Comparison of mucosal B- and T-cell responses in Helicobacter pylori-infected subjects in a developing and a developed country.

Helicobacter pylori is highly endemic in developing countries, but comparatively little is known about mucosal immune responses to H. pylori in these settings. Therefore, we have compared B- and T-cell responses, with a focus on the gastrointestinal mucosa, in H. pylori-infected adults in a developing (Bangladesh) and a developed (Sweden) country. We found comparable numbers of CD19(+) B cells and CD4 (+)T cells and similar levels of H. pylori-specific IgA antibodies in gastric mucosa from Bangladeshi and Swedish volunteers. However, about threefold higher numbers of CD19(+) B cells and 12-fold increased levels of H. pylori-specific IgA antibodies were found in the duodenum of Bangladeshi subjects. The gastric and duodenal immune responses in Bangladeshi asymptomatic carriers and duodenal ulcer patients were comparable. Bangladeshi subjects had about twofold lower titers of H. pylori-specific IgA and IgG antibodies in the circulation compared with Swedish volunteers. In conclusion, our findings suggest that Bangladeshi individuals have comparable gastric immune responses, but lower systemic antibody responses to H. pylori, compared with Swedish volunteers. Increased inflammation is present in the duodenum of Bangladeshi volunteers, maybe as a result of frequent exposure to enteric infections in these individuals.

Long-term re-infection rate after Helicobacter pylori eradication in Bangladeshi adults.

BACKGROUND AND AIM: Bangladesh is a developing country with a very high prevalence of Helicobacter pylori infection, which has been ascribed to overcrowding and poor sanitary conditions. It has generally been accepted that the re-infection rate is higher in countries with a high prevalence of H. pylori infection. Short-term follow-up studies support this assumption but no long-term studies are available to confirm or refute this assertion. The present study was aimed to define the long-term H. pylori re-infection rate (6 years after successful eradication) in duodenal ulcer patients. METHODS: In a previous study, 90 patients were successfully eradicated for H. pylori and followed-up for 24 months. 17/90 were found to be re-infected (18% re-infection rate per year in the first 12 months) [Gastroenterology 2001;792-798]. The remaining 73 patients were targeted for long-term follow-up. 26/73 were lost to follow-up; 6 symptomatic patients were tested H. pylori positive in the period between 24 and 60 months post-eradication. The remaining 41 patients were evaluated 72 months after successful eradication. The evaluation included clinical history taking, a (13)C-urea breath test (UBT), and endoscopy. RESULTS: Of the 41 H. pylori-eradicated patients analyzed after 72 months, 16 were H. pylori-positive. If the 6 patients, who were tested positive between 24 and 60 months, are added, the total re-infection cases amount to 22 subjects in the period between 24 and 72 months. Therefore, an overall annual re-infection rate 6 years after eradication of 5.02% can be calculated. Six of the 23 symptomatic patients had duodenal ulcer relapse, 5/6 were H. pylori re-infected and one was H. pylori-negative at 72 months post-treatment. CONCLUSION: The long-term annual H. pylori re-infection rate in Bangladeshi adults is markedly higher than in Western countries but lower than anticipated. In this study, duodenal ulcer relapse is clearly related to H. pylori re-infection.

Salmonella enterica serovar Typhi-specific immunoglobulin A antibody responses in plasma and antibody in lymphocyte supernatant specimens in Bangladeshi patients with suspected typhoid fever.

Many currently available diagnostic tests for typhoid fever lack sensitivity and/or specificity, especially in areas of the world where the disease is endemic. In order to identify a diagnostic test that better correlates with typhoid fever, we evaluated immune responses to Salmonella enterica serovar Typhi (serovar Typhi) in individuals with suspected typhoid fever in Dhaka, Bangladesh. We enrolled 112 individuals with suspected typhoid fever, cultured day 0 blood for serovar Typhi organisms, and performed Widal assays on days 0, 5, and 20. We harvested peripheral blood lymphocytes and analyzed antibody levels in supernatants collected on days 0, 5, and 20 (using an antibody-in-lymphocyte-supernatant [ALS] assay), as well as in plasma on these days. We measured ALS reactivity to a serovar Typhi membrane preparation (MP), a formalin-inactivated whole-cell preparation, and serovar Typhi lipopolysaccharide. We measured responses in healthy Bangladeshi, as well as in Bangladeshi febrile patients with confirmed dengue fever or leptospirosis. We categorized suspected typhoid fever individuals into different groups (groups I to V) based on blood culture results, Widal titer, and clinical features. Responses to MP antigen in the immunoglobulin A isotype were detectable at the time of presentation in the plasma of 81% of patients. The ALS assay, however, tested positive in all patients with documented or highly suspicious typhoid, suggesting that such a response could be the basis of improved diagnostic point-of-care-assay for serovar Typhi infection. It can be important for use in epidemiological studies, as well as in difficult cases involving fevers of unknown origin.

Isolation of tetracycline-resistant clinical Helicobacter pylori without mutations in 16S rRNA gene in Bangladesh.

The occurrence of 16S rRNA gene mutations associated with resistance to tetracycline in H. pylori isolated in Bangladesh was investigated. Tetracycline susceptibility was determined by the agar dilution method. The 16S rRNA genes of these isolates were sequenced and analyzed. A tetracycline accumulation assay was performed. DNA sequence and transformation tests of nine tetracycline-resistant (MIC = 2 microg/ml) Bangladeshi H. pylori clinical isolates showed that in no case was the resistance due to mutations in the 16S rRNA gene, the only known cause of tetracycline resistance in this pathogen. Tetracycline accumulation assays implicated altered uptake or efflux.

T2182C mutation in 23S rRNA is associated with clarithromycin resistance in Helicobacter pylori isolates obtained in Bangladesh.

Twelve clarithromycin-resistant (MIC, > or = 1 microg/ml) Helicobacter pylori isolates were analyzed for point mutations in the 23S rRNA gene. Sequence analysis of all of the resistant isolates revealed a T-to-C transition mutation at position 2182. Transformation experiments confirmed that a single T-to-C transition mutation at position 2182 is associated with clarithromycin resistance.

Antimicrobial susceptibility of Helicobacter pylori strains isolated in Bangladesh.

Antimicrobial susceptibility of 120 Helicobacter pylori isolates to metronidazole, tetracycline, clarithromycin, and amoxicillin was determined, and 77.5, 15, 10, and 6.6% of the isolates, respectively, were resistant. Only rdxA inactivation and both rdxA and frxA inactivation were responsible for metronidazole resistance in 66% (8 of 12) and 33% (4 of 12) of the isolates, respectively.