Molecular epidemiology of Helicobacter pylori in England: prevalence of cag pathogenicity island markers and IS605 presence in relation to patient age and severity of gastric disease

Association of Helicobacter pylori Infection and Host Cytokine Gene Polymorphism with Gastric Cancer

The global cancer burden of new cases of various types rose with millions of death in 2018. Based on the data extracted by GLOBOCAN 2018, gastric cancer (GC) is the third leading cause of mortality related to cancer across the globe. Carcinogenic or oncogenic infections associated with Helicobacter pylori (Hp) are regarded as one of the essential risk factors for GC development. It contributes to the increased production of cytokines that cause inflammation prior to their growth in the host cells. Hp infections and specific types of polymorphisms within the host cells encoding cytokines are significant contributors to the host's increased susceptibility in terms of the development of GC. Against the backdrop of such an observation is that only a small portion of the cells infected can become malignant. The diversities are a consequence of the differences in the pathogenic pathway of the Hp, susceptibility of the host, environmental conditions, and interplay between these factors. It is evident that hosts carrying cytokine genes with high inflammatory levels and polymorphism tend to exhibit an increased risk of development of GC, with special emphasis being placed on the host cytokines gene polymorphisms.

CagE, cagA and cagA 3' region polymorphism of Helicobacter pylori and their association with the intra-gastric diseases in Moroccan population

Helicobacter pylori infection is the most important etiological factor in gastroduodenal diseases development. Its evolution is influenced by several factors, including bacterial virulence genes such as cagA and cagE. This work aimed to evaluate the predictive value of cagE alone and in combination with cagA and CagA-EPIYA-C motifs number as a marker of the infection evolution. A total of 823 H. pylori DNA extracted from biopsies of consenting patients suffering from gastritis, peptic ulcer, or gastric cancer. The cagE, cagA status and cagA 3' region polymorphism were determined by PCR. The analysis shows that the risk of duodenal ulcer is 1.97-fold higher (CI = 1.18-3.30) in patients infected by strains cagA+/cagE+. And the risk of gastric cancer is 5.19-fold higher (CI = 1.18-22.70) in patients harboring strains cagE+/2EPIYA-C. The results suggest that cagE in combination with cagA-EPIYA-C motifs number can be used as predictive biomarker of H. pylori infection evolution.

Association of IS605 and cag-PAI of Helicobacter pylori Isolated from Patients with Gastrointestinal Diseases in Taiwan

Background. The cag pathogenicity island (cag-PAI) is one of the most important virulent determinants of Helicobacter pylori. An insertion sequence (IS) element of cag-PAI (IS605) has been found to generate H. pylori strains with varying virulence. Aim. To evaluate the impact of IS605 and cag-PAI on H. pylori strains isolated from Taiwanese patients with severity of gastric diseases. Methods. H. pylori isolates were cultured from gastric biopsies from 99 patients with peptic ulcer, chronic gastritis, and gastric carcinoma. Six distinct, well-separated colonies were isolated from each patient and analyzed by genotyping. Results. cagA, cagE, cagM, cagT, orf10, and orf13 were found to be present in 90.0%–100.0% of the H. pylori isolates. A total deletion of cagA, cagE, cagM, cagT, orf10, and orf13 was found in 1 isolate (1.0%). The IS605 element was found to be positive in 15.2% of the isolates. The presence of IS605 was higher in H. pylori isolated from patients with gastric carcinoma (25.0%) than in patients with duodenal ulcer (6.5%) or chronic gastritis (6.3%) (P < 0.001). Conclusions. The majority of the patients examined had intact cag-PAI. IS605 was present in 15.2% and was higher in H. pylori isolated from patients with gastric carcinoma than in those with peptic ulcer.

Relatedness of Helicobacter pylori populations to gastric carcinogenesis

Helicobacter pylori (H. pylori) is a Gram-negative bacterium that infects half of the human population. The infection is associated with chronic inflammation of the gastric mucosa and peptic ulcers. It is also a major risk factor for gastric cancer. Phylogenetic analysis of global strains reveals there are seven populations of H. pylori, including hpAfrica1, hpAfrica2, hpEastAsia, hpEurope, hpNEAfrica, hpAsia2 and hpSahul. These populations are consistent with their geographical origins, and possibly result from geographical separation of the bacterium leading to reduced bacterial recombination in some populations. For each population, H. pylori has evolved to possess genomic contents distinguishable from others. The hpEurope population is distinct in that it has the largest genome of 1.65 mbp on average, and the highest number of coding sequences. This confers its competitive advantage over other populations but at the cost of a lower infection rate. The large genomic size could be a cause of the frequent occurrence of the deletion of the cag pathogenicity island in H. pylori strains from hpEurope. The incidence of gastric cancer varies among different geographical regions. This can be attributed in part to different rates of infection of H. pylori. Recent studies found that different populations of H. pylori vary in their carcinogenic potential and contribute to the variation in incidence of gastric cancer among geographical regions. This could be related to the ancestral origin of H. pylori. Further studies are indicated to investigate the bacterial factors contributing to differential virulence and their influence on the clinical features in infected individuals.

Insertion sequence- and tandem repeat-based genotyping techniques for Xanthomonas citri pv. mangiferaeindicae

Molecular fingerprinting techniques that have the potential to identify or subtype bacteria at the strain level are needed for improving diagnosis and understanding of the epidemiology of pathogens such as Xanthomonas citri pv. mangiferaeindicae, which causes mango bacterial canker disease. We developed a ligation-mediated polymerase chain reaction targeting the IS1595 insertion sequence as a means to differentiate pv. mangiferaeindicae from the closely related pv. anacardii (responsible for cashew bacterial spot), which has the potential to infect mango but not to cause significant disease. This technique produced weakly polymorphic fingerprints composed of ≈70 amplified fragments per strain for a worldwide collection of X. citri pv. mangiferaeindicae but produced no or very weak amplification for pv. anacardii strains. Together, 12 tandem repeat markers were able to subtype X. citri pv. mangiferaeindicae at the strain level, distinguishing 231 haplotypes from a worldwide collection of 299 strains. Multilocus variable number of tandem repeats analysis (MLVA), IS1595-ligation-mediated polymerase chain reaction, and amplified fragment length polymorphism showed differences in discriminatory power and were congruent in describing the diversity of this strain collection, suggesting low levels of recombination. The potential of the MLVA scheme for molecular epidemiology studies of X. citri pv. mangiferaeindicae is discussed.

Prevalence of Helicobacter pylori genotypes (vacA, cagA, cagE and virB11) in gastric cancer in Brazilian's patients: an association with histopathological parameters

PURPOSE

To investigate the frequency and the association of vacA alleles, cagA, cagE and virB11 genes of Helicobacter pylori from patients with gastric cancer, considering the clinic histopathological parameters.

METHODS

One hundred and one gastric adenocarcinoma tissues were assessed by PCR to detect H. pylori and vacA alleles, cagA, cagE and virB11.

RESULTS

The distribution of cases according to the presence of the genes studied showed that the group containing vacA s1m1, cagA, cagE and virB11 H. pylori genes was significantly more frequent, followed by the group with at least one marker on the right side and left of the island. They were also present in the early stages and were the most frequent in nearly all histopathological grades.

CONCLUSIONS

This study verified that vacAs1m1 and cag-PAI genes, cagA, cagE and virB11 are important H. pylori markers for gastric cancer development. Also, this study corroborates the importance of cagE and cagA together as cag-PAI marker.

Intact cag pathogenicity island of Helicobacter pylori without disease association in Kolkata, India

Several genes including the cagA in the cag pathogenicity island (cag PAI) of Helicobacter pylori are thought to be associated with the gastroduodenal diseases and hence variation in the genetic structure of the cag PAI might be responsible for different clinical outcomes. Our study was undertaken to characterize the cag PAI of H. pylori strains from duodenal ulcer (DU) patients and asymptomatic or non-ulcer dyspepsia (NUD/AV) subjects from Kolkata, India. Strains isolated from 52 individuals (30DU and 22NUD/AV) were analyzed by PCR using 83 different primers for the entire cag PAI and also by dot-blot hybridization. Unlike H. pylori strains isolated from other parts of India, 82.6% of the strains used in this study had intact cag PAI, 9.6% had partially deleted cag PAI, and 7.7% of the strains lacked the entire cag PAI. Dot-blot hybridization yielded positive signals in 100% and 93.8% of PCR-negative strains for HP0522-523 and HP0532-HP0534 genes, respectively. An intact cagA promoter region was also detected in all cagA-positive strains. Furthermore, the expression of cagA mRNA was confirmed by RT-PCR for the representative strains from both DU and NUD/AV subjects indicating the active cagA promoter regions of these strains. A total of 66.7% of Kolkata strains produced a ∼390-bp shorter amplicon than the standard strain 26695 for the HP0527 gene, homologue of virB10. However, sequence analyses confirmed that the deletion did not alter the reading frame of the gene, and mRNA transcripts were detected by RT-PCR analysis. The strains isolated from DU and NUD/AV express CagA protein and possess a functional type IV secretion system, as revealed by Western blot analyses. Interestingly, no significant differences in cag PAI genetic structure were found between DU and NUD/AV individuals suggesting that other bacterial virulence factors, host susceptibility, and environmental determinants also influence the disease outcome at least in certain geographical locations.

The prevalence of cagA and cagE genes in Helicobacter pylori strains isolated from different patient groups by polymerase chain reaction

The aim of this study was to investigate the prevalence of cagA and cagE genes in H. pylori strains isolated from different patient groups with Non-Ulcer Dyspepsia (NUD), Duodenal Ulcer (DU), Gastric Ulcer (GU) and Gastric Cancer (GC). The patients admitted to the gastroenterology unit at Sharyati hospital in Tehran in 2006 were included in this study. Gastric biopsy specimens were obtained from the antrum of the stomach from each patient then cultured for detection of H. pylori. Identification of H. pylori was performed according to the standard bacteriological methods. Genomic DNA was extracted using a commercially available Qia gene kit. PCR was done using primers cagA-F, cagA-R and cagE-F, cagE-R to detect the target genes cagA and cagE, respectively. Amplified products of target genes were confirmed by sequencing. The cagA and cagE were detected among 85 and 86% of H. pylori isolates, respectively. Prevalence of cagA and cagE genes in the patients with NUD, DU, GU and GC were 22 (64.7%), 28 (100%), 18 (90%), 10 (100%) and 25 (73.5%), 27 (96.4%), 19 (95%), 7 (70%), respectively. The current study demonstrated a significant correlation between peptic ulceration and the presence of H. pylori isolates carrying cagE and cagA genes in Iranian patients.

Helicobacter pylori genotyping and sequencing using paraffin-embedded biopsies from residents of colombian areas with contrasting gastric cancer risks

BACKGROUND

cagA-positive and vacA s1 and m1 genotypes of Helicobacter pylori are associated with an elevated risk of gastric cancer (GC). We determined these genotypes using paraffin-embedded gastric biopsy specimens harvested from infected individuals and compared genotype distributions in two Colombian populations residing in geographic regions with a high and low incidence of GC.

METHODS

DNA from paraffin-embedded gastric biopsies from 107 adults was amplified using primers specific for cagA, for the cag'empty site', for the s and m alleles of vacA, and for H. pylori 16S rRNA.

RESULTS

H. pylori infection was detected by molecular assays in 97 (90.7%) biopsies. Complete genotyping of cagA and vacA was achieved in 94 (96.9%) cases. The presence of cagA was detected in 78 of 97 cases (80.4%); when considered separately, cagA and vacA s regions were not significantly associated with a particular geographic area. The vacA m1 allele and s1m1 genotypes were more common in the area of high risk for GC (p = .037 and p = .044, respectively), while the vacA m2 allele and s2m2 genotypes were more prevalent in the low-risk area. The prevalence of the combination of cagA-positive, vacA s1m1 genotypes was 84.3% and 60.5% for high and low risk areas, respectively (p = .011).

CONCLUSIONS

H. pylori cagA and vacA genotyping from paraffin-embedded gastric biopsies permitted reliable typability and discrimination. The more virulent cagA-positive s1m1 strains, as well as vacA m1 genotype, were more prevalent in high risk than in low risk areas, which may contribute to the difference in GC risk between those two regions.

The cag pathogenicity island of Helicobacter pylori is disrupted in the majority of patient isolates from different human populations

The cag pathogenicity island (cag-PAI) is one of the major virulence determinants of Helicobacter pylori. The chromosomal integrity of this island or the lack thereof is speculated to play an important role in the progress of the gastroduodenal pathology caused by H. pylori. We determined the integrity of the cag-PAI by using specific flanking and internally anchored PCR primers to know the biogeographical distribution of strains carrying fully integral cag-PAI with proinflammatory behavior in vivo. Genotypes based on eight selected loci were studied in 335 isolates obtained from eight different geographic regions. The cag-PAI appeared to be disrupted in the majority of patient isolates throughout the world. Conservation of cag-PAI was highest in Japanese isolates (57.1%). However, only 18.6% of the Peruvian and 12% of the Indian isolates carried an intact cag-PAI. The integrity of cag-PAI in European and African strains was minimal. All 10 strains from Costa Rica had rearrangements. Overall, a majority of the strains of East Asian ancestry were found to have intact cag-PAI compared to strains of other descent. We also found that the cagE and cagT genes were less often rearranged (18%) than the cagA gene (27%). We attempted to relate cag-PAI rearrangement patterns to disease outcome. Deletion frequencies of cagA, cagE, and cagT genes were higher in benign cases than in isolates from severe ulcers and gastric cancer. Conversely, the cagA promoter and the left end of the cag-PAI were frequently rearranged or deleted in isolates linked to severe pathology. Analysis of the cag-PAI genotypes with a different biogeoclimatic history will contribute to our understanding of the pathogen-host interaction in health and disease.

Analysis of the cag pathogenicity island and IS605 of Helicobacter pylori strains isolated from patients with gastric cancer in Japan

BACKGROUND

CagA protein is encoded by the cagA gene, which is part of the cag pathogenicity island (PAI) in Helicobacter pylori. Insertion sequence (IS) elements are a diverse set of specialized DNA segments that can move to new sites in bacterial genomes.

AIM

To determine the role of cagPAI and IS605 in the development of gastric cancer, we analysed cagPAI from patients with gastric cancer and compared the results with the host's CagA antibody status.

METHODS

H. pylori strains were isolated from 29 gastric cancer patients, and CagA status was determined by measuring serum antibody against CagA. The cagPAI region and IS605 were determined by PCR.

RESULTS

CagA seropositivity tended to be higher in the IS605/PAI+ group (5/7, 71.4%) than in the IS605/PAI- group (9/22, 40.9%). Association with cag13 was more frequent in the IS605+ group (92.3%; 12/13) than in the IS605- group (25.0%; 4/16; P = 0.0005).

CONCLUSIONS

cag13 may be associated with the presence of IS605 in gastric cancer patients.

Analysis of geospecific markers for Helicobacter pylori variants in patients from Japan and Nigeria by triple-locus nucleotide sequence typing

Human migrations and geographical separation over long periods may have resulted in ecologically distinct populations of Helicobacter pylori infecting individuals in different continents. This study used nucleotide sequence analysis with the aim of defining population-specific genomic motifs in isolates from East Asian and African dyspeptic patients. Sequences of internal fragments (542-627 bp) of three housekeeping genes (ureI, ahpC and atpA) were analysed for 85 isolates from individuals in Japan and China (30 isolates), Nigeria and South Africa (14 isolates), the United Kingdom (32 isolates), and nine miscellaneous reference strains. Phylogenetic analyses showed a high degree of intra-set relatedness amongst sequences from the Japanese and Nigerian isolates, with each robustly segregated as distinct lineages irrespective of cagA presence and vacA allelic type. All strains had unique combined sequence types except for identical paired (antrum/corpus) isolates. Population-specific polymorphisms were identified within each gene which were combined to provide unique motifs defining the Japanese and Nigerian regional populations. The alleles were present at variable frequencies in UK and South African isolates. The findings provide unique evidence of positive selection for conserved nucleotide sites linked to the geographical separation in Japan of a strain subpopulation for which we propose the designation H. pylori geovar 'orientalis'.

Correlation between cag pathogenicity island composition and Helicobacter pylori-associated gastroduodenal disease

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.

Distribution of cagG gene in Helicobacter pylori isolates from Chinese patients with different gastroduodenal diseases and its clinical and pathological significance

AIM: To determine the distribution of cagG gene of Helicobacter pylori (H pylori) isolates cultured from patients with various digestive diseases and its relationship with gastroduodenal diseases.

METHODS: cagG was amplified by polymerase chain reaction in 145 H pylori isolates cultured from patients with chronic gastritis (n = 72), duodenal ulcer (n = 48), gastric ulcer (n = 17), or gastric and duodenal ulcer (n = 8), and the relationship between cagG status and the grade of gastric mucosal inflammation was determined.

RESULTS: cagG was present in 91.7% of the 145 H pylori isolates, with the rates were 90.3%, 93.8%, 88.2% and 100.0%, respectively, in those from patients with chronic gastritis, duodenal ulcer, gastric ulcer, and gastric and duodenal ulcer. There was no significant difference among the four groups (P > 0.05). The average grade of gastric mucosal inflammation in the antrum and corpus was 1.819 ± 0.325 and 1.768 ± 0.312, respectively in cagG positive patients, whereas the average inflammation grade was 1.649 ± 0.297, 1.598 ± 0.278 respectively in cagG negative cases (P > 0.05).

CONCLUSION: cagG gene of H pylori was quite conservative, and most H pylori strains in Chinese patients were cagG positive. cagG status was not related to clinical outcome or the degree of gastric mucosal inflammation. Therefore, cagG can not be used as a single marker for discrimination of H pylori strains with respect to a specific digestive disease.

Identification of cagA tyrosine phosphorylation DNA motifs in Helicobacter pylori isolates from peptic ulcer patients by novel PCR-restriction fragment length polymorphism and real-time fluorescence PCR assays

Cag pathogenicity island-containing Helicobacter pylori (type I) induces signal transduction pathways resulting in tyrosine phosphorylation of proteins adjacent to the site of bacterial adhesion on host gastric epithelial cells. Conventional block PCR-restriction fragment length polymorphism (RFLP) and real-time LightCycler (LC) PCR hybridization assays, validated by direct sequencing, were designed to test for the presence of three nucleotide sequences corresponding to tyrosine phosphorylation motifs (TPMs) A, B, and C in 84 isolates of H. pylori type I from patients in England. Overall, the PCR assays demonstrated that one or more TPMs were present in 62 strains (75%). Motif A was common (71% of strains), whereas motifs B and C were rarer (8% of strains). Strains lacking a TPM were typically vacuolating cytotoxin genotype vacA m2. Motif A was widely distributed in relation to disease severity and was more commonly (but not significantly [P = 0.071]) associated with gastric ulcer than with duodenal ulcer (86 versus 56%). The LC hybridization assay provided a rapid means of detecting all three motifs, but RFLP analysis was more specific for TPM-A. TPMs provide novel additional strain markers for defining cagA variation, including identification of RFLP types within TPM-A. The presence of a particular TPM was not of direct diagnostic value, either singly or in combination, but the higher proportion of TPM-A strains in gastric ulcer patients merits further investigation.

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.

Investigation of the biological relevance of Helicobacter pylori cagE locus diversity, presence of CagA tyrosine phosphorylation motifs and vacuolating cytotoxin genotype on IL-8 induction in gastric epithelial cells

Isolates of Helicobacter pylori from dyspeptic patients in England and South Africa were tested for ability to induce interleukin-8 (IL-8) in gastric cells. All isolates were cagA-positive, which was used as a marker for the presence of the cag pathogenicity island. The aims were to determine if activities were related to diversity within cagE (HP0544), a locus encoding a key component in the Type IV secretion system, and if disease severity might be linked to a combination of strain features. We found that isolates were heterogeneous in ability to induce IL-8 activity with the 23 positive isolates (59%) showing activities ranging from 260 to 3200 pg ml(-1). The cagE locus was detected in most isolates and RFLP analysis of a 1.52-kb internal fragment showed interstrain diversity with 12 combined (MboI/NlaIII) types. Most cagE genotypes were not associated with IL-8 induction, however two genotypes were found only in IL-8-inducing strains and one genotype was associated with lack of IL-8 induction. IL-8 activity was not associated with either the number or composition of cagA tyrosine phosphorylation motifs and vacA m-type. Although we found a weak association between cagE type and the ability to induce IL-8, our results imply that gastric cell factors or bacterial factors other than vacA, cagA and cagE are involved in the induction of IL-8 and the development of severe gastric disease.

Clinical relevance of the cagA, vacA and iceA genotypes of Helicobacter pylori in Brazilian clinical isolates

Infection with Helicobacter pylori strains harboring determinants of pathogenicity may lead to a strong inflammatory response in gastric mucosa. In this work, we examined the frequency of the cagA, vacA and iceA genotypes in H. pylori strains isolated from Brazilian patients and correlated these with the clinical manifestations. H. pylori was isolated from 165 patients [30 with non-ulcer dyspepsia cases (NUD); 93 peptic ulcer disease (PUD): 31 gastric ulcers (GU) and 62 duodenal ulcer disease (DU); 18 with erosive gastritis (EG); and 24 gastroesophageal reflux disease (GERD)]. Allelic variants of cagA, vacA and iceA were identified using the polymerase chain reaction. More than one H. pylori strain was detected in 28 cases (17%), and these were excluded from the statistical analysis. We were unable to confirm an association between iceA status and clinical outcome. There was a strong association between the genotype cagA-positive vacA s1 and PUD. However, logistic regression analysis showed that vacA s1 was the only predictive factor for PUD (OR=4.19; 95% CI 1.95-8.98). The presence of the less virulent strain vacA s2 was related to GERD (OR=8.59; 95% CI 2.85-25.91). Our results support the hypothesis that virulent strains may protect against the development of GERD.

Distribution of distinct vacA, cagA and iceA alleles in Helicobacter pylori in Hong Kong

BACKGROUND

There is a substantial genetic heterogeneity among Helicobacter pylori strains, and certain genotypes have been suggested to be associated with the virulence of this pathogen. The aim of this study was to investigate the distribution of H. pylori vacA, cagA and iceA genotypes and their association with duodenal ulcer disease in Hong Kong.

MATERIALS AND METHODS

Gastric biopsies of 72 H. pylori infected patients were analyzed by specific polymerase chain reactions.

RESULTS

Of the 72 cases, 69 (95.8%) had vacA signal sequence s1c strains, and three (4.2%) had s1a strains. vacA middle region sequences, m1b and m2, were detected in 23 (31.9%) and 46 (63.9%), respectively. Six (8.3%) cases contained multiple vacA subtypes. vacA s2 allele was only observed in three (4.3%) cases, which were also infected with s1c subtype. cagA was present in 64 (88.9%) of 72 patients, and iceA1 subtype was detected in 46 (63.9%) cases. Neither cagA nor vacA and iceA were associated with duodenal ulcer disease.

CONCLUSION

The distribution of vacA, cagA and iceA alleles in H. pylori strains in Hong Kong is similar to that in east Asia. There is a difference in the distribution of genotypes between strains in Hong Kong and those in mainland China, although strains in the two regions exhibit a very close relation. The association of these virulence genes and duodenal ulcer disease needs reappraisal, particularly under geographic considerations.

Conservation and microdiversity of the phospholipase A (pldA) gene of Helicobacter pylori infecting dyspeptics from different countries

Phospholipase activity is important in bacterial pathogenicity and could contribute to the pathogenic role of Helicobacter pylori by degradation of the gastric mucus, and in maintaining long-term colonisation. Our aim was to determine the degree of variation in the phospholipase A gene (pldA) of H. pylori from different geographic locations, and to investigate links between pldA genotype and clinical disease severity, as well as with variation in cagA status and vacA genotypes. PCR-restriction fragment length polymorphism (RFLP) analysis with MboI and HaeIII was used to study 124 isolates from 10 countries that included the two genome-sequenced strains (26695 and J99), as well as Tx30a and NCTC 11637 (type strain). The 925-bp pldA fragment was amplified with a frequency of 90%. The presence of pldA was confirmed in the other strains using an alternative forward primer. Isolates were distinguished by PCR-RFLP analysis with 10 MboI and four HaeIII restriction patterns that combined to give 25 distinct pldA RFLP types. The pldA M2H2 strain genotype was most common (20%) in the UK but similar strains came from several other countries. Microdiversity was evident in pldA sequences of strains representing different RFLP types, and five M2H2 strains each had a distinct pldA sequence type. Intragenic variation was independent of gastric disease severity as well as strain cagA status and vacA genotype, with the exception of eight geographically diverse strains all with the pldA M4H3/cagA+/vacA s1m1 genotype predominantly from peptic ulcer patients. The study indicated a spectrum of genotypic variants and was supportive of a pldA function in H. pylori colonisation and persistence rather than in chronicity of infection.