Horizontal versus familial transmission of Helicobacter pylori. PLoS Pathog. 2008;4:e1000180. [PMID: 18949030 PMCID: PMC2563686 DOI: 10.1371/journal.ppat.1000180]

Geographic distribution of methyltransferases of Helicobacter pylori: evidence of human host population isolation and migration

Background

Helicobacter pylori colonizes the human stomach and is associated with gastritis, peptic ulcer, and gastric cancer. This ubiquitous association between H. pylori and humans is thought to be present since the origin of modern humans. The H. pylori genome encodes for an exceptional number of restriction and modifications (R-M) systems. To evaluate if R-M systems are an adequate tool to determine the geographic distribution of H. pylori strains, we typed 221 strains from Africa, America, Asia, and Europe, and evaluated the expression of different 29 methyltransferases.

Results

Independence tests and logistic regression models revealed that ten R-M systems correlate with geographical localization. The distribution pattern of these methyltransferases may have been originated by co-divergence of regional H. pylori after its human host migrated out of Africa. The expression of specific methyltransferases in the H. pylori population may also reflect the genetic and cultural background of its human host. Methyltransferases common to all strains, M. HhaI and M. NaeI, are likely conserved in H. pylori, and may have been present in the bacteria genome since the human diaspora out of Africa.

Conclusion

This study indicates that some methyltransferases are useful geomarkers, which allow discrimination of bacterial populations, and that can be added to our tools to investigate human migrations.

The epidemiology of Helicobacter pylori and public health implications

This article presents a review of the literature on the epidemiology and public health implications of Helicobacter pylori infection published from April 2008 through to March 2009. The authors used MeSH terms "Helicobacter infections epidemiology,""Helicobacter infections prevention and control" to search multiple databases (PubMed, Embase, Cochrane, Cochrane Library, EBMR, BIOSIS), and independently searched PubMed using the term "Helicobacter" with "Epidemiology,""Transmission,""Prevalence" or "Environment." Articles without topical relevance were excluded. Two additional papers known to the authors were added. The identified literature is summarized by subtopic: reviews; prevalence; incidence; transmission; risk factors; and public health policy.

Comparative genomics of Helicobacter pylori

Genomic sequences have been determined for a number of strains of Helicobacter pylori (H. pylori) and related bacteria. With the development of microarray analysis and the wide use of subtractive hybridization techniques, comparative studies have been carried out with respect to the interstrain differences between H. pylori and inter-species differences in the genome of related bacteria. It was found that the core genome of H. pylori constitutes 1111 genes that are determinants of the species properties. A great pool of auxillary genes are mainly from the categories of cag pathogenicity islands, outer membrane proteins, restriction-modification system and hypothetical proteins of unknown function. Persistence of H. pylori in the human stomach leads to the diversification of the genome. Comparative genomics suggest that a host jump has occurs from humans to felines. Candidate genes specific for the development of the gastric diseases were identified. With the aid of proteomics, population genetics and other molecular methods, future comparative genomic studies would dramatically promote our understanding of the evolution, pathogenesis and microbiology of H. pylori.

Presence of high numbers of transcriptionally active Helicobacter pylori in vomitus from Bangladeshi patients suffering from acute gastroenteritis

BACKGROUND

Helicobacter pylori is one of the most prevalent human bacterial pathogens; however, its transmission pathways remain unknown. New infections of H. pylori during outbreaks of gastroenteritis have been suggested previously, and to explore this transmission route further H. pylori was quantified in vomitus and diarrheal stool of patients suffering from acute gastroenteritis in Dhaka, Bangladesh.

MATERIALS AND METHODS

Vomitus and stool samples from 28 patients seeking care at the International Centre for Diarrhoeal Disease Research hospital were analyzed for presence of H. pylori and other pathogens using quantitative culturing, real-time polymerase chain reaction (PCR), and H. pylori stool antigen test. Bacterial gene expression was analyzed using reverse transcriptase real-time PCR.

RESULTS

The results of real-time PCR show that 23 (88%) of the 26 vomitus samples and 17 (74%) of the 23 stool samples were H. pylori positive, while stool antigen test show that 14 (67%) of the 21 stool samples were H. pylori positive. H. pylori could not be isolated by culture. Analysis using quantitative culture and real-time PCR to detect Vibrio cholerae showed strong correlation between these methods, and validating real-time PCR. Analysis of H. pylori virulence gene transcription in vomitus, diarrheal stool, antral and duodenal biopsy specimens, and in vitro cultures showed that cagA, flaA, and ureA were highly transcribed in vomitus, biopsy specimens, and cultures, whereas hpaA and vacA were expressed at lower levels. No H. pylori gene expression was detected in diarrheal stool.

CONCLUSIONS

We conclude that high numbers of transcriptionally active H. pylori are shed in vomitus, which indicates that new infections may be disseminated through vomiting.

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.