from 1:2-1:8 to find the end-points of their growth inhibition concentrations and the experiment was repeated in triplicates. The synergistic effect between honey, amoxycillin and clarithromycin was done in triplicates by placing honey at various distances between each antibiotic after swabbing chocolate agar with 1x 10(4) cfu/ml of H. pylori. The plates were incubated as before.

RESULTS

All honey samples produced growth inhibition zones with H. pylori no at dilution of honey but had different zone sizes at 1:2-1:8 dilutions. Black Forest honey had the highest antibacterial activity followed by Langnese honey. None of the honeys had a synergistic effect with either clarithromycin or amoxycillin.

CONCLUSION

We conclude that, in vitro, some honey brands possess antibacterial activity against H. pylori and that no synergy or antagonism was observed between honey and clarithromycin or honey and amoxicillin using H. pylori as a test organism. Though no synergy or antagonism was observed between honey, amoxicillin or clarithromycin, it has been suggested that the use of honey with triple therapy regimen may help shorten the time required to eliminate H. pylori from stomach lining of patients with gastritis or duodenal ulcer caused by H. pylori infection.

Incidence of Helicobacter Pylori Infections and Therapy for Anastomotic ulcers and Residual Gastritis in Patients with Residual Stomachs

Seventy-seven patients with the vestibular portion of their stomachs resected (residual stomach) due to ulcers or stomach cancers were included in this study. Fifty-five (71.4%) of these patients had Helicobacter pylori infections. H. pylori was found in all patients with stomach cancer, esophageal cancer, or esophageal venous varicosity, and in 86.7% of patients with esophagitis, 78.6% with residual gastritis, 70.0% with anastomotic ulcers, and in 51.6% of patients with normal mucosa in their resected stomachs. The in vitro antibacterial activities of amoxicillin, erythromycin, clarithromycin, minocycline, nalidixic acid, ofloxacin, lansoprazole, and omeprazole were determined against 10 clinical isolates of H. pylori. All agents except ofloxacin, nalidixic acid and omeprazole showed satisfactory bactericidal activities. The clinical and bacteriological efficacies of a combined treatment regimen with lansoprazole and clarithromycin were evaluated in 10 patients with anastomotic ulcers and 6 patients with residual stomach inflammation after informed consent. The clinical efficacy of this treatment in these 16 patients was excellent for 3 patients, good for 12 patients, and fair for the other patient. Collectively, the treatment was effective in 15/16 (93.8%) of patients. The bacteriological efficacy of this treatment regimen was evaluated in 14 patients, with no evidence of H. pylori 13 (92.9%) patients.