Detection of Helicobacter pylori in gastric biopsy tissue by polymerase chain reaction

A Newly Developed Nested PCR Assay for the Detection of Helicobacter pylori in the Oral Cavity

GOALS

To develop a new nested polymerase chain reaction (PCR) assay for identifying Helicobacter pylori DNA from dental plaque.

BACKGROUND

H. pylori is one of the most common chronic bacterial pathogens in humans. The accurate detection of this organism is essential for proper patient management and for the eradication of the bacteria following treatment.

STUDY

Forty-nine patients (24 males and 25 females; mean age: 51; range, 19 to 94 y) were investigated for the presence of H. pylori in dental plaque by single-step PCR and nested PCR and in the stomach by single-step PCR, nested PCR, and histologic examination.

RESULTS

The newly developed nested PCR assay identified H. pylori DNA in gastric biopsies of 18 patients who were histologically classified as H. pylori-positive and 2 additional biopsies of patients who were H. pylori-negative by histologic examination (20/49; 40.8%). Dental plaque samples collected before and after endoscopy from the 49 patients revealed that single-step PCR did not detect H. pylori but nested PCR was able to detect H. pylori DNA in 40.8% (20/49) patients. Nested PCR gave a higher detection rate (40.8%, 20/49) than that of histology (36.7%, 18/49) and single-step PCR. When nested PCR results were compared with histology results there was no significant difference between the 2 methods.

CONCLUSIONS

Our newly developed nested PCR assay is at least as sensitive as histology and may be useful for H. pylori detection in patients unfit for endoscopic examination.

Diagnosis of Helicobacter pylori: What should be the gold standard?

Since the discovery of Helicobacter pylori (H. pylori) in 1983, numerous detection methods for the presence of the bacterium have been developed. Each one of them has been associated with advantages and disadvantages. Noninvasive tests such as serology, ¹³C urea breath test (UBT) and stool antigen tests are usually preferred by the clinicians. Serology has its own limitation especially in endemic areas while ¹³C UBT is technically very demanding. The stool antigen detection method, although specific, is usually associated with poor sensitivity. The ¹³C UBT is believed to be specific, but with present revelation of the fact that stomach is colonized by many other urease producing bacteria makes it questionable. Histology, culture, rapid urease test and polymerase chain reaction (PCR) are the tests which are carried out on antral biopsies collected by invasive means. Histology has been proposed to be very sensitive and specific but the question is how by simply looking the morphology of the bacteria in the microscope, one can claim that the curved bacterium is exclusively H. pylori. Rapid urease test (RUT), the doctor’s test, is also challenged because the presence of other urease producing bacteria in the stomach cannot be denied. Moreover, RUT has been reported with poor sensitivity specially, when density of the bacterium is low. Isolation of H. pylori is essential to investigate its growth requirements, antibiotic susceptibility testing, studying virulence factor to develop vaccine and many more explorations. It has also got several disadvantages i.e., special condition for transporting, media, incubation and few days waiting for the colonies to appear, apart from the speed essentially needed to process the specimens. Till date, majority of the microbiological laboratories in the world are not equipped and trained to isolate such fastidious bacterium. The option left is PCR methods to detect H. pylori’s DNA in gastric mucosa, gastric juice, saliva, dental plaques and environmental specimens. There are speculations for false positivity due to detection of non-pylori Helicobacters due to genetic sharing; and false negativity due to low bacterial counts and presence of PCR inhibitors. However, specimen collection, transportation and processing do not require speed and special conditions. PCR based diagnosis may be considered as gold standard by designing primers extremely specific to H. pylori and targeting at least more than one conserved genes. Similarly specificity of PCR may be improved by use of internal Primers. Further, nested PCR will take care of false negatives by countering the effect of PCR inhibitors and low bacterial counts. Therefore, nested PCR based methods if performed properly, may be proposed as gold standard test.

Sitafloxacin-based third-line rescue regimens for Helicobacter pylori infection in Japan

BACKGROUNDS

Quinolone-based regimens have been used as the rescue for eradication of Helicobacter pylori. Sitafloxacin is known to have low minimum inhibitory concentration for H. pylori. Here, we compared two sitafloxacin-based eradication regimens as rescue for the eradication of H. pylori.

METHODS

We attempted to eradicate H. pylori in 180 Japanese patients who had never failed in eradication of H. pylori with the triple proton pump inhibitor/amoxicillin/clarithromycin therapy (1st line) and the triple proton pump inhibitor/amoxicillin/metronidazole therapy (2nd line). They were assigned to either the triple therapy with rabeprazole 10 mg b.i.d./q.i.d., amoxicillin 500 mg q.i.d, and sitafloxacin 100 mg b.i.d. (RAS) for 1 or 2 weeks or the triple therapy with rabeprazole 10 mg b.i.d./q.i.d., metronidazole 250 mg b.i.d., and sitafloxacin 100 mg b.i.d. (RMS) for 1 or 2 weeks. Eradication was assessed via the (13) C-urea breath test and rapid urease test.

RESULTS

Intention-to-treat and per-protocol analyses of eradication rates were 84.1% (37/44) and 86.4% (37/43) with RAS for 1 week, 88.9% (40/45) and 90.9% (40/44) for RAS for 2 weeks, 90.9% (40/44) and 90.9% (40/44) for 1 week-RMS and 87.2% (41/47) and 91.1% (41/45) with RMS for 2 weeks. We noted no statistical significant differences in eradication rates among four regimens.

CONCLUSION

All of the above-described rescue regimens proved relatively equally useful in the eradication of H. pylori. Of them, RAS for 2 weeks and RMS for 1 or 2 weeks could attain the rescue eradication rates higher than 90% by per-protocol analysis.

VCP phosphorylation-dependent interaction partners prevent apoptosis in Helicobacter pylori-infected gastric epithelial cells

Previous studies have demonstrated that valosin-containing protein (VCP) is associated with H. pylori-induced gastric carcinogenesis. By identifying the interactome of VCP overexpressed in AGS cells using a subtractive proteomics approach, we aimed to characterize the cellular responses mediated by VCP and its functional roles in H. pylori-associated gastric cancer. VCP immunoprecipitations followed by proteomic analysis identified 288 putative interacting proteins, 18 VCP-binding proteins belonged to the PI3K/Akt signaling pathway. H. pylori infection increased the interaction between Akt and VCP, Akt-dependent phosphorylation of VCP, levels of ubiquitinated proteins, and aggresome formation in AGS cells. Furthermore, phosphorylated VCP co-localized with the aggresome, bound ubiquitinated proteins, and increased the degradation of cellular regulators to protect H. pylori-infected AGS cells from apoptosis. Our study demonstrates that VCP phosphorylation following H. pylori infection promotes both gastric epithelial cell survival, mediated by the PI3K/Akt pathway, and the degradation of cellular regulators. These findings provide novel insights into the mechanisms of H. pylori infection induced gastric carcinogenesis.

Helicobacter pylori virulence genes detected by string PCR in children from an urban community in northeastern Brazil

The accuracy of a nested PCR in gastric DNA obtained by a string test for the diagnosis of Helicobacter pylori infection in asymptomatic children was 94.0%. The cagA-positive toxigenic vacAs1m1 strains were the most prevalent strains, indicating that this population is colonized early by the strains associated with gastric cancer.

Absence ofHelicobacter pyloriin healthy laryngeal mucosa

Objectives:

To evaluate the presence ofHelicobacter pyloriin healthy laryngeal mucosa.

Design:

Prospective analysis ofHelicobacter pyloricolonisation in healthy laryngeal mucosa, using the13C urea breath test and polymerase chain reaction analysis.

Subjects:

Twenty randomly chosen men (28–78 years) without laryngeal pathology or gastrointestinal disease were investigated. All subjects were scheduled for elective operative procedures, under general, endotracheal anaesthesia. Cytobrush samples were taken forHelicobacter pyloriDNA detection. Nested polymerase chain reaction testing was performed on DNA solutions using two primer pairs from the urease A gene of theHelicobacter pylorigenome. The13C urea breath test was performed on two exhalation samples.

Results:

Eight (40 per cent) of the subjects were positive for urease on urea breath testing; none were positive forHelicobacter pyloriDNA on polymerase chain reaction testing.

Conclusion:

Based on these results, we do not considerHelicobacter pylorito be a normal constituent of healthy laryngeal microflora.

Helicobacter pylori transiently in the mouth may participate in the transmission of infection

Helicobacter pylori infection is associated with peptic ulcer and gastric carcinoma. The oral cavity may be a reservoir for H. pylori; however, the results of studies on this subject are controversial. We employed single-step and nested polymerase chain reactions (PCR) to detect the presence of the vacA, ureA and 16S rDNA genes of H. pylori in the stomach, saliva and dental plaque of 30 subjects. The results were confirmed by sequencing. Nested 16S rDNA and ureA amplification was achieved in 80% of gastric, 30% of saliva and 20% of dental plaque specimens. Sequencing of 10, seven and four 16S rDNA products from stomach, saliva and dental plaque, respectively, showed > 99% identity with H. pylori. Sequencing of the other four oral cavity PCR products showed similarity with Campylobacter and Wolinella species. Additionally, the vacA genotype identified in the samples of different sites was the same within a given subject.H. pylori may be found in the oral cavity of patients with gastric infection, thus it could be a source of transmission. However, results obtained with detection methods based only on PCR should be interpreted with caution because other microorganisms that are phylogenetically very close to H. pylori are also present in the mouth.

Molecular identification of Helicobacter DNA in human gastric adenocarcinoma tissues using Helicobacter species-specific 16S rRNA PCR amplification and pyrosequencing analysis

Helicobacter pylori (H. pylori) is a microaerophilic gram-negative bacterium known to be associated with chronic gastritis, peptic ulcer and gastric adenocarcinoma. In the present study, the presence of Helicobacter DNA was investigated using a Helicobacter species-specific 16S rRNA PCR amplification and pyrosequencing analysis in 51 resected gastric adenocarcinomas. DNA was extracted from paraffin-embedded tissues of resected gastric adenocarcinomas. PCR primers were designed to amplify the 133-bp PCR fragment in highly conserved regions of the 16S rRNA gene. The sequence of the PCR products was analyzed using a PSQ 96 system with SQA software. The pyrosequencing analysis of 16S rRNA showed that H. pylori was present in 47 (92.2%) of the 51 gastric adenocarcinomas. In the 4 H. pylori-negative cases, Helicobacter cinaedi (2 cases), Helicobacter mustelae (1 case) and Campylobacter hyointestinalis (1 case) were detected. Pyrosequencing technology was useful in the identification and differentiation of H. pylori from other species by analyzing the gene encoding 16S rRNA. Gastric adenocarcinoma tissues contain bacteria, and the majority are H. pylori. Helicobacter cinaedi, Helicobacter mustelae and Campylobacter hyointestinalis rarely occur. The roles of these organisms in the pathogenesis of gastric adenocarcinoma remain unclear.

Effective prevention and treatment of Helicobacter pylori infection using a combination of catechins and sialic acid in AGS cells and BALB/c mice

The increasing emergence of Helicobacter pylori strains resistant to antibiotics may cause unsuccessful treatment. An alternative agent or mixture with anti-H. pylori effect is urgently required to reduce H. pylori infection. We explored the preventive and therapeutic potential of a combination of catechins and sialic acid on H. pylori-infected human gastric cells in vitro and in mice in vivo. We evaluated the anti-H. pylori activity of catechins and/or sialic acid using the agar dilution and checkerboard methods. The effect of catechins and/or sialic acid on H. pylori infection-induced oxidative stress and apoptosis/autophagy in cell culture was explored using an ultrasensitive chemiluminescence analyzer, immunocytochemistry, and Western blotting. Specific pathogen-free BALB/c mice were divided into uninfected control, infected control, pretreated, and post-treated groups. The effects of catechins/sialic acid were determined by histology and immunocytochemistry. The combination of catechins and sialic acid showed synergistic or additive anti-H. pylori activity and significantly reduced inducible nitric oxide synthase expression and Bax/Bcl-2-mediated apoptosis but enhanced Beclin-1-mediated autophagy. All mice infected with H. pylori displayed gastritis and accumulation of 3-nitrotyrosine and 4-hydroxynonenal. Pretreatment with catechins/sialic acid completely prevented H. pylori infection and resulted in normal histology. Post-treatment with catechins/sialic acid decreased the bacterial load and gastritis score and eradicated up to 60% of H. pylori infections in a dose-dependent manner. This is the first demonstration to our knowledge of a nonprobiotic, nonantibiotic treatment that is 100% effective in preventing and has promising possibilities for treating H. pylori infection. Further studies are needed to confirm this result in humans.

Prevalence of virulence-associated genotypes of Helicobacter pylori and correlation with severity of gastric pathology in patients from western Sicily, Italy

In a bacterium like Helicobacter pylori, which is characterized by a recombinant population structure, the associated presence of genes encoding virulence factors might be considered an expression of a selective advantage conferred to strains with certain genotypes and, therefore, a potentially useful tool for predicting the clinical outcome of infections. However, differences in the geographical and ethnic prevalence of the H. pylori virulence-associated genotypes can affect their clinical predictive value and need to be considered in advance. In this study we carried out such an evaluation in a group of patients living in Sicily, the largest and most populous island in the Mediterranean Sea. cagA, vacA, babA2, hopQ, oipA, sabA, and hopZ were the H. pylori virulence-associated genes assayed; their presence, expression status or allelic homologs were detected in H. pylori DNA samples and/or isolated strains, obtained by gastric biopsy from 90 Sicilian patients with chronic gastritis, inactive (n = 37), active (n = 26), or active with peptic ulcer (n = 27). Genotypes cagA (+), vacAs1, vacAm1, babA2 (+), and hopQ I, I/II were identified in 51.8, 80.4, 35.2, 47.3, and 67.7% of the different samples respectively. Only these genotypes were associated with each other and with the active form of chronic gastritis, irrespective of the presence of a peptic ulcer. In our isolates their prevalence was more similar to values observed in the north of Italy and France than to those observed in Spain or other Mediterranean countries that are closer and climatically more similar to western Sicily.

Helicobacter pylori detection and antimicrobial susceptibility testing

The discovery of Helicobacter pylori in 1982 was the starting point of a revolution concerning the concepts and management of gastroduodenal diseases. It is now well accepted that the most common stomach disease, peptic ulcer disease, is an infectious disease, and all consensus conferences agree that the causative agent, H. pylori, must be treated with antibiotics. Furthermore, the concept emerged that this bacterium could be the trigger of various malignant diseases of the stomach, and it is now a model for chronic bacterial infections causing cancer. Most of the many different techniques involved in diagnosis of H. pylori infection are performed in clinical microbiology laboratories. The aim of this article is to review the current status of these methods and their application, highlighting the important progress which has been made in the past decade. Both invasive and noninvasive techniques will be reviewed.

Isolation of Helicobacter pylori from the intestinal mucosa of patients with Crohn's disease

BACKGROUND

Helicobacter species are associated with inflammatory bowel disease in rodents and in nonhuman primates. Therefore, we prospectively investigated the presence of Helicobacter species in the intestinal mucosa of patients with and without Crohn's disease by culture and polymerase chain reaction (PCR) assays.

MATERIALS AND METHODS

Mucosal fragments were obtained from the ileum, different colon regions, and rectum of 43 patients with Crohn's disease and of 74 patients without inflammatory bowel disease.

RESULTS

Helicobacter pylori strains, identified by 16S rRNA gene sequencing, were more frequently isolated and PCR-detected in the intestinal mucosa of patients with ulcerative colitis-like Crohn's disease than in intestinal mucosa of the control group. Otherwise, anti-H. pylori immunoglobulin G levels were significantly lower in fibrostenosing and fistulating Crohn's disease subgroups. No other Helicobacter species were found in the intestinal mucosa of the patients.

CONCLUSIONS

Although our results suggest an association between the presence of H. pylori in the intestine and ulcerative colitis-like phenotype of Crohn's disease, H. pylori infection in the actual causality of Crohn's disease is still to be determined.

Helicobacter species in the intestinal mucosa of patients with ulcerative colitis

In a search for Helicobacter species in the intestinal mucosae of 42 patients with ulcerative colitis (UC) and 74 without UC, only H. pylori was found. Although the bacterium was detected in UC patients by culture (7.1%) and nested PCR (19.0%), its presence was not associated with the disease (P = 0.13).

Infection with cagA-positive and cagA-negative types of Helicobacter pylori among children and adolescents with gastrointestinal symptoms in Latvia

In order to determine the prevalence of concomitant cagA-positive and cagA-negative Helicobacter pylori genotypes in individual subjects, a group of 56 symptomatic patients (aged 8-18 years) was studied. Among 31 patients culture-positive for Helicobacter pylori, only cagA-positive colonies were isolated from 18 patients, both cagA-positive and cagA-negative genotypes were isolated from 4 patients, and in 9 patients all of the individual colonies isolated were cagA-negative, but in seven of them a pool of colonies was positive for cagA. Thus, the presence of both cagA-positive and cagA-negative genotypes in the same individual was identified in 11 of the 31 culture-positive patients tested, and most of the patients predominantly colonized by cagA-negative strains also harbored a small amount of cagA-positive strains. Previous or current infection with cagA-positive strains of Helicobacter pylori was observed in 50 of the 56 patients studied.

Detection of Helicobacter pylori in gastric mucosa of patients with gastroduodenal diseases by PCR-restriction analysis using the RNA polymerase gene (rpoB)

A novel PCR restriction analysis method using the RNA polymerase beta-subunit- coding gene (rpoB) was employed to both detect and identify Helicobacter pylori in biopsy specimens and culture isolates. The rpoB DNAs (458 bp) were specifically amplified by PCR with the Helicobacter-specific primers (HF and HR). Based on the determined rpoB sequences of the culture isolates, an H. pylori-specific restriction site, Tru9I, was found. H. pylori can be identified by observing two discernible DNA fragments (288 and 138 bp) after Tru9I digestion and agarose gel electrophoresis. The rpoB PCR and subsequent restriction analysis (PRA) enabled the specific detection and identification of H. pylori in biopsy specimens from patients with gastroduodenal diseases. The rpoB PRA conferred a compatible or a slightly higher positive rate (53.7%) than did the Campylobacter-like organism (CLO) test (50.4%) and glmM PCR (48.8%), suggesting that it is useful for diagnosing an H. pylori infection without culture in the clinical laboratory.

Real-time quantitative PCR for detection of Helicobacter pylori

Helicobacter pylori is one of the most common chronic infections in humans, in whom it is a key etiological factor in peptic ulcer disease, gastric mucosa-associated lymphoid tissue lymphoma, and gastric adenocarcinoma. Humans are the bacterium's only host. Here we report the development of a real-time quantitative (Q) PCR-based assay to measure ureC gene copy number to detect H. pylori, based on the fact that there is only one copy of the ureC gene per bacterium. Upon optimization of LightCycler Q-PCR conditions, we obtained a standard curve with a linear range (correlation coefficient = 1) across six logs of DNA concentration. We were able to accurately quantify as few as 1,000 bacteria in our assay. Analysis of variance on 15 randomly selected clinical samples showed good reproducibility of this assay. Comparison of Q-PCR results with bacterial culture and histopathological results from an additional 85 clinical biopsy samples showed a significant difference for the presence of H. pylori. Many samples that were negative for H. pylori by culture and histopathology were positive by Q-PCR. Contamination of PCR by H. pylori or H. pylori genetic material could not be ruled out. In summary, we developed a rapid, sensitive, and real-time Q-PCR method for detecting H. pylori. This technique offers a significant improvement over other available methods for detecting H. pylori in clinical and research samples.

The evaluation of diagnostic methods for the detection of Helicobacter pylori in gastric biopsy specimens

PCR is a rapid, sensitive and accurate method for the specific detection of Helicobacter pylori from gastric biopsy specimens. In our study, 104 gastric tissue specimens from symptomatic adult patients were examined by staining, culture, PCR and nested PCR methods for detection of H. pylori. According to our results, positivity was achieved in 24% (25/104) with Giemsa staining, 34% (36/104) with histopathology, 36% (38/104) with PCR and 41% (43/104) with nested PCR respectively, whereas H. pylori was isolated in only 33% (35/104) of the cultures on the biopsy specimens. Both the sensitivity and the positive predictive value of the nested PCR method were 100%, and both the specificity and negative predictive value were 98%. As a conclusion, our results suggest the nested PCR as a highly valuable method in the detection of H. pylori with a reasonably high sensitivity and specificity.

Demonstration of Chlamydia pneumoniae in atherosclerotic arteries from various vascular regions

Chlamydia pneumoniae (CP) has been reported to be a pathogenic agent in the mechanism leading to atherosclerosis. The majority of available data is focused mainly on coronary artery disease whereas the distribution of CP in different areas, associated with atherosclerotic disorders, has not been completely clarified. In this study we investigated the presence of CP in atheromasic plaques from five different vascular areas (basilary artery, coronary artery, thoracic aorta, abdominal aorta, renal arteries) using nested polymerase chain reaction (PCR) and immunohistochemical staining (IHC), in order to establish the putative association of CP with atherosclerotic disease. The same atheromasic plaques were also tested for the presence of Helicobacter pylori (HP) and cytomegalovirus (CMV), other putative agents of atherosclerosis, using a nested PCR technique. Our data indicate that the presence of CP can be demonstrated in 100% of patients tested, considering globally the five areas of analysis. On the other hand the presence of HP has been demonstrated in four out of 18 patients (22.2%), and CMV only in three out of 18 (16.6%). Our results strongly suggest an association between CP and atherosclerosis and highlight the need for the detection of CP in multiple vascular areas of the same patient.

Chlamydia pneumoniae detection in atherosclerotic plaques in Italy

Italian investigations have shown an association between Chlamydia pneumoniae infection and atherosclerosis. With the use of several diagnostic techniques, including serology, a microimmunofluorescence test, and nucleic acid amplification methods, a temporal association was found between acute C. pneumoniae reinfection and acute myocardial infarction, suggesting that an acute infection superimposed on a chronic or latent infection may trigger the onset of acute myocardial infarction. C. pneumoniae but not Helicobacter pylori or Mycoplasma pneumoniae was found in atherosclerotic plaques of abdominal aortic aneurysms and the carotid artery. A reverse transcriptase-polymerase chain reaction process confirmed the presence of viable C. pneumoniae in carotid atheromas. Nucleic amplification of peripheral blood mononuclear cells may enable the identification of subjects carrying C. pneumoniae in the vascular wall. Macrolide treatment reduced fibrinogen and C-reactive protein plasma levels and C. pneumoniae burden in patients with atherosclerotic diseases.

PCR and RFLP analysis for identification and typing of Helicobacter pylori strains isolated from gastric biopsy specimens

Helicobacter pylori (H. pylori) infection is the most common gastrointestinal tract infection which plays an important role in the ethiopathogenesis of peptic ulcer and gastritis. In recent years, molecular biological methods have been presented for detection of H. pylori in addition to histopathological and microbiological methods. Among these methods, polymerase chain reaction (PCR) and following restriction fragment length polymorphism analyses (RFLP) are highly sensitive methods for diagnosis and follow up of patients. In this present study our aim was to amplify H. pylori urease A and B genes by PCR and perform RFLP analysis. Gastric biopsy specimens from 17 female and 18 male patients were included in the study. Amplified PCR products were subjected to RFLP analysis and typing of the bacteria in pre and posttreatment specimens were performed. H. pylori urease A and B gene amplification was observed in 32 pretreatment samples and in 8 of 21 posttreatment specimens. As a result, PCR is a sensitive method to determine the H. pylori infection. RFLP, which is another effective method in order to demonstrate the reinfection of H. pylori.

Helicobacter pylori detection in human biopsies: a competitive PCR assay with internal control reveals false results

A polymerase chain reaction assay (PCR) for the diagnosis of Helicobacter pylori in human gastric biopsies was developed. To prevent false-negative results while performing PCR on human tissues, an internal control is necessary. Primer set ACT1-ACT2 which specifically amplifies a 542-bp fragment of the 16S rRNA gene of H. pylori was used. dUTP and hot-start were used to prevent false-positives from carryover of previous products and avoid non-specific extension products. A competitive internal control DNA fragment was constructed to detect the presence of inhibitors. Biopsies from 101 unselected patients with gastric symptoms were tested. PCR results were compared with results from microscopy of histological sections and conventional culturing for H. pylori. Forty-two percent of the biopsies were found to contain compounds inhibiting the PCR. The addition of the internal control assures the performance of the PCR assay and is an important quality control parameter.

Rapid PCR detection of Helicobacter pylori-associated virulence and resistance genes directly from gastric biopsy material

We have developed a PCR-based method to detect macrolide resistance and the virulence gene cagA in Helicobacter pylori within 24 h, thereby improving the lengthy process of culture-based approaches. Total DNA was prepared directly from stomach biopsy specimens. The procedure proved to be rapid and reliable and could be utilized for diagnostic purposes.

Serodiagnosis of Helicobacter pylori infection in Korean patients using enzyme-linked immunosorbent assay

Helicobacter pylori (H. pylori) is a gram-negative spiral bacteria that are associated with gastritis, peptic ulcer and gastric cancer. We have developed enzyme-linked immunosorbent assay (ELISA) that detects serum anti-H. pylori immunoglobulin G antibodies using H. pylori strains isolated from Korean patients. To assess the sensitivity and specificity of our assay system with different commercial kits, serum samples from 249 Korean patients with a variety of gastrointestinal diseases were tested. Among 249 Korean patients, 178 (71.5%) were positive in culture and/or urease test. The sensitivity and specificity between our assay system and four other commercial kits (Bio-Rad, DAKO, ROCHE, and IPR) were as follows: 97.8% and 92%, 94.3% and 53%, 56.5% and 92%, 83.3% and 96%, 58.2% and 92%, respectively. All sera showing discordant immunoassay results between different ELISA kits were confirmed by immunoblot analysis. These results indicate that our assay system showed a highly accurate and reliable results in diagnosis of H. pylori infection in Korean patients.

Nested primers improve sensitivity in the detection of Helicobacter pylori by the polymerase chain reaction

To investigate potential routes of spread of infection by the polymerase chain reaction (PCR) it is important that the technique is effective in the types of specimen to be investigated. To establish the limits of detection of Helicobacter pylori by PCR in clinical material from the gastric mucosa, faeces, dental plaque and oral rinses, samples were seeded with known numbers of bacteria. DNA extraction was followed by amplification with primers from the urease C gene. Nested primers were used to amplify the PCR product which was detected using a digoxigenin-labelled probe. Faeces or plaque inhibited the single reaction 10(2)-10(6) fold. A second amplification using nested primers and probing increased the sensitivity to a level similar to that obtained with pure culture. This method is potentially useful with less likelihood of false negative results when trying to detect H. pylori by PCR in highly contaminated, clinical material.

Detection of Helicobacter pylori in various oral lesions by nested polymerase chain reaction (PCR)

Nested PCR was used for the detection of Helicobacter pylori DNA in specimens collected from seven different topographic sites in the oral cavity. Out of 161 patients, only 21 (13.04%) were positive. There was no correlation between H. pylori status and patient diagnosis and age. No preferential site for bacterial colonization was found in the oral cavity, nor was an association established between a bacterial presence and ulcerated versus non-ulcerated lesions. The results indicate that the oral mucosa does not appear to represent a preferred site of colonization for H. pylori. Furthermore, the evidence presented in this paper suggests that H. pylori is not pathogenic in the oral cavity, nor is it associated with common oral pathologic processes.

Strategy for the detection of Helicobacter species by amplification of 16S rRNA genes and identification of H. felis in a human gastric biopsy

The aim of the present work was to develop polymerase chain reactions (PCRs) based on the conserved nucleotide sequence of the 16S rRNA gene for detection of bacteria of the Helicobacter genus in human antral biopsy samples. The assay for Helicobacter spp was developed by amplifying a 399-bp 16S rRNA gene sequence specific to the genus Helicobacter. The identity of the amplicon was confirmed by hybridization with an internal probe and by restriction by endonuclease VspI showing two expected fragments of 295 and 104 base pairs. A total of 65 dyspeptic patients from France and New Caledonia were screened for Helicobacter spp infection through the use of the following diagnostic assays on biopsy specimens collected through endoscopy: direct detection of bacteria in histological sections by Giemsa and Warthin Starry staining, urease test and bacterial isolation, PCR for Helicobacter pylori ureC/glmM gene, and PCR targeted to 16S rRNA genes. The 16S rRNA gene PCR assay was able to detect down to 680 bacterial cells, as assessed by agarose gel electrophoresis, and down to 4 bacterial cells by hybridization of amplicon with the internal probe. The 16S rRNA PCR test was 100% specific and sensitive; results obtained with this test were in agreement with the visualization of bacteria by histology. Urease test and culture were 86.4% and 22.7% sensitive, and 96.5 and 100% specific, respectively. The H. pylori ureC/glmM gene-based PCR was 100% specific and only 95.4% sensitive, since one biopsy from a Melanesian patient contained a Helicobacter strain other than H. pylori. For this Melanesian patient, a branch-specific PCR targeting the epsilon branch of Proteobacteria was used to amplify a 967-bp amplicon. This amplicon was sequenced and matched with the H. felis sequence. This was confirmed using an H. felis-specific urease PCR test.

Molecular diagnosis of Helicobacter pylori

H. pylori infection can be diagnosed with many different tests. If the patient is undergoing endoscopy with gastric biopsies, culture and histology remain the diagnostic methods of choice. Indirect tests include rapid urease tests, urea breath tests, and serology. Molecular methods such as PCR offer marginal improvements when done on biopsy material, but has the advantage of being able to accurately identify H. pylori in areas outside the stomach where cultures usually fail. PCR can detect low numbers of organisms in gastric juice, bile, stool and oral secretions. Because of its high sensitivity it can also be used for epidemiologic investigations of environmental sources. However, the largest role for PCR may be in molecular fingerprinting. Arbitrary Primer PCR (RAPD) on the whole bacterial genome can reliably and accurately distinguish between isolates. PCR-based RFLP analysis can separate isolates based on restriction fragment sizes in a smaller amplified genome segment. REP-PCR can group isolates into clusters that appear to have different clinical expressions. These methods promise to shed new light on the transmission and pathogenicity of H. pylori.

Detection of Chlamydia pneumoniae but not Helicobacter pylori in atherosclerotic plaques of aortic aneurysms

Recent reports suggest an association between Chlamydia pneumoniae and Helicobacter pylori bacteria and atherosclerosis. We studied 51 patients (mean age, 68.3 years) who underwent abdominal aortic aneurysm surgery. For each patient we performed a microimmunofluorescence test for immunoglobulin G (IgG), IgA, and IgM antibodies to C. pneumoniae specific antigen (TW-183). Anti-H. pylori antibodies were determined by means of an EIA-G test. Each aortic aneurysm surgical specimen was sampled into multiple sections of 0.3 cm2 each and frozen at -20 degrees C. Two samples of each aneurysm were used for a nested PCR with two sets of C. pneumoniae and two sets of H. pylori specific primers. Specimens were treated with a solution containing 20 mM Tris-HCl, Tween 20-Nonidet P-40 (0.5% [vol/vol] each), and 100 micrograms of proteinase K per ml and incubated at 60 degrees C for 1 h and at 98 degrees C for 10 min. DNA was extracted twice with phenol-chloroform-isoamylic alcohol and precipitated with sodium acetate-ethanol by standard methods. Forty-one patients were seropositive for C. pneumoniae with past-infection patterns in 32 patients (16 < or = IgG < 512; 32 < or = IgA < 256) and high antibody titers in 9 patients (IgG > or = 512). In 26 of 51 patients, C. pneumoniae DNA was detected in aortic aneurysm plaque specimens. Of these patients, 23 had a serologic past-infection pattern, 2 had an acute reinfection pattern, and 1 was seronegative. Forty-seven of 51 patients were seropositive for H. pylori. In all cases PCR showed no evidence of H. pylori presence in plaque specimens. This study provides data on a possible C. pneumoniae involvement in the pathogenesis of aortic aneurysm and additional evidence for an association between this agent and atherosclerosis. Conversely, notwithstanding a high H. pylori seroprevalence observed, our results tend to rule out the possibility of a direct involvement of H. pylori in atherosclerosis.

Comparison between resectable gastric adenocarcinomas seropositive and seronegative for Helicobacter pylori

The preoperative seropositivity of Helicobacter pylori was determined in 128 patients who had undergone gastrectomy for primary gastric adenocarcinoma during the past 5 years. The overall seroprevalence of H. pylori was 64 per cent. Gastric cancers positive for H. pylori were associated with tumours located in the lower third of the stomach which were of localized type (Borrmann I and II) (P < 0.05), but not with age, sex, blood type, tumour size, invasion depth, lymph node metastases, histological type, DNA ploidy or type of surgery. The cumulative 5-year survival curves after surgical resection were significantly better in patients who were positive for H. pylori. Multivariate analysis revealed that seropositivity for H. pylori was not an independent prognostic factor. Pathological tumour node metastasis staging was the only prognostic indicator. Better prognosis for those with H. pylori-seropositive gastric cancer may be attributed to the more advanced stage of H. pylori-seronegative gastric cancers. The potential role of H. pylori in gastric cancer carcinogenesis and its biological significance warrant further investigation.

Comparison of PCR and other diagnostic techniques for detection of Helicobacter pylori infection in dyspeptic patients

A sensitive and specific PCR-based assay to detect the Helicobacter pylori 16S rRNA gene present in formalin-fixed paraffin-embedded gastric biopsy specimens has been developed. A total of 95 patients with dyspepsia were evaluated for the presence of chronic active gastritis and an infection with H. pylori through the use of diagnostic assays based on biopsy specimens and serology. The "gold standard" for the presence of the bacteria was direct detection in histological sections of biopsy specimens by Giemsa stain. The results obtained with the PCR assay performed on the biopsy specimens (94% sensitivity and 100% specificity) were equivalent to the detection of H. pylori immunoglobulin G antibodies by the commercially available second-generation Cobas Core anti-H. pylori immunoglobulin G enzyme immunoassay (94% sensitivity and 98% specificity) for the diagnosis of H. pylori infection. Urease testing and bacterial culture of the biopsy specimens were inferior (88 and 70% sensitivity and 96% and 98% specificity, respectively). A Western blot (immunoblot) analysis had slightly greater sensitivity (96%), although specificity was reduced to 93%. This research prototype PCR assay was shown to be highly reliable for the detection of infection with H. pylori and the presence of chronic active gastritis in the population studied.