Detection and typing of Helicobacter pylori cagA/vacA genes by radioactive,one-step polymerase chain reaction in stool samples from children

The detection and molecular typing of Helicobacter pylori virulence genes in human stool specimens by polymerase chain reaction (PCR) require an adequate amount of bacterial DNA and an appropriately adjusted PCR protocol. DNA was isolated from stool samples of 39 H. pylori-infected and nine uninfected Colombian children using the QIAamp Kit following the manufacturer's instructions but with modifications. DNA templates were amplified for the vacA s and m regions and for the cagA gene by PCR using radioactively labeled (32P) primers. The modifications in the standard Qiagen protocol of stool DNA extraction increased the final concentration of eluted total stool DNA 4.7 times (117 +/- 17 versus 22 +/- 3 ng/microl; P < 0.0001). Nevertheless, its amplification by regular PCR programs (30-40 cycles) did not generate visible signals because of the very low ratio of H. pylori DNA to other DNA. PCR for 80 cycles successfully amplified vacA in 36/39 samples (sensitivity, 92.3%) and cagA fragments in 21/39 (53.8%) fecal DNA samples. Both s and m vacA regions were amplified in 33/36 (91.7%) DNA samples. The s1m1 genotype was the most commonly isolated variant, accounting for 17/36 or 47.2% of positive samples. The s2m2 genotype was ascertained to be frequent also (14/36 or 38.9%). Almost all (94.1%) s1m1 genotypes were cagA positive. The majority of s2m2 genotypes (78.6%) were not associated with the cagA gene. Neither cagA nor vacA fragments were amplified from DNA isolates of H. pylori-uninfected children nor from DNA isolated from six gastrointestinal bacterial strains (specificity, 100%). The data suggest that the proposed modified technique of DNA extraction and PCR assay of stool samples may be an effective and reliable noninvasive tool for the detection and typing of H. pylori cagA/vacA virulence genes in infected individuals.     

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.     

A positive assay for identification of cagA negative strains of Helicobacter pylori

A new PCR protocol was developed for the positive identification of cagA negative Helicobacter pylori strains. Amplification of a portion of the genome across the insertion point of the cag pathogenicity island (the ES-"empty site") generated a 106-bp fragment, which produces a positive signal for cagA negative strains. Combined with the results of the cagA assay, the signals for ES allowed the complete characterization of the patients' cagA status. DNA sequencing analysis confirmed the identity of the ES fragment. The new protocol and cagA assay were applied to 22 DNA preparations isolated from stools from H. pylori infected adult patients and to 21 DNA preparations isolated from stools from H. pylori infected children. The same analysis was also performed on nine colonies of H. pylori derived from gastric biopsies of nine of the adult patients. The total number of cagA positive cases from adult patients was 14 or 63.6% (11 mono- and 3 mixed) and of the cagA negative cases (or ES positive) was 9 or 40.9% (6 mono- and 3 mixed). Of the 21 stool DNA samples from children, 6 (28.6%) were cagA positive, 12 (57.1%) were cagA negative and 3 (14.3%) were positive for cagA and for the ES simultaneously. The proportions of mixed cagA positive and cagA negative H. pylori infections were almost equal in adults and children (13.6% and 14.3%, respectively). No reaction products of the proper fragment sizes for cagA or the empty site (ES) were obtained from any of the stool DNA samples of 10 H. pylori uninfected subjects (100% specificity). This noninvasive assay discriminates consistently cagA negative cases from cagA positive strains and from amplification failures. It can be a useful tool for clinical and epidemiological studies of H. pylori infection.     

Sequence Analysis of East Asian cagA of Helicobacter pylori Isolated from Asymptomatic Healthy Japanese and Thai Individuals

CagA, especially East Asian type, is one of the most important virulence factors of Helicobacter pylori, which is believed to contribute to the gastric cancer development. There is extreme sequence heterogeneity on 3' region of cagA gene, demonstrated by the sequence analysis of cagA of H. pylori strains isolated from gastric disease patients. However, whether such heterogeneity of the cagA gene sequence is related to the pathogenicity of H. pylori in the gastric cancer development is not certain. Therefore, in this study, the 3' region of cagA sequences isolated from asymptomatic healthy individuals in Japan and Thailand, which show high and low gastric cancer prevalence, respectively, were analyzed and compared with those from patients with gastric cancer. The CagA sequences analysis in 21 and 12 H. pylori DNA samples obtained from Japanese and Thai individuals, respectively, by the molecular phylogenetic method showed that the sequences were more conserved in the Thai individuals (concordance rates among Thai sequences, 93.9-100%) than in the Japanese individuals (concordance rates among Japanese sequences, 82.8-100%) as shown by unrooted neighbor-joining (N-J) consensus trees constructed with the sequence between Asn869 and Ala967 in CagA. CagA sequences in gastric cancer patients were obtained from published data; analysis of these sequences revealed that CagA sequences from almost all Thai individuals were concentrated in one branch. In contrast, CagA sequences from Japanese individuals were uniformly distributed throughout the N-J consensus tree. These results suggest that the difference in the CagA sequences between asymptomatic healthy Japanese and Thai individuals may be linked to the incidence of gastric cancer in Japan and Thailand.     

兰州地区幽门螺杆菌分离株主要毒力基因的研究

本文首次报道了兰州地区胃病患者幽门螺杆菌分离株主要毒力基因ｕｒｅＡ ｖａｃＡ 和ｃａｇＡ的 ＰＣＲ 检测情况。共获 ４１ 株Ｈｐ 分离株,分别来自于慢性胃炎病人（３２ 株）、胃－十二指肠溃疡病人（７株）和胃癌病人（２ 株）。检测结果表明,４１ 株Ｈｐ 分离株的ｕｒｅＡ,ｖａｃＡ 及ｃａｇＡ 的阳性率分别为１００％ ,１００％ 和９７．６％ ;含有ｕｒｅＡ,ｖａｃＡ 和ｃａｇＡ 基因的Ｈｐ 与人类胃部疾患密切相关,而ｃａｇＡ 基因的存在可能与更加严重的胃部疾病有关。Ｈｐ 毒力基因的检测结果与其它地区Ｈｐ 分离株的检测结果相似。作者建议,对ｕｒｅＡ 基因的ＰＣＲ 检测可以作为鉴定Ｈｐ 的一个指标。     

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.     

Determination of Helicobacter pylori cagA, vacA genotypes with real-time PCR melting curve analysis.

OBJECTIVES: genotypes of Helicobacter pylori are the focus of interest because they play a prominent role in mucosal injury. The purpose of this study was to determine cagA and vacA genotypes of H. pylori using real-time polymerase chain reaction (PCR) method with a double strain DNA binding SYBR Green I.dye, and to compare this with those of two immunohistochemical methods. METHODS: forty-three paraffin-embedded biopsy tissue samples were examined by histology, epidermal growth factor receptor (EGFR), proliferating cell nuclear antigen (PCNA) immunohistochemistry and melting curve analysis of real-time PCR. RESULTS: the presence of cagA gene was associated with a significantly higher frequency of gastritis (P=0.003) than that of vacA gene with intestinal metaplasia (P=0.045). Significant difference was found between the presence of cagA gene and EGFR expression in intestinal metaplasia cases in comparison with cagA negative samples (P=0.0418). Statistically significant difference was detected between increased cell proliferation and the presence of gastritis. CONCLUSIONS: this method seems to be suitable for H. pylori genotype determination. Sensitivity, speed and simplicity are key areas in the development of PCR assays for H. pylori. Results supported the notion that infection with cagA positive H. pylori strain causes more augmentated cell proliferation in the stomach mucosa.     

胃癌与幽门螺杆菌cagA、hrgA基因相关性的研究

目的:探讨幽门螺杆菌(Hpylori)菌株中cagA和hrgA基因对胃癌的致病作用及其检测的意义。方法:胃癌及消化性溃疡术后切除标本,组织学检查,快速尿素酶法和PCR检测。结果:40例标本经组织学检查24例为胃腺癌,2例为胃黏膜相关淋巴样组织(MALT)瘤,14例为消化性溃疡。经快速尿素酶法检测,胃腺癌中,12例H pylori( ),消化性溃疡中,12例H pylori( )。经PCR检测,胃腺癌中,18例hrgA( ),6例hrgA(-),20例cagA( ),4例cagA(-);消化性溃疡中,6例hrgA( ),8例hrgA(-),12例cagA( ),2例cagA(-)。结论:H pylori感染与胃癌的发生有密切关系。PCR检测较快速尿素酶法准确。检测cagA和hrgA基因对了解Hpylori菌株的致病性、估计疾病程度、了解病变预后及临床治疗都具有重要意义。     

Occurrence of Helicobacter pylori DNA in the coastal environment of southern Italy (Straits of Messina)

AIMS: The occurrence of Helicobacter pylori in the coastal zone of the Straits of Messina (Italy) as free-living and associated with plankton was studied. METHODS AND RESULTS: Monthly sampling of seawater and plankton was carried out from April 2002 to March, 2003. All environmental samples analysed by cultural method, did not show the presence of H. pylori. The DNA extracted from all environmental samples was tested by PCR by using primers for H. pylori 16S rRNA, ureA and cagA. 16S rRNA PCR yielded amplified products of 522-bp in 15 of 36 (41.7%) of the environmental samples. By using the ureA primers to amplify the urea signal sequences, the predicted PCR products of 491-bp were obtained from eight (22.2%) of 36 environmental samples. PCR with cagA primers yielded amplified products of 349-bp in DNA extracted of seven of 36 (19.4%) of the environmental samples. When 16S rRNA, ureA and cagA amplified gene sequences were aligned with H. pylori 26695 and J99 genome sequences, we obtained a percentage of alignment over 90%. CONCLUSIONS: The detection of H. pylori genes in marine samples allows us to consider the marine environment a possible reservoir for this pathogenic bacterium. SIGNIFICANCE AND IMPACT OF THE STUDY: The direct detection of H. pylori genes may be relevant in order to consider the marine environment as significant reservoir for this bacterium.     

Non-invasive genotyping of Helicobacter pylori cagA, vacA, and hopQ from asymptomatic children

Background: Helicobacter pylori infection is usually acquired in childhood, but little is known about its natural history in asymptomatic children, primarily due to the paucity of non‐invasive diagnostic methods. H. pylori strains harboring cagA and specific alleles of hopQ and vacA are associated with increased risk for gastric cancer. Many studies of H. pylori virulence markers in children have the bias that symptomatic subjects are selected for endoscopy, and these children may harbor the most virulent strains. Our aim is to genotype cagA, hopQ, and vacA alleles in stool DNA samples of healthy Colombian children residing in an area with high incidence of gastric cancer, to avoid selection bias resulting from endoscopy. Methods: H. pylori status of 86 asymptomatic children was assessed by ¹³C‐urea breath test (UBT) and PCR. H. pylori 16S rRNA, cagA, hopQ, and vacA genes were amplified from stool DNA samples and sequenced. Results: UBT was positive in 69 (80.2%) of 86 children; in stool DNA analysis, 78.3% were positive by 16S rRNA PCR. cagA, vacA, and hopQ were detected in 66.1%, 84.6%, and 72.3% of stool DNA samples from 16S rRNA‐positive children. Of the children’s DNA samples, which revealed vacA and hopQ alleles, 91.7% showed vacA s1 and 73.7% showed type I hopQ. Type I hopQ alleles were associated with cagA positivity and vacA s1 genotypes (p < 0.0001). Conclusions: Using stool DNA samples, virulence markers of H. pylori were successfully genotyped in a high percentage of the asymptomatic infected children, revealing a high prevalence of genotypes associated with virulence. Type I hopQ alleles were associated with the presence of cagA and the vacA s1 genotype.     

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.     

Quantitative detection for low levels of Helicobacter pylori infection in experimentally infected mice by real-time PCR

Accurate diagnosis of Helicobacter pylori infection is important in both clinical practice and clinical research. Molecular methods are highly specific and sensitive, and various PCR-based tests have been developed to detect H. pylori in gastric biopsy specimens. We optimized a sensitive and specific quantitative SYBR Green I real-time PCR assay for detection of H. pylori based on amplification of the fragment of a 26-kDa Helicobacter species-specific antigen gene that allows for detection of 5 bacterial cells per PCR sample. Under the assay conditions, SYBR Green I real-time PCR is highly reproducible with a precise log-linear relation in the range of six orders of magnitude of bacterial DNA concentrations. For accurate comparison of H. pylori infection in different tissue samples, the amount of total host DNA in each sample is normalized by TaqMan real-time PCR of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) pseudogenes. The developed method was validated in prophilactically immunized and experimentally infected mice and revealed a level of H. pylori gastric colonisation that was below the limit of detection for a rapid urease test. This new method established for a quantitative analysis of H. pylori in the host's stomach may be useful in experimental studies evaluating new anti-H. pylori drugs and vaccines.     

The size of cagA based on repeat sequence has the responsibility of the location of Helicobacter pylori in the gastric mucus and the degree of gastric mucosal inflammation

The aim of this study was to examine whether there is a relationship between cagA size of Japanese Helicobacter pylori strains and the location of these strains in the mucous layer, the degree of gastric inflammation and acid survival. Upper gastrointestinal endoscopies were done to 144 patients with dyspeptic symptom with informed consent, sera, biopsy specimens and H. pylori strains were obtained, and gastric histology and susceptibility to pH 3 of the strains were evaluated. To determine cagA size of Japanese strains using PCR, cagA of strain CPY3401 was sequenced. 74 H. pylori samples (72 cagA+) were obtained from the body and 56 samples (56 cagA +) obtained from the antrum. cagA size of 72 H. pylori strains from the body was mainly classified into 3 groups (short (48), middle (8), long (9), and others (7)) by PCR and all of that of 56 strains from the antrum except 2 was short. The size of cagA of isolated strains from the body is associated with enhanced gastritis, acid survival, and the location in the mucus. The long size cagA of which strain is acid sensitive, may be a strong selective pressure on strain that colonizes close to the host, which enhanced gastritis.     

Helicobacter pylori cagA Gene Polymorphism Affects the Total Antioxidant Capacity of Human Saliva

Background:  We aimed to evaluate the total antioxidant capacity (TAC) of saliva in healthy Helicobacter pylori -positive and negative saliva individuals.
Materials and Methods:  A total of 102 human saliva samples were checked for the presence of H. pylori DNA ( ureA and cagA gene fragments).
TAC of saliva was estimated by ABTS radical cation (ABTS^{• +} ) decolorization assay.
Results:  PCR analysis revealed that 36 subjects were ureA-/cagA- , 24 were ureA+/cagA- and 42 were ureA+/cagA+ . Smoking habits had no evident effect on H. pylori infection.
We found that TAC of the ureA-/cagA- material, after 10 seconds reaction reflecting fast-reacting antioxidants, was significantly higher than of ureA+/cagA- and ureA+/cagA+ samples (p < .01 and p < .001, respectively). Similar results were obtained for reaction time of 3 minutes measuring slow-reacting antioxidants (p < .001). We also estimated ureA+/cagA- and ureA+/cagA+ samples alone and reported a statistically significant decrease in the TAC_3min value of ureA+/cagA+ compared with ureA+/cagA- samples (p < .05).
Conclusions:  Our data demonstrated that altered redox equilibrium may be associated with more frequent occurrence of H. pylori in the saliva samples.     

Mixed Infection with cagA-Positive and cagA-Negative Strains of Helicobacter pylori

Background Helicobacter pylori infection has been implicated strongly in the pathogenesis of gastritis, peptic ulcer disease, gastric adenocarcinoma, and gastric lymphoma, but the reasons for these widely different clinical outcomes are unknown. The aim of this study was to determine whether these differences could be due in part to mixed infection in the same individual, with bacteria having differences in pathogenic factors associated with ulcers.
Materials and Methods. The cagA gene of H. pylori was used to test for mixed infection because it is present in only some strains, and its presence has been associated with ulcers. Polymerase chain reaction (PCR) assays for the cagA gene were applied to H. pylori culture isolates and endoscopic gastric aspirates. Individual bacterial clones were tested for genetic similarity by random primer amplification and restriction endonuclease digestion of urease gene PCR products.
Results. The majority of H. pylori -positive patients had strongly cagA -positive culture isolates and endoscopic samples (62.5% and 69.6%, respectively). However, many of these patients had evidence of mixed infection with cagA negative and cagA positive strais in cultures isolates and endoscopic samples (25% and 17.4%, respectively). Mixed infection was found to be due to genetically unrelated strains in two patients in whom genetic analysis was performed.
Conclusion. Mixed infection with differences in substrain pathogenic factors might occur in H. pylori infection and might contribute to differences in clinical outcome.     

No correlation of babA2 with vacA and cagA genotypes of Helicobacter pylori and grading of gastritis from peptic ulcer disease patients in Brazil

BACKGROUND: The babA2 gene, which encodes a blood-group antigen-binding adhesin that mediates attachment of Helicobacter pylori to human Lewis(b) antigens on gastric epithelial cells, has been associated with a higher risk of peptic ulcer and gastric cancer. The purpose of this study was to ascertain the frequency of babA2 genotype in H. pylori strains of patients with peptic ulcer and to correlate with other virulence factors. MATERIALS AND METHODS: vacA, cagA, and babA2 genotypes of H. pylori were determined by using polymerase chain reaction (PCR). DNA was extracted from positive urease test gastric samples of 150 patients with peptic ulcer. Antrum and corpus biopsies were taken for histologic examination according to the updated Sydney system classification. RESULTS: babA2 genotype was present in 104 (69.3%) and cagA in 113 (75.3%) gastric samples. No significant correlation was observed between babA2 and vacAs1 genotype or between babA2 and cagA status. The correlation of vacAs1 genotype with positive cagA was statistically significant ( p < .001). The babA2-positive strain was more frequently found from the gastric samples of men, than of women (p = .01). Strains harboring cagA, vacAs1, and babA2 genotypes had no association to the grading of gastritis, presence of glandular atrophy, or intestinal metaplasia. The simultaneous presence of cagA, vacAs1, and babA2 was found in 32.6% of the H. pylori strains. CONCLUSIONS: babA2 genotype is frequently found in H. pylori strains from peptic ulcer disease in Brazil, although it has no significant correlation to the worsening of the gastritis and to other virulence markers such as vacAs1 and cagA.     

The status of the cagA gene does not predict Helicobacter pylori-associated peptic ulcer disease in Singapore

Discrepancies among reports from different geographical regions worldwide on the association between the presence of cagA and peptic ulcer disease prompted this study on the predictive value of the cagA gene in Helicobacter pylori-associated gastroduodenal diseases in the Singapore population. H. pylori strains were obtained from 169 patients with a peptic ulcer, 83 with non-ulcer dyspepsia, and nine with gastric cancer. The presence of the cagA gene was evaluated by polymerase chain reaction (PCR). The expected 400 bp PCR product coding for the cagA gene was present in 232/261 (89%) H. pylori isolates. Of these, 151/169 (89%) strains from patients with peptic ulcer, 73/83 (88%) strains from patients with non-ulcer dyspepsia and 8/9 (89%) strains from cancer patients were positive for the cagA gene. There was no statistically significant difference between the prevalence of cagA-positive strains from patients with distinct clinical outcomes (p > 0.05). The prevalence of cagA-positive strains in the Singapore population is high regardless of clinical disease status. The results suggest that the cagA gene is not a universal virulence marker of H. pylori.     

Human gastric mucins differently regulate Helicobacter pylori proliferation, gene expression and interactions with host cells

Helicobacter pylori colonizes the mucus niche of the gastric mucosa and is a risk factor for gastritis, ulcers and cancer. The main components of the mucus layer are heavily glycosylated mucins, to which H. pylori can adhere. Mucin glycosylation differs between individuals and changes during disease. Here we have examined the H. pylori response to purified mucins from a range of tumor and normal human gastric tissue samples. Our results demonstrate that mucins from different individuals differ in how they modulate both proliferation and gene expression of H. pylori. The mucin effect on proliferation varied significantly between samples, and ranged from stimulatory to inhibitory, depending on the type of mucins and the ability of the mucins to bind to H. pylori. Tumor-derived mucins and mucins from the surface mucosa had potential to stimulate proliferation, while gland-derived mucins tended to inhibit proliferation and mucins from healthy uninfected individuals showed little effect. Artificial glycoconjugates containing H. pylori ligands also modulated H. pylori proliferation, albeit to a lesser degree than human mucins. Expression of genes important for the pathogenicity of H. pylori (babA, sabA, cagA, flaA and ureA) appeared co-regulated in response to mucins. The addition of mucins to co-cultures of H. pylori and gastric epithelial cells protected the viability of the cells and modulated the cytokine production in a manner that differed between individuals, was partially dependent of adhesion of H. pylori to the gastric cells, but also revealed that other mucin factors in addition to adhesion are important for H. pylori-induced host signaling. The combined data reveal host-specific effects on proliferation, gene expression and virulence of H. pylori due to the gastric mucin environment, demonstrating a dynamic interplay between the bacterium and its host.     

Gastric Juice Polymerase Chain Reaction: An Alternative to Histology in the Diagnosis of Helicobacter pylori Infection

Background. Infection from Helicobacter pylori plays a role in several gastroduodenal diseases. The recent availability of molecular techniques, particularly the polymerase chain reaction (PCR), allows us to detect small amounts of this bacterium. The aims of this study were to compare PCR and histological findings and to ascertain the clinical usefulness of H. pylori PCR identification in different biological samples.
Materials and Methods. We studied 94 consecutive patients. Saliva, gastric juice, and four antral and four body biopsies were obtained from each patients. H. pylori was evaluated histologically in two antral and two body biopsies (Giemsa or Warthin-Starry stain). After extraction, DNA was submitted for PCR amplification using the two primers HPU1 and HPU2, which amplified a 411-bp product from the urease gene A.
Results. Forty-nine patients were H. pylori -positive at histological workup. The sensitivity of PCR was 92% for gastric juice, 73% for antral biopsies, 61% for body biopsies, and 13% for saliva. Of the 45 H. pylori -negative patients at histological assessment, 7 (16%) had positive findings on PCR, mainly when gastric juice was examined.
Conclusions. These results indicate that PCR is as sensitive as histological assessment. We suggest that PCR H. pylori detection in gastric juice is a sensitive method for diagnosing this infection.