Review article: clinic-based testing for Helicobacter pylori infection by enzyme immunoassay of faeces, urine and saliva

States and hotspots in Helicobacter pylori research from 2002 to 2021: A bibliometric analysis

BACKGROUND

Recently, numerous publications on Helicobacter pylori (H. pylori) have been published, but bibliometric analyses on this research field are scarce. To address this gap, we conducted a bibliometric analysis to provide a comprehensive overview and to explore the current research states and hotspots in this field.

MATERIALS AND METHODS

Publications on H. pylori from 2002 to 2021 were retrieved from the Web of Science Core Collection database (WoSCC). Trends in publications and citations were analyzed using Excel 2021. VOSviewer and Citespace were used to perform bibliometrics analysis.

RESULTS

36,266 publications on H. pylori were retrieved from the WoSCC database. In general, we observed an increasing trend in the number of publications over the past 20 years. The United States was the most productive and influential country, with the largest proportion of both publications and total citations. Helicobacter, US Department of Veterans Affairs, and Graham, David were the most productive journals, institutions and authors, respectively. Further analysis the co-occurrence and burst detection of keywords revealed that the most common keywords were "Helicobacter pylori," "gastric cancer," and "gastritis," all keywords were divided into eight main clusters, and the most important current research hotspot was the relationship between H. pylori infection and the changes of gut microbiota.

CONCLUSIONS

The United States has been the most productive and influential country on H. pylori research, and H. pylori-related research remains an active research field. The relationship between H. pylori infection and the changes of gut microbiota is a research hotspot attracting significant attention.

Helicobacter pylori Infection, Its Laboratory Diagnosis, and Antimicrobial Resistance: a Perspective of Clinical Relevance

Despite the recent decrease in overall prevalence of Helicobacter pylori infection, morbidity and mortality rates associated with gastric cancer remain high. The antimicrobial resistance developments and treatment failure are fueling the global burden of H. pylori-associated gastric complications. Accurate diagnosis remains the opening move for treatment and eradication of infections caused by microorganisms. Although several reports have been published on diagnostic approaches for H. pylori infection, most lack the data regarding diagnosis from a clinical perspective. Therefore, we provide an intensive, comprehensive, and updated description of the currently available diagnostic methods that can help clinicians, infection diagnosis professionals, and H. pylori researchers working on infection epidemiology to broaden their understanding and to select appropriate diagnostic methods. We also emphasize appropriate diagnostic approaches based on clinical settings (either clinical diagnosis or mass screening), patient factors (either age or other predisposing factors), and clinical factors (either upper gastrointestinal bleeding or partial gastrectomy) and appropriate methods to be considered for evaluating eradication efficacy. Furthermore, to cope with the increasing trend of antimicrobial resistance, a better understanding of its emergence and current diagnostic approaches for resistance detection remain inevitable.

<p>Observation of Changes in <em>Helicobacter pylori</em> Antigen and Antibody Positivity According to Non-Invasive Tests Before and After <em>Helicobacter pylori</em> Eradication Therapy in Symptomatic Patients</p>

Background

Non-invasive tests can help with the diagnosis of Helicobacter pylori (H. pylori) infection and in determining patient prognosis following H. pylori eradication therapy. The aim of the study was to detect H. pylori antigens in the stool in symptomatic patients and to observe changes in the antigen test results following H. pylori eradication therapy.

Methods

A prospective study was conducted. Blood, urine and stool samples were collected from 62 dyspeptic patients. Anti-H. pylori IgM and IgG antibodies were detected in the serum by ELISA, anti-H. pylori IgG antibodies were detected in the urine by ICT and H. pylori antigens were detected in the stool by ELISA. Among the 62 patients, 39 (62.90%) were positive with all three methods. These 39 patients were asked to complete a 2-week course of medication and return after 6 weeks following completion of therapy to undergo repeated tests. In total, 3 dropped out of the study.

Results

Among the 62 dyspeptic patients, 41 (66.13%) were positive for serum IgG according to ELISA, 39 (62.90%) were positive for urine IgG according to ICT, 8 (12.90%) were positive for serum IgM according to ELISA, and 42 (67.74%) were positive for HpSA according to ELISA. After eradication therapy, 18 (50.00%) patients were positive for serum IgG, 19 (52.78%) were positive for urine IgG, 4 (11.11%) were positive for serum IgM and 5 (13.88%) were positive for HpSA. The difference in HpSA positivity before and after eradication therapy was statistically significant (P <0.05).

Conclusion

This study involved non-invasive procedures that can be used as first-line screening tools for the detection of active H. pylori infection to observe the role of HpSA test in diagnosis and assessment of prognosis following eradication therapy for H. pylori.

The Diagnostic Tests for Detection of Helicobacter pylori Infection

Helicobacter pylori causes one of the most common infections in human populations. The role of this bacterium in chronic gastritis, gastric ulcer, gastric cancer, as well as extra-digestive diseases such as ischemic heart disease and chronic obstructive pulmonary diseases, is well known. Prevention and control of these diseases can occur by early diagnosis and eradication of H. pylori infection. At present, different methods have been established to detect H. pylori infection. The biopsy-based tests, which are known as invasive methods, such as rapid urease test and histology, have the highest specificity among the others. Similarly, culture of biopsy samples is used for diagnosis of H. pylori infection. It has a high specificity value, and also allows us to perform antibiotic sensitivity testing. On the contrary, polymerase chain reaction and other molecular methods have good sensitivity and specificity, and can be used for detection of H. pylori infection, its virulence factors, and eradication success after treatment. While serological tests are more appropriate for epidemiological studies, their main weakness for clinical use is low specificity. Overall, specificity and sensitivity, cost, usefulness, and limitation of tests should be considered for selection of detection methods of H. pylori in each country.

Development of a single-step immunoassay microdevice based on a graphene oxide-containing hydrogel possessing fluorescence quenching and size separation functions

An immunoassay, which is an indispensable analytical method both in biological research and in medical fields was successfully integrated into a "single-step" by developing a microdevice composed of a graphene oxide (GO)-containing hydrogel and a poly (dimethylsiloxane) (PDMS) microchannel array with a polyethylene glycol (PEG) coating containing a fluorescently-labelled antibody. Here we used 2-hydroxyethylmethacrylate (HEMA) as a monomer that is easily, and homogeneously, mixed with GO to synthesize the hydrogel. The fluorescence quenching and size separation functions were then optimized by controlling the ratios of HEMA and GO. Free fluorescently-labelled antibody was successfully separated from the immunoreaction mixture by the hydrogel network structure, and the fluorescence was subsequently quenched by GO. In comparison to the previously reported immunoassay system using GO, the present system achieved a very high fluorescence resonance energy transfer (FRET) efficiency (∼90%), due to the use of direct adsorption of the fluorescently-labelled antibody to the GO surface; in contrast, the former reported method relied on indirect adsorption of the fluorescently-labelled antibody via immunocomplex formation at the GO surface. Finally, the single-step immunoassay microdevice was made by combining the developed hydrogel and the PDMS microchannel with a coating containing the fluorescently-labelled antibody, and successfully applied for the single-step analysis of IgM levels in diluted human serum by simple introduction of the sample via capillary action.

Fast and single-step immunoassay based on fluorescence quenching within a square glass capillary immobilizing graphene oxide-antibody conjugate and fluorescently labelled antibody

A single-step, easy-to-use, and fast capillary-type immunoassay device composed of a polyethylene glycol (PEG) coating containing two kinds of antibody-reagents, including an antibody-graphene oxide conjugate and fluorescently labelled antibody, was developed in this study. The working principle involved the spontaneous dissolution of the PEG coating, diffusion of reagents, and subsequent immunoreaction, triggered by the capillary action-mediated introduction of a sample solution. In a sample solution containing the target antigen, two types of antibody reagents form a sandwich-type antigen-antibody complex and fluorescence quenching takes place via fluorescence resonance energy transfer between the labelled fluorescent molecules and graphene oxide. Antigen concentration can be measured based on the decrease in fluorescence intensity. An antigen concentration-dependent response was obtained for the model target protein sample (human IgG, 0.2-10 μg mL(-1)). The present method can shorten the reaction time to within 1 min (approximately 40 s), while conventional methods using the same reagents require reaction times of approximately 20 min because of the large reaction scale. The proposed method is one of the fastest immunoassays ever reported. Finally, the present device was used to measure human IgG in diluted serum samples to demonstrate that this method can be used for fast medical diagnosis.

A single-step enzyme immunoassay capillary sensor composed of functional multilayer coatings for the diagnosis of marker proteins

A single-step, easy-to-use enzyme immunoassay capillary sensor, composed of substrate-immobilized hydrophobic coating, hydrogel coating, and soluble coating containing an enzyme-labeled antibody, was developed.

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.

Helicobacter pylori: A chameleon-like approach to life

Helicobacter pylori (H. pylori) is widely adaptable for colonization in human stomachs in more than half of the world’s population. The microorganism is characterized by an unusual capability of arranging itself in both genotypic and phenotypic ways. Stressing conditions, including antimicrobial agents in sub-inhibitory concentrations, facilitate entering the viable but nonculturable state in which bacterial cells acquire the coccoid form. This morphotype represents an important strategy for bacterial survival in unsuitable conditions and also allows escape from the immune system. H. pylori is capable of forming biofilm outside and inside the host. For the bacterial population, the sessile growth mode represents an ideal environment for gene rearrangement, as it allows the acquiring of important tools aimed to improve bacterial “fitness” and species preservation. Biofilm formation in H. pylori in the human host also leads to recalcitrance to antibiotic treatment, thus hampering eradication. These lifestyle changes of H. pylori allow for a “safe haven” for its survival and persistence according to different ecological niches, and strongly emphasize the need for careful H. pylori surveillance to improve management of the infection.

Floating chip mounting system driven by repulsive force of permanent magnets for multiple on-site SPR immunoassay measurements

We have developed a measurement chip installation/removal mechanism for a surface plasmon resonance (SPR) immunoassay analysis instrument designed for frequent testing, which requires a rapid and easy technique for changing chips. The key components of the mechanism are refractive index matching gel coated on the rear of the SPR chip and a float that presses the chip down. The refractive index matching gel made it possible to optically couple the chip and the prism of the SPR instrument easily via elastic deformation with no air bubbles. The float has an autonomous attitude control function that keeps the chip parallel in relation to the SPR instrument by employing the repulsive force of permanent magnets between the float and a float guide located in the SPR instrument. This function is realized by balancing the upward elastic force of the gel and the downward force of the float, which experiences a leveling force from the float guide. This system makes it possible to start an SPR measurement immediately after chip installation and to remove the chip immediately after the measurement with a simple and easy method that does not require any fine adjustment. Our sensor chip, which we installed using this mounting system, successfully performed an immunoassay measurement on a model antigen (spiked human-IgG) in a model real sample (non-homogenized milk) that included many kinds of interfering foreign substances without any sample pre-treatment. The ease of the chip installation/removal operation and simple measurement procedure are suitable for frequent on-site agricultural, environmental and medical testing.

Passive fluidic chip composed of integrated vertical capillary tubes developed for on-site SPR immunoassay analysis targeting real samples

We have successfully developed a surface plasmon resonance (SPR) measurement system for the on-site immunoassay of real samples. The system is composed of a portable SPR instrument (290 mm(W) × 160 mm(D) × 120 mm(H)) and a microfluidic immunoassay chip (16 mm(W) × 16 mm(D) × 4 mm(H)) that needs no external pump system. An integrated vertical capillary tube functions as a large volume (150 μL) passive pump and a waste reservoir that has sufficient capacity for several refill operations. An immunoassay was carried out that employed the direct injection of a buffer and a test sample in sequence into a microfluidic chip that included 9 antibody bands and 10 reference reagent bands immobilized in the flow channel. By subtracting a reliable averaged reference sensorgram from the antibody, we effectively reduced the influence of the non-specific binding, and then our chip successfully detected the specific binding of spiked IgG in non-homogeneous milk. IgG is a model antigen that is certain not to be present in non-homogeneous milk, and non-homogeneous milk is a model of real sample that includes many interfering foreign substances that induce non-specific binding. The direct injection of a real sample with no pretreatment enabled us to complete the entire immunoassay in several minutes. This ease of operation and short measuring time are acceptable for on-site agricultural, environmental and medical testing.

The source of Helicobacter pylori infection in the neonatal period

AIMS

To investigate the transmission of Helicobacter pylori in the perinatal period.

METHODS

H. pylori status of 180 women was preliminarily screened by serology and stool antigen test (SAT) within the fourth day after delivery and a positive value was confirmed by (13)C-urea breath test. Infants were analyzed by SAT at 1, 6, 12 and 18 months of age. H. pylori status was also investigated in the medical and paramedical staff of the Neonatology Unit.

RESULTS

H. pylori infection was found in 34.4% of the women. At the 1(st) month of age, 5 out of 172 newborns (2.9%) were H. pylori positive by SAT. Three out of the five positive infants were born to H. pylori non-infected mothers. Formula feeding (P=0.02) and admission in intermediate-risk neonatal unit (P=0.01) were significantly related to a positive H. pylori result. Medical and paramedical staff of the neonatology unit was found H. pylori positive in 34.8% of cases. All five H. pylori positive children spontaneously cleared the infection.

CONCLUSIONS

Perinatal H. pylori SAT positive status is low in our area, and it may be found both in infants from infected or non-infected mothers. Formula feeding and admission in intermediate-risk neonatal unit appear to be related with H. pylori infection.

Development of an immunochromatographic assay specifically detecting pandemic H1N1 (2009) influenza virus

The pandemic caused by a new type of influenza virus, pandemic H1N1 (2009) influenza virus A (AH1pdm), has had a major worldwide impact. Since hemagglutinin (HA) genes are among the most specific genes in the influenza virus genome, AH1pdm can be definitively diagnosed by viral gene analysis targeting the HA genes. This type of analysis, however, cannot be easily performed in clinical settings. While commercially available rapid diagnosis kits (RDKs) based on immunochromatography can be used to detect nucleoproteins (NPs) of influenza A and B viruses in clinical samples, there are no such kits that are specific for AH1pdm. We show here that an RDK using a combination of monoclonal antibodies against NP can be used to specifically detect AH1pdm. The RDK recognized AH1pdm virus isolates but did not recognize seasonal H1N1 and H3N2 and influenza B viruses, indicating that the specificity of the RDK is 100%. A parallel comparison of RDK with a commercial influenza A/B virus kit revealed that both types of kits had equal sensitivities in detecting their respective viruses. Preliminary evaluation of clinical samples from 5 individuals with PCR-confirmed human AH1pdm infection showed that the RDK was positive for all samples, with the same detection intensity as that of a commercial influenza A/B virus kit. This RDK, together with a new vaccine and the stockpiling of anti-influenza drugs, will make aggressive measures to contain AH1pdm infections possible.

Effects of extremely low-frequency electromagnetic fields on Helicobacter pylori biofilm

The aim of this work was to investigate the effects of exposure to extremely low-frequency electromagnetic fields (ELF-EMF) both on biofilm formation and on mature biofilm of Helicobacter pylori. Bacterial cultures and 2-day-old biofilm of H. pylori ATCC 43629 were exposed to ELF-EMF (50 Hz frequency-1 mT intensity) for 2 days to assess their effect on the cell adhesion and on the mature biofilm detachment, respectively. All the exposed cultures and the respective sham exposed controls were studied for: the cell viability status, the cell morphological analysis, the biofilm mass measurement, the genotypic profile, and the luxS and amiA gene expression. The ELF-EMF acted on the bacterial population during the biofilm formation displaying significant differences in cell viability, as well as, in morphotypes measured by the prevalence of spiral forms (58.41%) in respect to the controls (33.14%), whereas, on mature biofilm, no significant differences were found when compared to the controls. The measurement of biofilm cell mass was significantly reduced in exposed cultures in both examined experimental conditions. No changes in DNA patterns were recorded, whereas a modulation in amiA gene expression was detected. An exposure to ELF-EMF of H. pylori biofilm induces phenotypic changes on adhering bacteria and decreases the cell adhesion unbalancing the bacterial population therefore reducing the H. pylori capability to protect itself.

Production of polyclonal antibody against alkyl hydroperoxide reductase of Helicobacter pylori and its antigenicity

Stool-antigen detection kits for diagnosis of Helicobacter pylori infection have been widely used because of their full non-invasive nature. Because Helicobacter pylori strains show a distinctive genetic diversity, it is important to find a protein that is a common antigen of various strains and shows a strong immunogenicity for the development of a stool- antigen detection kit. Alkyl hydroperoxide reductase (AhpC) of Helicobacter pylori strongly reacts with the sera of patients with gastritis and peptic ulcer. Therefore, AhpC seems to be an excellent candidate as a target protein for this study. Accordingly, polyclonal antiserum against AhpC was produced in adult New Zealand white rabbits by using AhpC in the gel bands without adding Freund's adjuvant. In addition, isolation and purification of AhpC were perfomed by preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis and electroelution. In this study, a simple method was used for rapid production of polyclonal antibody against AhpC of H. pylori, which avoids both the long-term AhpC purification and the addition of Freund's adjuvant. One-dimensional preparative gel electrophoresis allows a single and short purification step; the high-resolution capacity of this technique leads to a high level of purity of the protein and consequently to a very high specificity of the antibody. Moreover, this method avoids contamination by other non-specific proteins, which often appear during the purification process by column chromatographic techniques, which may also decrease the purity of the immunogen. The present method is simple, rapid and cost-effective, and also makes it possible to produce antibody for stool-antigen enzyme immunoassay in a short time and at low cost.

Characterization of an Helicobacter pylori environmental strain

AIMS

To investigate the main genotypic virulence markers and the phenotypic features of an environmental Helicobacter pylori strain, named MDC1.

METHODS AND RESULTS

The H. pylori MDC1 genotypic status was evaluated by PCR amplification. The mosaicism in vacA alleles was expressed by the s1m1 allelic combination, as found in strains which are strong vacuolating cytotoxin producers; the number of cagA variable EPIYA motifs displayed P1P2P3P3 pattern and the iceA1 was recorded between the iceA allelic types and the babA2 gene found in strains causing more severe disease. The biofilm formation was evaluated on a polystyrene surface in static conditions by scanning electron microscopy and confocal scanning laser microscopy. Helicobacter pylori MDC1 displayed a dense mature biofilm with cells in a coccoid morphology persistent in time in which the expression of the luxS gene, related to the quorum-sensing signalling, was always detected.

CONCLUSIONS

Helicobacter pylori MDC1 strain had the main virulence markers closely related to gastric pathogenesis and displayed a well-structured biofilm which allowed this bacterium to be more protected in the environment.

SIGNIFICANCE AND IMPACT OF THE STUDY

The persistence of the environmental virulent H. pylori strain in a clustered state suggests a long-term survival of this bacterial community outside of the host, enabling the bacterial transmission with important clinical repercussions.

Immunochromatographic monoclonal test for detection of Helicobacter pylori antigen in stool is useful in children from high-prevalence developing country

BACKGROUND

Tests to detect Helicobacter pylori antigens in feces for diagnosis of infection in children demonstrate controversial results. One novel and fast monoclonal test improves diagnostic accuracy in adults, but clinical evidence of its usefulness at pediatric age is insufficient to date. The objective of this work was to evaluate the diagnostic accuracy of this test in a sample of Mexican children.

METHODS

We conducted a transversal study in 150 selected children with digestive symptoms suggestive of organic disease in whom a clinical history was conducted in addition to a fast monoclonal test (ImmunoCardSTAT HpSA, Meridian Diagnostics) performed by immunochromatography. Patients were submitted to endoscopy and histopathologic study.

RESULTS

Of the 150 children (mean age 7.8 +/- 4.7 years), 107 (71.3%) were positive for the test, and presence of H. pylori was confirmed histologically in 109 (72.7%) children, with sensitivity of 96.3% (95% CI = 95.8-96.8), specificity of 95.1% (95% CI = 93.9-96.4), and accuracy of 96.0% (95% CI, -95.6 to -96.3); pretest probability was 0.73, while post-test probability was 0.98. Infection rate and test accuracy increased with age.

CONCLUSIONS

This test is useful for detecting H. pylori infection in children of all ages, and is a good alternative for screening studies in developing countries with elevated prevalence, due to its being fast, noninvasive, inexpensive, and easy to carry out.

Detection rate of Helicobacter pylori stool antigen in newborn infants and small children

AIMS

To investigate the prevalence of H. pylori antigen in the stools of Norwegian neonates and small children.

METHODS

A total of 249 children aged 0 days-3 years were tested for the presence of H. pylori antigen in feces using the HpSA immunoassay. For verification purposes, a selection of samples were analyzed with PCR targeting the 16 S rDNA Helicobacter gene.

RESULTS

H. pylori antigen in stool was detected in 52% (36/69) of the neonates, in 15% (7/46) of infants aged 7 days-1 month, and in 5% (7/134) of children aged 1 month-3 years. In neonates, H. pylori antigen detection was significantly associated with mode of delivery: 59% (30/51) with uncomplicated vaginal births were HpSA positive compared to only 10% (1/10) of infants delivered by cesarean section (P=0.02). Positive PCR results were found in 35% (9/26) of HpSA positive samples. Sequencing of PCR products revealed 97-100% homology with gene sequences from both H. pylori and other Helicobacter species.

CONCLUSIONS

The low H. pylori antigen detection rate in children >1 month of age is in accordance with previous prevalence studies from Western countries. The unexpected finding of a high H. pylori antigen detection rate in neonates suggests that transient colonization may occur in the neonatal period.

The current status of Helicobacter pylori vaccines: a review

Helicobacter pylori, a Gram-negative flagellate bacterium that infects the stomach of more than half of the global population, is regarded as the leading cause of chronic gastritis, peptic ulcer disease, and even gastric adenocarcinoma in some individuals. Although the bacterium induces strong humoral and cellular immune responses, it can persist in the host for decades. It has several virulence factors, some of them having vaccine potential as judged by immunoproteomic analysis. A few vaccination studies involving a small number of infected or uninfected humans with various H. pylori formulations such as the recombinant urease, killed whole cells, and live Salmonella vectors presenting the subunit antigens have not provided satisfactory results. One trial that used the recombinant H. pylori urease coadministered with native Escherichia coli enterotoxin (LT) demonstrated a reduction of H. pylori load in infected participants. Although extensive studies in the mouse model have demonstrated the feasibility of both therapeutic and prophylactic immunizations, the mechanism of vaccine-induced protection is poorly understood as several factors such as immunoglobulin and various cytokines do not contribute to protection. Transcriptome analyses in mice have indicated the role of nonclassical immune factors in vaccine-induced protection. The role of regulatory T cells in the persistence of H. pylori infection has also been suggested. A recently developed experimental H. pylori infection model in humans may be used for testing several new adjuvants and vaccine delivery systems that have been currently obtained. The use of vaccines with appropriate immunogens, routes of immunization, and adjuvants along with a better understanding of the mechanism of immune protection may provide more favorable results.

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.

The clinical applications and accuracy of 2 rapid near-patient tests in detecting Helicobacter pylori infection

Noninvasive methods for assessing Helicobacter pylori infection status are now an integral part of managing patients with upper gastrointestinal complaints. The aim of this study is to evaluate the feasibility and diagnostic accuracy of 2 rapid tests: a urine-based H. pylori antibody detection method (Rapirun) and a stool-based H. pylori antigen detection method (immunocard STAT! HpSA). The combined use of the mentioned 2 tests was also evaluated, which has not been described in previous similar studies. Urine and stool specimens were collected from patients who were arranged for gastroendoscopic examination. The urine and stool specimens were tested with Rapirun and immunocard STAT! HpSA separately. The estimated reaction time was about 15 to 20 min for the former and 5 to 10 min for the latter. H. pylori infection was confirmed with 4 tests: culture, histology, rapid urease test, and the (13)C-urea breath test. Obtained results from both kits were compared with confirmed results. One hundred twenty patients were eligible for analysis. Of them, 62 tested positive for H. pylori infection and 58 were negative by the confirmation criteria. The urine Rapirun test relative to the confirmed results showed sensitivity, specificity, and accuracy as 87.1% (confidence interval [CI] = 81.1-93.1%), 89.7% (CI = 84.2-95.1%), and 88.3%, respectively. The stool immunocard STAT! HpSA test relative to the confirmed results showed sensitivity, specificity, and accuracy as 96.8% (CI = 93.6-99.9%), 82.8% (CI = 76.0-89.5%), and 90%, respectively. The combined-use method of both tests revealed sensitivity, specificity, and accuracy as 98.4% (CI = 96.1-100%), 81.0% (CI = 74.0-88.1%), and 90%, respectively. These 2 urine and stool tests have a satisfactory accuracy around 90% in detecting H. pylori infection. In consideration of the advantages of cheapness, timesaving, and ease of use, both can be used as rapid near-patient tests in general practice. The combined use of both tests was also promising in detecting H. pylori infection.

Comparison of invasive methods and two different stool antigen tests for diagnosis of H pylori infection in patients with gastric bleeding

AIM: To compare two different H pylori stool antigen tests as noninvasive diagnostic methods.

METHODS: The study population consisted of 22 upper gastrointestinal system bleeding patients. Urea breath test (UBT), rapid urease test (RUT) and histopathological examination were applied to all patients. Stool specimens from these patients were examined by rapid STRİP!HpSA and one step simple H pylori antigen cassette test for the detection of H pylori antigens.

RESULTS: For these 22 patients, 15 (68.2%) were diagnosed as positive and seven (31.8%) were diagnosed negative for H pylori infection by the gold standard methods. Whereas 10 (45.5%) were positive and 12 (54.5%) were diagnosed negative by the rapid STRİP!HpSA test. The sensitivity, specificity, positive and negative predictive values were 60%, 86%, 90% and 50%, respectively. When compared to the gold standard methods, these differences were not significant. However, six patients (27.3%) were positive, and 16 (72.7%) were negative by the simple H pylori stool antigen cassette test. The sensitivity, specificity, positive and negative predictive values were 33%, 86%, 83% and 38%, respectively. Compared to the gold standard methods, the simple H pylori stool antigen cassette test results were significantly different (P = 0.012).

CONCLUSION: Rapid STRİP!HpSA test could be used as a routine diagnostic tool in the microbiology laboratory for assessing clinical significance and eradication control of H pylori in upper gastrointestinal system bleeding patients.

Evaluation of a novel rapid one-step immunochromatographic assay for detection of monoclonal Helicobacter pylori antigen in stool samples from children

A new rapid one-step immunochromatographic test using monoclonal antibodies for detection of Helicobacter pylori antigen in stool in children was evaluated on coded stool samples from 159 children (mean age, 9.7 +/- 5.0 years; 118 from Munich, 41 from Vienna): 86 children were H. pylori infected defined by positive culture and/or > or =2 other positive tests ([13C]urea breath test, histology, rapid urease test), and 73 children showed concordant negative results. Seventy-nine patients (12.1 +/- 3.8 years; 42 from Munich; 37 from Vienna) were tested 6 to 8 weeks after anti-Helicobacter pylori therapy with urea breath test and stool test. In Munich, all 160 tests (118 pre- and 42 posttreatment) were independently read by two observers. Equivocal results were excluded for calculation of sensitivity and specificity but were considered as false to assess accuracy. The two observers in Munich agreed in 63 out of 65 positive and 89 out of 95 negative results, while eight times (5.0%) they judged the test as equivocal. Pretreatment and posttreatment results for sensitivity were 88.1% (79.2 to 94.1) and 88.9% (51.8 to 99.7), specificity 88.1% (77.8 to 94.1) and 93.9% (85.2 to 98.3), and accuracy 83.5% and 81.5%, respectively. We conclude that the new monoclonal immunochromatographic quick test shows a good interobserver agreement, but equivocal results occur in 5%. Performance is comparable before and after therapy. The test may become a good alternative in children in settings where a [13C]urea breath test or a reliable enzyme immunoassay stool test are not available.

Use of a novel enzyme immunoassay based on detection of circulating antigen in serum for diagnosis of Helicobacter pylori infection

Recently, noninvasive diagnostic tests for Helicobacter pylori infection have gained in significance. We have developed a sensitive and specific noninvasive immunoassay based on the detection of an H. pylori circulating antigen (HpCA) in sera from H. pylori-infected individuals. Monospecific antibody and Western blot analyses were used to demonstrate the presence of the target antigen in H. pylori cell lysate and serum samples. A novel enzyme-linked immunosorbent assay (ELISA) was developed for the detection of HpCA in serum. Endoscopic biopsy specimens from the gastric antra of 221 individuals (143 males and 78 females) with dyspeptic symptoms were evaluated for H. pylori infection, with culture used as a "gold standard" for diagnosis. The target H. pylori antigen was identified at 58 kDa. HpCA has been detected by ELISA with high degrees of sensitivity, specificity, and efficiency (>90%), and ELISA results show no significant difference (P > 0.05) from results of H. pylori culture of gastric biopsy specimens. The test's positive and negative predictive values were also high (95 and 86%, respectively). In conclusion, a sensitive and specific immunoassay was developed for the detection of HpCA in human serum. This test can be applied for noninvasive laboratory and field diagnoses of H. pylori infection.

Accuracy of a monoclonal antibody-based stool antigen test in the diagnosis of Helicobacter pylori infection

BACKGROUND

Recent availability of tests for Helicobacter pylori antigens in stool samples has provided potentially useful tools for epidemiological studies and clinical settings. The aim of this study was to evaluate a monoclonal antibody-based H. pylori antigen stool test in the primary diagnosis of H. pylori infection, and to study the test performance after patients were treated with lanzoprazole, and after eradication therapy.

METHODS

The study included 122 dyspeptic patients. At gastroscopy, biopsy specimens were obtained for culture and histology. Stool antigen and [14C]-urea breath tests were performed concurrently. Positive culture alone or a positive [14C]-urea breath test in combination with positive histology defined the reference standard. Forty-three Hp +ve patients were treated with lanzoprazole for 2 to 4 weeks, and stool antigen tests were performed on days 1 and 7 post-treatment. After eradication therapy, 32 patients were re-examined for H. pylori infection.

RESULTS

Prevalence of H. pylori was 44.3%. Sensitivity and specificity for the stool antigen test in the primary diagnosis of H. pylori infection were 98% and 94%, with positive and negative likelihood ratios of 16.7 and 0.02, respectively. All patients had positive stool tests immediately after lanzoprazole treatment, whereas 2 patients had negative stool tests after 7 days. Triple therapy rendered all patients stool test negative.

CONCLUSIONS

The monoclonal antibody-based stool antigen test is an accurate tool in the primary diagnosis of H. pylori infection and after eradication therapy. Lanzoprazole treatment does not influence the clinical performance of the test.

Appropriate strategies for testing and treating Helicobacter pylori in children: when and how?

Helicobacter pylori infection is acquired primarily during childhood and carries a significant lifetime risk for morbidity. In developing countries, approximately 70% of children are infected with the bacterium by their 15th birthday. In the United States, the rate of H pylori infection among children varies widely--approximately 10% of all 10-year-olds are infected; however, this figure is substantially higher among populations of immigrant children and children born of recent immigrants to the United States. H pylori transmission is primarily "person-to-person" via fecal-oral, gastric-oral, or oral-oral routes, with evidence suggesting contaminated water as a potential source of infection. Risk factors for infection in childhood include an infected family member, having > or =2 siblings, crowded living conditions, lower socioeconomic means, and attendance at a daycare facility. The natural history of H pylori infection includes an increased lifetime risk for peptic ulcer and gastric adenocarcinoma or lymphoma. In children and adults who develop H pylori-related peptic ulcer, cure of the infection is associated with a <5% rate of ulcer recurrence. The ideal mode of H pylori detection among children is unclear--currently available serology and whole blood tests are unreliable, while the urea breath test and stool antigen tests have not been studied adequately. Children with confirmed H pylori-related peptic ulcer disease, iron-deficiency (sideropenic) anemia, or a first-degree relative with gastric cancer should be treated for the infection using 1 of 3 available 10- to 14-day triple therapy regimens recommended by the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition.

Stool antigen test for the diagnosis of Helicobacter pylori infection: a systematic review

Our aim was to review systematically the diagnostic accuracy of the Helicobacter pylori stool antigen test. Bibliographical searches were performed in several electronic databases and abstracts from congresses up to May 2003. Eighty-nine studies (10,858 patients) evaluated the stool antigen test in untreated patients. Mean sensitivity, specificity, positive predictive value and negative predictive value were 91%, 93%, 92% and 87%, respectively. Analysis of the eight studies (1399 patients) in which pretreatment evaluation of the monoclonal stool antigen test was performed showed better (p < .001) results (96%, 97%, 96% and 97%, respectively), with a clearer distinction between positive and negative results. Thirty-nine studies (3147 patients) evaluated the stool antigen test for the confirmation of H. pylori eradication 4-8 weeks after therapy, with accuracies of 86%, 92%, 76% and 93% for mean sensitivity, specificity, positive predictive value and negative predictive value, respectively. Results were similar when a gold standard based on at least two methods was used. Relatively low accuracy was reported in some posttreatment studies with the polyclonal stool antigen test. However, excellent results (p < .001) were achieved in all the six studies evaluating the monoclonal stool antigen test 4-8 weeks posttreatment. Results evaluating the stool antigen test < 4 weeks posttreatment are contradictory. Proton-pump inhibitors seem to affect the accuracy of the stool antigen test. Sensitivity and/or specificity in patients with gastrointestinal bleeding may be suboptimal. The stool antigen test performs well in children. Finally, the stool antigen test seems to be a cost-effective method.

Detection of Helicobacter pylori DNA in feces and saliva by polymerase chain reaction: a review

The polymerase chain reaction (PCR), known for its high sensitivity and specificity, has been used for the detection of Helicobacter pylori DNA in bodily materials such as feces and saliva. Since fecal specimens contain PCR inhibitors, DNA before PCR amplification has been purified using various biochemical, immunological and physical pre-PCR steps. Several PCR protocols, differing from each other in the selection of genomic targets and primers, have produced varying degrees of specificity and sensitivity in detecting H. pylori DNA. PCR identified antimicrobial resistance of H. pylori in feces. It also detected virulence factor genes such as the cytotoxin-associated gene (cagA) and vacuolating cytotoxin gene (vacA) in feces and saliva. While the cagA gene was detected in 50-60% of fecal specimens, it was found in 25% of salivary specimens from patients. There was considerable variation in the detection rate of H. pylori DNA in salivary samples. The detection rate in saliva with the most effective primer pair was lower than that observed in feces, making saliva a less suitable specimen for the diagnosis of H. pylori infection. There is controversy regarding the permanent presence of H. pylori in saliva. Whether the salivary and gastric specimens of an individual harbor identical or different strains has not been resolved. PCR cannot distinguish between living and dead organisms. However, it can offer quick results on fecal and salivary specimens, which may contain fastidious and slow-growing H. pylori in low numbers.

Non-invasive diagnosis of Helicobacter pylori infection: simplified 13C-urea breath test, stool antigen testing, or DNA PCR in human feces in a clinical laboratory setting?

OBJECTIVES

(1) To compare two stool antigen EIAs (HpSA, FemtoLab) and PCR of ureaseA and cagA in feces, with (13)C-urea breath test (UBT). (2) To ascertain whether a simplified UBT (breath collection time = 10 min) is as reliable as the standard assay (30 min).

DESIGN AND METHODS

Helicobacter pylori status was recorded in Group 1 (n = 187) by UBT, H. pylori stool antigen, ureA and cagA PCR in feces. UBT with 10, 20 and 30 min sampling was performed in Group 2 patients (n = 283).

RESULTS

The sensitivity and specificity of HpSA, FemtoLab, and ureA were 67% and 99%, 90% and 96%, 35% and 98%, respectively. cagA results were positive in 16/48 H. pylori-positive, and in 5/100 H. pylori-negative patients. The results of UBT with a 10- and 30-min sampling strictly overlapped.

CONCLUSION

UBT with 10 min breath collection and FemtoLab stool antigen assay are the most reliable non-invasive tests to diagnose H. pylori infection.