Free recombination within
            <i>Helicobacter pylori</i>

Suerbaum, Sebastian; Smith, John Maynard; Bapumia, Khairun; Morelli, Giovanna; Smith, Noel H.; Kunstmann, Erdmute; Dyrek, I Sabelle; Achtman, Mark

doi:10.1073/pnas.95.21.12619

Cited by 561 publications

(564 citation statements)

References 43 publications

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“…Population recombination rate (ρ)-H. pylori, N. gonorrhoeae, N. meningitidis, and S. pneumoniae showed high mean levels (ρ> 50) of intragenic recombination across loci, which supports prior conclusions (e.g., Maynard-Smith et al, 1993;Suerbaum et al, 1998;Feil et al, 1999Feil et al, ,2000aFeil et al, ,2001). B. cereus, H. influenzae, Streptococcus agalactiae, and Streptococcus pyogenes showed moderate levels of recombination (15 < ρ ≤ 50).…”

Section: Species Comparisonssupporting

confidence: 74%

Population genetics of microbial pathogens estimated from multilocus sequence typing (MLST) data

Pérez‐Losada

Browne

Madsen

et al. 2006

Infection, Genetics and Evolution

145

107

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The inference of population recombination (ρ), population mutation (Θ), and adaptive selection is of great interest in microbial population genetics. These parameters can be efficiently estimated using explicit statistical frameworks (evolutionary models) that describe their effect on gene sequences. Within this framework, we estimated ρand Θ using a coalescent approach, and adaptive (or destabilizing) selection under heterogeneous codon-based and amino acid property models in microbial sequences from MLST databases. We analyzed a total of 91 different housekeeping gene regions (loci) corresponding to one fungal and sixteen bacterial pathogens. Our results show that these three population parameters vary extensively across species and loci, but they do not seem to be correlated. For the most part, estimated recombination rates among species agree well with previous studies. Over all taxa, the ρ/Θ ratio suggests that each factor contributes similarly to the emergence of variant alleles. Comparisons of Θ estimated under finite-and infinite-site models indicate that recurrent mutation (i.e., multiple mutations at some sites) can increase Θ by up to 39%. Significant evidence of molecular adaptation was detected in 28 loci from 13 pathogens. Three of these loci showed concordant patterns of adaptive selection in two to four different species.

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Section: Species Comparisonssupporting

confidence: 74%

Population genetics of microbial pathogens estimated from multilocus sequence typing (MLST) data

Pérez‐Losada

Browne

Madsen

et al. 2006

Infection, Genetics and Evolution

145

107

View full text Add to dashboard Cite

show abstract

“…Moreover, our approach enabled us to accurately predict the number of EPIYA motifs in cases of mixed infections, where closely related subclones bearing the same RAPD profile, but divergent numbers of EPIYA motifs, were isolated from the same host. It is a common observation that such a pool of H. pylori clones may exist in a dynamic equilibrium within potentially all H. pylori-positive hosts (11) and reflect the continuous selective environmental pressure created by acidity and individual host immune responses, as well as factors relating to antibiotic consumption and diet (10,31). Such H. pylori isolates may contain two or more closely related subclones bearing the same RAPD profile and therefore be indistinguishable in common clinical practice.…”

Section: Discussionmentioning

confidence: 99%

Strategy To Characterize the Number and Type of Repeating EPIYA Phosphorylation Motifs in the Carboxyl Terminus of CagA Protein inHelicobacter pyloriClinical Isolates

et al. 2007

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Cytotoxin-associated gene A (CagA) diversity with regard to EPIYA-A, -B, -C, or -D phosphorylation motifs may play an important role in Helicobacter pylori pathogenesis, and therefore determination of these motifs in H. pylori clinical isolates can become a useful prognostic tool. We propose a strategy for the accurate determination of CagA EPIYA motifs in clinical strains, based upon one-step PCR amplification using primers that flank the EPIYA coding region. We thus analyzed 135 H. pylori isolates derived from 75 adults and 60 children Greek patients. A total of 34 cases were found to be EPIYA PCR negative and were consequently verified as cagA negative by cagA-specific PCR, empty-site cagA PCR, and Western blotting. Sequencing of the remaining 101 PCR-positive amplicons confirmed that an accurate prediction of the number of EPIYA motifs on the basis of size distribution of the PCR products was feasible in all cases. Furthermore, our assay could identify closely related H. pylori subclones within the same patient, harboring different numbers of EPIYA repeats. The prevalence of CagA proteins with three EPIYA motifs (ABC) or four EPIYA motifs (ABCC) was the same within the adult and children groups. However, CagA species with more than four EPIYA motifs were observed exclusively within adults (8.6%), suggesting that CagA-positive strains may acquire additional EPIYA-C motifs throughout adulthood. Our strategy requires no initial cagA screening of the clinical isolates and can accurately predict the number of EPIYA repeats in single or multiple closely related subclones bearing different numbers of EPIYA motifs in their CagA, which may coexist within the same patient.

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“…This enzyme converts urea, pumped into the cell via a pH-gated urea channel, to carbon dioxide and ammonia [66]. H. pylori displays significant genetic diversity due to ongoing DNA mutation during colonization of a specific host [2,67,68]. Colonization rates of its human host depend on socioeconomic, ethnic, geographical, and age-related factors [69,70].…”

Section: About H Pylorimentioning

confidence: 99%

Helicobacter pylori eradication: Novel therapy for immune thrombocytopenic purpura? A review of the literature

et al. 2005

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Eradication of Helicobacter pylori (H. pylori ) from the gastric mucosa has been associated with improvement of several systemic diseases, including immune thrombocytopenic purpura (ITP). Over the last 5 years, several studies have reported improved platelet counts in H. pylori-positive ITP patients following standard triple H. pylori eradication therapy. Review of published studies in which eradication of H. pylori has been performed in the ITP population indicates an overall response rate of 52% in 193 subjects in whom H. pylori was eradicated. Cohorts from Japan and Italy report higher response rates. There is no established mechanism to explain how this organism, which does not invade the gastric mucosa, could be implicated in the pathogenesis of this immune-based platelet disorder. Several theories including molecular mimicry, platelet aggregation, and immunomodulatory effects of macrolides have been proposed to explain the platelet response to anti-H. pylori therapy. Large randomized-controlled studies enrolling patients from various ethnic backgrounds will be necessary to determine the response rate and mechanism of response and to gain a better understanding of the pathogenesis of ITP. Am.

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Free recombination within Helicobacter pylori

Cited by 561 publications

References 43 publications

Population genetics of microbial pathogens estimated from multilocus sequence typing (MLST) data

Population genetics of microbial pathogens estimated from multilocus sequence typing (MLST) data

Strategy To Characterize the Number and Type of Repeating EPIYA Phosphorylation Motifs in the Carboxyl Terminus of CagA Protein inHelicobacter pyloriClinical Isolates

Helicobacter pylori eradication: Novel therapy for immune thrombocytopenic purpura? A review of the literature

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