Magnetic immuno-PCR assay with inhibitor removal for direct detection of Helicobacter pylori in human feces

Is Immuno-PCR Better than ELISA Test for Detection of Toxoplasma gondii IgG Antibody?

INTRODUCTION

IgG antibodies against T. gondii persist for years, and can act as a reliable serological biomarker for the diagnosis of previous exposure to this parasite. Hence, the current investigation was designed to compare diagnostic power of immuno-polymerase chain reaction (iPCR) and enzyme-linked immunosorbent assay (ELISA) methods for detection of T. gondii IgG antibody.

METHODS

Immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies against T. gondii were measured by the ELISA method in 81 participants. In addition, detection of acute and chronic toxoplasmosis was performed via the ELISA IgG avidity. The set-up of iPCR was carried out and then, serum IgG of subjects were detected using the iPCR method.

RESULTS

Of 81 samples, 4 (4.9%) and 30 (37%) cases were be found positive for IgM and IgG against T. gondii in the ELISA method, respectively. Moreover, of 81 specimens, 42 (51.9%) and 39 (48.1%) samples had low-avidity IgG and high-avidity IgG by the IgG avidity kit, respectively. While, 59 (72.8%) of 81 samples were detected positive using the iPCR technique. Kappa (κ) value coefficient, between the iPCR and ELISA (for IgG) showed a strong agreement (0.360, p value < 0.001). A value of 0.25 I.U./ml for serum IgG [area under curve (AUC) = 0.720 (CI = 0.613-0.827); p = 0.002] was the cut-off value to differentiating between positive and negative toxoplasmosis (with sensitivity 66.0% and specificity 60.0%).

CONCLUSION

Our findings indicated despite a strong agreement shown between iPCR and ELISA methods, the diagnostic power of iPCR technique was more sensitive than ELISA test for detection of T. gondii IgG antibody. However, more complementary investigations are widely needed in this regard.

Simple modification to improve reliability of copro-DNA examinations for diagnosing Echinococcus multilocularis infections in red foxes

Epidemiological studies of Echinococcus multilocularis infections in definitive hosts require a reliable and economic diagnostic method. In this study, the current copro-DNA examination technique was modified by increasing the faecal amounts tested and adding a step to neutralize the faeces before DNA extraction. Reliability of the modified method was evaluated using rectal faecal samples from red foxes and comparing them with intestinal worms detected using the sedimentation and counting technique (SCT) following necropsy. The modified copro-DNA examination method demonstrated 93.9% sensitivity (138/147) on the SCT. Its detectability increased depending on the worm burden, and the sensitivity was 100% in cases harbouring over 1000 worms. From 111 SCT-negative cases, six (5.4%) were copro-DNA-positive, and all were confirmed as E. multilocularis via sequencing analysis. Five of the remaining 105 SCT-negative cases (4.8%) retained polymerase chain reaction (PCR) inhibitors in the extracted solution, suggesting that approximately 5% of the red fox faeces retained these inhibitors after treatment with the present copro-DNA extraction method. Although further evaluation is needed for faeces deposited in the wild, the present copro-DNA examination technique will help monitor the E. multilocularis prevalence in definitive hosts. When used for detailed evaluations of endemicity (e.g. changes in infection pressure or spread in non-endemic areas), the absence of PCR inhibitors should be confirmed, and multiple trials on faecal subsamples are recommended.

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.

Review: Diagnostic accuracy of PCR-based detection tests for Helicobacter Pylori in stool samples

BACKGROUND

Although different methods have been established to detect Helicobacter pylori (H. pylori) infection, identifying infected patients is an ongoing challenge. The aim of this meta-analysis was to provide pooled diagnostic accuracy measures for stool PCR test in the diagnosis of H. pylori infection.

METHODS

In this study, a systematic review and meta-analysis were carried out on various sources, including MEDLINE, Web of Sciences, and the Cochrane Library from April 1, 1999, to May 1, 2016. This meta-analysis adheres to the guidelines provided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses report (PRISMA Statement). The clinical value of DNA stool PCR test was based on the pooled false positive, false negative, true positive, and true negative of different genes.

RESULTS

Twenty-six of 328 studies identified met the eligibility criteria. Stool PCR test had a performance of 71% (95% CI: 68-73) sensitivity, 96% (95% CI: 94-97) specificity, and 65.6 (95% CI: 30.2-142.5) diagnostic odds ratio (DOR) in diagnosis of H. pylori. The DOR of genes which showed the highest performance of stool PCR tests was as follows: 23S rRNA 152.5 (95% CI: 55.5-418.9), 16S rRNA 67.9 (95%CI: 6.4-714.3), and glmM 68.1 (95%CI: 20.1-231.7).

CONCLUSIONS

The sensitivity and specificity of stool PCR test are relatively in the same spectrum of other diagnostic methods for the detection of H. pylori infection. In descending order of significance, the most diagnostic candidate genes using PCR detection were 23S rRNA, 16S rRNA, and glmM. PCR for 23S rRNA gene which has the highest performance could be applicable to detect H. pylori infection.

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.

Detection of clarithromycin-resistant Helicobacter pylori by stool PCR in children: a comprehensive review of literature

BACKGROUND

Helicobacter pylori infection is acquired mainly during childhood. To eradicate H. pylori, clarithromycin-based triple therapy has been recommended in children and adults by the latest Maastricht Consensus. However, the prevalence of clarithromycin-resistant H. pylori was higher in children than that in adults. Therefore, rapid, reliable and noninvasive methods for detecting clarithromycin-resistant H. pylori strains should be developed for children.

MATERIALS AND METHODS

Studies on evaluating stool PCR in detecting clarithromycin-resistant H. pylori and epidemiological surveys of the prevalence of clarithromycin-resistant H. pylori in children were searched in PubMed (from 1966 to December, 2011) for reviewing.

RESULTS

The average rates of primary clarithromycin-resistant H. pylori ranged from less than 10% to more than 40% in different regions. The rates of secondary resistance to clarithromycin were higher than primary resistance in the same population. In H. pylori isolated from children, the frequent point mutations that are responsible for the clarithromycin resistance included A2143G, A2142G, A2142C and A2144G, and they varied geographically. Comparing with culture-based susceptibility tests, stool PCR performed excellently for their rapidity, independence of bacterial growth, reproducibility and easy standardization. However, stool PCR showed lower sensitivity but perfect specificity in detection of clarithromycin-resistant H. pylori in children. Methodology and mixed infections of resistant H. pylori strains might contribute to the considerable discrepancies of stool PCR results.

CONCLUSION

Detection of clarithromycin-resistant H. pylori by stool PCR for children are reliable, rapid, noninvasive methods that are worthy of further clinical promotion. However, more evaluations of stool PCR in detection of clarithromycin-resistant H. pylori in children need to be conducted.

Utility of stool sample-based tests for the diagnosis of Helicobacter pylori infection in children

OBJECTIVE

Helicobacter pylori antigen or DNA in stool are meant to detect the bacteria; however, in children the colonization of the gastric mucosa by H pylori is usually weak and fecal excretion of antigen or DNA varies considerably, challenging the utility of these tests in this age group. The aim of the present study was to carry out a systematic review and meta-analysis to evaluate the performance of stool H pylori DNA and antigen tests for the diagnosis of infection in children.

METHODS

We conducted a systematic review and meta-analysis to assess the accuracy of stool tests for diagnosis of H pylori infection in children. We searched PubMed, EMBASE, and LILACS databases. Selection criteria included participation of at least 30 children and the use of a criterion standard for H pylori diagnosis. In a comprehensive search, we identified 48 studies.

RESULTS

Regarding antigen-detection tests, enzyme-linked immunosorbent assay (ELISA) monoclonal antibodies showed the best performance, with sensitivity and specificity of 97%, positive likelihood ratio (LR+) of 29.9, and negative likelihood ratio (LR-) of 0.03. ELISA polyclonal antibodies had sensitivity of 92%, specificity of 93%, LR+ of 16.2, LR- of 0.09, and high heterogeneity (P < 0.0001). One-step monoclonal antibody tests demonstrated sensitivity of 88%, specificity of 93%, LR+ of 10.6, and LR- of 0.11. For DNA detection, polymerase chain reaction-based test showed sensitivity of 80.8%, specificity of 98%, LR+ of 17.1, and LR- of 0.18.

CONCLUSIONS

Detection of H pylori antigen in stools with ELISA monoclonal antibodies is a noninvasive efficient test for diagnosis of infection in children. One-step tests showed low accuracy and more studies are needed to obtain a useful office-based screening test. The available molecular tests are still unreliable.

14C-urea breath test is safe for pediatric patients

Helicobacter pylori (H. pylori) infection, quite prevalent in the developing countries, is considered to be one of the causative factors for various gastric pathologies and other nongastric diseases. It is believed that H. pylori infection is almost always acquired in early childhood and persists throughout life unless specific treatment is given. The (13/14)C-urea breath test (UBT) is now considered to be a 'gold standard' technique for the detection of H. pylori infection. However, because of the lack of facilities and high cost, the preferred nonradioactive ¹³C-UBT cannot be performed on pediatric patients in developing countries, whereas the radioactive ¹⁴C-UBT is not used on children because of the fear of radiation exposure. When using 37 kBq (1 μCi) of ¹⁴C-urea for the ¹⁴C-UBT, the patient is not exposed to more radiation than is acquired from the natural environment in one day, as almost all the ingested radioactivity is excreted from the body (urine and breath) within 72-120 h. This article reviews the importance of the ¹⁴C-UBT for the detection of H. pylori and justifies the radiation safety aspects of its use in children without any fear of 'radiation phobia' where the facility for ¹³C-UBT is lacking.

Transmission pathway of Helicobacter pylori: does food play a role in rural and urban areas?

Helicobacter pylori is a Gram-negative microaerophilic bacterium that has colonized the human gastric mucosa. This infection is very common and affects more than half of the human population. The prevalence is however unbalanced between rural developing areas (more than 80%) and urban developed areas (less than 40%). H. pylori is responsible for several pathologies, such as gastritis, peptic ulcer and gastric cancer but its transmission pathway is still not clear. The risk factors for H. pylori infection include poor social and economic development; poor hygienic practices; absence of hygienic drinking water; and unsanitary prepared food. There is evidence supporting a gastro-oral, oral-oral and faecal-oral transmission, but no predominant mechanism of transmission has been yet identified. Transmission may occur in a vertical mode (e.g. from parents to child) or in a horizontal mode (across individuals or from environmental contamination). In either case, the involvement of water and food cannot be excluded as vehicles or sources of infection. Indirect evidence of presence of H. pylori in water and food, namely the detection of its DNA and survival studies after artificial contamination of food and water has been described. This paper reviews data both favourable and against the role of water and food in the transmission of H. pylori, exploring their role as a potential transmission vehicle for person-to-person and food-chain transmission. The likelihood of the transmission pathway in developing rural and developed urban areas appears to be different. In developed areas, person-to-person transmission within families appears to be dominant, while in the rural developing areas the transmission pathway appears to be more complex. In this later case, the transmission by contaminated food, water, or via intensive contact between infants and non-parental caretakers may have a greater influence than within-family transmission.

Application of Stool-PCR test for diagnosis of Helicobacter pylori infection in children

AIM: To evaluate the usefulness of stool-PCR test for diagnosis of Helicobacter pylori (H pylori) infection in pediatric populations.

METHODS: Based on endoscopic features (including nodular gastritis, erosive duodenitis and ulcer) and/or a positive rapid urease test (RUT) obtained during endoscopy, 28 children from a group of children admitted to the Children's Medical Center of Tehran for persistent upper gastrointestinal problems were selected to compare biopsy-based tests with stool-PCR. Their gastric activity and bacterial density were graded by the updated Sydney system, and their first stool after endoscopy was stored at -70°C. Biopsies were cultured on modified campy-blood agar plates and identified by gram-staining, biochemical tests, and PCR. Two methods of phenol-chloroform and boiling were used for DNA extraction from H pylori isolates. Isolation of DNA from stool was performed using a stool DNA extraction kit (Bioneer Inc, Korea). PCR was performed using primers for detection of vacA, cagA, and 16srRNA genes in both isolates and stool.

RESULTS: Sixteen out of 28 child patients (57%) were classified as H pylori positive by biopsy-based tests, of which 11 (39%) were also positive by stool-PCR. Sensitivity and specificity of stool-PCR was 62.5% and 92.3% respectively. H pylori was observed in histological sections for 10 out of 11 stool-positive patients. Association was observed between higher score of H pylori in histology and positivity of stool-PCR. Also association was observed between the more severe form of gastritis and a positive stool-PCR.

CONCLUSION: Association between higher score of H pylori in histology and a positive stool-PCR make it a very useful test for detection of H pylori active infection in children. We also suggest that a simple stool-PCR method can be a useful test for detection of H pylori virulence genes in stool.

Progress in developing accurate tests for the diagnosis of Helicobacter pylori infection

Helicobacter pylori is a chronic infectious agent as defined the major pathogen causing gastritis, gastric and duodenal ulcer, gastric carcinoma and mucosa-associated lymphoid tissue lymphoma, however little is known about its role in functional dyspepsia. H. pylori is the only microorganism known to inhabit the human stomach and the gastric mucosal cells. Chronic H. pylori infection of the stomach is increasingly recognized as a major risk factor for the development of gastroduodenal disease. H. pylori can be detected by non-invasive and invasive methods, the latter requiring endoscopy.

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.

A rapid method for extracting oocyst DNA from Cryptosporidium-positive human faeces for outbreak investigations

We describe a rapid method for extracting and concentrating Cryptosporidium oocysts from human faecal samples with subsequent DNA preparation for mainstream PCR applications. This method consists of extracting faecal lipids using a modified water-ether treatment and releasing DNA from semi-purified oocysts by freeze thawing in lysis buffer. Following immunomagnetisable separation (IMS), recovery rates of 29.5%, 43.2% and 49.8% were obtained from oocyst-negative solid, semi-solid and liquid faeces, respectively, seeded with 100 +/- 2 C. parvum oocysts, which were enumerated by flow cytometry. A retrospective analysis was conducted on 92 positive human faecal samples including 78 oocyst-positive cases from 2 UK cryptosporidiosis outbreaks (outbreak A = 34 samples, outbreak B = 44 samples) and 14 oocyst-positive, sporadic cases. We used primers targeting the Cryptosporidium oocyst wall protein gene (COWP; STN-COWP), the 18S rRNA (direct PCR) and the dihydrofolate reductase gene (dhfr, MAS-PCR) fragments to evaluate extracted DNA by PCR. PCR inhibitors were present in 20 samples when template was co-amplified with the 18S rRNA gene primers and an internal control. Template dilution (1/5) in polyvinylpyrrolidone (10 mg ml(-1), pH 8.0) transformed four PCR-negative samples to PCR-positive and increased amplicon intensity in previously positive samples. Eighteen of 20 PCR-negative samples produced visible amplicons when Taq polymerase concentration in the STN-COWP PCR was increased from 2.5 to 5 U. The STN-COWP PCR assay amplified 90 of 92 samples (97.8%) and the MAS-PCR assay amplified 70 of 92 samples (76.1%) tested. In the absence of inhibitors, DNA equivalent to 3 C. parvum oocysts was amplified.

Species-specific identification by inhibitor-controlled PCR of ruminant components contaminating industrial crude porcine heparin

With the emergence of bovine spongiform encephalopathy, the source of pharmaceutical heparin is currently restricted to porcine intestinal mucosa. To control the species origin of industrial crude heparin, molecular biology methods relying on species-specific protein or DNA analysis should be developed to identify the ruminant components that might be contaminants in industrial crude porcine heparin (ICPH). Because heparin contained in ICPH is a strong PCR inhibitory substance, it is necessary to explore DNA extraction methods specific for ICPH and develop analysis methods that could monitor the presence of PCR inhibitory substances. In the present studies, DNA was extracted from ICPH by seven methods, and their abilities to remove the PCR inhibitory substances were compared using inhibitory-controlled PCR (IC-PCR). The results showed that, based on the optimization of the final concentration of the internal processing control (IPC), IC-PCR was a rapid, sensitive and efficient way to monitor the presence of PCR inhibitory substances contained in DNA extracted from ICPH, and only the agarose gel purification method could be used to completely eliminate the PCR inhibitory substances contained in ICPH.

Detection of Helicobacter pylori DNA by a simple stool PCR method in adult dyspeptic patients

INTRODUCTION

Helicobacter pylori is the major agent causing peptic ulcer, gastric cancer and mucosa-associated lymphoid tissue (MALT) gastric lymphoma. A simple stool polymerase chain reaction (PCR) method was performed and compared with the gold standards for the diagnosis of H. pylori infection.

MATERIAL AND METHODS

A total of 54 adult patients (mean age, 46.41 +/- 13.12 years) with dyspeptic symptoms from Gastroenterology at Dokuz Eylül University Hospital between May and November 2003 were included. Two antrum and corpus biopsies were taken from each patient. Infection by H. pylori was defined as positivity and negativity of the gold standards. DNA extraction of stool specimens was done using QIAamp DNA Stool Mini Kit (QIAGEN) and PCR conditions included amplification and reamplification steps using the H. pylori ureA gene specific primers (HPU1, HPU2) and were visualized on 1% agarose gel stained with ethidium bromide.

RESULTS

Forty-six of 54 patients (85.2%) were diagnosed positive and eight (14.8%) were negative for H. pylori infection by the gold standard methods. Thirty-two patients were positive (59.3%) and 22 of them (40.7%) were detected negative by stool PCR method. The stool PCR method and gold standard methods showed a statistical difference for the detection of H. pylori infection (p < .0001). Sensitivity, specificity, likelihood ratio, and positive and negative predictive values were 65.22%, 75%, 2.61%, 93.75%, and 27.7%, respectively.

DISCUSSION

The PCR on the stool specimens resulted as being a very specific test. We suggest that a simple stool PCR method that we developed can be used to detect H. pylori, virulence genes, and in drug resistance studies either first line diagnostic methods in the laboratory or in the clinical management of dyspeptic patients.

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.

Immuno-PCR for Detection of Antigen to Angiostrongylus cantonensis Circulating Fifth-Stage Worms

Background: Definitive diagnosis of infestation with Angiostrongylus cantonensis is difficult because the parasitic nematode is undetectable in the cerebrospinal fluid (CSF) of one-half of afflicted patients and the diagnostic sensitivity of ELISA for circulating worm antigens in patient sera is low. We studied immuno-PCR as a diagnostic tool.

Methods: We studied 30 controls and 60 afflicted patients (30 confirmed by parasitologic analysis of CSF). We used a monoclonal antibody to capture circulating A. cantonensis antigens in serum samples. A DNA label generated by PCR amplification with biotinylated primer was bound by use of streptavidin to a biotinylated third antibody. Circulating antigens sandwiched by monoclonal antibody were detected by PCR amplification of the DNA label.

Results: The detection limit of the ELISA was 100–1000 times higher than that of the immuno-PCR. The concentrations of circulating antigens in patients were markedly higher than those in controls (Wilcoxon rank-sum test, P &lt;0.001). At a cutoff of 0.1 ng/L, sensitivity and specificity for immunodiagnosis of patients with angiostrongyliasis by immuno-PCR were 98% (95% confidence interval, 91–99%) and 100% (93–100%), respectively. The test was positive in all parasitologically confirmed cases.

Conclusions: Immuno-PCR is a promising technique for diagnosis of A. cantonensis infestation.

Diagnosis of porcine proliferative enteropathy: detection of Lawsonia intracellularis by pathological examinations, polymerase chain reaction and cell culture inoculation

A total of 21 pigs aged 7-17 weeks with clinical symptoms suggestive for Porcine Proliferative Enteropathy were examined for Lawsonia intracellularis by analysing the following parameters: (i) intestinal gross and histological lesions, (ii) presence of comma-shaped bacteria in enterocytes by Warthin-Starry and a modified Ziehl-Neelsen stain, (iii) PCR amplification of L. intracellularis DNA from intestinal mucosa by using two oligonucleotide primer pairs targeting a 255-bp DNA fragment of the 16S rDNA-gene and a 319-bp DNA fragment of the L. intracellularis chromosome. Specificity of PCR reactions was confirmed by using DNA extracted from the L. intracellularis reference strain N343 (ATCC 55672) as well as by DNA sequence comparisons of PCR amplification products with data bank entries. Intestinal gross lesion indicative for PPE were observed in 20 pigs (95.2%). For all 21 pigs, the L. intracellularis aetiology was confirmed by histological as well as bacterioscopical examinations. Specific PCR amplification products were obtained from 20 pigs (95.2%). Taking PCR positivity as the definite criterion, L. intracellularis was diagnosed in 20 pigs from 11 herds in seven Swiss cantons (Argovia, Berne, Fribourg, Grisons, Lucerne, Schwyz, Thurgovia). To grow L. intracellularisin vitro, the cell culture method of Lawson et al. (J. Clin. Microbiol. 1993: 31, 1136-1142) was adopted. Inocula prepared from heavily infected fresh and frozen ileal mucosa of 15 pigs were cultured in rat enterocytic IEC-18 cells (ATCC CRL 1589). Six cell culture passages of 10 days each were completed. The reference strain N343 was examined for cultivability, accordingly. Except for occasional specific PCR amplifications from cell cultures up to the second passage, any indications for growth of L. intracellularis in IEC-18 cells were not found.

Diagnosis of Helicobacter pylori infection

Numerous studies are still published on diagnostic tests for Helicobacter pylori, essentially for noninvasive tests. The urea breath test is applied in different types of patients, and there are attempts to have quicker and simpler protocols. Stool tests using monoclonal antibodies are now evaluated while serology is still a subject of interest. The progress in PCR (multiplex PCR, real-time PCR) has also stimulated the research in this area of invasive tests, in order to get insight into virulence factors, macrolide susceptibility and to detect H. pylori in nonconventional specimens.

Immune responses to differentiated forms of Helicobacter pylori in children with epigastric pain

Helicobacter pylori infection affects human populations of all ages. This gastric bacterium exists in spiral form and the reported viable but nonculturable coccoid form. The present study aims to examine the probable role of the coccoid form in H. pylori infection by comparing the seroprevalences of the spiral and the coccoid forms in children with epigastric pain. Four hundred eighty-nine children (mean age, 8.5 years) with epigastric pain formed the basis of this study. Five hundred ninety-nine schoolchildren of comparable ages and with no record of dyspepsia served as controls. The seroprevalence of antigens prepared from both morphological forms was examined by enzyme-linked immunosorbent assay. The results showed that 65 (13.3%) and 273 (55.8%) of 489 symptomatic children were seropositive for antigens of the H. pylori spiral and coccoid forms, respectively. In contrast, only 7.0% of the control group had elevated levels of immunoglobulin G antibodies against the spiral form, while 26.5% were positive for antibodies against the coccoid form. There were no significant differences between genders or among ethnic groups. The study showed a rise in seroprevalence corresponding with age: 7.1% for those < or =5 years to 21.4% for those > or =11 years. The seroprevalence of antigens of the H. pylori spiral and coccoid forms in children with epigastric pain was twofold higher than that in the control subjects. Interestingly, there was a fourfold increase in seropositivity for coccoid-form antigen compared to that for the spiral-form antigen among the symptomatic pediatric patients as well as the control group, indicating a possible infective role of the coccoid form of H. pylori in the pediatric patients with epigastric pain.

Detection of specific Helicobacter pylori DNA and antigens in stool samples in dyspeptic patients and healthy subjects

In this study stool samples from dyspeptic patients and healthy subjects were used for detection of specific Helicobacter pylori antigens and DNA by immunoenzymatic test (PPHpSA) and semi-nested PCR (ureA-PCR), respectively. The H. pylori status was estimated by invasive endoscopy-based rapid urease test and histology or noninvasive urea breath test (UBT), and by serology (ELISA, Western blot). The coincidence of H. pylori-negative invasive tests or UBT and negative antigen or DNA stool tests was very high (mean 95%). The PPHpSA results were found positive for 56% and ureA-PCR for 26% of individuals with H. pylori infection confirmed by invasive tests or UBT. The detection of specific H. pylori antigens and especially DNA in feces is not sufficient as a one-step diagnosis of H. pylori infection.

Helicobacter cetorum sp. nov., a urease-positive Helicobacter species isolated from dolphins and whales

A novel helicobacter with the proposed name Helicobacter cetorum, sp. nov. (type strain MIT 99-5656; GenBank accession number AF 292378), was cultured from the main stomach of two wild, stranded Atlantic white-sided dolphins (Lagenorhynchus acutus) and from the feces of three captive cetaceans (a Pacific white-sided dolphin [Lagenorhynchus obliquidens]; an Atlantic bottlenose dolphin [Tursiops truncatus]; and a beluga whale [Delphinapterus leucas]). The infected captive cetaceans were either subclinical, or clinical signs included intermittent regurgitation, inappetance, weight loss, and lethargy. Ulcers were observed in the esophagus and forestomach during endoscopic examination in two of the three captive animals. In the third animal, esophageal linear erosions were visualized endoscopically, and histopathological evaluation of the main stomach revealed multifocal lymphoplasmacytic gastritis with silver-stained spiral-shaped bacteria. Helicobacter cetorum is a fusiform gram-negative bacterium with a single bipolar flagellum. The isolates grow under microaerobic conditions at 37 and 42 degrees C but not at 25 degrees C. H. cetorum is urease, catalase, and oxidase positive, and it is sensitive to cephalothin. The isolates from the wild, stranded dolphins were sensitive to nalidixic acid, whereas the isolates from the collection animals were resistant. By 16S rRNA sequencing it was determined that H. cetorum represented a distinct taxon that clusters most closely with H. pylori. Further studies are necessary to determine the role of H. cetorum in the development of gastric ulcers and gastritis of cetaceans. This is the first description and formal naming of a novel Helicobacter species from a marine mammal.

Epidemiology and diagnosis of Helicobacter pylori infection

There have been no major breakthroughs in the field of epidemiology and diagnosis of Helicobacter pylori infection over the last year, thus for this reason, these two topics will be treated in the same chapter. Information on the incidence of infection, as in the study of Malaty et al. are now being published from long-term cohort follow-ups. The route of transmission of H. pylori remains controversial, with circumstantial evidence for infection via exposure to animals, contaminated water supplies and oral reservoirs being reported. The value of citric acid to improve urea breath test (UBT) results has been documented. A novel stool test has been released on the market and we are awaiting more information, while detection of antibodies in urine gave satisfactory results. However, the most interesting data comes from the study of McColl et al. who clearly proved on a large sample and a 1-year follow-up that the 'test and treat' strategy using UBT, as proposed in the Maastricht Consensus Report, is definitely the method to use.