Helicobacter pylori vacA and cagA genotypes in patients from northeastern Brazil with upper gastrointestinal diseases

Helicobacter pylori causes chronic gastric inflammation and significantly increases the risk of duodenal and gastric ulcer disease and distal gastric carcinoma. In this study, we evaluated the Helicobacter pylori vacA and cagA genotypes in patients from a Brazilian region where there is a high prevalence of gastric cancer. Polymerase chain reaction (PCR) was used to investigate vacA mosaicism and cagA status in the gastric mucosa of 134 H. pylori-positive patients, including 76 with gastritis: 28 with peptic ulcer disease and 30 with gastric cancer. The s1m1 variant was the predominant vacA genotype observed, whereas the s1 allele was more frequently observed in patients with more severe diseases associated with H. pylori infection [p = 0.03, odds ratio (OR) = 5.72, 95% confidence interval (CI) = 1.15-38.60]. Furthermore, all of the s1 alleles were s1b. Mixed vacA m1/m2 strains were found more frequently in patients with gastric cancer and a cagA-positive status was significantly associated with gastric cancer (p = 0.016, OR = 10.36, 95% CI = 1.35-217.31). Patients with gastric cancer (21/21, 100%, p = 0.006) or peptic ulcers (20/21, 95%, p = 0.02) were more frequently colonised by more virulent H. pylori strains compared to gastritis patients (41/61, 67.2%). In conclusion, in the northeastern of Brazil, which is one of the regions with the highest prevalence of gastric cancer in the country, infection with the most virulent H. pylori strains, carrying the cagA gene and s1m1 vacA alleles, predominates and is correlated with more severe H. pylori-associated diseases.     

Clinical and pathological importance of vacA allele heterogeneity and cagA status in peptic ulcer disease in patients from North Brazil

We have examined the prevalence of gene cagA and vacA alleles in 129 patients, 69 with gastritis and 60 with peptic ulcer diseases from North Brazil and their relation with histopathological data. vacA and cagA genotype were determined by polymerase chain reaction. Hematoxylin-eosin staining was used for histological diagnosis. 96.6% of the patients were colonized by Helicobacter pylori strains harboring single vacA genotype (nont-mixed infection). Among them, 11.8% had subtype s1a, 67.8% had subtype s1b, and 17% subtype s2. In regard to the middle region analysis, m1 alleles were found in 75.4% and m2 in 21.2% of patients. The cagA gene was detected in 78% patients infected with H. pylori and was associated with the s1-m1 vacA genotype. The H. pylori strains, vacA s1b m1/cagA-positive, were associated with increased risk of peptic ulcer disease and higher amounts of lymphocytic and neutrophilic infiltrates and the presence of intestinal metaplasia. These findings show that cagA and vacA genotyping may have clinical relevance in Brazil.     

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.     

Prevalence of cagA and vacA genes in isolates from patients with Helicobacter pylori-associated gastroduodenal diseases in Recife, Pernambuco, Brazil

Geographical differences in the prevalence of Helicobacter pylori genes and their association with disease severity have been identified. This study analyzes the prevalences of the cagA gene and alleles of the vacA gene in H. pylori-associated gastroduodenal diseases in isolates from Recife, PE, Brazil. Gastric biopsy of 61 H. pylori-positive patients were submitted to DNA extraction and gene amplification by polymerase chain reaction. Among the 61 patients, 21 suffered from duodenal ulcer (DU) and 40 from gastritis (GT). The prevalence of H. pylori strains harbouring the cagA gene was higher in the DU group (90.5%) than in the GT group (60%) (p=0.02). The vacA gene was amplified in 56 out of 61 biopsies, of which 43 (76.8%) contained bacteria carrying the s1 allele and 13 (23.2%) the s2. However, the prevalence of the vacA s1 genotyping was the same in either DU or GT group. The majority of the s1-typed strains, 39 (90.7%) out of 43, were subtype s1b. In resume there was a strong association between the H. pylori cagA+ gene and DU. However, there were no differences between the DU and GT groups in relation to the vacA s1 and s2 alleles distribution, albeit the subtype s1b was predominant.     

High-level genetic diversity in the vapD chromosomal region of Helicobacter pylori.

Helicobacter pylori isolates from different patients are characterized by diversity in the nucleotide sequences of individual genes, variation in genome size, and variation in gene order. Genetic diversity is particularly striking in vacuolating cytotoxin (vacA) alleles. In this study, five open reading frames (ORFs) were identified within a 4.2-kb region downstream from vacA in H. pylori 60190. One of these ORFs was closely related to the virulence-associated protein D (vapD) gene of Dichelobacter nodosus (64.9% nucleotide identity). A probe derived from vapD of H. pylori 60190 hybridized with only 19 (61.3%) of 31 H. pylori strains tested. Sequence analysis of the vapD region in vapD-negative H. pylori strains revealed that there were two different families of approximately 0.5-kb DNA segments, which were both unrelated to vapD. The presence of vapD was not associated with any specific family of vacA alleles. These findings are consistent with a recombinational population structure for H. pylori.     

Detection and typing of Helicobacter pylori cagA/vacA genes by radioactive,one-step polymerase chain reaction in stool samples from children

The detection and molecular typing of Helicobacter pylori virulence genes in human stool specimens by polymerase chain reaction (PCR) require an adequate amount of bacterial DNA and an appropriately adjusted PCR protocol. DNA was isolated from stool samples of 39 H. pylori-infected and nine uninfected Colombian children using the QIAamp Kit following the manufacturer's instructions but with modifications. DNA templates were amplified for the vacA s and m regions and for the cagA gene by PCR using radioactively labeled (32P) primers. The modifications in the standard Qiagen protocol of stool DNA extraction increased the final concentration of eluted total stool DNA 4.7 times (117 +/- 17 versus 22 +/- 3 ng/microl; P < 0.0001). Nevertheless, its amplification by regular PCR programs (30-40 cycles) did not generate visible signals because of the very low ratio of H. pylori DNA to other DNA. PCR for 80 cycles successfully amplified vacA in 36/39 samples (sensitivity, 92.3%) and cagA fragments in 21/39 (53.8%) fecal DNA samples. Both s and m vacA regions were amplified in 33/36 (91.7%) DNA samples. The s1m1 genotype was the most commonly isolated variant, accounting for 17/36 or 47.2% of positive samples. The s2m2 genotype was ascertained to be frequent also (14/36 or 38.9%). Almost all (94.1%) s1m1 genotypes were cagA positive. The majority of s2m2 genotypes (78.6%) were not associated with the cagA gene. Neither cagA nor vacA fragments were amplified from DNA isolates of H. pylori-uninfected children nor from DNA isolated from six gastrointestinal bacterial strains (specificity, 100%). The data suggest that the proposed modified technique of DNA extraction and PCR assay of stool samples may be an effective and reliable noninvasive tool for the detection and typing of H. pylori cagA/vacA virulence genes in infected individuals.     

Genotypes of Helicobacter pylori in Polish population

Here we have studied the genetic diversity of Helicobacter pylori strains recovered from 64 individual patients, 5 family members and 13 unsuccessfully treated patients. The recovered bacteria were finger-printed by the PCR-RFLP and RAPD methods and virulence associated loci (cagPAI, vacA) were PCR studied. Unique differentiation of every independently isolated strain from not-related persons was possible by RAPD technique. In PCR-RFLP technique several profile groups (7 and 15) for particular endonuclease tested were found. Eleven patients carried strains of the same gene profile (PCR-RFLP) and the same overall genotype (RAPD) before and after therapy. In the family studies, essentially the same strain was found in different relatives in three cases, and different strains were found in the other two cases. Island of cagPAI was present in 79% of all strains tested, half and one-fifth of all strains tested presented, s1am2 and s1m1 alleles of vacA gene, respectively. Independently from identity or diversity of pre- and post-treatment strains and strains recovered from the family members we have been observed identical cagPAI/vacA genotypes. These results suggest that H. pylori infections in Poland can be mixed, although just one strain may often predominate, and that inter-family transmission may be significant even in this high risk society. The genetic feature of virulence-associated loci are similar to those seen elsewhere in Europe, although strains that carry the cagPAI and the potentially more toxigenic alleles of the vacA gene are more common. RAPD technique is proven as most differentiating, however PCR-RFLP allows for easy recognition of mixed infection with two or more different strains. Molecular typing study in case of children therapy may allow reduce rate of relapses by reduction of possible transmission from family source.     

Determinants of non-toxicity in the gastric pathogen Helicobacter pylori

The Helicobacter pylori vacuolating cytotoxin gene, vacA, is naturally polymorphic, the two most diverse regions being the signal region (which can be type s1 or s2) and the mid region (m1 or m2). Previous work has shown which features of vacA make peptic ulcer and gastric cancer-associated type s1/m1 and s1/m2 strains toxic. vacA s2/m2 strains are associated with lower peptic ulcer and gastric cancer risk and are non-toxic. We now define the features of vacA that determine the non-toxicity of these strains. To do this, we deleted parts of vacA and constructed isogenic hybrid strains in which regions of vacA were exchanged between toxigenic and non-toxigenic strains. We showed that a naturally occurring 12-amino acid hydrophilic N-terminal extension found on s2 VacA blocks vacuolating activity as its removal (to make the strain s1-like) confers activity. The mid region of s2/m2 vacA does not cause the non-vacuolating phenotype, but if VacA is unblocked, it confers cell line specificity of vacuolation as in natural s1/m2 strains. Chromosomal replacement of vacA in a non-toxigenic strain with vacA from a toxigenic strain confers full vacuolating activity proving that this activity is entirely controlled by elements within vacA. This work defines why H. pylori strains with different vacA allelic structures have differing toxicity and provides a rational basis for vacA typing schemes.     

Claritromycin resistance and Helicobacter pylori genotypes in Italy

The relationship between H. pylori clarithromycin resistance and genetic pattern distribution has been differently explained from different geographic areas. Therefore, we aimed to assess the clarithromycin resistance rate, to evaluate the bacterial genetic pattern, and to search for a possible association between clarithromycin resistance and cagA or vacA genes. This prospective study enrolled 62 consecutive H. pylori infected patients. The infection was established by histology and rapid urease test. Clarithromycin resistance, cagA and vacA status, including s/m subtypes, were assessed on paraffin-embedded antral biopsy specimens by TaqMan real time polymerase chain reaction (PCR). Primary clarithromycin resistance was detected in 24.1 % of cases. The prevalence of cagA was 69.3 %, and a single vacA mosaicism was observed in 95.1 % cases. In detail, the s1m1 was observed in 23 (38.9 %) patients, the s1m2 in 22 (37.2 %), and the s2m2 in 14 (23.7 %), whereas the s2m1 combination was never found. The prevalence of cagA and the vacA alleles distribution did not significantly differ between susceptible and resistant strains. Primary clarithromycin resistance is high in our area. The s1m1 and s1m2 are the most frequent vacA mosaicisms. There is no a relationship between clarithromycin resistance and bacterial genotypic pattern and/or cagA positivity.     

Prevalence of Helicobacter pylori pathogenicity-associated cagA and vacA genotypes among Pakistani dyspeptic patients

The cytotoxin-associated gene A ( cagA ), and the vacuolating cytotoxin gene A ( vacA ) products are considered the most important pathogenic determinants of Helicobacter pylori , a gram-negative bacterium causing gastrointestinal disorders such as duodenal ulcers, gastritis and mucosa-associated lymphoid tissue disease. A higher prevalence of H. pylori has been reported in various regions in the Pakistani population; however, no data are available about the virulence-associated genetic determinants. The objective of this study was to determine the prevalence of virulence-associated genes, cagA, vacA and particularly vacA allelic variants among dyspeptic patients from Pakistan. Gastric biopsy samples were obtained from 78 adult patients presenting dyspepsia symptoms. DNA was isolated and analyzed for the presence of H. pylori and its genotypes by PCR. Genus-specific PCR involving 16S rRNA gene revealed that 66 of the 78 patients were positive for H. pylori , an overall prevalence of 84.6% for this particular study. The most common vacA genotype was s1b/m2 (54.5%) followed by s1a/m1 (19.7%). cagA was positive in 24.2% of the cases and strongly associated with s1a/m1, vacA . The prevalence of virulent cagA , and vacA allelic form s1a/m1 was lower than that reported from neighboring countries.     

Prevalence of Helicobacter pylori vacA, cagA, cagE, iceA, babA2 genotypes and correlation with clinical outcome in Turkish patients with dyspepsia

BACKGROUND: Distinct virulence factors of Helicobacter pylori have been associated with clinical outcome of the infection; however, considerable variations have been reported from different geographic regions and data on genotypes of Turkish H. pylori isolates are sparse. AIM: To determine the prevalence of specific genotypes of H. pylori in Turkish patients with dyspepsia. MATERIALS AND METHODS: Ninety-three H. pylori-positive patients [30 with non-ulcer dyspepsia (NUD), 30 with duodenal ulcer (DU), and 33 with gastric cancer (GC)] who were admitted to our endoscopy unit due to dyspepsia were enrolled in the study. H. pylori infection was confirmed in all patients by histology and rapid urease test (RUT). The presence of vacA alleles, cagA, cagE, iceA, and babA2 genotypes were determined by polymerase chain reaction (PCR). Chi-squared test and Fisher's exact test were used for statistical comparisons and multivariate regression analysis was performed to find out independent predictors of different clinical outcomes. RESULTS: Turkish strains examined predominantly possessed the vacA s1,m2 (48.4%) and s1,m1 (40.7%) genotypes. The vacA s1a genotype was detected in 66.7, 96.4, and 87.9% of isolates from patients with NUD, DU, and GC, respectively, and its presence was significantly associated with that of DU (p = .004), GC (p = .043), and cagA gene (p = .021). None of the cases was found to harbor the s1c genotype. The frequencies of the cagA and cagE genes among studied isolates were 73.6 and 59.3%, respectively. The cagA gene was significantly associated with the presence of DU (p = .004) and GC (p = .003), and the cagE gene, too, was significantly associated with the presence of DU (p = .002) and GC (p = .000). All H. pylori isolates possessed the iceA gene. In all, 68 isolates (74.7%) were positive for iceA1 and 23 (25.3%) for iceA2. The frequency of icea1 gene was significantly higher in cases with GC (85%) than in cases with NUD (60%) (p = .026). The frequency of babA2 gene was 23.3, 46.4, and 87.9% in isolates of patients with NUD, DU, and GC, respectively. When compared to cases with NUD (p = .000) and DU (p = .000), the presence of babA2 gene was significantly higher in cases with GC. Multivariate regression analysis disclosed cagE (p = .006) and vacA s1a (p = .027) genotypes to be independent predictors of DU and babA2 (p = .000) and cagE (p = .013) genotypes to be independent predictors of GC. CONCLUSIONS: H. pylori vacA s1a, cagA, cagE genotypes have significant relations with the presence of DU and GC, and iceA1, babA2 with GC in Turkish patients with dyspepsia, whereas cagE and vacA s1a genotypes are independent predictors of DU, and babA2 and cagE genotypes are independent predictors of GC.     

Genotypic,phenotypic, and clinical characteristics of isolates of<Emphasis Type="Italic">Helicobacter pylori</Emphasis> from San Luis,Argentina

The vacA and cagA genotypes of Helicobacter pylori exhibited distinct geographic distribution and correlation with severity of disease. In the above genotypes (obtained from 150 H. pylori-positive patients--139 with gastritis, 10 with ulcer and 1 patient with gastric cancer) combinations vacA s1/m1 and s2/m2 were detected using PCR in 75 and 25% of isolates, respectively, in patients with chronic gastritis. The of s1/m1 and s2/m2 combinations were also detected from ulcers (60 and 40%, respectively). The cagA was detected in 30% of isolates. Concentrated culture supernatants of 7 (64%) out of 11 H. pylori strains induced vacuolization in Vero cells in titers ranging from 1:5 to 1:40. The vacA s1 genotype was significantly associated with, but not predictive of the presence of vacuolating cytotoxin activity and the cagA gene.     

Distinctiveness of genotypes of Helicobacter pylori in Calcutta, India

The genotypes of 78 strains of Helicobacter pylori from Calcutta, India (55 from ulcer patients and 23 from more-benign infections), were studied, with a focus on putative virulence genes and neutral DNA markers that were likely to be phylogenetically informative. PCR tests indicated that 80 to 90% of Calcutta strains carried the cag pathogenicity island (PAI) and potentially toxigenic vacAs1 alleles of the vacuolating cytotoxin gene (vacA), independent of disease status. This was higher than in the West (where cag PAI(+) vacAs1 genotypes are disease associated) but lower than in east Asia. The iceA2 gene was weakly disease associated in Calcutta, whereas in the West the alternative but unrelated iceA1 gene at the same locus is weakly disease associated. DNA sequence motifs of vacAm1 (middle region) alleles formed a cluster that was distinct from those of east Asia and the West, whereas the cagA sequences of Calcutta and Western strains were closely related. An internal deletion found in 20% of Calcutta iceA1 genes was not seen in any of approximately 200 strains studied from other geographic regions and thus seemed to be unique to this H. pylori population. Two mobile DNAs that were rare in east Asian strains were also common in Calcutta. About 90% of Calcutta strains were metronidazole resistant. These findings support the idea that H. pylori gene pools differ regionally and emphasize the potential importance of studies of Indian and other non-Western H. pylori populations in developing a global understanding of this gastric pathogen and associated disease.     

Binding of lactoferrin and free secretory component to enterotoxigenic Escherichia coli

To compare the genomic variation of Helicobacter pylori in samples obtained from patients with perforated peptic ulcer, living in the same area of Estonia but belonging to different nationalities, 50 non-consecutive patients (32 Estonians and 18 Russians) admitted in the Tartu University Hospital in 1997-1999 were studied. Gastric samples of antral mucosa were obtained during operation and analysed histologically and with PCR for detection of different genotypes of H. pylori (cagA and vacA s and m subtypes). Among the 50 perforated peptic ulcer patients with histologically proven H. pylori colonisation no sample of gastric mucosa showed the s1b subtype of the vacA gene. The perforated peptic ulcer patients were mainly infected with cagA (82%) and s1 (98%) genotypes of H. pylori. The distribution of s1a/m1, s1a/m2 and s2/m2 subtypes of vacA genes was statistically different in Estonian and Russian patients (P<0.05). In conclusion differences in the distribution of vacA s and m subtypes of H. pylori were revealed between Estonian and Russian patients with perforated peptic ulcer from Southern Estonia.     

Evolution of functional polymorphism in the gene coding for the Helicobacter pylori cytotoxin

There are two functionally different alleles of the Helicobacter pylori vacA gene, which code for proteins with different in target cell specificity. The alleles (m1 and m2) differ by approximately 50% in amino acid sequence in a 300 amino acid region, the m-region, which determines specificity. An analysis of partial likelihood anomalies in a set of eight Chinese and six Western vacA genes revealed highly significant phylogenetic deviation of a region of the gene including the m-region. Phylogenetic analysis of the conserved regions of these genes failed to reveal any distinction between m1 alleles and m2 alleles, however clear cut geographic variation was observed. In the m-region, the m1 alleles also show separate clustering of Chinese and Western isolates, however the m-region of the m2 alleles has a phylogenetic structure markedly different from the rest of the gene. The data indicate that the m2 m-region was acquired and spread through the population by horizontal transfer of DNA.     

cagA gene and vacA alleles in Spanish Helicobacter pylori clinical isolates from patients of different ages

The prevalence of the cagA gene and vacA alleles in 124 Spanish Helicobacter pylori clinical isolates from patients of different ages ranging from 3 to 78 years was studied (21 patients < or = 10 years, 30 patients 11-20 years, 17 patients 21-40 years, 31 patients 41-60 years and 25 patients 61-80 years). The cagA gene and vacA s1 or vacA s2 alleles were identified by PCR from the strain. 66.9% of the isolates were cagA+ and 33.1% cagA-. vacA s1 was detected in 48.4% of the isolates and vacA s2 in 51.6%. 44.4% of patients were cagA+/vacA s1, 22.5% were cagA+/vacA s2, 4% were cagA-/vacA s1 and 29% were cagA-/vacA s2. The percentage of cagA+ isolates and the vacA s1 alleles in the different groups were as follows: 23.8% and 28.6% in 0-10 years, 40% and 30% in 11-20 years, 88.2% and 70.6% in 21-40 years, 90.3% and 70.9% in 41-60 years and 92% and 44% in the 61-78 years group. 93% (54/58) of isolates found in ulcer patients and 90.9% (10/11) of isolates from gastritis patients older than 20 years were cagA+. In patients younger than 20 years ulcer disease was rare with 60% of isolates being cagA+ (3/5) compared with 31.6% cagA+ isolates (12/38) in patients suffering from gastritis in the younger group. The prevalence of the cagA gene and vacA s1 allele increased with age, being more frequent in older patients than in younger.     

Genotyping of cagA and vacA, Lewis antigen status, and analysis of the poly-(C) tract in the alpha(1,3)-fucosyltransferase gene of Irish Helicobacter pylori isolates

Much work has focused on trying to identify markers in Helicobacter pylori that might allow the eventual disease outcome of an infection to be predicted. In this study we examined the cagA and vacA genotype, and Lewis status in a panel of 43 Irish H. pylori clinical isolates, and investigated a possible correlation with disease pathology. In addition, differences in the poly-(C) tract of the alpha(1,3)-fucosyltransferase gene were examined to identify a possible correlation with gene expression. Only three of 43 isolates were cagA-negative, whereas the remaining 40 isolates, independent of pathology, were cagA-positive. In all the strains we examined, the vacA signal-sequence was type s1a. For the vacA mid-region 12/43 isolates were type m1 and 31/43 isolates were type m2. These data, and examination of isolates from different pathology groups, suggests that there is no correlation between virulence and vacA genotype in the Irish population of H. pylori isolates. Western blotting of whole cell lysates from 32 H. pylori isolates showed 3/32 displayed only the Le(x) epitope, 12/32 only the Le(y), 13/32 both epitopes and 4/32 neither epitope. No apparent association between Lewis phenotype and disease pathology was evident. A range of lengths of poly-(C) tract were observed in the alpha(1, 3)-fucosyltransferase gene, however the length of the tract in an isolate did not correlate with the Lewis structures present. We conclude that future studies on H. pylori pathogenesis should not alone focus on the importance of molecular markers, but also on the host response, including genetic background and immune responsiveness.     

Diversity of Helicobacter pylori cagA and vacA genes in Costa Rica: its relationship with atrophic gastritis and gastric cancer

BACKGROUND: Associations between Helicobacter pylori gene diversity and gastric cancer have not been reported on in Costa Rica, despite its being one of the countries with the highest gastric cancer incidence and mortality rates in the world. The aim of this study was to determine the prevalence of H. pylori cagA and vacA genes and investigate whether it could be correlated with atrophic gastritis (AG) and gastric cancer (GC) in Costa Rica. MATERIALS AND METHODS: Genomic DNAs from isolates of 104 patients classified into two groups: non-atrophic gastritis group (n = 68) and atrophic gastritis group (n = 36), were subjected to PCR-based genotyping of cagA and vacA genes and their correlation with clinical outcome was investigated. Total DNA extractions from gastric tissues of 25 H. pylori-infected gastric cancer patients were utilized for comparative purposes. RESULTS: The presence of cagA (75.3%), vacA s1b (75.3%), and vacA m1 (74.2%) was detected, and colonization by strains with different vacA genotypes in the same stomach was found in 9.7% of the patients. Age- and sex-adjusted vacA s1b and vacA m1 were associated with GC while only vacA m1 was significantly associated with AG. A tendency for association between cagA and vacA s1b, and AG was reported. CONCLUSIONS: The prevalence status of the cagA and vacA (s1/m1) genes in Costa Rica seems to fall between that found in European/North American and East Asian countries, and both cagA and vacA seem to have clinical relevance in this country.     

A model of Helicobacter pylori persistence in a case of gastric cancer

The aim of this work was to analyze several clones of Helicobacter pylori isolated from a patient with gastric cancer, to evaluate i) genetic variability ii) virulence factors profile and iii) antimicrobial susceptibility against the drugs commonly used in the H. pylori therapy. A total of 32 H. pylori clones isolated from a biopsy sample coming from a patient with gastric cancer previously treated for H. pylori infection, were analyzed for: the genetic variability by amplified fragment polymorphism analysis; the vacA, cagA virulence status by PCR; the antimicrobial susceptibility by minimum inhibitory concentrations with the agar dilution method towards amoxicillin, clarithromycin, levofloxacin and tinidazole. The patient showed a mixed infection with the presence of at least 3 different strains. The clones isolated possessed the vacA, cagA virulence factors with a different allelic combination (vacA s1/i1/m1; s1/i1i2/m1; s2/i2/m2; s2/i1i2/m2) together with repeated cagA EPIYA motif pattern P1P2P3P3P3. Moreover, a pattern of multi-drug resistance was disclosed in the different clones. The presence of multiple H. pylori strains colonizing the same patient, with the main virulence factors displaying a different allelic combination and a different multi-drug resistance among isolates, point out the role of genetic variability generating, in time, more virulent and adapted strains.     

幽门螺杆菌vacA和cagA基因全长分子系统发育分析

文章从GenBank中下载所有含有vacA和cagA基因的H.pylori菌株的VacA和CagA全长氨基酸序列,利用ClastalX 2.0和MEGA 5.05软件构建VacA和CagA分子系统发育树,探讨两基因之间的分子系统发育关系和不同聚类群的临床感染结果与基因型特征。结果显示,VacA和CagA具有高度相似的分子系统发育树,并且所有H.pylori菌株在系统发育树中具有相同的分布特点,分别聚类为东亚株群1、2和西方株群3个聚类群。其中东亚株群1患萎缩性胃炎比例较高,vacA基因型以s1c/m1b和s1a/m1b为主,cagA基因型以EPIYA-ABD为主;东亚株群2患十二指肠溃疡的比例较高,vacA基因型以s1c/m2和s1a/m2为主,cagA基因型以EPIYA-AB’C为主;西方株群患十二指肠溃疡和胃炎的比例相当,萎缩性胃炎比例较低,vacA基因型以s1a/m1a和s1b/m1a为主,cagA基因型以EPIYA-AB/B’CC为主。这些结果说明,vacA和cagA基因可能具有共进化的遗传关系;东亚株群1、2和西方株群分别具有不同的vacA和cagA基因亚型,这可能与其临床感染结果密切相关,因此,在进行H.pylori相关性疾病分析时,有必要结合vacA和cagA基因型的亚型做深入分析。