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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

兰州地区幽门螺杆菌分离株主要毒力基因的研究

本文首次报道了兰州地区胃病患者幽门螺杆菌分离株主要毒力基因ｕｒｅＡ ｖａｃＡ 和ｃａｇＡ的 ＰＣＲ 检测情况。共获 ４１ 株Ｈｐ 分离株,分别来自于慢性胃炎病人（３２ 株）、胃－十二指肠溃疡病人（７株）和胃癌病人（２ 株）。检测结果表明,４１ 株Ｈｐ 分离株的ｕｒｅＡ,ｖａｃＡ 及ｃａｇＡ 的阳性率分别为１００％ ,１００％ 和９７．６％ ;含有ｕｒｅＡ,ｖａｃＡ 和ｃａｇＡ 基因的Ｈｐ 与人类胃部疾患密切相关,而ｃａｇＡ 基因的存在可能与更加严重的胃部疾病有关。Ｈｐ 毒力基因的检测结果与其它地区Ｈｐ 分离株的检测结果相似。作者建议,对ｕｒｅＡ 基因的ＰＣＲ 检测可以作为鉴定Ｈｐ 的一个指标。     

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.     

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.     

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。     

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.     

The diversity of vacA and cagA genes of Helicobacter pylori in East Asia

It has been reported that Helicobacter pylori infection with the type I strain, which expresses the VacA and CagA antigens, is associated with duodenal ulcer. We examined the diversity of vacA and cagA genes in 143 isolates obtained from patients with duodenal ulcer or chronic gastritis in East Asia (two different areas of Japan, Fukui and Okinawa, and also in Hangzhou, China) by polymerase chain reaction (PCR) and sequence analysis. Diversities of cagA and vacA genes were detected in East Asia. The prevalence of cagA-positive H. pylori was significantly different between Fukui and Okinawa (P=0.0032). The prevalence of Western type CagA was significantly higher in Okinawa than in Fukui (P<0.0001). However, there was no significant association between the genotype of cagA and clinical outcome. In Japan, the predominant vacA genotype was s1c/m1b. In contrast, in Hangzhou, the predominant vacA genotype was s1c/m2, and they were all East Asian CagA-positive. These findings suggest that a distinct distribution of the vacA and cagA genotypes is present in East Asia, regardless of clinical outcome.     

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.     

The evaluation of vacA gene alleles frequency in Helicobacter pylori strains in children and adults in Podlaskie region

The frequency of Helicobacter pylori infection in population can depend on the organism resistance, genetic condition, and bacterial strains virulence. A vacA gene, of mosaic structure, which encodes vacuolating cytotoxin is one of the known genes of H. pylori. The existence of several different genotypes of s and m regions enables the formation of numerous combinations of vacA gene genome. The studies on vacA genotype revealed that the frequency of occurrence of H. pylori containing s1 or s2, as well as m1 and m2 alleles varies in different parts of the world. The aim of the studies performed in the group of children and adults was to evaluate the prevalence of particular vacA gene alleles distribution in the population of the Podlasie province. The allele s1, which occurred in 84.3% of the examined group (86.8% in children and 81.3% in adults), turned out to be the most frequently observed of the signal encoding region. Statistically significant differences in s1 and s2 alleles distribution in relation to a dwelling place were not detected. The allele m2 (42.1% in children and 59% in adults) was the allele of midregion, most frequently occurring in our studies. The allele m2 was observed more often in H. pylori strains in the inhabitants from the urban areas (data statistically significant).     

幽门螺杆菌毒力基因型与胃癌的相关性研究

目的:研究中国东部地区幽门螺杆菌(H.pylori)cagA、vacA和iceA1毒力基因型的分布状况及其与胃癌的相关性。方法:从52例病人胃黏膜活检组织(31例慢性浅表性胃炎,21例胃癌)中分离培养H.pylori,用PCR方法扩增分离菌株的cagA、iceA1、vacAs,i,m区毒力基因片段,统计并分析上述毒力因素与胃癌发生的相关性。结果:在52例菌株中,cagA、vacAs1/i1/m1、vacAs1/i1/m2和iceA1的阳性率分别是92.3%(48/52),48.1%(25/52),48.1%(25/52),90.4%(47/52);所有的胃癌分离株中均为cagA(+)vacAs1/i1(+)型,vacAm1、vacAm2和iceA1在胃癌组中的阳性率分别是47.6%(10/21),52.4%(11/21),95.2%(20/21),与胃炎组相比,上述基因型的阳性率差异均无显著统计学意义(P>0.05)。结论:cagA、vacAs1/i1/m1、vacAs1/i1/m2和iceA1是中国东部地区H.pylori的优势基因型;cagA、vacAs1、vacAi1和iceA1毒力基因型的存在与胃癌的发生无相关性。     

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 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.     

Determination of Helicobacter pylori vacA allelic types by single-step multiplex PCR

AIMS: To develop and evaluate a novel multiplex PCR assay that enables definition of Helicobacter pylori vacA allelic type in a single reaction. METHODS AND RESULTS: Application of the one-step system to DNA extracts from 22 cultures of known vacA genotype demonstrated that it was highly accurate. Analysis of 15 matched gastric biopsy/culture pairs generated exactly correlating genotype profiles. vacA genotypes were determined from an additional 62/70 gastric biopsies from dyspeptic patients of known H. pylori positive status by the one-step assay, compared with 63/70 by the original two-reaction test. Types s1/m1, s1/m2 and s2/m2 were identified in 51.9%, 31.2% and 16.9% of biopsies, respectively. CONCLUSIONS: The multiplex PCR system developed enables rapid one-step vacA genotyping that is accurate, easy to interpret and more economical than the alternative multiple-reaction tests. Application of this system to gastric biopsies from patients in South-east England demonstrated that s1/m1 was the most common genotype, while s1/m2 and s2/m2 were less prevalent. SIGNIFICANCE AND IMPACT OF THE STUDY: This simple one-step system can be applied direct to antral gastric biopsies without the need for culture, thereby facilitating rapid surveillance of vacA genotype in relation to geographical location and disease status.