<i>cag</i>A positive and negative <i>Helicobacter pylori</i>strains are simultaneously present in the stomach of most patients with non-ulcer dyspepsia: relevance to histological damage

Figura, Natale; Vindigni, Carla; Covacci, A; Presenti, L; Burroni, Daniela; Vernillo, Remo; Banducci, T; Roviello, Franco; Marrelli, Daniele; Biscontri, Marco; S, Kristodhullu; Gennari, C; Vaira, Dino

doi:10.1136/gut.42.6.772

Cited by 77 publications

(40 citation statements)

References 26 publications

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“…Although the coexistence of cagA-positive and cagA-negative H. pylori strains has been described for a single patient and even for a single biopsy specimen (15,39), our analysis showed that the proportions of cagA-negative colonies may be quite variable in gastric biopsy specimens obtained from different subjects and that cagA negativity is almost always associated with cagE and/or virB11 negativity. Collectively, these data suggest that future studies aimed at finding correlations between H. pylori cag genotypes and different clinical outcomes need to take into account the fact that each biopsy specimen encompasses a complex mixture of H. pylori subtypes.…”

Section: Discussioncontrasting

confidence: 51%

Heterogeneity of cag Genotypes in Helicobacter pylori Isolates from Human Biopsy Specimens

Tomasini¹,

Zanussi²,

Sozzi

et al. 2003

J Clin Microbiol

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The Helicobacter pylori chromosomal cluster of genes known as the cytotoxin-associated gene (cag) island may have different compositions in infecting strains. In this study, we analyzed 150 single colonies obtained from gastric biopsy specimens from 10 patients infected with cagA-positive H. pylori strains and sweep isolates (isolates harvested with sweep in different points of the plate) from 6 patients infected with cagA-negative strains. Three loci in the cag island (cagA, cagE, and virB11) and the conserved gene glmM (ureC) were investigated by PCR. The levels of anti-H. pylori and anti-CagA antibodies in patient sera were also measured. For subjects infected with cagA-negative strains, all sweep isolates were also negative for cagE and virB11, suggesting the complete absence of the cag island. For subjects infected with cagA-positive strains, most of the isolates were positive for all three genes studied, whereas 24.7% of the isolates had a partial or total deletion of the cag island. cagA, cagE, and virB11 were, respectively, present in 87.3, 77.3, and 90% of the colonies. The deletion of virB11 was always associated with the deletion of cagA and/or cagE. H. pylori colonies with different cag genotypes were isolated within a single gastric biopsy specimen from 3 of the 10 patients and were further characterized by random amplified polymorphic DNA (RAPD) analysis and by sequencing of an arbitrarily selected gene segment. Although the colonies had different cag genotypes, their RAPD profiles were highly similar within each patient, and the nucleotide sequences of the selected gene segment were identical. All of the patients had detectable antibodies against H. pylori, and 9 of 10 had anti-CagA antibodies. In conclusion, we show that a single infecting H. pylori strain may include variable proportions of colony subtypes with different cag genotypes. The extension of our analysis to patients with well-characterized gastric diseases may provide significant information on the relationship between cag genotypes and clinical outcomes of H. pylori infections.Helicobacter pylori is a gram-negative spiral bacterium that colonizes the human stomach. Infection with H. pylori is associated with chronic gastritis, peptic ulcer, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma (25).Although the pathogenesis of H. pylori infection is not completely understood, several putative virulence factors may contribute to mucosal damage (5, 26). The cytotoxin-associated gene (cag) island, an approximately 40-kb cluster of genes in the H. pylori chromosome, probably was inherited by horizontal transfer from an unknown microorganism. Many of the cag genes have homology to those of other bacteria encoding virulence factors and a type IV secretion system. Therefore, they may play an important role in microbial virulence and pathogenicity (6, 10). Among H. pylori isolates, the presence of insertion elements causes differences in the compositions of the cag island; the consequent cag instability may produce d...

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Section: Discussioncontrasting

confidence: 51%

Heterogeneity of cag Genotypes in Helicobacter pylori Isolates from Human Biopsy Specimens

Tomasini¹,

Zanussi²,

Sozzi

et al. 2003

J Clin Microbiol

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“…The entire cluster is available as Table 4, which is published as supplemental data on the PNAS web site www.pnas.org. a subpopulation of bacteria isolated from a single infected individual (27). H. pylori can reside for decades in the exclusive niche of the human stomach with few competing resident bacteria, where it can diversify as a population, mutate, excise sequences, and sample the genetic material of transient superinfecting H. pylori strains and other bacteria (12,28).…”

Section: Resultsmentioning

confidence: 99%

A whole-genome microarray reveals genetic diversity among Helicobacter pylori strains

Salama

Guillemin²,

McDaniel³

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

528

446

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Helicobacter pylori colonizes the stomach of half of the world's population, causing a wide spectrum of disease ranging from asymptomatic gastritis to ulcers to gastric cancer. Although the basis for these diverse clinical outcomes is not understood, more severe disease is associated with strains harboring a pathogenicity island. To characterize the genetic diversity of more and less virulent strains, we examined the genomic content of 15 H. pylori clinical isolates by using a whole genome H. pylori DNA microarray. We found that a full 22% of H. pylori genes are dispensable in one or more strains, thus defining a minimal functional core of 1281 H. pylori genes. While the core genes encode most metabolic and cellular processes, the strain-specific genes include genes unique to H. pylori, restriction modification genes, transposases, and genes encoding cell surface proteins, which may aid the bacteria under specific circumstances during their long-term infection of genetically diverse hosts. We observed distinct patterns of the strainspecific gene distribution along the chromosome, which may result from different mechanisms of gene acquisition and loss. Among the strain-specific genes, we have found a class of candidate virulence genes identified by their coinheritance with the pathogenicity island. Helicobacter pylori is a highly host-adapted bacterial pathogen that establishes a chronic infection in the human stomach and has no known animal or environmental reservoirs (1). Epidemiological and serological studies have revealed that H. pylori strains containing the CagA protein are associated with more severe disease (2) and harbor a 40-kb pathogenicity island (PAI) (3, 4). The PAI encodes a bacterial type IV secretory system that secretes and translocates the CagA protein into host cells (5-8), where it is phosphorylated by a host-cell kinase and causes morphological changes (7). The PAI also induces IL-8 production by host cells independent of the CagA protein (9 -11). Efforts to classify H. pylori strains further by DNA fingerprinting uncovered extensive diversity (12, 13). The sequencing of two H. pylori genomes from independent strains, both containing the PAI, revealed that much of this diversity is silent at the amino acid level and thus at the functional gene level (14, 15). Here we used a H. pylori DNA microarray to examine the genomic composition of H. pylori clinical isolates containing and lacking the PAI at the level of individual genes to characterize the extent of genetic diversity between strains and to search for new candidate virulence determinants. Materials and MethodsPCR Primer Design. The elements of our microarray consisted of large (mean size, 817 base pairs; 10th percentile, 130 base pairs; 90th percentile, 1,967 base pairs) DNA fragments corresponding to unique segments of individual open reading frames (ORFs). These fragments were generated by PCRs using gene-specific primers. We aimed to include in our array the superset of ORFs from both published genomes. When an ORF was present in bo...

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“…This observation can be explained by three alternative mechanisms. First, a mixed population of both cagA-positive and cagA-negative strains is present in the gastric environment, although only cagA-negative clones have been isolated and analyzed (19,20). Second, the patient could have been colonized by a cagA-positive strain at an earlier stage of the infection.…”

Section: Vol 71 2003mentioning

confidence: 99%

Correlation betweencagPathogenicity Island Composition andHelicobacter pylori-Associated Gastroduodenal Disease

et al. 2003

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Helicobacter pylori infection is associated with a variety of outcomes ranging from seemingly asymptomatic coexistence to peptic ulcer disease and gastric cancer. The cag pathogenicity island (PAI) contains genes associated with a more aggressive phenotype and has been suggested to be a determinant of severe disease outcome. The cagA gene has served as a marker for the cag PAI. However, the presence of this single gene does not necessarily indicate the presence of a complete set of cag PAI genes. We have analyzed the composition of the cag PAI in 66 clinical isolates obtained from patients with duodenal ulcer, gastric cancer, and nonulcer dyspepsia. Hybridization of DNA to microarrays containing all the genes of the cag PAI showed that 76 and 9% of the strains contained all or none of the cag PAI genes, respectively. Partial deletions of the cag PAI were found in 10 isolates (15%), of which 3 were cagA negative. The ability to induce interleukin-8 (IL-8) production in AGS cells was correlated to the presence of a complete cag PAI. Strains carrying only parts of the island induced IL-8 at levels significantly lower than those induced by cag PAI-positive isolates. The presence of an intact cag PAI correlates with development of more severe pathology, and such strains were found more frequently in patients with severe gastroduodenal disease (odds ratio, 5.13; 95% confidence interval, 1.5 to 17.4). Partial deletions of the cag PAI appear to be sufficient to render the organism less pathogenic.

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cagA positive and negative Helicobacter pyloristrains are simultaneously present in the stomach of most patients with non-ulcer dyspepsia: relevance to histological damage

Cited by 77 publications

References 26 publications

Heterogeneity of cag Genotypes in Helicobacter pylori Isolates from Human Biopsy Specimens

Heterogeneity of cag Genotypes in Helicobacter pylori Isolates from Human Biopsy Specimens

A whole-genome microarray reveals genetic diversity among Helicobacter pylori strains

Correlation betweencagPathogenicity Island Composition andHelicobacter pylori-Associated Gastroduodenal Disease

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