CagA status and virulence of Helicobacter pylori strains. Results of a French multicentric prospective study

Previous experimental and epidemiological studies with few patients suggested that the presence of the cagA gene was a virulence factor for Helicobacter pylori (H. pylori). AIM: To establish in this large epidemiological cohort study the relationship between the histological virulence of H. pylori infection and the cagA status of the bacteria. METHODS: This prospective cohort study (6 month follow-up) was conducted on adult patients undergoing endoscopy for upper gastrointestinal symptoms. The cagA status of H. pylori-positive patients was established using the polymerase chain reaction (PCR) method on an antral biopsy. A score of histological virulence (inflammation, activity) was recorded on the basis of the Sydney system (on antral, angular and fundic biopsies). Eradication treatment given was not imposed and a clinical follow-up was performed at 3 and 6 months. H. pylori eradication was verified by a 13C urea breath test at 3 months. RESULTS: Four hundred and twenty two centers recruited 652 patients (mean age: 51 +/- 15 years, 55% female). Upper GI endoscopy was abnormal in 80% of the patients of whom 68% had a gastritis aspect; 38% were infected by H. pylori, and among them 51% were cagA-positive. The histological virulence scores associated with the cagA-positive strains were significantly higher than those associated with the cagA-negative strains, globally (P = 0.0035), in the antrum (P = 0.0063), and in the angulus (P = 0.046), but not in the fundus (P = 0.05). The cagA status was correlated neither with the symptom severity at inclusion and at 6 months (P > 0.05), nor with the H. pylori eradication rate at 3 months (75% in cagA-positive and 70% in cagA-negative strains, P = 0.52). CONCLUSION: This study on a large cohort of patients confirms the greater histological virulence of H. pylori cagA-positive strains. However, this virulence was not associated with more severe symptoms nor with an increase in resistance to H. pylori eradication treatment.     

The role of cagA Helicobacter pylori strains in gastro-oesophageal reflux disease

BACKGROUND AND AIMS: The role of Helicobacter pylori infection in gastro-oesophageal reflux disease is controversial. The aim of this study was to evaluate the prevalence of colonization by cagA-positive and cagA-negative H. pylori strains in the spectrum of gastro-oesophageal reflux disease. METHODS: A total of 108 patients (50 male/58 female; mean age, 50.3 years) with dyspepsia and peptic ulcer or erosive gastritis/duodenitis were categorized into patients without reflux and patients with reflux oesophagitis graded from I to IV. All patients underwent upper endoscopy with biopsies of the antrum. H. pylori was detected by histology, urease test and polymerase chain reaction. The cagA status was diagnosed in the gastric biopsy by polymerase chain reaction. RESULTS: The overall prevalence of H. pylori colonization in patients with reflux was 68.6% and was 70.2% in those without oesophageal disease (P = 0.862). Colonization by cagA-positive strains was also not statistically different between the two groups (31.4% versus 40.4%, P = 0.332). However, patients with grades II-IV reflux oesophagitis were less colonized by the bacterium (36.4%) than patients with grade I oesophagitis (77.5%) (P = 0.009). H. pylori cagA-positive strains were also less likely to colonize the stomach of patients with grades II-IV oesophagitis (0%), than grade I reflux oesophagitis (40%) patients and controls (40.4%). CONCLUSIONS: Infection of the stomach by H. pylori and especially by H. pylori cagA strains may play a protective role against the development of the most severe forms of gastro-oesophageal reflux disease.     

Gastric epithelial cell proliferation and cagA status in Helicobacter pylori gastritis at different gastric sites

OBJECTIVE: Helicobacter pylori infection causes hyperproliferation which is believed to predispose to the development of gastric carcinoma. The aim of this study was to analyze epithelial cell proliferation topographically in H. pylori gastritis in relationship to cagA status. MATERIAL AND METHODS: The proliferative index (PI: Ki-67-labeled nuclei/total number of foveolar nuclei) was determined in gastric mucosa biopsies taken at the antrum (lesser and greater curvatures), incisura, and corpus (greater curvature) from 78 patients with H. pylori gastritis and 20 H. pylori-negative patients. H. pylori and cagA status were determined by polymerase chain reaction (PCR) and serology. RESULTS: PIs were significantly higher in H. pylori- and cagA-positive patients, in comparison with H. pylori- and cagA-negative patients, at all sites (p相似文献   

Helicobacter pylori density and cagA status in cirrhotic patients: a case-control study

BACKGROUND AND AIM: Despite a similar Helicobacter pylori prevalence, peptic ulcer is more frequent in cirrhotic patients than in controls. We evaluated whether cirrhotic patients had an increased bacterial density and/or a higher prevalence of H. pylori cagA-positive strains than controls. METHODS: A total of 36 dyspeptic cirrhotic patients with H. pylori infection and 72 matched controls were enrolled. H. pylori infection was detected at histology on Giemsa staining, bacterial density was assessed using difference over baseline (DOB) values at 13C urea breath test, and cagA status was established at serology. RESULTS: Overall, both DOB values and prevalence of cagA did not significantly differ between cirrhotic patients and controls. However, peptic ulcer controls showed significantly higher DOB value (27.9 +/- 17.4 vs 19.4 +/- 9.3, respectively; P = 0.009) and cagA positive rate (85%vs 48%; P = 0.01) than non-ulcer dyspepsia patients. Although not statistically significant, a similar trend was observed in cirrhotic patients with peptic ulcer for DOB values (26.5 +/- 16.3 vs 18.3/1000 +/- 9.2, respectively; P = 0.07), whereas the cagA-positive rate was similar between peptic ulcer and non-ulcer dyspepsia patients (60%vs 50%; P = 0.30). CONCLUSIONS: The present data showed that both bacterial density and cagA prevalence did not differ between cirrhotic patients and controls.     

Functional dyspepsia is associated with cagA-positive Helicobacter pylori strains

BACKGROUND: The antigen CagA can be used as a marker for virulence of Helicobacter pylori. It is tempting to assume that H. pylori strains positive for cytotoxin-associated gene A (cagA) could be responsible for functional dyspepsia. A cross-sectional study was performed in patients presenting with functional dyspepsia to correlate the clinical presentation with the presence of cagA-positive and -negative H. pylori strains. METHODS: Consecutive patients referred for endoscopy were studied. An inclusion criterion was the absence of any endoscopic abnormality. Biopsy specimens were obtained from the gastric antrum for HE and immunoperoxidase stain, rapid urease test, and culture. A serum sample was taken for detection of IgG antibodies against H. pylori as well as CagA. A validated questionnaire of 14 questions regarding the upper gastrointestinal tract was used for assessment of the clinical presentation. Nine questions were scored on a 5-point Likert scale. RESULTS: 422 patients were included, 222 were H. pylori-positive, the remaining 200 were H. pylori-negative. Mean symptom score in patients with cagA-positive strains was significantly higher than in patients with cagA-negative strains. No difference was present if cagA-negative patients were compared with H. pylori-negative dyspeptics. Four different complaints were more prevalent in the cagA-positive patients compared with cagA-negatives. When cagA-positive patients were compared with H. pylori-negative dyspeptics, seven complaints were significantly more prevalent in cagA-positives; when cagA-negatives were compared this number was only two. CONCLUSIONS: Functional dyspeptics with cagA-positive H. pylori strains have more dyspeptic symptoms and higher symptom scores than patients with cagA-negative H. pylori strains as well as H. pylori-negative functional dyspeptics.     

Detection of Helicobacter pylori cagA gene by polymerase chain reaction in faecal samples.

OBJECTIVE: The polymerase chain reaction (PCR) has been extensively and successfully used to detect Helicobacter pylori in gastric juice and gastric biopsies. In contrast, the results obtained using faeces as biological samples for PCR are rather conflicting. This may be due to the presence of faecal inhibitory compounds (polysaccharides) which can inhibit the amplification reaction. The aim of this study was to characterize the H. pylori genotype in faecal samples by using specific primers for the cagA gene. To overcome the problem of contamination by polysaccharides, we used a filter-based extraction technique already applied in a previous study. METHODS: Antral and body biopsies were obtained from 30 symptomatic patients undergoing upper endoscopy. PCR was used to detect the presence of H. pylori organisms in faecal samples by using primers selected for the urease gene A. In addition, H. pylori organisms were characterized both in faecal samples and paraffin-embedded biopsies by PCR with specific primers for the cagA gene. RESULTS: All patients showed a positive CLO test (rapid urease test) and evidence of H. pylori by Warthin-Starry stain. PCR detected the urease A gene in the faecal samples of all patients. The cagA gene was detected in the faecal and biopsy samples of 18 subjects (60%). Duodenal ulcer and/or antral erosions were observed in 15 of the 18 cagA-positive patients (83.3%) and in five of the 12 cagA-negative patients (41.7%). Endoscopic features of normal mucosa or gastritis were observed in three cagA-positive patients (16.7%) and in seven cagA-negative patients (56.3%). cagA-positive status was found to be significantly related to the endoscopic features of duodenal ulceration and/or antral erosions. CONCLUSIONS: Our findings prove that faeces are suitable samples for the detection of cagA status. Moreover, they confirm the existence of a significant relationship between cagA-positive status and duodenal ulcer and/or antral erosions.     

Relevance of underlying disease and bacterial vacA and cagA status on the efficacy of Helicobacter pylori eradication

AIM: To study the effects of Helicobacter pylori associated diseases and the bacterial vacA and cagA statuses on the efficacy of H. pylori eradication. METHODS: A prospective study in a consecutive series of outpatients of a gastroenterological institution and of a primary practice. A series of 146 H. pylori positive patients with peptic ulcer disease (PUD; n = 40) or nonulcer dyspepsia (NUD; n = 106) were evaluated. H. pylori vacA genotpyes and cagA status were determined directly in gastric biopsy specimens by polymerase chain reaction. The patients were treated with triple-therapy regimens consisting of a proton pump inhibitor and two antibiotics twice daily for 7 days. Reevaluation of H. pylori was determined 4-5 weeks later by endoscopy or 13C urea breath test. RESULTS: 123 patients completed the study. In 8 patients, colonization with two or more H. pylori strains was found. The overall cure rate was 84.6% (104/123). The eradication rates were significantly higher in patients with PUD (94.4%, 34/36) than in those with NUD (81.6%, 71/87; p < 0.05). In patients with cagA-positive H. pylori strains, the eradication rate was 89.0% (73/82) as compared with 78.8% (26/33) in those with cagA-negative strains (p = 0.15). The vacA genotype had no effect on the efficacy of H. pylori eradication. CONCLUSION: Using 1-week triple-therapy regimens, treatment of H. pylori infection is more effective in patients with PUD than in those with NUD.     

Development of Helicobacter pylori Infection Model in BALB/c Mice with Domestic cagA-Positive and-Negative Strains in Taiwan

We aimed to develop an H. pylori-infected mousemodel using clinically stored strains in Taiwan and totest whether development of H. pylori infection in an invivo animal model is related to the status of the cagA gene. A total of 100 male BALB/cmice, 6-8 weeks old, including 80 in the experimentalgroup and 20 in the control group, were used. Twoclinically stored H. pylori isolates, a cagA-positive and a cagA-negative strain, were selected toinduce the H. pylori infection in half (N = 40) of themice in the experimental group. Bacterial isolates of0.8 × 10⁹ CFU/ml were orally inoculatedin each mouse of the experimental group for threeconsecutive days. Ten mice in the control group weresacrificed to confirm the initial absence of H. pylori.Eight weeks after inoculation of the experimental group and no inoculation of the remaining 10mice of the control group, each mouse was killed.Gastrectomy was then performed for rapid urease test(CLOtest) and histology. In the control group, none of 20 mice had positive results from the CLOtestor histology. In contrast, excluding eight of 80 micethat died before the eighth week, 90.3% (65/72) of themice challenged with H. pylori showed persistent presence of H. pylori by histology. Theseverity of gastritis at the eighth week was moreevident in H. pylori-infected mice than in control andnoninfected mice (P < 0.05). Although gastritis wasmore severe in mice inoculated with thecagA-positive strain than with the cagA-negative strain,the rates of H. pylori infection in mice were notdifferent between cagA-positive and -negative strains(91.4% vs 89.2%, P > 0.05). In summary, storedstrains of H. pylori can be applied to induce aninfection model in BALB/c mice. The less virulentcagA-negative strain can induce H. pylori infection inmice as effectively as the cagA-positive strain. Thehigh prevalence of cagA-positive strains in Taiwanesepatients may be related to factors other than only thecagA gene of the bacteria.     

Effects of Helicobacter pylori on proliferation of gastric epithelial cells in vitro

OBJECTIVE: H. pylori infection of the gastric mucosa has been associated with an increase in gastric epithelial cell proliferation. However, in vitro adherence of H. pylori to gastric epithelial cells is associated with reduced cell proliferation. Reduction of epithelial cell proliferation may contribute to ulcer formation and delay ulcer healing. The following study was undertaken to elucidate the ability of cagA-positive and -negative strains to impede gastric epithelial cell proliferation. METHODS: A human gastric adenocarcinoma cell line (AGS) was overlaid with either cagA-positive or cagA-negative H. pylori strains suspended in cell culture medium. Proliferation of AGS cells was analyzed by performing direct cell counts and by measuring metabolism of a soluble tetrazolium compound (MTS), after exposure to H. pylori for 24 h. RESULTS: When compared with control cells cultured in medium alone, AGS cell proliferation was reduced by 45.6% and 28.5% due to exposure to cagA-negative and cagA-positive strains, respectively. When bacterial-induced cytotoxicity was assessed by measuring release of lactose dehydrogenase (LDH) into the culture medium, cagA-positive strains were shown to induce significantly more cytotoxicity than cagA-negative strains. CONCLUSIONS: These experiments demonstrate that H. pylori exposure to AGS cells significantly reduces cell proliferation. However, cagA-positive strains that induce more cell injury reduce cell proliferation to a lesser extent than cagA-negative strains. Persistent replication of gastric epithelial cells injured by exposure to cagA-positive strains may be partially responsible for the stronger association with gastric cancer in persons infected with cagA-positive H. pylori strains.     

Colonization with cagA-positive Helicobacter pylori strains in intestinal metaplasia of the esophagus and the esophagogastric junction

OBJECTIVES: Recent studies indicate that colonization with cagA-positive Helicobacter pylori (H. pylori) strains may protect against gastroesophageal reflux disease (GERD) and its complications, but the role of cagA in the etiology of Barrett's esophagus has so far been poorly investigated. The pathogenesis of intestinal metaplasia (IM) at an endoscopically normal esophagogastric junction (EGJ) is still unclear, and the role of the H. pylori virulence factor cagA in it has not been investigated. The aim of our study was to assess the relationship between H. pylori and cagA-positive H. pylori in particular and IM at an endoscopically normal EGJ and Barrett's esophagus. METHODS: Serum samples were obtained from 62 patients without IM, 43 patients with IM at an endoscopically normal junction, and 51 patients with Barrett's esophagus. IM was defined as presence of goblet cells with positive staining with Alcian blue. The prevalence of H. pylori and cagA was investigated by assessment of IgG antibody levels as determined by ELISA. RESULTS: The overall H. pylori prevalence was 59% (92/156), and the cagA prevalence was 29% (46/156). Although 63% (39/62) of IM negative subjects and 74% (32/43) of those with IM at the junction were H. pylori positive, only 41% (21/51) of Barrett's patients tested positive. The differences between the IM negative and the Barrett's group (p = 0.02) and between IM at the junction and Barrett's were significant (p = 0.002). The relative cagA prevalence (percentage with cagA positivity and H. pylori positivity) was 56% (22/39) in patients who were IM negative, 59% (19/32) in those with IM at the junction, and 24% (5/21) in those with Barrett's. The prevalence of anti-CagA was significantly lower in patients with Barrett's esophagus compared with patients who were IM negative (p = 0.002) and those who had IM at the junction (p < 0.001). No difference in cagA prevalence was seen between the latter groups. CONCLUSIONS: These findings are in line with the concept that H. pylori and cagA-positive strains in particular protect against the development of Barrett's esophagus. In contrast, our findings do not support the theory that IM at an endoscopically normal esophagogastric junction is associated with H. pylori or cagA-positive strains. IM at the junction and Barrett's esophagus seem to have different etiologies.     

Prevalence of vacA, cagA and babA2 genes in Cuban Helicobacter pylori isolates

AIM： To investigate the prevalence of vacuolating cytotoxin （vacA）, cytotoxin associated gene A （cagA） and blood adhesion binding antigen （babA2） genotypes of Helicobacter pylori （H pylori） isolates from Cuban dyspeptic patients. METHODS： DNA was extracted from Hpylori-positive cultures taken from 130 dyspeptic patients. Genotyping was performed by PCR, using specific primers for vacA （s1, s2, m1, m2）, cagA and babA2 genes. Endoscopic observations and histological examinations were used to determine patient pathologies. RESULTS： vacA alleles s1, s2, m1 and m2 were detected in 96 （73.8%）, 34 （26.2%）, 75 （57.7%） and 52 isolates （40%）, respectively, while the cagA gene was detected in 95 isolates （73.2%）. One hundred and seven isolates （82.3%） were babA2-positive. A significant correlation was observed between vacAs1m1 and cagA and between vacAs1ml and babA2 genotypes （P 〈 0.001 and P 〈 0.05, respectively） and between babA2 genotype and cagA status （P 〈 0.05）; but, no correlation was observed between vacAsl and babA2 genotypes. Eighty five （65.4%） and 73 （56.2%） strains were type 1 （vacAsl-cagA-positive） and ＂triplepositive＂ （vacAs1-cagA-babA2-positive）, respectively, and their presence was significantly associated with duodenal ulcer （P 〈 0.01 and P 〈 0.001, respectively）. CONCLUSION： The distribution of the main virulence factors in the Cuban strains in this study resembled that of the Western-type strains, and the more virulent H pylori isolates were significantly associated with duodenal ulcer, ulcer disease being the worst pathology observed in the group studied.     

Factors associated with Helicobacter pylori infection by a cagA-positive strain in children

Although infection with a cagA-positive Helicobacter pylori strain is considered a risk factor for the development of duodenal peptic ulcer in adults, this association has not been demonstrated in children. The presence of cagA was investigated by polymerase chain reaction in H. pylori strains isolated from 27 children with duodenal ulcer and 53 without duodenal ulcer. All patients (100%) with duodenal ulcer and 33 (62.3%) without ulcer were colonized by a cagA-positive strain (P=.00007). A cagA-positive status was also associated with a more marked macroscopic gastritis, with a greater inflammatory infiltrate of both mononuclear and polymorphonuclear cells in the antral and oxyntic gastric mucosae and degenerative and regenerative changes of the gastric mucosa. Increased cagA positivity was also associated with increased age, but no association between cagA-positive status and sex was observed.     

Genes inside the cagPAI of Helicobacter pylori are not associated with gastric cancer in Japan

BACKGROUND/AIMS: In Japan, infection with cagA-positive H. pylori is not associated with gastric cancer unlike Western populations. Both cagE and Agrobacterium VirD4 homologue are genes inside the cagPAI. The aim of this study was to examine whether the presence of genes inside the cagPAI, cagA, cagE and Agrobacterium VirD4 homologue, is associated with gastric cancer in Japan. METHODOLOGY: Thirty-nine patients with gastric cancer and 39 subjects with only chronic gastritis were infected with H. pylori. Seventy-eight H. pylori strains were isolated from gastric biopsies and the presence of 23S rRNA, cagA, cagE, and VirD4 homologue were studied by polymerase chain reaction. RESULTS: The positivity of cagA was 97.4% in patients with gastric cancer, and 92.3% in control subjects. Thirty-six strains (92.3%) isolated from patients and 35 strains (89.7%) from control subjects had both cagE and VirD4. All the 3 cagA-negative strains did not have both cagE and VirD4. There were no significant differences in the positivities of cagA, cagE, and VirD4 between patients and control subjects. CONCLUSIONS: cagE and VirD4 were possessed by most Japanese strains, and thus the structure of the cagPAI of H. pylori might not be associated with the development of gastric cancer in Japan.     

Effects of cagA+ and cagA- strains of Helicobacter pylori on the human gastric mucus layer thickness

BACKGROUND: Infection with cytotoxin-associated gene A (cagA) Helicobacter pylori is associated with severe gastric diseases, with contradictory views being expressed concerning the effect of H. pylori on the gastric mucus thickness. The aim of the present study was to differentiate between the effect of cagA+ and cagA- strains on gastric mucus thickness. METHODS: Ninety-nine patients without peptic ulcers who were not on medication were randomly recruited from consecutive endoscopy clinics: six biopsies (five antral, one body) were obtained from each patient. Cryostat sections (18 microm) were cut and stained using the modified periodic acid-Schiff/Alcian blue technique. Mucus thickness was measured using computer-assisted light microscopy. The H. pylori status was assessed by histology, Campylobacter-like organism (CLO)test and culture, and cagA+ status determined by polymerase chain reaction (PCR). RESULTS: There was no significant difference (P = 0.784) in mean mucus thickness between cagA+ (52.7 +/- 1.2 microm, n = 10), cagA- (46.6 +/- 1.1 microm, n = 18) or H. pylori-negative patients (51.3 +/- 1.1 microm, n = 30). In cagA- patients, mucus thickness was significantly reduced with increased H. pylori colonization density, Spearman (r(s)) = -0.805, P < 0.0001. In contrast, in cagA+ patients there was a weak positive, but not significant, association between mucus thickness and H. pylori colonization density, r(s) = 0.333, P = 0.381. CONCLUSIONS: The human gastric mucus thickness is not affected by infection with cagA+ or cagA- strains of H. pylori compared with uninfected. Although a trend of increased mucus thickness with cagA+ infection was observed.     

Human gastric mucosal hydrophobicity does not decrease with Helicobacter pylori infection or chronological age.

BACKGROUND AND AIMS: Infection with cytotoxin-associated gene A (cagA) Helicobacter pylori is associated with severe gastric diseases. Previous studies in humans have reported a decreased gastric hydrophobicity with H pylori infection. The aim of the present study was to differentiate between the effect of cagA+ and cagA- strains on gastric mucus hydrophobicity. METHODS: One hundred patients without peptic ulcers and not on medication were randomly recruited from endoscopy clinics; each patient had six biopsies. Contact angle measurements were performed using a goniometer assisted by computer software. H pylori status was assessed by histology, Campylobacter-like organism test and culture, and cagA+ status was determined by polymerase chain reaction. RESULTS: In age- and sex-matched patients, there was no significant difference (P=0.27) in contact angle between H pylori-positive (61+/-2.8 degrees ) and H pylori-negative patients (65.5+/-3.0 degrees ). There was also no significant difference (P=0.36) in contact angle among H pylori-negative, cagA- and cagA+ patients (65.5+/-3.0 degrees , 58.6+/-3.6 degrees and 63.4+/-4.9 degrees , respectively). However, a trend of increased mean contact angles in cagA+ compared with cagA- and H pylori-negative patients was observed in patients 50 years and younger (68.3+/-8.3 degrees , 61.1+/-6.1 degrees and 63.6+/-2.2 degrees , respectively; P=0.70) and in patients without atrophy (71.1+/-8 degrees , 59.6+/-4 degrees and 66+/-2 degrees , respectively; P=0.30). In addition, there was no significant correlation between contact angles and patient age (r=0.104, P=0.306). CONCLUSIONS: The present study shows that H pylori infection and the chronological age have no effect on the gastric mucus hydrophobicity, but it highlights a trend of increased mucus hydrophobicity with cagA+ infection that needs to be supported by future studies.     

High prevalence of cagA-positive strains in Helicobacter pylori-infected, healthy, young Chinese adults

BACKGROUND: Cytotoxin-associated gene A (cagA) has been implicated as a potential pathogenic marker for Helicobacter pylori-induced severe gastroduodenal diseases. Although the prevalence of cagA-positive strains has been reported in patient populations from developed countries, only limited information from developing countries is available. METHODS: Polymerase chain reaction (PCR) in combination with immunoblot analysis was used to determine the prevalence of cagA and its adjacent cagE genes and to evaluate the expression of CagA protein in 55 H. pylori clinical isolates from China. RESULTS: The expected PCR products derived from H. pylori cagA and cagE genes were identified in all Chinese H. pylori clinical isolates. Similarly, the CagA protein was detected in all 40 isolates tested. CONCLUSIONS: These results demonstrated that the presence of the cagA gene correlated well with expression of the CagA protein in all surveyed Chinese H. pylori isolates and that infection with cagA-positive H. pylori strains is highly common in China and independent of clinical presentation.     

Bleeding peptic ulcers and presence of Helicobacter pylori by various tests: a case-control study

BACKGROUND: Virulence factors of Helicobacter pylori are associated with peptic ulcer disease and may be also associated with bleeding peptic ulcers (BPU). AIM: To determine whether H. pylori and/or the cytotoxin-associated gene (cagA) can increase the risk of bleeding in peptic ulcers. PATIENTS: Sixty-seven patients were studied. Thirty had BPU, 20 had non-bleeding peptic ulcers (NBPU), and 17 were control subjects (NPU). METHODS: The prevalence of H. pylori was assessed by the urease fast test, histological examination, serology, and 16S ribosomal RNA and cagA gene amplification by polymerase chain reaction (PCR). RESULTS: Histology and PCR showed greater sensitivity for diagnosis of H. pylori under bleeding circumstances when compared with other tests. Association of H. pylori was greater in the NBPU group (odds ratio [OR] 4.91, P = 0.06) than in the BPU group (OR 1.27, P = NS) when compared with the control group. When the BPU and NBPU groups were compared, H. pylori was found more often in the NBPU group (OR 0.26, P < 0.10 ). The cagA-positive gene showed a similar distribution in the three groups. The titres for anti-CagA immunoglobulin A (IgA) antibodies were higher in NBPU patients (83%) than in BPU or control patients. Furthermore, anti-urease immunoglobulin G (IgG) was detected more frequently among BPU and NBPU patients. CONCLUSIONS: NBPU patients had the highest prevalence of H. pylori by PCR. It seems unlikely that either H. pylori or the cagA-positive gene act as significant risk factors for bleeding in peptic ulcers. The lower prevalence of the microorganism among patients who bleed cannot be explained as an artificial finding.