Genotypic, clinical, and demographic characteristics of children infected with Helicobacter pylori

Relationship between Helicobacter pylori Infection and Plasmacytoid and Myeloid Dendritic Cells in Peripheral Blood and Gastric Mucosa of Children

PURPOSE

To investigate the frequency and activation status of peripheral plasmacytoid DCs (pDCs) and myeloid DCs (mDCs) as well as gastric mucosa DC subset distribution in Helicobacter pylori- (H. pylori-) infected and noninfected children.

MATERIALS AND METHODS

Thirty-six children were studied; twenty-one had H. pylori. The frequencies of circulating pDCs (lineage-HLA-DR+CD123+) and mDCs (lineage-HLA-DR+CD11c+) and their activation status (CD83, CD86, and HLA-DR expression) were assessed by flow cytometry. Additionally, the densities of CD11c+, CD123+, CD83+, CD86+, and LAMP3+ cells in the gastric mucosa were determined by immunohistochemistry.

RESULTS

The frequency of circulating CD83+ mDCs was higher in H. pylori-infected children than in the noninfected controls. The pDCs demonstrated upregulated HLA-DR surface expression, but no change in CD86 expression. Additionally, the densities of gastric lamina propria CD11c+ cells and epithelial pDCs were increased. There was a significant association between frequency of circulating CD83+ mDCs and gastric lamina propria mDC infiltration.

CONCLUSION

This study shows that although H. pylori-infected children had an increased population of mature mDCs bearing CD83 in the peripheral blood, they lack mature CD83+ mDCs in the gastric mucosa, which may promote tolerance to local antigens rather than immunity. In addition, this may reduce excessive inflammatory activity as reported for children compared to adults.

Helicobacter pylori virulence genes

Helicobacter pylori (H. pylori) is one of the most important human pathogens, infecting approximately half of the global population. Despite its high prevalence, only a subset of H. pylori infected individuals develop serious gastroduodenal pathology. The pathogenesis of H. pylori infection and disease outcome is thus thought to be mediated by an intricate interplay between host, environmental and bacterial virulence factors. H. pylori has adapted to the harsh milieu of the human stomach through possession of various virulence genes that enable survival of the bacteria in the acidic environment, movement towards the gastric epithelium, and attachment to gastric epithelial cells. These virulence factors enable successful colonization of the gastric mucosa and sustain persistent H. pylori infection, causing chronic inflammation and tissue damage, which may eventually lead to the development of peptic ulcers and gastric cancer. Numerous studies have focused on the prevalence and role of putative H. pylori virulence genes in disease pathogenesis. While several virulence factors with various functions have been identified, disease associations appear to be less evident, especially among different study populations. This review presents key findings on the most important H. pylori virulence genes, including several bacterial adhesins and toxins, in children and adults, and focuses on their prevalence, clinical significance and potential relationships.

Prevalence of the Helicobacter pylori homA and homB genes and their correlation with histological parameters in children

The significance of Helicobacter pylori (H. pylori) virulence genes such as cagA and vacA has been extensively studied in children; however, data regarding the significance of homA and homB genes are scarce. The aim of our study was to evaluate the prevalence and clinical relevance of these genes in Slovenian children. All children diagnosed with H. pylori infection between 1993 and 2013 were included in the study (n = 343). DNA was extracted from biopsy specimens previously used for the rapid urease test. Five histological parameters were evaluated and the presence of the vacA, cagA, iceA, babA2, and homA and homB genes was determined by PCR amplification. The homA and homB genes were detected in 174/285 (61.1%) and 116/285 (40.7%) strains, respectively. The presence of the homA gene was significantly associated with the absence of the homB gene (P < 0.001); however, no associations were found between the presence of either the homA or homB genes and any of the other investigated virulence genes. Similarly, there were no correlations between the presence of the homA and homB genes and any of the histological parameters. In contrast, genotype profiles vacA s1m1/cagA+/babA2+/homB+, vacA s1m2/cagA+/babA2+/homA+, vacA s1m1/cagA+/babA2+/homA+, vacA s1m1/cagA+/babA2-/homA+, vacA s1m2/cagA-/babA2-/homA+, and vacA s2m2/cagA-/babA2-/homB+ were associated with a higher degree of gastric mucosal damage. Thus, although the homA and homB genes did not represent important individual virulence markers in this population, they may act synergistically with other H. pylori virulence genes, causing severe gastritis in children.

Prevalence of infection with cagA-positive Helicobacter pylori strains among children and adolescents in southern Brazil

CONTEXT

Helicobacter pylori (H. pylori) has a worldwide distribution, but the prevalence of infection, virulence factors, and clinical presentation vary widely according to the studied population. In Brazil, a continental country composed of several ethnicities and cultural habits, the behavior of infection also appears to vary, as many other studies have shown.

OBJECTIVES

Describe the prevalence of infection with cagA-positive H. pylori strains in a group of children and adolescents who underwent esophagogastroduodenoscopy in Porto Alegre, Rio Grande do Sul.

METHODS

Fifty-four gastric biopsy specimens of children and adolescents with H. pylori infection demonstrated by histology, urease test and molecular analysis were tested for the presence of cagA positive H. pylori strains by the polymerase chain reaction method.

RESULTS

The prevalence of cagA-positive H. pylori was 29.6% (95% confidence interval, 18 to 43.6%). There were no statistically significant differences in clinical or demographic characteristics or in the endoscopic and histological features of patients infected with cagA-positive strains as compared with those infected by cagA-negative strains.

CONCLUSIONS

he study showed a low prevalence of infection with cagA-positive H. pylori strains among children and adolescents who underwent EGD in southern Brazil, in comparison to studies conducted with children from other regions of Brazil. There was no association between the presence of cagA-positive strains and more severe clinical presentations in the studied sample.

Role of childhood infection in the sequelae of H. pylori disease

The persistence of Helicobacter pylori infection plays a fundamental role in the development of H. pylori-associated complications. Since the majority of infected persons acquire the bacteria during early childhood, an examination of the immunobiology of H. pylori infection in children compared with that of adults may help identify host factors that contribute to persistent infection. Therefore, we begin our review of the role of persistence in H. pylori disease with an assessment of the clinical features of H. pylori infection in children. We next review the bacterial factors that promote colonization and evasion of host defense mechanisms. We then focus our attention on the early host immunological factors that promote persistence of the infection and its complications in humans and mouse models. We also highlight topics in which further research is needed. An examination of how immunological factors cause divergent manifestations of H. pylori infection in children compared with adults may provide new insight for therapeutic modification or prevention of persistent H. pylori infection and its complications.

Prevalence of Helicobacter pylori virulence genotypes among children in Eastern Turkey

AIM: To identify the virulence genotypes of Helicobacter pylori (H. pylori) if present in children in Eastern Turkey and if those genotypes are mostly associated with severe clinical presentations.

METHODS: A total of 49 H. pylori positive Turkish children (42 with antral nodularity and 7 with peptic ulcer) who underwent upper gastrointestinal endoscopy with abdominal symptoms during the period from March 2011 to September 2012 were enrolled in this study. Antral nodularity was diagnosed endoscopically by two of the authors. We determined for the presence of cagA, vacA, cagE, iceA and babA2 genotypes of H. pylori isolates in DNA obtained directly from frozen gastric biopsy samples by polymerase chain reaction test using specific primers.

RESULTS: Of the 49 H. pylori isolates studied, 61.2%, 91.8%, 22.4%, 28.6%, 57.1% and 40.8% were positive for the cagA, vacA s1, cagE, iceA1, iceA2 and babA2 genes, respectively. We showed that the most common vacA subtype was s1a (79.6%). However, the s2 gene was found less frequently with an isolation rate of 8.2% of the H. pylori isolates. The genotypes iceA2 and vacA s1m2 were the most frequently found types in children with antral nodularity. In addition, the genotypes iceA1, babA2 and vacA s1m1 were found in similar ratios in all the H. pylori isolates obtained from children with peptic ulcer. The genotypes vacA s2m1 and s1c were not observed in any of isolates studied.

CONCLUSION: This study showed that vacA s1m2, cagA and iceA2 were the most common genotypes, and no association between antral nodularity and genotypes was observed.

Association between Helicobacter pylori, cagA, and vacA Status and Clinical Presentation in Iranian Children

OBJECTIVE

Seroprevalence of H. pylori infection in Iran exceeds 65% of pediatric population. In this study, we intended to find association between the virulence genes (cagA and vacA) and clinical presentations.

METHODS

H. pylori isolates were achieved from the gastric mucosa of children. In each case, the gastric biopsy specimens were cultured and the organisms identified. Detection of different genotypes was carried out by PCR method.

FINDINGS

A total of 106 biopsy specimens were cultured and 33 H. pylori isolates obtained. Among these 33 H. pylori strains 24 (73%) were cagA-positive. Genotypes of vacA s1m2, s1m1, s2m2, and s2m1 were 45.5%, 30.3%, 21.2%, and 3%, respectively. Most female patients were infected with genotype s1m2. The vacA-m1 strains were significantly more common in patients with nodular gastritis. There were no statistical differences between the vacA and cagA genotypes and clinical outcomes.

CONCLUSION

The frequency of cagA genotype was high. In this study, nodular gastritis was a common finding and was rather significantly associated with m1 allele of vacA.

Helicobacter pylori genotypes can predict gastric tissue histopathology: a longitudinal study of Iranian patients

INTRODUCTION

Several factors have been suggested to account for differences in the virulence of Helicobacter pylori infections in various populations. Evidence suggests the existence of different strains of H. pylori with different degrees of virulence. The present study aimed to investigate the gastric histopathology in Iranian patients infected with H. pylori and to investigate the relationship between the severity of gastritis and four different bacterial virulence-associated genotypes.

METHODS AND MATERIALS

All of the patients with positive results from a pathological examination, a rapid urease test, and PCR analysis for H. pylori infection were consecutively included into the study. The classification and grading of gastritis were performed according to the Sydney System. Esophagitis was classified endoscopically according to the Savary-Miller grading system. The primers used in this study targeted 16S rRNa (521 bp), Urease A (411 bp), Cag A (400 bp), and 26 kDa (303 bp).

RESULTS

Twenty-eight patients were included in the study. The presence of Cag A showed a significant relationship with higher gastritis grades (3.0±0.7 vs. 2.3±0.9, p=0.024) and higher scores for H. pylori infection (3.0±0.7 vs. 2.3±0.7, p=0.027). The patients infected with 26 kDa-positive H. pylori had significantly higher infection scores (3.5±0.6 vs. 2.5±0.6, p=0.020).

CONCLUSION

This study showed that CagA-positive H. pylori infection is associated with more severe gastritis and with increased bacterial density and inflammation in the biopsy specimens. The 303-bp positive genotype was also significantly associated with higher grades of esophagitis. Additional in-depth trials will be helpful in extending our findings.

In situ expression of cagA and risk of gastroduodenal disease in Helicobacter pylori-infected children

BACKGROUND AND AIM

Gastroduodenal disease is more common among adults and children with cagA+ Helicobacter pylori infection, but disease severity varies among those infected with cagA+ strains. We examined whether cagA in situ expression can predict disease manifestations among H pylori-infected children.

PATIENTS AND METHODS

Fifty-one children were selected from 805 patients with abdominal symptoms who underwent esophagogastroduodenoscopy with gastric biopsies. Endoscopic and histologic gastritis were scored and H pylori colonization was quantified by Genta stain and in situ hybridization expression of 16S rRNA and cagA.

RESULTS

Endoscopy was either normal (n = 14) or demonstrated nodularity (n = 18), gastric ulcer (n = 8) or duodenal ulcer (n = 11). H pylori was present in 7, 18, 6, and 10 children, respectively. Expression of 16S rRNA and cagA were significantly higher in children with ulcer compared with normal children. The fraction of H pylori bacteria expressing cagA in situ was higher in children with ulcer compared to those with endoscopic nodularity (P < 0.05).

CONCLUSIONS

Thus, cagA in situ expression is increased in H pylori-infected children with peptic ulcers and may play a role in the pathogenesis of peptic ulcer disease during childhood. Determination of in situ expression of cagA complements traditional isolation and in vitro testing of single-colony isolates.

Prevalence and clinical relevance of cagA, vacA, and iceA genotypes of Helicobacter pylori isolated from Slovenian children

BACKGROUND

Although infection with Helicobacter pylori in children mostly induces asymptomatic chronic gastritis, the clinical outcome of H pylori infection is generally unpredictable. To identify the risk subgroup of infected children who can progress toward serious gastrointestinal disease, we assessed the prevalence of H pylori virulence genes cagA, vacA, and iceA in children from southeastern Europe and correlated their presence with the severity of histological changes in the stomach.

MATERIALS AND METHODS

A total of 165 children (age range 4-18 years, mean 13 years) with H pylori infection were studied for a 6-year period. Virulence genes were determined by polymerase chain reaction from biopsy samples.

RESULTS

The cagA gene was present in 61.2% of patients. The predominant vacA genotype was s1m1 (42%), followed by s1m2 (28%), and s2m2 (24%). IceA genotypes iceA1 and iceA2 were detected in 62% and 31% of the samples, respectively. Multiple genotypes were found in 11.5% of isolates. The H pylori density score, the degree of chronic and acute inflammation, correlated with a cagA-positive status (P < 0.01, P < 0.01, P = 0.01, respectively). Higher bacterial infiltration (P < 0.01) and degree of chronic inflammation (P = 0.03) were detected in vacA s1-positive samples.

CONCLUSION

CagA, vacA s1m1, and iceA1 genotypes are the predominant genotypes of H pylori isolated from the southeastern European pediatric population. CagA and vacA s1 are important virulence determinants of H pylori in children, but were not found associated with an increased incidence of precancerous gastric lesions.

CagA and VacA polymorphisms do not correlate with severity of histopathological lesions in Helicobacter pylori-infected Greek children

The presence of various numbers of EPIYA tyrosine phosphorylation motifs in the CagA protein of Helicobacter pylori has been suggested to contribute to pathogenesis in adults. In this prospective study, we characterized H. pylori isolates from symptomatic children, with reference to the diversity of functional EPIYA motifs in the CagA protein and vacA isotypes, and assessed the potential correlation with the histopathological manifestations of the infection. We analyzed 105 H. pylori isolates from 98 children and determined the diversity of EPIYA motifs in CagA by amplification and sequencing of the 3' variable region of the cagA gene as well as vacA isotypes for the signal, middle, and intermediate regions. CagA phosphorylation and levels of secreted IL-8 were determined following in vitro infection of AGS gastric epithelial cells. Histopathological evaluation of H. pylori colonization, activity, and severity of the associated gastritis was performed according to the updated Sydney criteria. EPIYA A (GLKN[ST]EPIYAKVNKKK), EPIYA B (Q[V/A]ASPEPIY[A/T]QVAKKVNAKI), and EPIYA C (RS[V/A]SPEPIYATIDDLG) motifs were detected in the ABC (46.6%) and ABCC (17.1%) combinations. No isolates harboring more than two EPIYA C motifs in CagA were found. The presence of isogenic strains with variable numbers of CagA EPIYA C motifs within the same patient was detected in seven cases. Occurrence of increasing numbers of EPIYA C motifs correlated strongly with presence of a high-vacuolation (s1 or s2/i1/m1) phenotype and age. A weak positive correlation was observed between vacuolating vacA genotypes and presence of nodular gastritis. However, CagA- and VacA-dependent pathogenicities were not found to contribute to severity of histopathology manifestations in H. pylori-infected children.

Helicobacter pylori, helminth infections and growth: a cross-sectional study in a high prevalence population

AIM

Helicobacter pylori (H. pylori) infection is usually acquired in childhood and may adversely affect growth, although data are inconsistent. This study investigated growth parameters in a paediatric cohort with a high prevalence of H. pylori and helminth infection.

METHODS

A cross-sectional study of African refugee children (<16 years) recruited at their initial health assessment following resettlement in Australia. Detailed demographic, infection and anthropometric data were obtained. H. pylori infection was diagnosed by monoclonal faecal antigen enzyme immunoassay testing (MFAT). Growth restriction was defined as children with any anthropometric measures below the fifth centile for age and gender.

RESULTS

H. pylori infection was detected in 149/182 (81.9%). Children with H. pylori infection were older (mean 8.5 years, standard deviation (SD) 4.2 years vs. 5.8 years, SD 4.5 years, p < 0.001). No gender differences were observed. After adjustment for age, H. pylori did not adversely affect body mass index or other anthropometric measurements. Helminth infections were common (41.8%) but not associated with reduced growth or with H. pylori infection.

CONCLUSION

H. pylori and helminth infections are prevalent in African refugee children but neither is associated with growth restriction. Longitudinal growth velocity studies are necessary to identify any long-term consequences of H. pylori on childhood growth.

Pediatric Helicobacter pylori isolates display distinct gene coding capacities and virulence gene marker profiles

Helicobacter pylori strains display remarkable genetic diversity, and the presence of strains bearing the toxigenic vacA s1 allele, a complete cag pathogenicity island (PAI), cagA alleles containing multiple EPIYA phosphorylation sites, and expressing the BabA adhesin correlates with development of gastroduodenal disease in adults. To better understand the genetic variability present among pediatric strains and its relationship to disease, we characterized H. pylori strains infecting 47 pediatric North American patients. Prevalence of mixed infection was assessed by random amplified polymorphic DNA analysis of multiple H. pylori clones from each patient. Microarray-based comparative genomic hybridization was used to examine the genomic content of the pediatric strains. The cagA and vacA alleles were further characterized by allele-specific PCR. A range of EPIYA motif configurations were observed for the cagA gene, which was present in strains from 22 patients (47%), but only 19 (41%) patients contained a complete cag PAI. Thirty patients (64%) were infected with a strain having the vacA s1 allele, and 28 patients (60%) had the babA gene. The presence of a functional cag PAI was correlated with ulcer disease (P = 0.0095). In spite of declining rates of H. pylori infection in North America, at least 11% of patients had mixed infection. Pediatric strains differ in their spectrum of strain-variable genes and percentage of absent genes in comparison to adult strains. Most children were infected with H. pylori strains lacking the cag PAI, but the presence of a complete cag PAI, in contrast to other virulence markers, was associated with more severe gastroduodenal disease.

cagA, vacA, and iceA genotypes of Helicobacter pylori in Korean children

BACKGROUND

Several putative virulence factors for Helicobacter pylori have been identified including cagA, vacA, and iceA. The aims of the present study were to study the distribution of cagA, vacA, and iceA genotypes in children with H. pylori gastritis and to examine the association of genotypes with severity of gastritis.

METHODS

H. pylori DNA was extracted from antral biopsy specimens from 33 children with H. pylori gastritis. Specific polymerase chain reaction assays were used for three genes: cagA, vacA, and iceA. The features of gastritis were graded in accordance with the updated Sydney System.

RESULTS

Of the 33 children, 31 (94%) were cagA positive. Twenty-four (72%) had s1c genotype and nine (27%) had s1a. The m1 genotype was seen in 27 (82%) and m2 was found in five (15%). The iceA1 genotype was detected in 25 (76%). Scores of neutrophil activity, chronic inflammation, and H. pylori density were independent of cagA, vacA and iceA status.

CONCLUSION

The cagA-positive vacA s1c/m1 iceA1 genotype was predominant in Korean children with recurrent abdominal pain and H. pylori gastritis. The cagA, vacA and iceA genotype were not associated with the severity of gastritis.

Culture of Helicobacter pylori from stool samples in children

We evaluated two protocols for isolation of Helicobacter pylori in stool from biopsied and nonbiopsied children. Twenty-three child patients whose presumptive positivity or negativity was diagnosed by endoscopy and a rapid urease test at site were used to compare biopsy-based tests with stool-based tests (H. pylori stool antigen test and stool culture). Their gastric activity and bacterial density were graded by the updated Sydney system. Biopsy and stool specimens were cultured on Campy-blood and Belo horizonte agar plates after enrichment in selective Campy-Thio medium. To compare two stool culture protocols, stools from 20 nonbiopsied children were tested by the HpSA test and cultured either as above or after treatment with cholestyramine. Grown colonies were screened by Gram staining, slide agglutination using anti-H. pylori monoclonal IgG; positive isolates were tested by biochemical tests and polymerase chain reaction for H. pylori-specific ureA gene. Coccoid H. pylori was isolated in stool samples from the biopsied patients whose bacterial density was two to four in histology. Their oxidase was slightly positive but became positive after two subcultures, while additional biochemical tests confirmed the isolation of H. pylori. Similar coccoid but oxidase positive H. pylori was isolated from three nonbiopsied children with the protocol of cholestyramine treatment only. The density of bacteria in the stomach may influence the recovery of H. pylori from stool; inactivation of bile with cholestyramine improves the yield in culture and favors isolation of an enhanced metabolic form of bacteria.

Helicobacter pylori genotypes in children from a population at high gastric cancer risk: no association with gastroduodenal histopathology

OBJECTIVES

Both bacterial and host determinants underlying differences in histopathology and clinical outcome in H. pylori pediatric infection, as compared to adults, are still poorly documented. Pediatric studies may provide important insights on H. pylori infection immunopathogenesis, particularly in high gastric cancer risk populations. The present study concerns H. pylori genotypic diversity of isolates in children from a population with high gastric cancer risk, and its association with demographic and clinical variables, including gastroduodenal endoscopic and histopathological features.

METHODS

A total of 119 subjects (mean age 10.3 yr, 1.5-18.0 yr) with H. pylori infection were studied. H. pylori vacA, cagA, and iceA genotypes were determined (PCR) in antral-obtained primary cultures; histopathological evaluation was performed in corpus, antrum, and duodenum biopsy specimens.

RESULTS

cagA-, vacA s2m2, and iceA2 were the most prevalent genotypes. No association was observed between H. pylori genotypes and subject demographic and clinical variables, with the exception of a significant association between vacA s2 genotype and lower corpus inflammation score (p< 0.03).

CONCLUSIONS

In this pediatric cohort, H. pylori genotype profiles were distinct from those reported in adult subjects in the same area, with a lower prevalence of the putative more virulent genotypes. Moreover, they were not associated with clinical expression of gastroduodenal disease, suggesting the potential role of host and/or environmental factors for the development of clinical disease at a later age.

Identification of markers for Helicobacter pylori strains isolated from children with peptic ulcer disease by suppressive subtractive hybridization

Peptic ulcer disease (PUD) occurs after a long-term Helicobacter pylori infection. However, the disease can develop earlier, and rare cases have been observed in children, suggesting that these H. pylori strains may be more virulent. We used suppressive subtractive hybridization for comparative genomics between H. pylori strains isolated from a 5-year-old child with duodenal ulcer and from a sex- and age-matched child with gastritis only. The prevalence of the 30 tester-specific subtracted sequences was determined on a collection of H. pylori strains from children (15 ulcers and 30 gastritis) and from adults (46 ulcers and 44 gastritis). Two of these sequences, jhp0562 (80.0% versus 33.3%, P = 0.008) and jhp0870 (80.0% versus 36.7%, P = 0.015), were highly associated with PUD in children and a third sequence, jhp0828, was less associated (40.0% versus 10.0%, P = 0.048). Among adult strains, none of the 30 sequences was associated with PUD. However, both jhp0562 and jhp0870 were less prevalent in adenocarcinoma strains than in PUD strains from children and adults, the difference being statistically significant for jhp0870. In conclusion, two H. pylori genes were identified as being strongly associated with PUD in children, and their putative roles as an outer membrane protein for jhp0870 and in lipopolysaccharide biosynthesis for jhp0562, suggest that they may be novel virulence factors of H. pylori.

Application of a stool antigen test to evaluate the incidence of Helicobacter pylori infection in children and adolescents from Tehran, Iran

Helicobacter pylori infection is acquired mainly in childhood, especially in developing countries, where a low-cost, rapid diagnostic technique which is reliable for all age groups may be useful for the management of H. pylori infection. For this purpose, we used an HpSA test (Equipar) to detect H. pylori infection in children and adolescents from Tehran, Iran. Thirty-five children who were positive or negative for H. pylori infection by endoscopy-based tests were used as positive and negative controls for the HpSA test. Stools were collected from 430 randomly selected children and adolescents (4 to 18 years old) from southwest, near the center, and northwest of Tehran. A questionnaire that included presence of recurrent abdominal pain (RAP), family history of infection and/or peptic ulcer disease (PUD), and income of parents was completed. A good agreement was found between the results of endoscopy-based tests and those of the HpSA test; the sensitivity and specificity of the Equipar-HpSA test were 100% and 83.4%, respectively. Among 430 children and adolescents, 47% were positive by the HpSA test, of whom 82% had RAP. No difference in incidence was observed between the two sexes; the various categories of age showed an increasing incidence, ranging from 24% (ages 4 to 6) to 58% (ages 16 to 18). The rate of infection in children and adolescents from the southwest was significantly higher (70%) than the rate in those from the northwest (32%), and a family history of H. pylori infection or PUD was observed in 59% of the HpSA positive subjects. The HpSA test is a useful test to detect H. pylori infection in children and adolescents from developing countries.

Helicobacter pylori infection and abdominal symptoms among Swedish school children

BACKGROUND

The role of Helicobacter pylori infection in the etiology of abdominal symptoms remains unclear. Our aim was to investigate the association between type-specific H. pylori infection and gastrointestinal symptoms among school children in Stockholm, Sweden.

METHODS

In a community-based cross-sectional study, 695 children aged 10-12 years participated with a blood sample and a questionnaire on sociodemographic characteristics and gastrointestinal symptoms, including minor abdominal pain not necessitating medical consultation, during the preceding six months. Infection was investigated by an enzyme-linked immuno-sorbent assay and confirmed by immunoblot and urea breath test.

RESULTS

Abdominal pain was reported by 440 (63%) children and recurrent abdominal pain (RAP) by 88 (13%). Of 112 (16%) infected children, 73% had antibodies to CagA and 59% to VacA. There was no positive association between H. pylori status and the occurrence of abdominal pain; in fact, the association with any abdominal pain report was inverse (odds ratio [OR] 0,5; 95% Confidence Interval [CI] 0.3-0.8), while RAP was unrelated to the infection (OR 1.0; 95% CI 0.5-2.1) when adjusted for gender, age and family background variables. The prevalence of RAP tended to be lower among children harboring CagA+/VacA+ infections than among the uninfected (adjusted OR 0.3; 95%CI 0.1-1.1). Furthermore, CagA+/VacA+ infected children reported less acid regurgitation (adjusted OR 0.2; 95% CI 0.1-0.5).

CONCLUSIONS

Taking background factors into account, the presence of H. pylori is not accompanied by an increased occurrence of abdominal symptoms in Swedish 10-12-year-olds. However, unexpected differential associations with strain specific infections may indicate a so far overlooked complex relationship that needs to be further confirmed.

Molecular biology methods for the characterization of Helicobacter pylori infections and their diagnosis

Helicobacter pylori infects approximately half of the human population; however, the outcome of infection is affected by many factors, including strain and host genotype characteristics and bacterial density within the stomach. Many molecular methods have been developed to provide information with respect to these characteristics. Methods that provide results within 24 h of endoscopy may be used to develop individualized treatment that is more effective, results in fewer side effects, cuts costs,decreases the number of treatment failures and results in the development of fewer antibiotic-resistant H. pylori strains.

Helicobacter pylori infection, iron absorption, and gastric acid secretion in Bangladeshi children

BACKGROUND

Nonheme-iron absorption requires an acidic milieu. Reduced gastric acid output as a consequence of Helicobacter pylori infection could be an important limiting factor for iron absorption.

OBJECTIVE

We measured gastric acid output and iron absorption from a non-water-soluble iron compound (ferrous fumarate) and a water-soluble iron compound (ferrous sulfate) in children with and without H. pylori infection.

DESIGN

Gastric acid output was quantified before (basal acid output, or BAO) and after pentagastrin stimulation (stimulated acid output, or SAO) in 2-5-y-old children with iron deficiency anemia who were (n = 13) or were not (n = 12) infected with H. pylori. Iron absorption was measured by using a double-stable-isotope technique. H. pylori-infected children were studied before and after eradication therapy.

RESULTS

BAO and SAO were significantly lower in the H. pylori-infected children (0.2 +/- 0.2 and 1.6 +/- 0.9 mmol/h, respectively) than in the uninfected children (0.9 +/- 0.7 and 3.1 +/- 0.9 mmol/h, respectively; P = 0.01 and P < 0.005). BAO and SAO improved to 0.8 +/- 1.3 and 3.3 +/- 2.4 mmol/h, respectively, after therapy. Iron absorption from ferrous sulfate was significantly greater than that from ferrous fumarate both before (geometric : 19.7% compared with 5.3%; P < 0.0001) and after (22.5% compared with 6.4%; P < 0.0001) treatment in H. pylori-infected children. Corresponding values for uninfected children were 15.6% and 5.4%, respectively (P < 0.001; n = 12).

CONCLUSIONS

Iron absorption from ferrous fumarate was significantly lower than that from ferrous sulfate in both H. pylori-infected and uninfected Bangladeshi children. Treatment of H. pylori infection improved gastric acid output but did not significantly influence iron absorption. The efficacy of ferrous fumarate in iron fortification programs to prevent iron deficiency in young children should be evaluated.

Genotypes of the Helicobacter pylori vacA signal sequence differ with age in Korea

BACKGROUND

Studies on Helicobacter pylori genotypes have focused on adults in developed countries, and data on the genotypes of Helicobacter pylori recovered from the children are rare.

MATERIALS AND METHODS

One hundred and twenty-eight biopsy samples from patients with H. pylori infection were studied. The patients' ages ranged from 9 to 83 years. PCR analysis for vacA genotypes was performed using DNA extracted from biopsy specimens.

RESULTS

Genotyping of the s-region showed s1a in 33 (25.8%) samples and s1c in 82 (64.1%) samples. When the specimens were grouped by age, the distribution of s-region genotype was found to be significantly different between groups (p = .002). The prevalence of s1a was 45.2% in patients < 20 years old, but 14.9% in patients > or = 50 years old. On the other hand, the prevalence of s1c or recombinant s1a-s1c was higher in those > or = 50 years old. The distribution of the m-region did not differ significantly with age (p = .110).

CONCLUSIONS

Strain populations infecting Korean adults and children differ.

Can pre-neoplastic lesions be detected in gastric biopsies of children with Helicobacter pylori infection?

BACKGROUND

Active gastritis, gastric mucosal atrophy and intestinal metaplasia are lesions associated with Helicobacter pylori infection. Atrophy and intestinal metaplasia are only seen in adults.

OBJECTIVES

We describe pediatric patients with atrophy and metaplasia, and compare the inflammatory response in these patients to controls.

METHODS

As part of a multicenter study of pediatric H. pylori infection, gastric biopsy specimens obtained during diagnostic upper endoscopy of 19 H. pylori-infected children and 45 uninfected controls were reviewed and graded by using the updated Sydney system. The inflammatory response was characterized using immunohistochemistry for T lymphocytes, B lymphocytes, and macrophages, and TUNEL assay for apoptosis.

RESULTS

Histology of H. pylori-infected and control biopsy specimens showed active gastritis in 32% and 2% respectively (P = 0.002). Mild intestinal metaplasia was found in 4 H. pylori-infected children, in two of whom it appeared to be accompanied by atrophy. Specimens from patients with H. pylori infection contained increased numbers of B lymphocytes in lymphoid nodules, and apoptosis in the superficial epithelium and inflammatory cells. T lymphocytes and macrophages appeared in similar numbers in specimens from controls and infected patients.

CONCLUSIONS

We describe intestinal metaplasia associated with H. pylori infection in children. Since atrophy usually precedes intestinal metaplasia in adults, we suggest that atrophy exists in children. High numbers of B lymphocytes and apoptosis in the surface epithelium are seen in patients with H. pylori infection and may be related to the development of atrophy and intestinal metaplasia.

Genotypes of Helicobacter pylori in children with upper abdominal pain

BACKGROUND

Studies related to genotypes of Helicobacter pylori infection and upper abdominal pain (UAP) in children are scarce all over the world. We prospectively analyzed the association between H. pylori infection and UAP in our study group of children and evaluated the vacA genotypes associated with this disorder.

METHODS

We investigated 34 children with UAP (group I) and another 110 children as controls without UAP (group II) for H. pylori infection, using antral biopsies by culture, rapid urease tests, histopathology and ureA polymerase chain reaction (PCR). Genotyping was performed using specific cagA and vacA primers on 52 H. pylori strains (group I = 21; 18 boys, mean age 10.33 +/- 2.47 years; group II = 31; boys 21, mean age 9.63 +/- 2.51 years).

RESULTS

A significant association between H. pylori infection and UAP was observed when compared to controls (21/34; 61.8%vs 31/110; 28.2%; P = 0.0004). cagA positive H. pylori strains were detected in 20 (95.2%) children with UAP and in 28 (90.3%) controls. Mixed infection was detected in 25% of children with no significant difference between the groups. On univariate regression analysis, s1a, m1 alleles and s1a/m1 genotype of vacA had significant associations with UAP (P = 0.018, 0.015 and 0.007, respectively), while s2 and m2 alleles and the s2/m2 genotype were significantly more frequent in controls (P = 0.034, 0.001 and 0.034, respectively).

CONCLUSIONS

H. pylori infection is strongly associated with UAP in children and a significantly higher proportion have s1a, m1 alleles and s1a/m1 genotype. The negative associations of vacA s2, m2 alleles and s2/m2 genotype with UAP indicate that they are unlikely to have an important role in this disorder.

Quantitative evaluation of inflammatory and immune responses in the early stages of chronic Helicobacter pylori infection

The early consequences of Helicobacter pylori infection and the role of bacterial virulence determinants in disease outcome remain to be established. The present study sought to measure the development of host inflammatory and immune responses and their relationship to the putative bacterial virulence factors cag pathogenicity island (cagPAI), vacA allele, and oipA in combination with bacterial colonization density in a feline model of the early stages of H. pylori infection. Gastric tissues obtained from infected and uninfected cats were evaluated for H. pylori ureB, cagPAI, vacA allele, and oipA and colonization density (urease, histology, and real-time PCR). Inflammation was assessed by measuring mRNA upregulation of gamma interferon (IFN-gamma), interleukin (IL)-1 alpha, IL-1 beta, IL-4, IL-6, IL-8, IL-10, and IL-12 p40 and histopathology. The mucosal immune response was characterized by morphometric analysis of lymphoid follicles and by differentiating lymphocyte populations with antibodies against surface markers. Infecting H. pylori strains were positive for vacAs1 but lacked cagPAI and an active oipA gene. Colonization density was uniform throughout the stomach. Upregulation of IFN-gamma, IL-1 alpha, IL-1 beta, and IL-8 and increased severity of inflammatory infiltrates and fibrosis were observed in infected cats. The median number and total area of lymphoid aggregates were 5 and 10 times greater, respectively, in the stomachs of infected than uninfected cats. Secondary lymphoid follicles in uninfected cats were rare and positive for BLA.36 and B220 but negative for CD3 and CD79 alpha, whereas in infected cats they were frequent and positive for BLA.36, CD79 alpha, and CD3 but negative for B220. Upregulation of IFN-gamma, IL-1 alpha, IL-1 beta, and IL-8 and marked hyperplasia of secondary lymphoid follicles are early consequences of H. pylori infection in cats. The response appears to be similar to that of infected people, particularly children, can develop independently of the pathogenicity factors cagPAI and oipA, and is not correlated with the degree of colonization density or urease activity.

Helicobacter pylori virulence genotypes in Portuguese children and adults with gastroduodenal pathology

The aim of this study was to evaluate the prevalence of virulence genotypes, namely cagA, vacA and babA2, of Helicobacter pylori strains isolated from Portuguese adults and children presenting gastroduodenal pathology. One hundred thirty-six strains were studied, 82 isolated from adult patients (50 with nonulcerative gastritis and 32 with active peptic ulcer) and 58 isolated from children (54 with nonulcerative gastritis and 4 with duodenal ulcer). Genotyping of cagA, vacA and babA2 was assessed by polymerase chain reaction. Overall, Helicobacter pylori strains carrying more virulent genotypes were much more prevalent in adults than in children, particularly the type I ( vacAs1- and cagA-positive) and the triple-positive ( vacAs1-, cagA- and babA2-positive) strains ( P<0.001). A subpopulation of adults and children with nonulcerative gastritis was also studied, and differences in the prevalence of virulent genotypes were observed, either for individual genotypes ( P=0.017 for cagA, P=0.010 for vacAs1) or in combinations, i.e. the type I genotype ( P=0.005) and the triple-positive strains ( P=0.031). There was no difference between the two populations in the distribution of babA2 and m1/m2 genotypes. Considering the cohort effect in the epidemiology of Helicobacter pylori infection, these results suggest that different strains might circulate during different periods of time, or that, after infection in childhood, individual strains will undergo changes during the course of infection.

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.

Helicobacter pylori cagA genotype and density of colonization in relation to gastric inflammation in children

OBJECTIVE

To assess the relationship between density determined by quantitative culture, status, and gastric histology in children.

METHODS

Children with clinical symptoms indicating pathology in the upper gastrointestinal tract were referred for endoscopy. From each child blood was taken for serology, and antral biopsies were obtained for quantitative culture of and histology. Histological assessment was performed according to the updated Sydney System. The status of cultured was determined by polymerase chain reaction (PCR) and serum IgG response to CagA by western blotting.

RESULTS

Adequate antral biopsies were obtained from 41 children with positive cultures. CagA IgG antibodies were found in 27 patients (66%), 25 of whom were also positive by the PCR. Two children infected with + strains as determined by the PCR were CagA seronegative. Infection with + strains was associated with significantly higher activity of inflammation and denser bacterial colonization in the antrum compared to negative strains. No correlation was observed between the density of colonization and chronic antral inflammation.

CONCLUSIONS

This study shows that infection of children with + strains of is associated with enhanced activity of antral inflammation and higher density of colonization. There is a good correlation between serum western blot and bacterial PCR positivity in determining status and a positive relationship between histology and quantitative culture in assessing density in paediatric patients.

East Asian genotypes of Helicobacter pylori strains in Amerindians provide evidence for its ancient human carriage

Phylogenies of indigenous microbes have been used as surrogates for the origins of the hosts that carry them. Conversely, polymorphisms may be used to date the spread of a microbial species when information about their host populations is available. Therefore, we examined polymorphisms in Helicobacter pylori, which persistently colonize the human stomach, to test the hypothesis that they have been ancient inhabitants of humans. Three H. pylori loci that previously have been shown to have phylogeographic affinity have been analyzed for two populations with different ethnic origins from Venezuela. In a group of Amerindian subjects from Amazonia, East Asian H. pylori genotypes were present for each of the loci examined but were absent in a mestizo population from Caracas. These findings provide evidence that H. pylori has been present in humans at least since ancestors of Amerindians migrated from Asia more than 11,000 years ago.

Determination of Helicobacter pylori vacA allelic types by single-step multiplex PCR

AIMS

To develop and evaluate a novel multiplex PCR assay that enables definition of Helicobacter pylori vacA allelic type in a single reaction.

METHODS AND RESULTS

Application of the one-step system to DNA extracts from 22 cultures of known vacA genotype demonstrated that it was highly accurate. Analysis of 15 matched gastric biopsy/culture pairs generated exactly correlating genotype profiles. vacA genotypes were determined from an additional 62/70 gastric biopsies from dyspeptic patients of known H. pylori positive status by the one-step assay, compared with 63/70 by the original two-reaction test. Types s1/m1, s1/m2 and s2/m2 were identified in 51.9%, 31.2% and 16.9% of biopsies, respectively.

CONCLUSIONS

The multiplex PCR system developed enables rapid one-step vacA genotyping that is accurate, easy to interpret and more economical than the alternative multiple-reaction tests. Application of this system to gastric biopsies from patients in South-east England demonstrated that s1/m1 was the most common genotype, while s1/m2 and s2/m2 were less prevalent.

SIGNIFICANCE AND IMPACT OF THE STUDY

This simple one-step system can be applied direct to antral gastric biopsies without the need for culture, thereby facilitating rapid surveillance of vacA genotype in relation to geographical location and disease status.

Evidence that cagA(+) Helicobacter pylori strains are disappearing more rapidly than cagA(-) strains

BACKGROUND AND AIMS

The prevalence of Helicobacter pylori colonisation in populations in developed country has been declining, as shown by community based serological surveys of adults in Vammala, Finland in 1973 and 1994. In this study, we determined whether the proportion of subjects colonised by cagA(+) or cagA(-) H pylori strains has changed as the overall prevalence of H pylori(+) has declined.

METHODS

We examined 911 sera from Vammala's study for antibodies to the CagA antigen of H pylori using a truncated CagA protein as the antigen in an ELISA and we examined the trend in acquisition and carriage of cagA(+) strains.

RESULTS

As expected, the prevalence of carriage of both cagA(+) and cagA(-) strains fell between 1973 and 1994 (p<0.001). However, the prevalence of cagA(+) strains among those <45 years declined (34% to 8%) significantly (p<0.001) more than for cagA(-) strains (12% to 6%). Of 221 subjects with paired serum samples, 12 (5.4%) changed H pylori status; the estimated seroconversion and reversion rates were 0.4% and 0.13% per year, respectively. Except for the few individuals who changed serostatus, absolute antibody levels to H pylori antigens, including CagA, changed little over the 21 year period.

CONCLUSIONS

The decline in CagA seroprevalence predominantly reflects declining acquisition of cag(+) strains in younger subjects. In addition, these data confirm that H pylori acquisition chiefly occurs during childhood but continues to occur during adulthood, albeit at low rates, in developed countries.

Helicobacter pylori infection in children

A number of scientific breakthroughs since H pylori first became recognized as a human pathogen have increased our understanding of the pathogenesis of gastroduodenal disease. In particular, advances in molecular bacteriology and the complete sequencing of the H pylori genome in 1999, and soon thereafter the human genome, provide tools allowing better delineation of the pathogenesis of disease. These molecular tools for both bacteria and host should now be applied to multicenter pediatric studies that evaluate disease outcome. More recent developments indicate that a better understanding of the microbial-host interaction is critical to furthering knowledge with respect to H pylori-induced diseases. Studies are needed to evaluate either DNA-based or more traditional protein-based vaccines, to evaluate more specific antimicrobials that confer minimal resistance, and to evaluate probiotics for the management of H pylori infection. Multicenter multinational studies of H pylori infection in the pediatric population, which include specific, randomized controlled eradication trials, are essential to extend current knowledge and develop better predictors of disease outcome.