Association of Helicobacter pylori and protozoal parasites in patients with chronic diarrhoea

Introduction An association of Helicobacter pylori and common protozoal parasites in patients with abdominal discomfort and chronic diarrhoea is unclear and may be pathological. Materials and methods One hundred and sixty-one patients with diarrhoea were compared to 114 age and sex matched controls. Stool samples were examined by microscopy and DNA extracted for PCR with specific primers for H. pylori and protozoal parasites Blastocystis sp., Entamoeba sp. (Entamoeba histolytica, Entamoeba dispar and Entamoeba moshkovskii) and Giardia duodenalis (G. duodenalis). Results There was a marked difference in the presence of parasites between patients and controls: no parasite 42/75%, one parasite 42/15%, two or more parasites 16/10%, respectively (p < 0.001). Patients with diarrhoea were more likely to be infected with Blastocystis sp (p < 0.001), E. histolytica (p = 0.027) and E moshkovskii (p = 0.003). There was no difference in the frequency of H. pylori (p = 0.528), G duodenalis (p = 0.697) or E dispar (p = 0.425). Thirty-three patients and 27 controls had H. pylori infection. Of these, 22 patients and 6 controls were infected with Blastocystis sp (p = 0.001), 6 patients and no controls were infected with E. histolytica (p = 0.02), whilst 7 patents and 9 controls were infected with E dispar (p = 0.292). Conclusion In this population, diarrhoea is linked to infection with Blastocystis sp, E. histolytica and E moshkoviskii. In H. pylori infection, diarrhoea is linked to Blastocystis sp and E. histolytica infection. These associations may be linked pathogenically.

Comparison of biopsy-based methods for the detection of Helicobacter pylori infection

Various biopsy-based methods for the detection of Helicobacter pylori are evaluated to determine their sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV), followed by polymerase chain reaction (PCR) for the 16S ribosomal RNA (rRNA) gene of H. pylori (16S PCR) to confirm the results. Seventyfive patients (65% [49] males, age range: 17-77 years, mean 42+/-14.6 years) with dyspeptic symptoms are included in the study. Gastric antrum biopsy specimens collected during endoscopy are tested using a urea agar base enriched with 40% urea solution (eUAB, Oxoid)), a commercial rapid urease test (Pronto Dry, Medical Instrument Corp, Switzerland), histopathology and 16S PCR. The eUAB test showed 97% sensitivity, 86% specificity, 84% PPV, 97% NPV and 91% accuracy when the diagnosis of H. pylori infection was made with positive Pronto Dry and histopathology. Pronto Dry showed 100% sensitivity, 82% specificity, 80% PPV, 100% NPV and 89% accuracy when the diagnosis of H. pylori infection was made on positive histopathology and eUAB. Thus, the eUAB can be used as a rapid urease test. It is economical and has a sensitivity and specificity comparable to a commercially available rapid urease test to detect urease activity of H. pylori in gastric biopsy.

Helicobacter pylori: correlation of the virulence marker iceA allele with clinical outcome in a high prevalence area

The association of Helicobacter pylori virulence marker 'induced by contact with epithelium A' (iceA) allele types was determined in H. pylori-related diseases and virulence markers. Gastric biopsies were obtained at EGD from patients for culture, histopathology and polymerase chain reaction (PCR) for iceA types, cagA and vacA alleles. Two hundred and eighty-four H. pylori isolates were examined. iceA type 1 was positive in 177 (62%) and iceA type 2 in 158 (56%). In iceA type 2, gastric ulcer was present in 34 (21%) (P < 0.001) and carcinoma in 28 (25%) (P = 0.002), compared to nine (8%) and 2 (2%) in iceA type 2-negative cases. For iceA type 2, 139 (88%) were associated with chronic active gastritis compared to 95 (75%) (P = 0.006) in iceA type 2-negative. H. pylori cagA was positive in 101 (64%) iceA type 2 strains compared to 57 (45%) in negative strains (P = 0.002). H. pylori iceA type 2 was dominant and associated with cagA, chronic active inflammation, gastric ulcer and carcinoma.

Seroprevalence of hepatitis E and Helicobacter pylori in a low socioeconomic area of a metropolitan city in a developing country

This study aims to determine the prevalence of coinfection of H. pylori and hepatitis E virus (HEV) in the paediatric age group in an urban slum area of Karachi and identify risk factors associated with co-infection. Five hundred and forty children aged one to 15 years were investigated. Blood samples were collected and questionnaires completed on socio-demographic characteristics. Anti-H. pylori, HEV IgG and IgM antibodies were analysed by enzyme immunoassays (EIAs). The seroprevalence of H. pylori antibody was 47.2%, while that of HEV IgG and IgM was 14.4% and 2.4%, respectively. 12.4% exhibited seroprevalence for both H. pylori and HEV (IgG). In 67 (26%) cases positive for H. pylori IgG, HEV IgG positivity was also seen (P < 0.001). Only 13 (5%) positive for H. pylori were also positive for HEV IgM (P < 0.001). Only 11 (4%) HEV IgG-positive cases were H. pylori antibody-negative (P < 0.001). Hepatitis E virus was common in children who had access to municipal piped water (P = 0.025). H. pylori was common in children who used a non-flush toilet system (P < 0.001). Children exposed to H. pylori infection were also exposed to the risk of HEV.

Virulence markers of Helicobacter pylori in patients with diarrhoea-dominant irritable bowel syndrome

Recent studies suggest that irritable bowel syndrome (IBS) is associated with low-grade inflammation. This study aims to determine the distribution of Helicobacter pylori cytotoxin-associated gene A (cagA) and vacuolating cytotoxin A (vacA) alleles (e.g., s1 and s2) in patients with diarrhoea-dominant IBS (IBS-D) as the latter causes vacuolation in colonic epithelial cells in vitro. One hundred and seventy patients meeting Rome III criteria for IBS-D (mean age: 40 +/- 15 years) were enrolled. Gastric biopsy was assessed histologically and DNA extraction was performed by polymerase chain reaction (PCR) for H. pylori genus 16S ribosomal DNA (16S rDNA), cagA and vacA allele s1 and s2. There was no age- or gender-related difference in H. pylori positivity in IBS-D compared to the control group. H. pylori was positive in 116 (68%) with IBS-D compared to 88 (55%) in the control group (P=0.01). cagA was positive in 73 (63%) with IBS-D compared to 42 (48%) in the control group (P=0.03). vacA s1 was positive in 61 (53%) with IBS-D compared to 32 (36%) in the control group (P=0.02). cagA s1 was positive in 39 (34%) with IBS-D compared to 13 (15%) in the control group (P=0.002).

Antibiotic susceptibility patterns of Helicobacter pylori and triple therapy in a high-prevalence area

This study aims to determine primary Helicobacter pylori resistance and its effect on eradication of the organism. Ninety-two patients with dyspeptic symptoms were enrolled. H. pylori was cultured and antibiotic sensitivity was determined by the Epsilometer test (Etest) for clarithromycin (CLR), amoxicillin (AMX) and metronidazole (MTR). 23S ribosomal RNA (rRNA) point mutations associated with clarithromycin resistance were also detected. Patients were treated with omeprazole (40 mg daily), CLR (500 mg) and AMX (1g twice a day) for 14 days. A 14C-urea breath test (14C-UBT) was repeated four weeks after completion of treatment to confirm eradication. Triple therapy failure was seen in 30 (33%) patients. The resistance rates were: CLR 33% (30/92), MTR 48% (44/92) and AMX 2% (2/92). Clarithromycin resistance (CLR-R) was present in the 16-39 age group in 21 (47%) (P = 0.007) compared to nine (19%) in the 40-79 age group. CLR resistance was seen in 30 H. pylori isolates, 20 (67%) from patients with non-ulcer dyspepsia (NUD), six (20%) with gastric ulcer (GU) and four (13%) with duodenal ulcer (DU). Triple therapy failure was associated with CLR-R in 28 (93%) (P < 0.001). CLR-R mutations were present in 30 (33%) and were associated with treatment failure in 27 (90%; P < 0.001). They were present in 20 (44%) isolates obtained from patients in the 16-39 age group (P = 0.018). Treatment failure was associated with A2142G mutation in 20 (67%; P < 0.001), A2143G mutation in 12 (40%; P < 0.001) and A2142C mutation in five (17%; P = 0.003). In conclusion, triple therapy failure was associated with CLR-R. Metronidazole resistance exceeded that of CLR, hence it cannot be substituted for CLR in a triple therapy.

Prevalences of Giardia lamblia and Cryptosporidium parvum infection in adults presenting with chronic diarrhoea

Giardia lamblia and Cryptosporidium parvum are both waterborne pathogens associated with diarrhoea in developing countries. In a recent study based at the Aga Khan University in Karachi, 334 adults aged 16-83 years (178 patients with chronic diarrhoea and 156 diarrhoea-free volunteers who acted as controls) were checked for infection with these parasites, using stool microscopy and/or PCR. Overall, 21 (6.3%) and 29 (8.7%) of the subjects were found positive for G. lamblia by microscopy and PCR, respectively, while the corresponding values for C. parvum were 13 (3.9%) and 14 (4.2%). Although, compared with the diarrhoea-free controls, the patients with diarrhoea were not significantly more likely to be found infected with Giardia, either by microscopy [15 (8.4%) v. six (3.8%); P=0.085] or PCR [19 (10.7%) v. 10 (6.4%); P=0.167], they were significantly more likely to be found infected with C. parvum, both by microscopy [11 (6.2%) v. two (1.3%); P=0.024] and by PCR [12 (6.7%) v. two (1.3%); P=0.014]. The 19 patients found PCR-positive for Giardia comprised 10 (67%) of the 15 found smear-positive for the same parasite but only nine (5%) of the 163 found smear-negative (k=0.545; P<0.001). Similarly, the 12 patients found PCR-positive for Cryptosporidium comprised all 11 (100%) patients found smear-positive for the same parasite but only one (0.6%) of the 167 found smear-negative (k=0.954; P<0.001). Although C. parvum was associated with chronic diarrhoea in the present study, the carriage of G. lamblia often appeared asymptomatic.

Low prevalence of the intact cag pathogenicity island in clinical isolates of Helicobacter pylori in Karachi, Pakistan

Clinical diseases that follow Helicobacter pylori infection are associated with expression of the cagA gene, a part of cytotoxin-associated gene pathogenicity island (cag-PAI). This study aims to determined whether or not the presence of cagA is associated with the presence of complete cag-PAI and to evaluate inflammatory changes associated with the five loci in the cag-PAI of H. pylori comprising cagA, cagA promoter region (cagAP), cagE, cagT and the left end of the cagA gene (LEC). H. pylori isolates were obtained from patients with dyspeptic symptoms. Clinical strains of H. pylori were screened by the polymerase chain reaction (PCR) for respective genes of the cag-PAI. Of 115 H. pylori isolates, 31 (28%) were positive for the five cag-PAI loci. H. pylori isolates with intact cag-PAI were associated with gastric carcinoma (GC; n=9 [60%]) and gastric ulcer (GU; n=5 [45%]) compared to non-ulcer dyspepsia (NUD; n=14 [18%]) (P=0.001 and P=0.049, respectively). In patients with intact cag-PAI, acute on chronic inflammation was present in 25 (81%) and was more common than chronic inflammation (P=0.013). The cagE and cagAP had deletions in 25 (37%) and 23 (35%) cases, respectively. The cagAP region was significantly associated with GC (n=12 [80%], P<0.001) and GU (n=9 [82%], P=0.001) compared to NUD (n=24 [30%] and with significant acute on chronic inflammation (n=40 [80%], P=0.007). The distribution of vacAs1a with intact cag-PAI in GC was 9 (60%) and in NUD was 10 (13%) (P<0.001). The presence of the cagA gene does not signify presence of an intact cag-PAI. Most of the H. pylori isolates studied had partial cag-PAI with missing cagE and cagA promoter regions.

Helicobacter pylori infection in children: population-based age-specific prevalence and risk factors in a developing country

AIM

We estimated the prevalence, age of acquisition and risk factors for Helicobacter pylori (H. pylori) seroprevalence in children aged 1-15 years.

METHODS

Exposure was assessed using ELISA. Parents responded to a questionnaire regarding number of individuals sharing house, rooms, water source, latrines, housing and assessment of socioeconomic status (SES) by Hollingshead Index.

RESULTS

Serum of 1976 children was tested. Helicobacter pylori seropositivity in children aged 11-15 years was 53.5% (OR: 2.0, 95% CI: 1.58-2.5). It increased with moderate crowding index (CRI) of 2-4 to 45.9% (OR: 1.23, 95% CI: 0.92-1.63) and to 51.2% with CRI >4 (OR: 1.52, 95% CI: 1.12-2.06). In middle SES, seropositivity was 50.5% (331/655) (OR: 1.7, 95% CI: 1.29-2.35), whereas in lower SES, it was 47.1% (500/1062) (OR: 1.5, 95% CI: 1.1-2.0). Multivariate analysis showed that Helicobacter pylori seroprevalence was high in children aged 6-10 and 11-15 years (OR: 1.5, 95% CI: 1.2-1.9 and OR: 1.9, 95% CI: 1.56-2.47 respectively), in lower-middle SES (OR: 1.6, 95% CI: 1.2-2.1 and OR: 1.5, 95% CI: 1.10-2.0 respectively) and in uneducated fathers (OR: 1.58, 95% CI: 1.27-1.95).

CONCLUSION

Helicobacter pylori seropositivity increases with age, in low-middle SES and is related to father's educational status. Reducing H. pylori seroprevalence will require improvement in sanitary conditions and educational status of the population.

In vitro susceptibility of Blastocystis hominis isolated from patients with irritable bowel syndrome

This study aims to determine the growth pattern and in vitro susceptibility of clinical isolates of Blastocystis hominis to different concentrations of metronidazole, furazolidone and ciprofloxacin. Stool specimens from 25 consecutive patients with irritable bowel syndrome presenting to the gastroenterology department of Aga Khan University Hospital between January and May 2003 are examined by microscopy and cultured for B. hominis. Drug susceptibility assays are performed for metronidazole, furazolidone, and ciprofloxacin using final concentrations of 0.01 mg/mL and 0.1 mg/mL. The effect of the drugs is assessed after B. hominis culture for 48 h. With furazolidone and metronidazole, 68% (17/25) and 60% (15/25) of B. hominis isolates, respectively, failed to grow at drug concentrations of both 0.01 mg/mL and 0.1 mg/mL. However, ciprofloxacin failed to suppress growth completely at both concentrations. B. hominis resistance to furazolidone, metronidazole and ciprofloxacin at 0.01 mg/mL was 32% (8/25), 40% (10/25) and 100% (25/25), respectively. B. hominis isolates varied in their degree of susceptibility to the three drugs studied, being greater with furazolidone than with metronidazole, and complete resistance with ciprofloxacin.

Irritable bowel syndrome in health care professionals in Pakistan

OBJECTIVE

To evaluate the symptomatology of irritable bowel syndrome (IBS) among health care professionals attending an IBS symposium in a tertiary care university hospital.

METHOD

A questionnaire designed to incorporate Manning and Rome II criteria was distributed among participants of an IBS symposium, most of them were health care professionals. A total of 100 questionnaires were distributed, 41 had symptoms fulfilling criteria of IBS. In these patients male: female ratio was 28:13 with age range 18-68.

RESULTS

The predominant symptom was abdominal pain 87.8 % (36/41) which was aggravated post-prandially 72.2% (29/41), relieved following defecation in 87% (35/41) with a sense of incomplete evacuation 85.3% (35/41) and distention after defecation in 80.4% (33/41). Anxiety and depression was present in 80% (33/41) as an extraintestinal symptom.

CONCLUSION

Irritable bowel syndrome is common in health care workers with intestinal and extraintestinal manifestations being equally common.

Helicobacter pylori cagA and vacA cytotoxin genes in Changsha, China

Cytotoxin-associated protein (cagA) and the vacuolating cytotoxin (vacA) encoded by cagA and vacA genes are virulence determinants of Helicobacter pylori. In earlier studies among Chinese patients, all H. pylori strains were cagA-positive and vacAs1a/m2 type. Here, we determine the cagA, vacA and allele status of H. pylori strains isolated from patients with upper gastrointestinal symptoms in Changsha, China. Forty strains of H. pylori isolated from patients with peptic ulcer disease between March 1997 and August 1999 were recovered from storage at -80 degrees C and studied by the polymerase chain reaction (PCR) for cagA and vacA genotypes. cagA was positive in 75% of H. pylori isolates. Patients with peptic ulcer demonstrated cagA in 83% (15/18), compared with 68% (15/22) patients with superficial gastritis. vacAs1 allele was carried in 82.5% (33/40) isolates, of which 52.5% (21/40) were subtype vacAs1a/m2 and 17.5% (7/40) were subtype vacAs1b/m2.

Helicobacter pylori detection in Chinese subjects: a comparison of two common DNA fingerprinting methods

This study aims to demonstrate DNA diversity in Helicobacter pylori strains obtained from patients with peptic ulcer disease and compare the results from two DNA fingerprinting techniques. H. pylori strains (n = 42), collected from June 1996 to August 1999, were cultured from storage at -80 degrees C. DNA diversity was determined by the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis, and random amplified polymorphic DNA (RAPD)-PCR. Isolates showed a significant DNA sequence diversity by both methods. RAPD-PCR demonstrated 33 distinct strain-specific band patterns, whereas PCR-RFLP demonstrated six distinct restriction patterns. PCR-RFLP identified four of the 42 strains as mixed growth, compared with RAPD-PCR which did not reveal any co-colonisation. Diversity among H. pylori clinical isolates was demonstrated distinctly by both methods; however, RAPD-PCR showed greater discriminatory power in distinguishing between isolates.

Antibiotic susceptibility of Helicobacter pylori in the Chinese population

AIM

To assess antibiotic susceptibility of Helicobacter pylori (H. pylori) strains to metronidazole, clarithromycin and tetracycline in the Chinese population, and to test the stability of antibiotic resistance in H. pylori 1 year after storage at -80 degrees C.

METHODS

Fifty H. pylori strains isolated from patients with peptic ulcer disease were recovered from storage at -80 degrees C. Susceptibility of these strains to metronidazole, clarithromycin and tetracycline was determined by using validated disk diffusion tests, which was repeated 1 year after storage at -80 degrees C. The DNA profiles of each strain were determined by using the polymerase chain reaction-based-random amplified polymorphic DNA fingerprinting technique (PCR-RAPD). This was repeated if any change in antibiotic susceptibility pattern was noticed.

RESULTS

The resistance rate was 50% to metronidazole and 8% to clarithromycin. None of the strains was resistant to tetracycline. A dual resistance to metronidazole and clarithromycin was demonstrated in three H. pylori strains. The antibiotic susceptibility test reproduced itself in 92% (36 of 39) of the strains 1 year later; the three strains with dual resistance exhibited susceptibility to both antibiotics. Variation in antibiotic susceptibility pattern in the three H. pylori strains was associated with change in the RAPD fingerprint.

CONCLUSION

The prevalence of resistance in H. pylori is high to metronidazole but low to clarithromycin in the Chinese population. The disk diffusion test appears to be a simple and reliable test, while antibiotic resistance in some H. pylori strains may disappear after long-term storage at -80 degrees C.

Polycolonization of Helicobacter pylori among Chinese subjects

OBJECTIVE

To investigate the situation among Chinese patients with regard to infection with multiple strains of Helicobacter pylori.

METHODS

Biopsy specimens for culture of H. pylori were obtained from gastric antrum, body and fundus of 20 patients during endoscopic investigation of upper gastrointestinal symptoms. H. pylori was identified by culture from one site in 16 and two or more sites in 10 of the 16 patients. Five isolated colonies of six strains of H. pylori from gastric antrum were subcultured and used for further analysis. Antibiotic susceptibility to metronidazole and clarithromycin was determined by disk diffusion test. Protein profiles of isolates were compared by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE). DNA diversity of the isolates was determined by arbitrarily primed polymerase chain reaction (AP-PCR) fingerprinting.

RESULTS

Of the 10 patients with multiple isolates, 70% (7/10) exhibited variation in susceptibility to metronidazole and 20% (2/10) to clarithromycin between different sites. In 83% of (5/6) single colonies, no variability was seen in metronidazole and clarithromycin susceptibility; they were either susceptible or resistant. Protein profiles of all isolates by SDS-PAGE were similar. Isolates from different patients produced clearly different AP-PCR fingerprints. In 50% of H. pylori strains isolated from different sites of the stomach, genetic diversity was demonstrated by different AP-PCR fingerprints. In 67% (4/6) strains, five single-colony fingerprints were similar.

CONCLUSIONS

Genetic variability has been found in H. pylori strains. Individual patients are infected with a single predominant genotype at a single site but can be colonized by multiple strains, and they may show different antibiotic susceptibilities. Individual colonies of the H. pylori population from a single site may not always yield identical DNA fingerprints and antibiotic sensitivities.

Diversity of Helicobacter pylori among Chinese persons with H. pylori infection

To determine whether there is diversity among clinical isolates of Helicobacter pylori in Chinese patients with peptic ulcer disease, 40 strains of H. pylori were isolated from antral biopsy specimens obtained at the gastroenterology clinic of Xiangya Hospital from January 1996 to June 1998. Total protein profile by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and DNA diversity by polymerase chain reaction-random amplified polymorphic DNA (PCR-RAPD) fingerprinting were performed with these isolates. All the isolates from peptic ulcer disease were relatively homogeneous in protein profiles, but they showed a great DNA sequence diversity by PCR-RAPD fingerprinting. In Chinese patients H. pylori demonstrated an enormous diversity. The diversity among clinical isolates of H. pylori could be distinctly demonstrated and this observation will be helpful in the management of intrafamilial and recurrent H. pylori infection. PCR-RAPD fingerprinting is an efficient method of distinguishing between clinical isolates of H. pylori.

Enhanced T-helper 2 lymphocyte responses: immune mechanism of Helicobacter pylori infection

Several lines of evidence implicate Helicobacter pylori (H. pylori) infection in gastroduodenal inflammation. However, the exact pathogenesis of H. pylori infection is not fully understood. T-helper (TH) lymphocytes may be subdivided into TH1 and TH2 cells based on the distinct patterns of cytokine production. TH1 reaction is associated with immunity or resistance to infection, while TH2 reaction is associated with the progression or persistence of infection. The production of interferon-gamma (INF-gamma) and interleukin 2 (IL-2), which are type 1 cytokines, is decreased in H. pylori infection. Enhanced production of type 2 cytokines (IL-4) and IL-6) is observed in individuals with H. pylori infection. Suppressed proliferative responses of peripheral blood and gastric lymphocytes have also been demonstrated in patients with H. pylori colonisation, suggesting that specific T-cell responses may be down-regulated by an enhanced TH2 reaction. Suppressed TH1 and enhanced TH2 responses in H. pylori infection may be involved in the immunopathogenesis of chronic H. pylori infection.

Effect of IL-4 on peripheral blood lymphocyte proliferation: implication in immunopathogenesis of H. pylori infection

Interleukin (IL) 4 is a type 2 cytokine which has a negative immunoregulatory role in human infection. IL-4 suppresses the production of interferon-gamma and enhances IL-10 synthesis. However, the effect of IL-4 on proliferative response of lymphocytes remains to be elucidated. We have previously reported an increase in production of IL-4 in subjects with Helicobacter pylori (H. pylori) infection. To evaluate whether the increased IL-4 is responsible for the down-regulation of immune responses in H. pylori infection, we observed the proliferative response of peripheral blood lymphocytes (PBL) co-cultured with phythaemagglutinin (PHA) or H. pylori in the presence and absence of added IL-4. As we have previously shown, PHA and H. pylori may increase PBL proliferation (P < 0.001). An increase in PBL proliferation was observed when PBL were co-cultured with PHA (P < 0.001) or H. pylori (P < 0.001) in the presence of IL-4 compared to that in the absence of IL-4. The optimal dose of IL-4 to give maximal lymphocyte proliferation is 50 pg/ml for the PHA-stimulated group or 100 pg/ml for the H. pylori-stimulated group. The data suggest that the increased IL-4 does not directly contribute to suppressed lymphocyte proliferation in H. pylori infection. Further studies will be required to determine the role of IL-4 in other aspects of down-regulation of immune responses in H. pylori infection.

Helicobacter pylori-induced lipid peroxidation in peripheral blood lymphocytes

Several lines of evidence implicate Helicobacter pylori infection in the pathogenesis of gastritis and peptic ulceration. To investigate whether H. pylori can cause lipid peroxidation in lymphocytes in vitro and to look for experimental evidence of lipid peroxidation induced by H. pylori, the lipid peroxide (LPO) level in peripheral blood lymphocytes was measured using the thiobarbituric acid fluorescence method. In the absence of added H. pylori, the LPO level in lymphocytes was 0.133 +/- 0.033 nmol/10(6) cells, and in the co-culture of H. pylori with peripheral blood mononuclear cells 0.340 +/- 0.097 nmol/10(6) cells. A significant difference was found between the two groups (p < 0.001). Antioxidants, either superoxide dismutase or catalase, could inhibit LPO production in lymphocytes. The present data provide further evidence that H. pylori can induce lipid peroxidation, which may be responsible for the pathogenesis of H. pylori-associated mucosal damage.