Sílvia B. Moura

Evaluation of [13C]urea breath test and Helicobacter pylori stool antigen test for diagnosis of H. pylori infection in children from a developing country.

ABSTRACT The [13C]urea breath test (13C-UBT) and Helicobacter pylori stool antigen test (HpSA) for the diagnosis of H. pylori infection in children were validated. The sensitivity, specificity, and positive and negative predictive values were 93.8, 99.1, 97.8, and 98.0%, respectively, for the 13C-UBT and 96.9, 100, 100, and 98.0%, respectively, for HpSA. Both tests are appropriate for diagnosing H. pylori infection in children.

Helicobacter trogontum sp. nov., isolated from the rat intestine

A new Helicobacter species that colonizes the colonic mucosa of Wistar and Holtzman rats was isolated and characterized. This bacterium was gram negative, its cells were rod shaped with pointed ends, and its protoplasmic cylinder was entwined with periplasmic fibers. It was catalase and oxidase positive, rapidly hydrolyzed urea, and was susceptible to metronidazole and resistant to cephalothin and nalidixic acid. The new organism was microaerophilic and grew at 42 degrees C, a feature that differentiates it from two other murine intestine colonizers, Helicobacter hepaticus and Helicobacter muridarum. On the basis of 16S rRNA sequence analysis data, the new organism was identified as a Helicobacter species that is most closely related to H. hepaticus. This bacterium is named Helicobacter trogontum. The type strain is strain LRB 8581 (= ATCC 700114).

Effect of Helicobacter pylori eradication on antral gastrin- and somatostatin-immunoreactive cell density and gastrin and somatostatin concentrations

The density of antral gastrin (G)- and somatostatin (D)-immunoreactive cells and the contents of antral gastrin and somatostatin were investigated in endoscopic antral biopsy specimens from patients with duodenal ulcer before and after eradication of Helicobacter pylori. After H. pylori eradication both antral somatostatin concentration (p = 0.0002) and antral D-cell density (p = 0.01) increased significantly. Conversely, although the number of G-cells was unchanged, antral (p = 0.0002) and serum (p = 0.001) gastrin contents decreased significantly. The number of oxyntic D-cells did not change significantly. These results strongly suggest that the hypergastrinaemia observed in H. pylori-positive patients may be due to a deficiency in antral somatostatin, which normally inhibits the synthesis and release of gastrin.

Spiral bacterium associated with gastric, ileal and caecal mucosa of mice

A spiral shaped bacterium was seen in smears and histological sections (stained by carbolfuchsin) of gastric, ileal and caecal mucosa as well as in stool smears from mice. A significant correlation between the presence of the spiral bacterium and the occurrence of gastritis was observed but the ileal and caecal mucosa seemed unaffected. The bacterium was Gram negative and grew on BHM and Skirrows medium, under microaerophilic conditions, at 37°C. Its major biochemical characteristics included positive catalase and oxidase reactions and a rapidly positive urease test. There were 2 or 3 spiral turns per cell and a tuft of up to 12 sheathed flagella on each pointed end. Entwined, braided periplasmic fibrils covered the surface of the cell. This spiral bacterium seemed to be part of the normal intestinal flora but was associated with gastritis.

Serodiagnosis of Helicobacter pylori infection by Cobas Core ELISA in adults from Minas Gerais, Brazil

We evaluated the accuracy of a 2nd generation ELISA to detect Helicobacter pylori infection in adults from a developing country in view of variations in sensitivity and specificity reported for different populations. We studied 97 non-consecutive patients who underwent endoscopy for evaluation of dispeptic symptoms. The presence of H. pylori was determined in antral biopsy specimens by culture, by the preformed urease test and in carbolfuchsin-stained smears. Patients were considered to be H. pylori positive if at least two of the three tests presented a positive result or if the culture was positive, and negative if the three tests were negative. Sixty-five adults (31 with peptic ulcer) were H. pylori positive and 32 adults were H. pylori negative. Antibodies were detected by Cobas Core anti-H. pylori EIA in 62 of 65 H. pylori-positive adults and in none of the negative adults. The sensitivity, specificity and positive and negative predictive values of the test were 95.4, 100, 100 and 91.4%, respectively. The Cobas Core anti-H. pylori EIA presented high sensitivity and specificity when employed for a population in Brazil, permitting the use of the test both to confirm the clinical diagnosis and to perform epidemiologic surveys.

Isolation of Helicobacter pylori from the Intestinal Mucosa of Patients with Crohn's Disease

Background:  Helicobacter species are associated with inflammatory bowel disease in rodents and in nonhuman primates. Therefore, we prospectively investigated the presence of Helicobacter species in the intestinal mucosa of patients with and without Crohns disease by culture and polymerase chain reaction (PCR) assays.

Helicobacter Species in the Intestinal Mucosa of Patients with Ulcerative Colitis

ABSTRACT In a search for Helicobacter species in the intestinal mucosae of 42 patients with ulcerative colitis (UC) and 74 without UC, only H. pylori was found. Although the bacterium was detected in UC patients by culture (7.1%) and nested PCR (19.0%), its presence was not associated with the disease (P = 0.13).

dupA polymorphisms and risk of Helicobacter pylori-associated diseases

The dupA of Helicobacter pylori has been suggested as a virulence marker associated with the development of duodenal ulcer disease. However, the studies performed in different geographical areas have shown that there are variations in the prevalence of dupA and its association with H. pylori clinical outcomes. Our group did not observe associations between the presence of dupA and H. pylori clinical outcomes in Brazil. On the other hand, we observed 2 mutations in the sequence of dupA that lead to stop codons: a deletion of an adenine at position 1311 and an insertion of an adenine at position 1426 of the gene. Our aim was to evaluate associations of the presence of dupA with duodenal ulcer and gastric cancer, considering dupA-positive only those H. pylori strains that do not have the mutations in the gene sequence. We also evaluated the effect of infection with a strain carrying an intact dupA on the gastric mucosa histology and IL-8 gastric levels. Colonization with strains that had the intact dupA was negatively associated with gastric carcinoma (p=0.001, OR=0.32, 95% CI=0.16-0.66). The presence of dupA was also associated with an increased degree of antral mucosa inflammation (p=0.01) and with decreased corpus atrophy (p<0.01) as well as with increased gastric mucosa IL-8 levels (p=0.04). In conclusion, the infection with a H. pylori strain containing the dupA without the stop codon polymorphisms is associated with a lower risk of development of gastric carcinoma in Brazilian subjects.

Toll-like receptor (TLR2, TLR4 and TLR5) gene polymorphisms and Helicobacter pylori infection in children with and without duodenal ulcer

Helicobacter pylori infection is mainly acquired in childhood, and polymorphisms in the host genes coding for Toll-like receptors (TLRs) may influence the innate and adaptive immune response to the infection, affecting the susceptibility to H. pylori or the disease outcomes. Our aim was to investigate whether TLR4, TLR2, and TLR5 polymorphisms were associated with H. pylori susceptibility and risk for duodenal ulcer in children. Gastric biopsy specimens were obtained at endoscopy for evaluation of H. pylori status, TLR4, TLR2 and TLR5 polymorphisms from 486 children (254 H. pylori-negative and 232 H. pylori-positive: 72 with and 160 without duodenal ulcer). cagA status of H. pylori infection was investigated by PCR. The levels of gastric cytokines were detected by ELISA. H. pylori-positivity or duodenal ulcer were not associated with TLR2, TLR4 or TLR5 polymorphisms. Otherwise, the presence of TLR4 polymorphic allele was associated with infection by cagA-positive strains and with increased gastric levels of interleukin-8 and interleukin-10. TLR4 polymorphism might ultimately contribute to more severe consequences of the infection in adulthood since it was associated with susceptibility to cagA-positive H. pylori infection early in life.

Seroconversion for Helicobacter pylori in adults from Brazil

We studied, prospectively, seroconversion for Helicobacter pylori in adults from a developing country and investigated risk factors for the acquisition of the microorganism in this population. A group of 213 volunteers of low socioeconomic level from a district in the metropolitan area of Belo Horizonte, south-east Brazil was evaluated. Anti-H. pylori IgG antibodies were measured by ELISA using Cobas Core anti-H. pylori EIA (Roche) in serum samples collected in 1992 and in 1997. The subjects were interviewed and sociodemographic data were collected. A total of 174 (81.7%) subjects presented anti-H. pylori antibodies on the occasion of the first visit. During 56 months of follow-up, 2 of 39 seronegative adults converted to seropositive with an annual infection rate of 1.1%, and 2 of 174 seropositive subjects reverted to seronegative (0.2%/year). The prevalence of infection increased significantly with age and an inverse association was observed between prevalence of infection and educational level. In conclusion, the results of the present study demonstrate that in a developing country there is a low but continuous risk of H. pylori infection in adulthood.