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

A Cross-Sectional Study on Molecular Detection of Helicobacter pylori cytotoxin-associated gene A and 16SrRNA Gene from Gastric Biopsy Specimens

Introduction:

The aim of the study is relative proportion of cytotoxin-associated gene A (cagA) virulence marker in Helicobacter pylori isolates and gastric biopsy samples by polymerase chain reaction (PCR).

Methods:

This cross-sectional study was conducted at a tertiary care hospital setting. Gastric biopsy tissues from 200 patients, suffering from upper gastrointestinal tract disorders, were examined for H. pylori infection using methods, such as hematoxylin and eosin (H and E) staining, 16S rRNA (Ribosomal ribonucleic acid), and cagA gene PCR. Chi-square and kappa statistics were used to find the association and agreement between the tests, respectively; P ≤ 0.05 was considered statistically significant. Screening tests' accuracy was calculated in terms of sensitivity and specificity along with positive and negative predictive values.

Results:

Out of 200 patients, H. pylori was detected in 14.5%, 48.5%, and 31% patients by H and E staining, 16S rRNA, and cagA PCR, respectively. Sensitivity and specificity of cagA PCR as compared to H and E staining were 89.6% and 78.9%, respectively.

Conclusions:

CagA detection directly from biopsy specimen by PCR can potentially and rapidly determine the patient's status, especially when at a higher risk of peptic ulcer.

Rapid and accurate detection of Helicobacter pylori from biopsy specimens using loop-mediated isothermal amplification

Loop-mediated isothermal amplification (LAMP) is a promising nucleic acid-based assay for quick, accurate and cost-effective diagnosis of many infectious agents. The purpose of this study was to assess the diagnostic value of LAMP for rapid and accurate detection of Helicobacter pylori in biopsy specimens. Patients suffering from one or several gastroduodenal disorders were enrolled in the study. Specificity, sensitivity, and the positive and negative predictive values of LAMP were compared with the gold standard result, which was the assembled result of culture, rapid urease test and polymerase chain reaction. Sensitivity, specificity, and the positive and negative predictive values of LAMP in comparison with the gold standard result were 100%, 30.76%, and 87.67% and 100% respectively [%95 CI]. As the diagnostic value of LAMP is favourable, the method is an optimum technique for diagnosis the presence of H. pylori in different clinical and environmental samples.

Identification of Helicobacter pylori in Saliva of Patients with and without Gastritis by Polymerase Chain Reaction

Aims and Objective:

The aim of this study was to identify the presence of Helicobacter pylori in saliva of patients with and without gastritis by polymerase chain reaction (PCR) method.

Materials and Methods:

The study comprised 20 patients in Group I presenting with various symptoms of gastritis and 10 asymptomatic subjects in Group II. The intestinal endoscopy antral biopsies were collected from 20 symptomatic patients with gastroduodenal disorders. The saliva specimens were taken from all patients before endoscopy. PCR was performed using genomic DNA, isolated from the saliva and the biopsies of the patients as the template to detect the presence of the 16S ribosomal RNA gene in H. pylori.

Results:

In Group I, 10 (50%) cases of clinical gastritis were positive for H. pylori by endoscopy biopsy and 10 (50%) were negative. Of the 10 endoscopy biopsy positive cases for H. pylori, eight were PCR positive in saliva and two were negative. Of the 10 endoscopy biopsy negative cases, three were PCR positive for H. pylori in saliva and seven were negative. In Groups II, four were symptomatic for gastritis and six were negative. Of the six gastritis negative cases, three were PCR positive, four were gastritis positive, and three were PCR positive. Sensitivity and specificity of PCR were found to be 80% and 70%, respectively. The positive predictive and negative predictive values of PCR in saliva were 72.7% and 77.7%, respectively.

Conclusion:

PCR analysis of saliva may be handy in identification of H. pylori and serves as a noninvasive technique to diagnose and monitor the prognosis.

Non-invasive diagnostic tests for Helicobacter pylori infection

BACKGROUND

Helicobacter pylori (H pylori) infection has been implicated in a number of malignancies and non-malignant conditions including peptic ulcers, non-ulcer dyspepsia, recurrent peptic ulcer bleeding, unexplained iron deficiency anaemia, idiopathic thrombocytopaenia purpura, and colorectal adenomas. The confirmatory diagnosis of H pylori is by endoscopic biopsy, followed by histopathological examination using haemotoxylin and eosin (H & E) stain or special stains such as Giemsa stain and Warthin-Starry stain. Special stains are more accurate than H & E stain. There is significant uncertainty about the diagnostic accuracy of non-invasive tests for diagnosis of H pylori.

OBJECTIVES

To compare the diagnostic accuracy of urea breath test, serology, and stool antigen test, used alone or in combination, for diagnosis of H pylori infection in symptomatic and asymptomatic people, so that eradication therapy for H pylori can be started.

SEARCH METHODS

We searched MEDLINE, Embase, the Science Citation Index and the National Institute for Health Research Health Technology Assessment Database on 4 March 2016. We screened references in the included studies to identify additional studies. We also conducted citation searches of relevant studies, most recently on 4 December 2016. We did not restrict studies by language or publication status, or whether data were collected prospectively or retrospectively.

SELECTION CRITERIA

We included diagnostic accuracy studies that evaluated at least one of the index tests (urea breath test using isotopes such as 13C or 14C, serology and stool antigen test) against the reference standard (histopathological examination using H & E stain, special stains or immunohistochemical stain) in people suspected of having H pylori infection.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the references to identify relevant studies and independently extracted data. We assessed the methodological quality of studies using the QUADAS-2 tool. We performed meta-analysis by using the hierarchical summary receiver operating characteristic (HSROC) model to estimate and compare SROC curves. Where appropriate, we used bivariate or univariate logistic regression models to estimate summary sensitivities and specificities.

MAIN RESULTS

We included 101 studies involving 11,003 participants, of which 5839 participants (53.1%) had H pylori infection. The prevalence of H pylori infection in the studies ranged from 15.2% to 94.7%, with a median prevalence of 53.7% (interquartile range 42.0% to 66.5%). Most of the studies (57%) included participants with dyspepsia and 53 studies excluded participants who recently had proton pump inhibitors or antibiotics.There was at least an unclear risk of bias or unclear applicability concern for each study.Of the 101 studies, 15 compared the accuracy of two index tests and two studies compared the accuracy of three index tests. Thirty-four studies (4242 participants) evaluated serology; 29 studies (2988 participants) evaluated stool antigen test; 34 studies (3139 participants) evaluated urea breath test-13C; 21 studies (1810 participants) evaluated urea breath test-14C; and two studies (127 participants) evaluated urea breath test but did not report the isotope used. The thresholds used to define test positivity and the staining techniques used for histopathological examination (reference standard) varied between studies. Due to sparse data for each threshold reported, it was not possible to identify the best threshold for each test.Using data from 99 studies in an indirect test comparison, there was statistical evidence of a difference in diagnostic accuracy between urea breath test-13C, urea breath test-14C, serology and stool antigen test (P = 0.024). The diagnostic odds ratios for urea breath test-13C, urea breath test-14C, serology, and stool antigen test were 153 (95% confidence interval (CI) 73.7 to 316), 105 (95% CI 74.0 to 150), 47.4 (95% CI 25.5 to 88.1) and 45.1 (95% CI 24.2 to 84.1). The sensitivity (95% CI) estimated at a fixed specificity of 0.90 (median from studies across the four tests), was 0.94 (95% CI 0.89 to 0.97) for urea breath test-13C, 0.92 (95% CI 0.89 to 0.94) for urea breath test-14C, 0.84 (95% CI 0.74 to 0.91) for serology, and 0.83 (95% CI 0.73 to 0.90) for stool antigen test. This implies that on average, given a specificity of 0.90 and prevalence of 53.7% (median specificity and prevalence in the studies), out of 1000 people tested for H pylori infection, there will be 46 false positives (people without H pylori infection who will be diagnosed as having H pylori infection). In this hypothetical cohort, urea breath test-13C, urea breath test-14C, serology, and stool antigen test will give 30 (95% CI 15 to 58), 42 (95% CI 30 to 58), 86 (95% CI 50 to 140), and 89 (95% CI 52 to 146) false negatives respectively (people with H pylori infection for whom the diagnosis of H pylori will be missed).Direct comparisons were based on few head-to-head studies. The ratios of diagnostic odds ratios (DORs) were 0.68 (95% CI 0.12 to 3.70; P = 0.56) for urea breath test-13C versus serology (seven studies), and 0.88 (95% CI 0.14 to 5.56; P = 0.84) for urea breath test-13C versus stool antigen test (seven studies). The 95% CIs of these estimates overlap with those of the ratios of DORs from the indirect comparison. Data were limited or unavailable for meta-analysis of other direct comparisons.

AUTHORS' CONCLUSIONS

In people without a history of gastrectomy and those who have not recently had antibiotics or proton ,pump inhibitors, urea breath tests had high diagnostic accuracy while serology and stool antigen tests were less accurate for diagnosis of Helicobacter pylori infection.This is based on an indirect test comparison (with potential for bias due to confounding), as evidence from direct comparisons was limited or unavailable. The thresholds used for these tests were highly variable and we were unable to identify specific thresholds that might be useful in clinical practice.We need further comparative studies of high methodological quality to obtain more reliable evidence of relative accuracy between the tests. Such studies should be conducted prospectively in a representative spectrum of participants and clearly reported to ensure low risk of bias. Most importantly, studies should prespecify and clearly report thresholds used, and should avoid inappropriate exclusions.

Evaluation of Invasive and Noninvasive Methods for the Diagnosis of Helicobacter Pylori Infection

Objective:

The present study was conducted to evaluate invasive and noninvasive diagnostic methods for detection of Helicobacter pylori (H. pylori) in patients admitted with dyspeptic complaints and to compare sensitivities and specificities.

Method:

Sets of four gastric biopsy specimens were obtained from a total of 126 patients included in the study. The presence of H. pylori was determined by invasive tests including culture, rapid urease test, polymerase chain reaction (PCR) and histopathology. Among noninvasive tests, urea breath test, serological tests and enzyme-linked immunosorbent assay (ELISA) were performed.

Results:

H. pylori was isolated in 79 (62.7%) gastric biopsy cultures, whereas positivity was concluded for 105 (83.3%) patients by rapid urease test, for 106 (84.1%) by PCR, for 110 (87.3%) by histopathology, for 119 (94.4%) by urea breath test, and for 107 (84.9%) by ELISA. In the present study, the culture findings and histopathological examination findings were accepted as gold standard. According to the gold standard, urea breath test had the highest sensitivity (96.5%) and the lowest specificity (30%), whereas culture and histopathology had the highest specificities (100%).

Conclusion:

The use of PCR invasively with gastric biopsy samples yielded parallel results with the gold standard. PCR can be recommended for routine use in the diagnosis of H. pylori.

Development and Diagnostic Evaluation of Loop-Mediated Isothermal Amplification Using a New Gene Target for Rapid Detection of Helicobacter pylori

BACKGROUND

Helicobacter pylori cause chronic gastritis and subsequent diseases like gastric and duodenal ulcers and gastric adenocarcinoma. Current methods for detecting H. pylori have several disadvantages and it is of utmost importance to develop a simple, quick, accurate, and cost-effective diagnostic test.

OBJECTIVES

The aim of this study was to set up and evaluate a diagnostic value of loop- mediated isothermal amplification (LAMP) for detecting H. pylori.

PATIENTS AND METHODS

The analytical sensitivity values (limit of detection) of LAMP and polymerase chain reaction (PCR) were determined using serial dilutions of H. pylori DNA. Analytical specificity of the methods using new designed primers targeted ureC gene was also determined.

RESULTS

The detection limits of the LAMP and PCR assay were similar and were 10 fg of pure DNA of H. pylori, which is equal to 6 copy numbers of H. pylori genome. Analytical specificity of the tests was 100% because the tests were positive only with H. pylori DNA.

CONCLUSIONS

The analytical sensitivity of LAMP and PCR methods, using the designed primers, was 8 times more than any other reported methods. The designed methods are specific and sensitive for detection of H. pylori in different clinical and environmental samples.

MicroRNA as biomarkers of mitochondrial toxicity

Mitochondrial toxicity can be difficult to detect as most cells can tolerate reduced activity as long as minimal capacity for function is maintained. However, once minimal capacity is lost, apoptosis or necrosis occurs quickly. Identification of more sensitive, early markers of mitochondrial toxicity was the objective of this work. Rotenone, a mitochondrial complex I inhibitor, and 3-nitropropionic acid (3-NP), a mitochondrial complex II inhibitor, were administered daily to male Sprague-Dawley rats at subcutaneous doses of 0.1 or 0.3mg/kg/day and intraperitoneal doses of 5 or 10mg/kg/day, respectively, for 1week. Samples of kidney, skeletal muscle (quadriceps femoris), and serum were collected for analysis of mitochondrial DNA (mtDNA) copy number and microRNA (miRNA) expression patterns. MtDNA was significantly decreased with administration of rotenone at 0.3mg/kg/day and 3-NP at 5 and 10mg/kg/day in the quadriceps femoris and with 3-NP at 10mg/kg/day in the kidney. Additionally, rotenone and 3-NP treatment produced changes to miRNA expression that were similar in direction (i.e. upregulation, downregulation) to those previously linked to mitochondrial functions, such as mitochondrial damage and biogenesis (miR-122, miR-202-3p); regulation of ATP synthesis, abolished oxidative phosphorylation, and loss of membrane potential due to increased reactive oxygen species (ROS) production (miR-338-5p, miR-546, miR-34c); and mitochondrial DNA damage and depletion (miR-546). These results suggest that miRNAs may be sensitive biomarkers for early detection of mitochondrial toxicity.

Coextraction and PCR Based Analysis of Nucleic Acids From Formalin-Fixed Paraffin-Embedded Specimens

BACKGROUND

Retrospective studies of archived human specimens, with known clinical follow-up, are used to identify predictive and prognostic molecular markers of disease. Due to biochemical differences, however, formalin-fixed paraffin embedded (FFPE) DNA and RNA have generally been extracted separately from either different tissue sections or from the same section by dividing the digested tissue. Our optimized co-extraction approach provides the option of collecting DNA, which would otherwise be discarded or degraded, for additional or subsequent studies because of the high importance and less availability of clinical FFPE specimen.

METHODS

Coextraction of DNA and RNA from a single gastric cancer FFPE specimen was optimized by using TRIzol and purifying DNA from the lower aqueous and RNA from the upper organic phases. The protocol involves modification of incubation period for 30 min with proteinase K in glycin-tris-ethylenediamine tetra acetic acid buffer before adding TRIzol.

RESULTS

All samples tested successfully performed semiquantitative gene expression by reverse transcriptase PCR. The quantity and quality of DNA from FFPE samples was high which resulted in successful PCR amplification. The isolated DNA also aided in detection of Helicobacter pylori by amplifying the ribosomal 16S gene in a multiplex PCR reaction along with cagA.

CONCLUSION

These results show that the RNA/DNA isolated by this method can be used for easy clinical diagnosis of disease-related gene expression as well as mutation and pathogen detection from a homogenous population of tumor cells.

Helicobacter pylori vacA d1 genotype predicts risk of gastric adenocarcinoma and peptic ulcers in northwestern Iran

BACKGROUND

There is a close relationship between Helicobacter pylori (H pylori)-specific factors and different gastroduodenal diseases. The present study aimed to investigate the prevalence of vacA d1, d2 genotypes in the H pylori isolates from patients with gastric adenocarcinoma, peptic ulcer disease (PUD) and gastritis in East Azerbaijan region, where the incidence of gastric cancer (GC) is high. Strains isolated from this area are likely to be of European ancestry.

MATERIALS AND METHODS

In this study, genotyping of the vacA d region of 115 isolates obtained from patients with different gastrodoudenal diseases was accomplished by PCR methods. In addition to PCR amplification of H pylori 16S rDNA, rapid urease tests or histological examination were used to confirm the presence of H pylori in biopsy specimens. Data were collected and analyzed using SPSS version 19.

RESULTS

Of the total of 83 H pylori isolates, 36 (43.4%) contained the d1 allele and 47 (56.6%) were subtype d2. The results of the multiple linear/logistic regression analysis showed high correlation between allele d1 and gastric adenocarcinoma or PUD.

CONCLUSIONS

This study suggests that the H pylori vacA d1 genotype helps predict risk for gastric adenocarcinoma and PUD in East Azerbaijan, Iran.

Real-time PCR improves Helicobacter pylori detection in patients with peptic ulcer bleeding

BACKGROUND AND AIMS

Histological and rapid urease tests to detect H. pylori in biopsy specimens obtained during peptic ulcer bleeding episodes (PUB) often produce false-negative results. We aimed to examine whether immunohistochemistry and real-time PCR can improve the sensitivity of these biopsies.

PATIENTS AND METHODS

We selected 52 histology-negative formalin-fixed paraffin-embedded biopsy specimens obtained during PUB episodes. Additional tests showed 10 were true negatives and 42 were false negatives. We also selected 17 histology-positive biopsy specimens obtained during PUB to use as controls. We performed immunohistochemistry staining and real-time PCR for 16S rRNA, ureA, and 23S rRNA for H. pylori genes on all specimens.

RESULTS

All controls were positive for H. pylori on all PCR assays and immunohistochemical staining. Regarding the 52 initially negative biopsies, all PCR tests were significantly more sensitive than immunohistochemical staining (p<0.01). Sensitivity and specificity were 55% and 80% for 16S rRNA PCR, 43% and 90% for ureA PCR, 41% and 80% for 23S rRNA PCR, and 7% and 100% for immunohistochemical staining, respectively. Combined analysis of PCR assays for two genes were significantly more sensitive than ureA or 23S rRNA PCR tests alone (p<0.05) and marginally better than 16S rRNA PCR alone. The best combination was 16S rRNA+ureA, with a sensitivity of 64% and a specificity of 80%.

CONCLUSIONS

Real-time PCR improves the detection of H. pylori infection in histology-negative formalin-fixed paraffin-embedded biopsy samples obtained during PUB episodes. The low reported prevalence of H. pylori in PUB may be due to the failure of conventional tests to detect infection.

Comparison of PCR with other diagnostic techniques for the detection of H. pylori infection in patients presenting with gastroduodenal symptons in Nigeria

The study was aimed at comparing PCR methods of direct detection from biopsy using the boiling method and one other method with two known gold standards (histology and CLO test) for the diagnosis of H. pylori in Nigeria. A total of 168 biopsies (three from antrum and one from corpus each) were taken from 42 patients presenting with various gastroduodenal symptons after informed consent was obtained from them.The biopsies were analysed using the CLO test kit and histology, while the boiling method as described by Holmes and Quigley (1981) was used to obtain DNA and then PCR using the 16S rRNA gene, glmM gene and cagA gene. With CLO test 15/42 (35.71%) were positive, histology 13/42 (30.95%) were positive, 16S rRNA 22/42 (52.38%) were positive, glmM 19/42 (45.24%) were positive, cagA 19/42 (45.24%) were positive. The sensitivity and specificity of the PCR tests with CLO as the gold standard showed that the tests were 100% sensitive and varied between 74.1% to 84.1% in specificity. The PPV and NPV showed that the NPV was almost 100%, while the PPV was between 68.2% and 75%. Using the histology as the gold standard, the sensitivity was almost 100% while the specificity, the PPV were reduced in comparison to the CLO test. The PCR test using the glmM gene appears to be the most reliable test for diagnosis of H. pylori in Nigeria most especially where culture is difficult due to the power outages.

Seroprevalence of Helicobacter pylori infection among children of low socioeconomic level in São Paulo

CONTEXT AND OBJECTIVE

Helicobacter pylori infection is mainly acquired during childhood, and is associated with significant morbidity in adults. The aim here was to evaluate the seroprevalence and risk factors of H. pylori infection among children of low socioeconomic level attended at a public hospital in São Paulo, Brazil.

DESIGN AND SETTING

Cross-sectional study, among patients attended at an outpatient clinic.

METHODS

326 children were evaluated (150 boys and 176 girls; mean age 6.82 ± 4.07 years) in a cross-sectional study. Patients with chronic diseases or previous H. pylori treatment, and those whose participation was not permitted by the adult responsible for the child, were excluded. The adults answered a demographic questionnaire and blood samples were collected. The serological test used was Cobas Core II, a second-generation test. Titers > 5 U/ml were considered positive.

RESULTS

H. pylori infection was diagnosed in 116 children (35.6%). Infected children were older than uninfected children (7.77 ± 4.08 years versus 5.59 ± 3.86 years; p < 0.0001). The seroprevalence increased from 20.8% among children aged two to four years, to 58.3% among those older than 12 years. There were no significant relationships between seropositivity and gender, color, breastfeeding, number of people in the home, number of rooms, bed sharing, living in a shantytown, maternal educational level, family income or nutritional status. In multivariate analysis, the only variable significantly associated with H. pylori seropositivity was age.

CONCLUSION

Infection had intermediate prevalence in the study population, and age was associated with higher prevalence.

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.

Detection of Helicobacter pylori in paraffin-embedded specimens from patients with chronic liver diseases, using the amplification method

Helicobacter DNA has been detected in the liver specimens of patients with various hepato-biliary diseases. The aim of this study was to investigate the presence of H. pylori DNA in the liver tissue of Iranian patients with chronic liver diseases (CLD). Genomic DNA was extracted from the paraffin sections of 46 liver biopsies of patients with CLD and 13 from patients with metastatic adenocarcinoma as a control group. Polymerase chain reaction (PCR) analysis was carried out using primers for H. pylori 16S rRNA and cagA genes. On analysis, 17 of the 46 patient samples were positive in H. pylori 16S rRNA PCR and 2 of the 13 were positive from the control group. None of the samples were positive for the cagA gene. This study showed the greater presence of H. pylori-like DNA in the liver samples from patients with CLD than in controls.

Helicobacter pyloridetection and genotyping in gastric biopsy specimens from Chennai patients (India)

The aim of the present study was to investigate the prevalence of Helicobacter pylori infection and the correlation between cagA and vacA (mid-region) genotypes with different clinical outcomes from Chennai, India, patients. Biopsies from the antrum were taken to assess the current H. pylori status by histology, rapid urease test (RUT), and PCR. The RUT and PCR analyses were carried out on a single biopsy specimen. Fasting sera were obtained from all patients and H. pylori status was determined by using ELISA. In addition, the correlations between cagA and vacA genotypes and the consequence of H. pylori infection were statistically examined. Prevalence of the cagA gene was found in 96% (90/94) of patients, and the vacA m2 subtype occurred in 60% (56/94), whereas 32% (30/94) showed the vacA m1 subtype. A significant association between the cagA and vacA m2 region (χ2 = 5.556; p < 0.01) was found in ulcer patients. The vacA m2 genotype showed a near-significant value (χ2 = 3.943; p < 0.047) in ulcer patients when compared with vacA m1. These findings suggest that H. pylori strains with the vacA m2 region were predominant in South India, especially in and around Chennai. This study also showed that PCR has a potential value for studying the cagA gene directly from biopsy specimens.

A better method for confirming Helicobacter pylori infection in Mongolian gerbils

BACKGROUND

Our aim was to evaluate the accuracy of the stool antigen test and the optimal time point for detecting Helicobacter pylori infection in a Mongolian gerbil model.

METHODS

We inoculated 8-week-old Mongolian gerbils with H. pylori (Vac A (+)/CagA(+)). The gerbil-infected model was developed as follows: H. pylori was put into broth (about 10(9) CFU/ml), and 50 gerbils were then fed with 1 ml intragastrically twice within a 3-day interval. Another ten gerbils were fed broth only. Twenty-six weeks after the inoculation, the gerbils were killed. The gastric mucosa was sampled for a series of examinations including culture, histology, rapid urease test, and polymerase chain reaction. Stool samples for a stool antigen test, H. pylori-specific stool antigen assay (HpSA), were collected during weeks 4, 6, 8, 12, and 26 after inoculation. Of the 50 gerbils inoculated with H. pylori, the inoculation was successful in 88%. Severe active gastritis, ulceration, and intestinal metaplasia were obvious.

RESULTS

The HpSA test results were sensitivity, 88.6%; specificity, 100%; positive predictive value (PPV), 100%; negative predictive value (NPV), 54.5%, and accuracy, 90%. The HpSA test began to be more sensitive and accurate (P < 0.05) beginning during week 6 after inoculation. We also found that H. pylori could be detected earlier and more easily in the group with high H. pylori density.

CONCLUSIONS

HpSA seems to be suitable for confirming colonization of gerbils with H. pylori. The optimal testing time point is around 6 weeks after inoculation. This test is a good choice for long-term observation of H. pylori infection in Mongolian gerbils.

Development of an internal control for evaluation and standardization of a quantitative PCR assay for detection of Helicobacter pylori in drinking water

Due to metabolic and morphological changes that can prevent Helicobacter pylori cells in water from growing on conventional media, an H. pylori-specific TaqMan quantitative PCR (qPCR) assay was developed that uses a 6-carboxyfluorescein-labeled probe (A. E. McDaniels, L. Wymer, C. Rankin, and R. Haugland, Water Res. 39:4808-4816, 2005). However, proper internal controls are needed to provide an accurate estimate of low numbers of H. pylori in drinking water. In this study, the 135-bp amplicon described by McDaniels et al. was modified at the probe binding region, using PCR mutagenesis. The fragment was incorporated into a single-copy plasmid to serve as a PCR-positive control and cloned into Escherichia coli to serve as a matrix spike. It was shown to have a detection limit of five copies, using a VIC dye-labeled probe. A DNA extraction kit was optimized that allowed sampling of an entire liter of water. Water samples spiked with the recombinant E. coli cells were shown to behave like H. pylori cells in the qPCR assay. The recombinant E. coli cells were optimized to be used at 10 cells/liter of water, where they were shown not to compete with 5 to 3,000 cells of H. pylori in a duplex qPCR assay. Four treated drinking water samples spiked with H. pylori (100 cells) demonstrated similar cycle threshold values if the chlorine disinfectant was first neutralized by sodium thiosulfate.

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.

Increased rate of Helicobacter pylori infection detected by PCR in biopsies with chronic gastritis

Histology is considered a sensitive method for detection of Helicobacter pylori, in gastric biopsies. We investigated the diagnostic potential of qualitative nested (nPCR) and quantitative PCR (qPCR) for detection of H. pylori using different primers on 126 archived gastric biopsies with inflammation and correlated the inflammatory changes with the presence and density of bacteria. H. pylori was detected in 42.8% biopsies by histology and PCR, an additional 15 samples were positive exclusively by PCR: nPCR was positive in all histologically positive samples, but qPCR failed to detect H. pylori in 10 biopsies. The inflammatory score was significantly higher in biopsies positive for H. pylori only by PCR showed a significant higher inflammatory score compared with negative biopsies (mean of neutrophils score, 1.60 vs. 0.90, P < 0.01; mean of mononuclear cells score, 2.27 vs. 1.67, P < 0.01), whereas the inflammatory score was similar compared with biopsies positive for H. pylori by histology (mean of neutrophils score, 1.60 vs. 1.56, not significant; mean of mononuclear cells score, 2.27 vs. 2.20, not significant). A weak correlation between inflammatory score and the density of H. pylori detected by histology was observed. The mean values of H. pylori DNA were significantly higher in histologic-positive than in histologic negative biopsies. We have shown that PCR can detect H. pylori in about 20% of histologic-negative gastric biopsies, indicating the clinical relevance of H. pylori detection by PCR in biopsies with characteristic inflammatory changes.

Polymerase chain reaction based analysis of the cytotoxin associated gene pathogenicity island of Helicobacter pylori from saliva: an approach for rapid molecular genotyping in relation to disease status

BACKGROUND AND AIMS

The genetic composition of the intricate cytotoxin associated gene pathogenicity island (cag PAI) of Helicobacter pylori is known to significantly influence the outcome of the disease. Hence, analysis of complete cag PAI of H. pylori isolated from saliva would be of immense importance in standardizing saliva as a reliable non-invasive diagnostic specimen and also to evaluate the type of H. pylori infection. The aim of the present study was to analyze the genes of cag PAI of H. pylori for their presence and correlating them with the disease status of the patients.

METHODS

One hundred and twenty patients (55 duodenal ulcer [DU], 25 gastric ulcer and 40 non-ulcer dyspepsia [NUD]) were investigated for the present study. Eight pairs of oligonucleotide primers (cagA1, cagA2, cagAP1, cagAP2, cagE, cagT, LEC1 and LEC2) of five different loci; cagA, cagA promoter region, cagE which represents cagI region, cagT and LEC representing cagII were used to detect the presence of the cag PAI genes by polymerase chain reaction.

RESULTS

The comprehensive analysis of the genes constituting cag PAI showed almost equivalent prevalence of all the genes between both the study groups (ulcer and NUD) included. Little significant difference was found in the percentage distribution in both the clinical groups. cagE and cagT were found in a larger proportion of the ulcer group (92.5% and 96.2%) compared with the NUD group (77.5% and 85%), respectively.

CONCLUSION

Saliva could be efficiently used as a non-invasive source for H. pylori and cagT might be an important locus of the cag PAI, thus greatly influencing the disease condition of the subjects.

Mucosal polymerase chain reaction for diagnosing Helicobacter pylori infection in patients with bleeding peptic ulcers

AIM: Helicobacter pylori (H pylori) has been linked to chronic gastritis, peptic ulcers, gastric cancer and MALT-lymphoma. Conventional invasive tests are less sensitive than non-invasive tests in diagnosing H pylori infection in patients with bleeding peptic ulcers. Polymerase chain reaction is a sensitive and accurate method for diagnosing H pylori infection. The aim of this study was to evaluate the diagnostic role of mucosal polymerase chain reaction for H pylori infection in patients with bleeding peptic ulcers.

METHODS: In patients with bleeding, non-bleeding peptic ulcers and chronic gastritis, we checked rapid urease test, histology, bacterial culture and mucosal polymerase chain reaction for detecting H pylori infection. Positive H pylori infection was defined as positive culture or both a positive histology and a positive rapid urease test. For mucosal polymerase chain reaction of H pylori, we checked vacA (s1a, s1b, s1c, s2, m1, m1T, m2), iceA1, iceA2 and cag A.

RESULTS: Between October 2000 and April 2002, 88 patients with bleeding peptic ulcers (males/females: 60/28, gastric ulcers/duodenal ulcers: 55/33), 81 patients with non-bleeding peptic ulcers (males/females: 54/27, gastric ulcers/duodenal ulcers: 45/36) and 37 patients with chronic gastritis (males/females: 24/13) were enrolled in this study. In patients with bleeding peptic ulcers, non-bleeding peptic ulcers and chronic gastritis, 45 patients (51%), 71 patients (88%) and 20 patients (54%) respectively were found to have positive H pylori infection (P<0.001). In patients with bleeding peptic ulcers, non-bleeding peptic ulcers and chronic gastritis, polymerase chain reaction for H pylori infection was positive in 54 patients (61%), 70 patients (86%) and 20 patients (54%) respectively (P<0.001). The sensitivity, positive predictive value and diagnostic accuracy of mucosal polymerase reaction for H pylori infection were significantly lower in patients with bleeding peptic ulcers (84%, 79% and 81%) than in patients with non-bleeding peptic ulcers (99%, 99% and 98%) (P<0.001, P<0.01 and P<0.001 respectively). The sensitivity, negative predictive value and diagnostic accuracy of mucosal polymerase reaction for H pylori were significantly lower in patients with bleeding peptic ulcers (84%, 83% and 81%) than in patients with chronic gastritis (100%, 100% and 100%) (P = 0.02, P = 0.02 and P = 0.001).

CONCLUSION: Mucosal polymerase chain reaction for detecting H pylori infection is not reliable in patients with bleeding peptic ulcers.

Laboratory diagnosis and susceptibility profile of Helicobacter pylori infection in the Philippines

Background

Helicobacter pylori diagnosis and susceptibility profile directs the applicability of recommended treatment regimens in our setting. To our knowledge, there is no published data on the culture and local susceptibility pattern of Helicobacter pylori in the Philippines.

Methods

52 dyspeptic adult patients undergoing endoscopy from the Outpatient Gastroenterology clinic of the University of the Philippines-Philippine General Hospital underwent multiple gastric biopsy and specimens were submitted for gram stain, culture, antimicrobial sensitivity testing, rapid urease test and histology. Antimicrobial susceptibility testing was done by Epsilometer testing (Etest) method against metronidazole, clarithromycin, amoxicillin, and tetracycline.

Results

Sixty percent (60%) of the study population was positive for H. pylori infection (mean age of 44 years ± 13), 70% were males. H. pylori culture showed a sensitivity of 45% (95% CI [29.5–62.1]), specificity of 98% (95%CI [81.5–100%]), positive likelihood ratio of 19.93 (95% CI [1.254–317.04]) and a negative likelihood ratio of 0.56 (95% CI [0.406–0.772]). All H. pylori strains isolated were sensitive to metronidazole, clarithromycin, amoxicillin and tetracycline.

Conclusion

Knowledge of the antibiotic susceptibility patterns in our setting allows us to be more cautious in the choice of first-line agents. Information on antibiotic susceptibility profile plays an important role in empiric antibiotic treatment and management of refractive cases.

Accurate, noninvasive detection of Helicobacter pylori DNA from stool samples: potential usefulness for monitoring treatment

A novel DNA assay demonstrating sensitive and accurate detection of Helicobacter pylori from stool samples is reported. Moreover, in three individuals tested for therapeutic response, the assay showed the disappearance of H. pylori DNA during treatment. Thus, this noninvasive molecular biology-based assay has the potential to be a powerful diagnostic tool given its ability to specifically identify H. pylori DNA.

Gastric antiulcer effect of Rhizophora mangle L

The effects of the freeze-dried aqueous extract from red mangrove bark on gastric ulceration induced by ethanol-hydrochloric acid were studied in rats. Mucosal damage was compared with that given with cimetidine. The effects of these agents on the quantity and quality of the gastric mucus were also determined. Oral treatment with red mangrove extract at 500 mg/kg body weight (b.w.) gave the highest level of gastric protection. Mucus content was increased and it was accompanied by a proportional increase in proteins. The group, which received cimetidine, showed no effect on the mucus secretion induced in this experimental model.

Accurate diagnosis of Helicobacter pylori. Polymerase chain reaction tests

Although PCR has improved considerably the sensitivity of the diagnosis of H. pylori infection, many studies have not shown conclusively the full potential of PCR in clinical diagnosis. In daily clinical practice, PCR does not have to be performed to establish H. pylori infection. PCR is still classified primarily as a research technique in the Helicobacter field. PCR or similar technology will expand in the future when automation and commercialized kits are available to most laboratories. The development of a noninvasive PCR test may prove useful because it may lead ultimately to the determination of the source and route of transmission of this important pathogen.

Management of Helicobacter pylori in duodenal ulcer: a cost-effectiveness analysis

BACKGROUND

Empirical eradication therapy of H. pylori has been proposed as a therapeutic alternative for duodenal ulcer.

AIM

To identify the cost-effectiveness of empirical eradication therapy vs. test-and-treatment for the management of patients already diagnosed with a duodenal ulcer.

METHODS

A decision analysis was performed to compare the cost-effectiveness of empirical eradication therapy of H. pylori diagnosed duodenal ulcer vs. eradication therapy after confirmatory diagnosis of Helicobacter pylori infection by means of several diagnostic tests.

RESULTS

The empirical eradication therapy of duodenal ulcer was found to be the most effective and cost-effective strategy of all the alternatives. Amongst the alternatives, which included the previous performance of confirmatory diagnostic tests, the best cost-effectiveness ratio used a serology test. The model was robust in the face of changes in the values of therapeutic effectiveness, sensitivity and specificity of the diagnostic tests, prevalence of H. pylori infection in duodenal ulcer, duration of the antisecretory therapy, and number of medical visits.

CONCLUSIONS

Based on our cost-effectiveness analysis, a treat approach is more effective and cost-effective than a test-and-treat approach in the clinical management of already diagnosed duodenal ulcer.

Evaluation of a PCR primer based on the isocitrate dehydrogenase gene for detection of Helicobacter pylori in feces

In order to improve detection and identification of Helicobacter pylori in highly contaminated samples, we evaluated new specific primers based on the DNA base sequence within the isocitrate dehydrogenase (icd) gene to amplify a 1,200-bp DNA segment. The specificity of the icd primer was tested against DNA derived from various bacteria, including 7 Helicobacter species and a panel of 1 gram-variable, 2 gram-positive, and 16 gram-negative bacteria, as well as DNA from houseflies and feces from H. pylori-negative patients. The primers permitted the detection of all clinical H. pylori isolates tested, but no reactions were observed with negative controls. Several procedures for DNA extraction from feces were evaluated using PCR with icd primers. The lower limits of detection of H. pylori DNA from two different sources containing the same number of H. pylori organisms, a pure culture and feces spiked with H. pylori, were established for each extraction method tested. The results were 8.0 x 10(3) CFU/ml for cultures of pure H. pylori, and 8.0 x 10(6) CFU/ml for H. pylori from feces, using the phenol-chloroform method; 8.0 x 10(2) and 7.0 x 10(3) CFU/ml, respectively, for a glass matrix and chaotropic solution protocol; 8.0 x 10(2) and 7.0 x 10(3) CFU/ml, respectively, for the QIAamp tissue kit; and 5.0 x 10(2) and 5.0 x 10(3) CFU/ml, respectively, for the XTRAX DNA extraction kit. We conclude that the use of the icd gene as a primer for PCR represents a specific and sensitive assay for detection of H. pylori in highly contaminated samples.

The cost-effectiveness of diagnostic testing strategies for Helicobacter pylori

OBJECTIVE

Several noninvasive methods are now available for diagnosing Helicobacter pylori infection. Because the prevalence of H. pylori infection is variable in patients requiring testing, the optimal testing strategies may vary under different conditions. The aim of this study was to evaluate the cost-effectiveness of competing diagnostic strategies for H. pylori in patients with varying H. pylori prevalence.

METHODS

A decision analysis was performed comparing the costs per number of correct diagnoses achieved by alternative sequential testing strategies. Estimates of H. pylori prevalence and test characteristics were derived from a systematic review of the MEDLINE bibliographic database. Cost estimates were derived from the 2000 Medicare Fee Schedule.

RESULTS

The enzyme-linked immunosorbent assay (ELISA) test had the lowest cost per correct diagnosis at low (30%), intermediate (60%), and high (90%) prevalence ($90-$95/correct diagnosis), but its diagnostic accuracy was low (80-84%). At low and intermediate prevalence the stool test was more accurate (93%), with an average cost of $126-$127 per correct diagnosis. Additional confirmatory testing of positive or negative tests increased the diagnostic accuracy of the stool test, but had high incremental costs. ELISA testing was preferable when prevalence rates were very high (90%), and using a confirmatory urea breath test for negative ELISA tests increased the diagnostic accuracy to 96%, with modest incremental costs. If the cost of the breath test was <$50 or if the cost of the stool test is >$82, breath testing became preferable to stool testing. If the cost of the stool test fell to <$20, it became preferable to ELISA. Similarly, if the cost of the ELISA serology was >$39 then stool testing became preferable at all prevalence rates. Fingerstick whole blood tests were not cost-effective.

CONCLUSIONS

The choice of an initial test for H. pylori detection depends on the prevalence of H. pylori infection and the value placed on increased diagnostic accuracy. Although ELISA results in the lowest cost-effectiveness ratios, in patients at low-intermediate pretest probability of infection, the stool test provides increased accuracy, with modest incremental costs.

Detection of Helicobacter pylori DNA in fecal samples from infected individuals

Stool, gastric biopsy, and serum samples were collected from 22 subjects. DNA from stool was extracted, amplified, and hybridized with primers specific for the 16S rRNA gene of Helicobacter pylori. DNA from gastric biopsy specimens was analyzed similarly for comparison. Universal primers were used to confirm successful extraction of DNA from samples. Histologic, serologic, and DNA analyses were scored in a blinded fashion. Universal primer amplification verified successful DNA extraction from all stool and gastric tissue specimens. The gastric tissue DNA assay was positive for H. pylori in 11 of the 22 subjects, correlating completely with histologic and serologic results. Stool DNA was positive for H. pylori by our molecular assay in 8 of these 11 H. pylori-positive subjects. All subjects who were negative by histologic, serologic, and gastric tissue DNA analyses were also negative by stool DNA analysis. Compared to histology, serology, and gastric tissue DNA analyses, the sensitivity of our stool DNA assay was 73%, with a specificity of 100%.

Reverse transcription-polymerase chain reaction in the diagnosis of Helicobacter pylori infection in Finnish children

BACKGROUND

The purpose of this study was to design a simplified polymerase chain reaction (PCR) technique for the detection of Helicobacter pylori and to compare it with conventional diagnostic methods-culture and histology of gastric biopsy specimens. In addition, the capability of this technique to detect H. pylori in the gastric mucosal biopsies of originally H. pylori-negative children with gastritis or recurrent abdominal pain was investigated.

METHODS

Reverse transcriptase polymerase chain reaction (RT-PCR) using polymerase from Thermus thermophilus was applied to detect H. pylori 16S rRNA. Twenty-five children H. pylori-positive by culture and/or histology were used as positive control subjects. Sixteen healthy H. pylori-negative children served as negative control subjects. Biopsy specimens from gastric antrum and corpus from 81 children were examined by RT-PCR. Altogether, 30 had histologic gastritis and 51 had nonspecific abdominal pain only, with no disease in histologic specimens. Histology and culture of H. pylori were negative in both patient groups.

RESULTS

Reverse transcription-polymerase chain reaction detected 24 of 25 tissue-positive and 0 of 16 tissue-negative cases, indicating 96% sensitivity and 100% specificity for the test. None of the culturally and histologically H. pylori-negative samples showed H. pylori colonization when analyzed by RT-PCR.

CONCLUSIONS

RT-PCR using Thermus thermophilus polymerase is a fast and simple means of detecting H. pylori in gastric biopsy specimens. It is at least as specific and sensitive as conventional methods. In pediatric patients it may be necessary to take more than two biopsy specimens to increase sensitivity in cases of local or patchy colonization.

The value of different detection methods of Helicobacter pylori during treatment

It has been suggested that profound acid inhibition by proton pump inhibitors affects the accuracy of H. pylori detection. This report aims to evaluate H. pylori status during treatment with four different invasive detection methods and to investigate if histopathological alterations during treatment can be used as an early marker for H. pylori eradication. Twenty-eight H. pylori-positive patients were studied randomized into two treatment groups: 14 patients received omeprazole, 20 mg plus amoxicillin 1,000 mg b.i.d (OA), and 14 patients received omeprazole, 20 mg and placebo b.i.d (OP) for 14 days. Biopsies from antrum and corpus of the stomach were collected on days 0, 10 and 42. H. pylori status was based on rapid urease test, cultivation, histology, and polymerase chain reaction (PCR). The biopsies were also graded according to the Sidney classification. In the OP and the OA group, 17% (2/12) and 92% (12/13) of the patients were H. pylori negative when tested during treatment (day 10). Four weeks after treatment none of the patients (0%) in the OP group and 61% (8/13) in the OA group had their H. pylori infection eradicated. PCR was up to 34% more sensitive than the other tests to detect H. pylori during treatment. There was a decrease in histological inflammation and activity in the antrum already during treatment in the OA group, but the decrease did not discriminate for successful treatment. During treatment with omeprazole alone or in combination with amoxicillin, H. pylori detection is impaired regardless of the detection method used. However, PCR appears to be more sensitive than other tests. Early changes in the histological appearance of the gastric mucosa do not predict H. pylori treatment outcome.

Evaluation of performances of three DNA enzyme immunoassays for detection of Helicobacter pylori PCR products from biopsy specimens

PCR is recognized as a promising method for the detection of Helicobacter pylori in gastric biopsy specimens. However, detection of PCR products by gel electrophoresis is difficult to implement in routine clinical laboratories. The aim of this study was to compare three new DNA enzyme immunoassays with the standard method in their ability to detect PCR products. The three assays were based on the amplification of a fragment of the ureC gene of H. pylori and a colorimetric hybridization assay. The first assay (GEN-ETI-K DNA enzyme immunoassay; Sorin, Sallugia, Italy) was based on the hybridization of amplified DNA with a probe bound in microtiter wells and detected with labelled anti-DNA antibody. The second assay (Pylori-prob; Biocode, Sclessin, Belgium) comprised a solid-phase sandwich hybridization system with a specific biotinylated probe being used for detection. Finally, the third assay (PCR enzyme-linked immunosorbent assay; Boehringer, Mannheim, Germany) was based on the hybridization of amplified DNA labelled with digoxigenin as a probe (used as a coating in microtiter wells) and detected with antidigoxigenin-peroxidase as conjugate. The sensitivity of the colorimetric assay was evaluated by using amplification products from PCR assays performed on several 10-fold dilutions of DNA from H. pylori CIP 101260, and the specificity was assessed with different urease-positive bacteria. Biopsy specimens from 199 patients were tested; 106 were classified as H. pylori positive, and 93 were classified as H. pylori negative by culture and/or histological examination as the "gold standard." The receiving operating characteristic curve was used to determine the best cutoff point for each assay. The detection of PCR products by colorimetric hybridization increases the sensitivity up to 100-fold compared to that with gel electrophoresis. The results are rapid (4 h) and easy to interpret and can be automated.

IgG and IgA antibodies in Helicobacter pylori infections

We compared Helicobacter pylori-specific IgG and IgA antibodies in serum, salivary and gastric juice of H. pylori-infected and noninfected patients using the ELISA method. Serum and salivary anti-H. pylori IgG and IgA titres were higher in H. pylori-positive than H. pylori-negative patients. Serum H. pylori IgG titres were higher than those of serum-specific IgA. In contrast, H. pylori IgA titres in saliva samples were higher than those of specific IgG. In all patients, the levels of IgG antibodies were very low in gastric juice. H. pylori-positive patients with increased levels of IgA in sera, also exhibited increased IgA levels in gastric juice. The determination of IgA antibodies in serum and saliva may be used as a test that complements the IgG antibody assay.

Absence of Helicobacter pylori DNA in salivary lymphoepithelial lesions

Helicobacter pylori is a common cause of chronic gastritis and has been implicated as the main agent responsible for the development of lymphomas of mucosa associated lymphoid tissue (MALT) in the stomach. An uncommon cause of salivary gland swelling is salivary lymphoepithelial lesion (SLEL), which shows histological features of acquired MALT and is associated with the development of MALT-type lymphomas. Since H. pylori has been identified in the oral cavity, we hypothesised that this organism might act as a potential antigen for the development of MALT in salivary glands. Routinely processed biopsies of 20 SLEL were screened for H. pylori DNA using a sensitive two-stage PCR technique to amplify the 16S ribosomal RNA gene. Immunoglobulin heavy chain gene monoclonality was determined by amplifying the VDJ gene using a nested PCR technique. All SLEL had histological features of organised MALT and 14 cases showed Ig heavy chain gene monoclonality consistent with MALT lymphoma. None of the SLEL contained H. pylori DNA. In contrast to the putative role of H. pylori as an antigenic stimulus in gastric MALT lymphomas, it appears not to play a role locally in the development of MALT or MALT lymphomas of the salivary gland.

Recurrence of Helicobacter pylori infection after successful eradication: nature and possible causes

Recurrence of Helicobacter pylori infection after successful eradication occurs and is associated with relapse of gastroduodenal diseases. The aims of this paper were to assess the incidence and identify the nature and possible causes of recurrence of the infection. A broad-based Medline search was performed to identify all related publications addressing recurrence of the infection between 1986 and 1995. The 12-month recurrence rate varied among the different studies from 0 to 41.5%. A few studies showed 18- to 24-month recurrence rates, which ranged between 0 and 21.4%. Limited data, obtained using molecular fingerprinting techniques, have shown that in most cases recurrence is due to recrudescence of the original strain; a few cases appear to be due to reinfection with a new strain. Recrudescence is most likely during the first 12 months after apparent eradication. Despite the high sensitivity and specificity of the available individual tests for detecting H. pylori infection in untreated patients, no technique alone is sensitive enough to monitor eradication when the four-week-rule definition for eradication is used. A combination of two or more techniques increases sensitivity. Sensitivity and specificity are increased when biopsies are taken from both gastric antrum and corpus. The best treatments have the lowest recurrence rates and recurrence is rare when the eradication rate is over 90%. Individual susceptibility and reexposure to H. pylori are suggested as two major causes of reinfection.

Polymerase chain reaction for the detection of Helicobacter pylori in formaldehyde-sublimate fixed, paraffin-embedded gastric biopsies

To improve morphologic detail and immunohistochemical staining, mercuric chloride-containing fixatives such as formaldehyde-sublimate (FS) has been widely used as an alternative for neutral buffered formalin. FS-fixed, paraffin-embedded tissue, however, is considered to be an unreliable source of DNA. We used an adapted DNA-extraction method for FS-fixed, paraffin-embedded tissue. In all cases tested we obtained amplifiable DNA with polymerase chain reaction (PCR), after FS-fixation and after fixation in neutral buffered formalin as well. A PCR assay for the 16S-rRNA region of Helicobacter pylori was developed amplifying a fragment of 145 bp. The specificity of this PCR assay was tested on a range of different microorganisms. PCR was performed on 46 archival FS-fixed paraffin-embedded gastric biopsies. The results were compared with histologic examination and with immunohistochemical detection using a polyclonal antibody against H. pylori. Both PCR and immunohistochemistry are very sensitive methods for the detection of H. pylori. A PCR offers the possibility of additional subtyping in archival FS-fixed, paraffin-embedded tissue.

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.

Evaluation of experimental therapeutics in a new mouse model of Helicobacter felis utilizing 16S rRNA polymerase chain reaction for detection

BACKGROUND

A new mouse model of Helicobacter felis infection, which mimics the human infection observed with H. pylori, has recently been developed utilizing polymerase chain reaction (PCR) based on the 16S rRNA gene sequence for detection of infection.

METHODS

We tested several therapeutic regimens in this model, including some currently utilized in the clinic and some shown ineffective in the clinic.

RESULTS

The therapeutic results obtained by PCR with this model are consistent with results observed in the published human H. pylori clinical trials and also with results obtained in another H. felis mouse model utilizing culture and histology.

CONCLUSIONS

These results support further use of this new model in screening for new therapeutic regimens for the management of Helicobacter disease.

Immunohistochemical detection of Helicobacter pylori in the surface mucous gel layer and its clinicopathological significance

BACKGROUND

Attempts have been made to develop an accurate method for detecting Helicobacter pylori in histological sections.

MATERIALS AND METHODS

Biopsy specimens were obtained from the stomachs of 167 patients with gastric ulcer (33), duodenal ulcer (52), gastroduodenal ulcer (15), chronic gastritis (45), and normal mucosa (22) before antimicrobial treatment and from 108 of these patients after treatment. Biopsy specimens were (1) cultured, (2) fixed in 10% buffered formalin, or (3) fixed in Carnoy's solution. The latter method was employed to preserve the surface mucous gel layer (SMGL) covering gastric surface mucous cells. Histological sections were stained with hematoxylin and eosin (H&E), with immunostaining using a commercially available polyclonal anti-H. pylori antibody.

RESULTS

Cultures were positive for H. pylori in 61% of the cases before treatment and in 16% after treatment; by H&E staining using formalin-fixed materials: 70% and 9%; by immunostaining using formalin-fixed materials: 78% and 21%; and by immunostaining using Carnoy-fixed materials: 85% and 41% of biopsy specimens, respectively. The difference in detection rates between materials fixed in formalin and those in Carnoy's solution was due to the detection of H. pylori in the SMGL by the latter, especially after antimicrobial treatment.

CONCLUSIONS

Immunostaining for H. pylori using materials fixed in Carnoy's solution revealed H. pylori in the SMGL as well as on the surface mucous cells and in the gastric pits and permitted the optimal detection of H. pylori in tissue sections.

A newly developed PCR assay of H. pylori in gastric biopsy, saliva, and feces. Evidence of high prevalence of H. pylori in saliva supports oral transmission

We have recently developed a new PCR assay for the detection of H. pylori. In this study, the polymerase chain reaction (PCR) assay was used to detect H. pylori in 88 gastric biopsy, 85 saliva, and 71 fecal specimens from 88 patients. H. pylori infection was confirmed in 71 of 88 patients by culture and/or histological stain of gastric biopsies. Serum IgG antibody to H. pylori was also measured and resulted in 97% sensitivity and 94% specificity. H. pylori DNA was detected by the PCR assay in gastric biopsy specimens from all 71 patients (100% sensitivity) with proven gastric H. pylori infection but not from 17 noninfected patients (100% specificity). In saliva specimens, H. pylori DNA was identified in 57 of the 68 patients (84%) with proven gastric H. pylori infection and in three of the 17 patients without gastric H. pylori infection. However, the PCR assay was only able to detect H. pylori DNA in the feces from 15 of 61 patients (25%) with proven gastric H. pylori infection and one of the 10 patients without gastric H. pylori infection. The results show that the PCR assay is reliable for detecting the presence of H. pylori in gastric biopsy and saliva specimens. The data indicate that H. pylori exists in a higher prevalence in saliva than feces and that the fecal-oral route may be an important means of transmission of this infection in developing countries but not as significant as previously suspected in the developed countries. It is likely that the oral-oral route is more prominent.

The application of epitope mapping in the development of a new serological test for Helicobacter pylori infection

Epitope mapping was applied to the derived amino acid sequences of the urease A and urease B genes of Helicobacter pylori. This identified 15 epitopes of which five were the most immunodominant. These were LTPKELD (Ure A), FISP, QIPTAF, EVGKVA and SIP (Ure B). Peptide 1 representing LTPKELD and peptide 2 representing EVGKVA were used to develop ELISA procedures for detecting antibody specific to H. pylori infection. The sensitivity, specificity and efficiency values for peptide 1 reactive IgM were 31.6, 92.8 and 52.5% and for peptide 1 IgG were 52.6, 35.7 and 45.4%. The corresponding values for peptide 2 IgM were 31.6, 100 and 60.6% and for peptide 2 IgG were 63.2, 71.4 and 66.6% respectively. When the tests were combined so that a positive for either peptide was counted as a positive overall the figures for IgM were 52.6, 92.8 and 69.6%. Thus epitope mapping delineated peptides against which specific IgM was produced in active H. pylori infection.

Detection of Helicobacter pylori in gastric biopsy and resection specimens

AIMS

To compare the sensitivity of detecting Helicobacter pylori in gastric biopsy and resection specimens using tinctorial and silver impregnation stains, immunohistochemistry and the polymerase chain reaction (PCR).

METHODS

Formalin fixed, paraffin wax embedded tissue from 33 gastric biopsy specimens (26 showing chronic gastritis and seven showing low grade mucosa associated lymphoid tissue (MALT) lymphoma) together with blocks of uninvolved mucosa from gastrectomy specimens for MALT lymphoma (five cases) were studied. Consecutive sections were stained using haematoxylin and eosin, Giemsa, the Warthin-Starry silver stain, and a polyclonal antibody directed against H pylori using an immunoperoxidase technique following heat induced antigen retrieval. PCR analysis of DNA extracted from a further section was carried out using primers which amplified a 411 base pair fragment of the urease A gene.

RESULTS

H pylori was detected in 14 (37%) sections stained with haematoxylin and eosin, 21 (55%) with Giemsa, 23 (61%) with Warthin-Starry, and 25 (66%) stained with the antibody. Seventeen (45%) cases were positive on PCR. Immunohistochemistry was positive in all cases in which H pylori was detected by other methods.

CONCLUSION

Immunohistochemistry using an immunoperoxidase technique following heat induced antigen retrieval for detecting H pylori in gastric biopsy and resection specimens is highly sensitive and easy to use.

A sensitive and specific PCR method to detect Helicobacter felis in a conventional mouse model

Although many detection methods have been used to determine Helicobacter colonization in small animal models, the sensitivity and specificity of these detection methods are limited. To improve the Helicobacter felis conventional mouse model for accurate evaluation of therapeutic regimens, we developed a PCR for detection of, and a competitive PCR for quantitation of, H. felis in viral antibody-free (VAF) mice. The PCR was based on the H. felis 16S rRNA gene. An internal control DNA was used for competitive quantitation of the PCR. VAF conventional Swiss-Webster mice were infected with an H. felis culture by oral gavage. At various times after H. felis challenge and therapy, stomach mucosa was collected and evaluated by PCR. PCR detected approximately 50 to 100 H. felis cells per mouse stomach and showed no cross-reaction with other bacteria commonly found in mouse stomachs. Colonization of H. felis in the mouse stomach was confirmed by culture isolation from germfree mice and histological examination of VAF mice. Response to therapy in this H. felis model correlated well with results seen in human clinical trials with H. pylori. A model utilizing PCR detection which may be useful for discovering new antibiotics and/or vaccines against Helicobacter ulcer disease has been developed.