Helicobacter pylori among siblings

Flagellin glycosylation with pseudaminic acid in Campylobacter and Helicobacter: prospects for development of novel therapeutics

Many pathogenic bacteria require flagella-mediated motility to colonise and persist in their hosts. Helicobacter pylori and Campylobacter jejuni are flagellated epsilonproteobacteria associated with several human pathologies, including gastritis, acute diarrhea, gastric carcinoma and neurological disorders. In both species, glycosylation of flagellin with an unusual sugar pseudaminic acid (Pse) plays a crucial role in the biosynthesis of functional flagella, and thereby in bacterial motility and pathogenesis. Pse is found only in pathogenic bacteria. Its biosynthesis via six consecutive enzymatic steps has been extensively studied in H. pylori and C. jejuni. This review highlights the importance of flagella glycosylation and details structural insights into the enzymes in the Pse pathway obtained via a combination of biochemical, crystallographic, and mutagenesis studies of the enzyme-substrate and -inhibitor complexes. It is anticipated that understanding the underlying structural and molecular basis of the catalytic mechanisms of the Pse-synthesising enzymes will pave the way for the development of novel antimicrobials.

Vertical Helicobacter pylori transmission from Mongolian gerbil mothers to pups

To identify the time frame and route of mother-to-child Helicobacter pylori infection, a Mongolian gerbil model was used. Four-week-old female Mongolian gerbils were infected with H. pylori, and then mated with uninfected males 2 months after infection. The offspring were sacrificed weekly after birth, and then serum, mother's milk from the stomach and gastric tissues were obtained from pups. Anti-H. pylori antibody titres were measured in sera and maternal milk using an ELISA. The stomach was cut in two in the sagittal plane, and then H. pylori colonization in mucosa was confirmed by culture and real-time RT-PCR in one specimen and by immunochemical staining in the other. Faeces and oral swabs were obtained from infected mothers, and H. pylori 16S rRNA was measured using real-time RT-PCR. H. pylori was not identified in cultures from the gastric mucosa of pups delivered by infected mothers, but H. pylori 16S rRNA was detected from 4 weeks after birth, suggesting that Mongolian gerbil pups become infected via maternal H. pylori transmission from 4 weeks of age. The anti-H. pylori antibody titre in sera of pups from infected mothers was maximum at 3 weeks of age and then rapidly decreased from 4 weeks of age. High antibody titres in mother's milk were detected during the suckling period, and GlcNAcα was detectable at 2–4 weeks of age, but disappeared as the offspring aged. Thus H. pylori seems to infect Mongolian gerbil pups from 4 weeks of age, in parallel with decreasing GlcNAcα expression in the gastric mucosa. These results suggested that H. pylori infection of Mongolian gerbil pups occurs via faecal–oral transmission from an infected mother.

Using macro-arrays to study routes of infection of Helicobacter pylori in three families

BACKGROUND

Analysis of the evolutionary dynamics of Helicobacter pylori allowed tracing the spread of infection through populations on different continents but transmission pathways between individual humans have not been clearly described.

MATERIALS AND METHODS

To investigate person-to-person transmission, we studied three families each including one child with persistence of symptoms after antibiotic treatment. Ten isolates from the antrum and corpus of stomach of each family member were analyzed both by sequencing of two housekeeping genes and macroarray tests.

RESULTS

A total of 134 (8.4%) out of the 1590 coding sequences (CDSs) tested, including cag PAI and insertion sequences, were present in some but not all isolates (and are therefore defined as variable CDSs). Most of the variable CDSs encoded proteins of unknown function (76/134) or were selfish DNA including that encoding restriction/modification enzymes (13/134). Isolates colonizing the stomach of one individual can vary by point mutations, as seen in hspA, or by the gain or loss of one to five CDSs. They were considered as (genetic) variants. The phylogenetic clustering of gene profiles obtained on macro-arrays allowed identifying the different strains infecting families. Two to five strains circulated within a family. Identical strains were present in at least two members of all three families supporting the accepted model of intrafamilial transmission. Surprisingly, the mother was not implicated in the transmission of H. pylori in the two French families. Sibling-to-sibling transmission and acquisition of H. pylori from outside the family appeared to be probable in the transmission pathways.

CONCLUSION

Macroarray analysis based on previously selected CDSs gives a comprehensive view of the genome diversity of a pathogen. This approach combined with information on the origin of the hspA and glmM alleles revealed that Helicobacter pylori infection may be acquired by more diverse routes than previously expected.

Helicobacter pylori infection in pregnant women from a U.S.-Mexico border population

Helicobacter pylori infection causes chronic digestive diseases that disproportionately affect Hispanics and other immigrant groups in the United States. Information on the epidemiology of H. pylori infection in pregnant women who reside along the U.S.-Mexico border is critical to understanding the dynamics of current H. pylori transmission patterns within families along the border. We describe the epidemiology of H. pylori infection in pregnant women recruited from Women, Infants, and Children (WIC) clinics in El Paso, Texas, and Mexican Social Security Institute maternal-child clinics in Ciudad Juarez, Mexico, from April 1998 to October 2000. We interviewed participants regarding environmental factors and tested their serum for IgG antibodies. We used logistic regression to estimate associations between environmental exposures and the odds of H. pylori prevalence. Definitive serological tests were available from 751 women. Seroprevalence was 74% in Juarez women and 56% in El Paso women. Prevalence increased with age, crowding, poor sanitation, and residence in Mexico, decreased with education, and was not associated with the woman's number of living children. In the U.S.-Mexico border region, women of reproductive age have a high prevalence of H. pylori infection, apparently related to poor socioeconomic conditions.

Tracing clonality of Helicobacter pylori infecting family members from analysis of DNA sequences of three housekeeping genes (ureI, atpA and ahpC), deduced amino acid sequences, and pathogenicity-associated markers (cagA and vacA)

Helicobacter pylori, a Gram-negative bacterium, is a causal agent of peptic ulcers and is estimated to infect the gastric mucosa of at least half of the world's population. As primary infections are acquired mainly by household contact, studies on family clusters provide a model for investigating transmission and the natural history of initial infection. Here, sequence typing exploiting genetic variation in core fragments of three key housekeeping loci (ureI, atpA and ahpC) was used to determine clonal descent amongst isolates of ten members of four families in Northern Ireland and a family with three generations in central England. Phylogenetic analysis of each locus for 73 strains of H. pylori from 11 countries indicated high background intraspecific diversity, apart from identical paired isolates from five unrelated patients and strains with identical sequence types (STs) detected in adult members of two families. In several families carrying strains with different STs, evidence of residual clonal descent was detected at one or two loci by comparison of nucleotide and amino acid sequences. Pathogenicity-associated genotypes were heterogeneous with respect to ST and amino acid type. Analysis of these three housekeeping genes provides unique evidence for precise tracing of clonal descent in isolates of H. pylori in family groups.

Helicobacter pylori intrafamilial infections: change in source of infection of a child from father to mother after eradication therapy

Biopsy specimens of the antrum and corpus were obtained from four Helicobacter pylori-infected members of a family and from the same boy (son 1) in whom the infection reappeared after simultaneous successful eradication treatment of three family members, excluding the mother. A total of 18 to 60 H. pylori isolates were obtained from each specimen and subjected to rRNA gene restriction pattern analysis. The father's isolates and the initial isolates from son 1 showed the same HindIII type, which was divided into three HaeIII subtypes. Isolates from the mother and a brother (son 2) and posttreatment isolates from son 1 showed a distinct HindIII type (with one minor subtype), which was divided into six HaeIII subtypes. All subtypes of the initial isolates from son 1 were present in the father's isolates, and all subtypes of the posttreatment isolates from son 1 were present in the mother's isolates but not in son 2's. Electron microscopic analysis of the biopsy specimens demonstrated extremely high levels of H. pylori colonization in the father's gastric mucosa. H. pylori adherence with a ruffle formation was also demonstrated. The findings suggest that son 1 was infected initially with the H. pylori strain of the father and son 2 was infected with the H. pylori strain of the mother and that after eradication therapy son 1 was reinfected with the H. pylori strain of the mother, who did not undergo eradication therapy.