Biomedical subjects

A van der Ende

Publications and source records attributed to A van der Ende.

At least 55 records · Page 3Linked to original sources

PubMed1999

Recombination and clonal groupings within Helicobacter pylori from different geographical regions.

A collection of 20 strains of Helicobacter pylori from several regions of the world was studied to better understand the population genetic structure and diversity of this species. Sequences of fragments from seven housekeeping genes (atpA, efp, mutY, ppa, trpC, ureI, yphC ) and two virulence-associated genes (cagA, vacA) showed high levels of synonymous sequence variation (mean percentage Ks of 10-27%) and lower levels of non-synonymous variation (mean percentage Ka of 0.2-5.6%). Cluster analysis of pairwise differences between alleles revealed the existence of two weakly clonal groupings, which included half of the strains investigated. All six strains isolated from Japanese and coastal Chinese were assigned to the 'Asian' clonal grouping, probably reflecting descent from a distinct common ancestor. The clonal groupings were not totally uniform; recombination, as measured by the homoplasy test and compatibility matrices, was extremely common within all genes tested, except cagA. The fact that clonal descent could still be discerned despite such frequent recombination possibly reflects founder effects and geographical separation and/or selection for particular alleles of these genes.

Aldose-Ketose Isomerases↗

PubMed1999

Relation between vacA subtypes, cytotoxin activity, and disease in Helicobacter pylori-infected patients from The Netherlands.

OBJECTIVE: The vacuolating cytotoxin of Helicobacter pylori (H. pylori) is encoded by vacA, of which allelic variation has been described. In the U.S., H. pylori strains with the signal sequence allele s1a are associated with enhanced gastric inflammation and with peptic ulcer disease (PUD). The m1 middle region allele is linked with more severe gastric epithelial damage. However, the distribution of H. pylori genotypes and the association with disease may be different in other geographical areas. The aim of this study was to establish whether vacA types among H. pylori isolates from Dutch patients are associated with disease. METHODS: The cytotoxin activity of the H. pylori isolates from 34 PUD patients and 46 patients with functional dyspepsia (FD) was assessed by an in vitro assay using HeLa cells as indicator cells. The vacA types and cagA status of the isolates were assessed by polymerase chain reaction (PCR). RESULTS: vacA s1-type H. pylori displayed cytotoxin activity more frequently than s2 vacA-type H. pylori (p = 0.003). This difference was not significant when only cagA+ H. pylori were considered. H. pylori isolates with the m1 vacA type exhibited a higher cytotoxin activity, independent of cagA (p = 0.006). Ninety-four percent (32/34) of the PUD patients and 74% (34/46) of the FD patients were infected with s1 vacA-type H. pylori (p = 0.04). When only cagA+ H. pylori were considered, s1 vacA type was not associated with disease. In addition, neither the s1a nor s1b subtypes correlated with disease. CONCLUSIONS: An association between vacA subtypes and disease could not be established in this patient population, due to the strong linkage between vacA s1 type and cagA.

Antigens, Bacterial↗

PubMed1999

Helicobacter pylori heat shock protein A: serologic responses and genetic diversity.

Helicobacter pylori synthesizes an unusual GroES homolog, heat shock protein A (HspA). The present study was aimed at an assessment of the serological response to HspA in a group of Chinese patients with defined gastroduodenal pathologies and determination of whether diversity is present in the nucleotide sequences encoding HspA in isolates from these patients. Serum samples collected from 154 patients who had an upper gastrointestinal pathology and the presence of H. pylori defined by biopsy were tested for an immunoglobulin G (IgG) serologic response to H. pylori HspA by an enzyme linked immunosorbant assay. HspA-encoding nucleotide sequences in H. pylori isolates from 14 patients (7 seropositive and 7 seronegative for HspA) were analyzed by PCR and direct sequencing of the PCR products. The sequencing results were compared to those of 48 isolates from other parts of the world. Of the 154 known H. pylori-positive patients, 54 (35.1%) were seropositive for HspA. The A domain (GroES homology) of HspA was highly conserved in the 14 isolates tested. Although the B domain (metal-binding site unique to H. pylori) resembled that in the known major variant, particular amino acid substitutions allowed definition of an HspA variant associated with isolates from East Asia. There were no associations between patient characteristics and HspA seropositivity or amino acid sequences. We confirmed in this study that the clinical outcomes of H. pylori infection are not related to HspA antigenicity or to sequence variation. However, B-domain sequence variation may be a marker for the study of the genetic diversity of H. pylori strains of different geographic origins.

Adult↗

PubMed1999

Deletion of porA by recombination between clusters of repetitive extragenic palindromic sequences in Neisseria meningitidis.

PorA is an important component in a vaccine against infection with Neisseria meningitidis. However, porA-negative meningococci were isolated from patients, thereby potentially limiting the role of PorA-mediated immunity. To analyze the mechanism by which the porA deletion occurred, the regions upstream and downstream of porA from three meningococcal strains (H44/76, H355, and 860183) were sequenced. The porA upstream region in strain 860183 contains a cluster of 22 repetitive palindromic RS3 core sequences (ATTCCC-N8-GGGAAT) and 10 RS3 core sequences (ATTCCC) in direct orientation. The cluster is flanked by neisserial repeats, so-called Correia elements, and can be subdivided into three repeats of 518 bp followed by a truncated repeat. The porA upstream region of the other two strains showed deletions, probably caused by a recombination between RS3 core sequences. The porA downstream region of H44/76 and H355 contains the IS1106 element followed by a cluster of 10 palindromic RS3 core sequences, 4 RS3 core sequences, and 1 other RS3 core sequence (GGGAAT) and is followed by a Correia element. This cluster can be subdivided into four direct repeats of 370 bp. Strain 860183 had two such repeats instead of four. Sequence analysis of the porA-negative variants indicated that the deletion of porA occurred via a recombination between two copies of the 116-bp region, containing two palindromic RS3 core sequences and a single RS3 core sequence. This region is homologous in the upstream and downstream clusters.

Base Sequence↗

PubMed1999

Antigenic variation of the class I outer membrane protein in hyperendemic Neisseria meningitidis strains in the netherlands.

Since 1980, the number of cases of meningococcal disease caused by serogroup B isolates with the P1.4 serosubtype has greatly increased in The Netherlands. Screening for this serosubtype in the strain collection of The Netherlands Reference Laboratory for Bacterial Meningitis revealed that a low number of P1.4 strains had been present in the Dutch meningococcal population since 1965. Genotyping of P1.4 strains showed that one cluster of strains, the hyperendemic lineage III (D. A. Caugant et al., J. Infect. Dis. 162:867-874, 1990), is responsible for the increase since 1980. The diversity of the porA genes, which encode the P1 protein on which serosubtyping is based, was studied for genotypically different P1.4 strains and for lineage III strains expressing antigenically different P1 proteins. Sequence analysis showed that porA genes of genotypically distinct strains that express antigenically indistinguishable P1 proteins are identical only in the epitope-encoding region, suggesting that this region has spread through the meningococcal population via horizontal gene transfer. Analysis of porA genes of lineage III strains showed that both horizontal gene transfer and partial deletion of the epitope-encoding region may contribute to the different antigenic properties for P1 of these strains. Phase variation of expression of the porA gene seems to account for most nonreacting strains. These results show that serosubtyping may underestimate the rise of a hyperendemic clone.

Amino Acid Sequence↗

PubMed1999

Interobserver variation in the histopathological scoring of Helicobacter pylori related gastritis.

AIM: To test the reproducibility between two histopathologists of features of Helicobacter pylori gastritis, using the updated Sydney classification. METHODS: 290 dyspeptic Dutch patients with biopsy proven H pylori infection were enrolled in the study. Gastric antral mucosal biopsy specimens were analysed before and after H pylori eradication treatment. The biopsies were scored semi-quantitatively by two histopathologists, according to the updated Sydney classification system. Variables analysed included the density of H pylori infection, the degree of chronic inflammation, inflammatory activity, atrophy, intestinal metaplasia, and surface epithelial damage. Before grading biopsy specimens, both pathologists reached a consensus on the scoring of gastritis through interactive sessions using a multiheaded microscope. Subsequently all biopsy specimens were graded. Interobserver variability was also analysed using weighted kappa scores. RESULTS: For interobserver agreement on scoring the various gastritis features a high degree of reproducibility was reached overall. Agreement on grading of atrophy was the lowest; however, moderate to good reproducibility was achieved, with weighted kappa values of 0.49 in the pretreatment biopsies and 0.52 in the post-treatment biopsies. Disagreement was most common in biopsy specimens with lesser degrees of atrophy. A high degree of agreement was obtained for intestinal metaplasia, with weighted kappa values of 0.72 in the pretreatment biopsies and 0.73 in the post-treatment biopsies. The best agreement was reached in the assessment of the density of H pylori both before and after H pylori eradication treatment, with excellent weighted kappa values of 0.76 and 0.95, respectively. The grade of reproducibility of inflammatory activity, superficial epithelial damage, and chronic inflammation was high, with weighted kappa values varying from 0.60 to 0.76 and 0.62 to 0.83 before and after eradication, respectively. CONCLUSIONS: Reproducibility of grading H pylori related gastritis is high using the updated Sydney system. Despite the novel criteria for scoring atrophy, there was imperfect agreement on this feature between two independent histopathologists.

Biopsy↗

PubMed1998

Prevalence of vacuolating cytotoxin production and distribution of distinct vacA alleles in Helicobacter pylori from China.

Studies of Helicobacter pylori from the West have linked production of vacuolating cytotoxin and a particular signal sequence (s1a) allele of the underlying vacA gene to peptic ulcer disease (PUD). Among Chinese H. pylori, most isolates from both PUD and gastritis patients were toxigenic (35/46 and 29/35, respectively). Polymerase chain reaction and DNA sequencing showed that 95 of 96 isolates carried vacA s1a alleles. In the mid-region, 78 of 96 isolates carried m2; 14 were m1-like but only 87% identical (DNA-level) to classical m1 and were designated m1b; the other 4 were unusual hybrids (m1b-type proximal, m2-type distal). Isolates with m1b and m1b-m2 alleles produced higher levels of vacuolating activity than did isolates with m2 alleles (P < .01). There was no association between any vacA allele and disease. These results suggest that the composition of H. pylori gene pools varies geographically and that other as-yet-unknown polymorphic H. pylori genes are important in PUD.

Alleles↗

PubMed1998

cagA-positive Helicobacter pylori populations in China and The Netherlands are distinct.

The aim of this research was to study whether and to what extent Chinese cagA-positive Helicobacter pylori isolates differ from those in The Netherlands. Analysis of random amplified polymorphic DNA (RAPD)-PCR-assessed DNA fingerprints of chromosomal DNA of 24 cagA-positive H. pylori isolates from Dutch (n = 12) and Chinese (n = 10) patients yielded the absence of clustering. Based on comparison of the sequence of a 243-nucleotide part of cagA, the Dutch (group I) and Chinese (group II) H. pylori isolates formed two separate branches with high confidence limits in the phylogenetic tree. These two clusters were not observed when the sequence of a 240-bp part of glmM was used in the comparison. The number of nonsynonymous substitutions was much higher in cagA than in glmM, indicating positive selection. The average levels of divergence of cagA at the nucleotide and protein levels between group I and II isolates were found to be high, 13.3 and 17.9%, respectively. Possibly, the pathogenicity island (PAI) that has been integrated into the chromosome of the ancestor of H. pylori now circulating in China contained a different cagA than the PAI that has been integrated into the chromosome of the ancestor of H. pylori now circulating in The Netherlands. We conclude that in China and The Netherlands, two distinct cagA-positive H. pylori populations are circulating.

Antigens, Bacterial↗

PubMed1998

Randomly amplified polymorphic DNA genotyping of serogroup A meningococci yields results similar to those obtained by multilocus enzyme electrophoresis and reveals new genotypes.

Randomly amplified polymorphic DNA (RAPD) genotyping was applied to one representative strain of each of the 84 electrophoretic types (ETs) of Neisseria meningitidis serogroup A previously defined by multilocus enzyme electrophoresis (MEE) (J.-F. Wang et al., Infect. Immun. 60:5267-5282, 1992). Twenty-seven additional isolates comprising six ETs were also tested. MEE and RAPD genotyping yielded similar dendrograms at the subgroup level. Similar results were obtained by both methods for 18 serogroup A meningococci isolated in The Netherlands between 1989 and 1993. Ten of these isolates defined a new subgroup, designated subgroup IX. One isolate belonged to the ET-5 complex, normally associated with serogroup B strains (D. A. Caugant et al., Proc. Natl. Acad. Sci. USA 83:4927-4931, 1986). By RAPD genotyping, meningococci can be linked to previously characterized genotypes by using a computerized database, and dendrograms based on cluster analyses can easily be generated. RAPD analysis offers advantages over MEE since intermediate numbers of isolates of serogroup A meningococci can quickly be assigned to known subgroups and new subgroups can be defined.

Bacterial Typing Techniques↗

PubMed1998

Influence of metronidazole resistance on efficacy of quadruple therapy for Helicobacter pylori eradication.

BACKGROUND: Metronidazole-containing eradication therapies are less effective for metronidazole resistant Helicobacter pylori. Although early data suggested improvement of the efficacy of bismuth triple therapy after the addition of acid suppressives, these findings were based on studies with small numbers of patients, incomplete post-eradication follow up, or omission of pretreatment susceptibility testing. AIMS: To study the efficacy of quadruple therapy in the Amsterdam area, where the efficacy of bismuth triple therapy has been proved to be affected by metronidazole resistance. PATIENTS AND METHODS: Eighty two consecutive dyspeptic H pylori positive patients with either metronidazole susceptible (group I) or metronidazole resistant H pylori strains (group II) received quadruple therapy for one week: omeprazole 20 mg twice daily; colloidal bismuth subcitrate 120 mg four times a day; tetracycline 500 mg four times a day; metronidazole 500 mg three times a day. Susceptibility to metronidazole was determined by the E-test. RESULTS: Intention to treat analysis showed that H pylori infection had been cured in 42/43 patients (98%) in group I and 32/39 patients (82%) in group II (p = 0.02). CONCLUSION: The efficacy of quadruple therapy is significantly impaired in patients infected with metronidazole resistant H pylori. Therefore a non-metronidazole-containing regimen should preferably be used in areas known to have a high prevalence of pretreatment metronidazole resistance.

Adult↗

PubMed1997

Effect of Helicobacter pylori eradication on gastritis in relation to cagA: a prospective 1-year follow-up study.

BACKGROUND & AIMS: Whether Helicobacter pylori eradication resolves intestinal metaplasia and atrophy and whether infection with cagA+ H. pylori is related to a specific clinical outcome are not known. The aim of this study was to investigate the role of H. pylori eradication on the course of intestinal metaplasia (IM) and atrophy in relation to cagA. METHODS: In a large prospective study, the cagA status of H. pylori isolated from consecutive dyspeptic patients was related to clinical outcome before and 1 year after successful eradication of H. pylori. At pretreatment and 4-6 weeks and on average 1 year after eradication therapy, the degree of gastritis and the status of H. pylori were assessed by culture and histopathology. RESULTS: Specimens of cagA+ H. pylori were recovered from 122 of 155 (79%) patients infected with H. pylori. Pretreatment degrees of gastritis activity, superficial epithelial damage, IM, and atrophy were significantly greater in patients infected with cagA+ H. pylori (P < 0.001). After successful eradication of H. pylori, a significant improvement of activity of gastritis and superficial epithelial damage occurred (P < 0.001), but the degree of IM and atrophy did not change, irrespective of the cagA status. CONCLUSIONS: The usefulness of H. pylori eradication to revert precancerous lesions such as IM and atrophy after 1-year follow-up is questionable.

Amoxicillin↗

PubMed1997

Effect of nationwide vaccination of 3-month-old infants in The Netherlands with conjugate Haemophilus influenzae type b vaccine: high efficacy and lack of herd immunity.

OBJECTIVE: The effect of nationwide vaccination in The Netherlands with conjugate Haemophilus influenzae type b vaccine on the incidence of H. influenzae meningitis was assessed in the first 3 years after the introduction of vaccination to the birth cohort at 3 months of age. STUDY DESIGN: Children in The Netherlands born after April 1, 1993, were vaccinated at the age of 3, 4, 5, and 11 months. Children older than 3 months at the inception of the H. influenzae type b vaccination program were not immunized. The number of cases among the vaccine cohort was compared with the number in a historical control group of children born in the period April 1, 1990, and April 1, 1993. RESULTS: The total number of patients with meningitis caused by H. influenzae type b reached a low, but constant level, that was expected for absence of herd immunity. Among children in the vaccine era group 22 cases occurred, whereas among the historical control group (prevaccine era) 342 cases were found. In the vaccine era cohort, 2 patients with H. influenzae type b meningitis had been vaccinated three times, 13 received one or no vaccine dose because of their age, and 7 were not vaccinated for religious or logistic reasons. The number of cases among nonvaccinated children older than 3 years and the number of H. influenzae meningitis cases caused by strains other than type b did not change. CONCLUSIONS: Conjugate H. influenzae type b vaccine prevents H. influenzae type b meningitis very effectively (99.4%) in children vaccinated twice or more. To reach rapid prevention of all H. influenzae type b disease simultaneous introduction of H. influenzae type b vaccination of children at various ages is recommended.

Cohort Studies↗

PubMed1997

Reinfection versus recrudescence in Helicobacter pylori infection.

Antimicrobial treatment of Helicobacter pylori is the proper management strategy in patients with ulcers. A high rate of H. pylori reinfection after successful eradication therapy however, may give rise to ulcer recurrence. The risk of reinfection, depending on the prevalence and the rate of acquisition of H. pylori infection, varies with socioeconomic status, age and geographical location. The rate of reinfection may vary in a similar way. The available data in the literature reveal that reinfection by H. pylori is low or absent in developed countries and may be lower than the initial rate of acquisition. In addition, reported cases of H. pylori reinfection are often cases of recrudescent H. pylori infection. Acquisition rate in developing countries is high, so the reinfection rate is expected to be higher than in developed countries. However, studies discriminating reinfection from recrudescence are lacking and therefore more data from developing regions are needed to settle if 'cured once, cured forever' holds true.

Age Factors↗

PubMed1997

Helicobacter pylori reinfection is virtually absent after successful eradication.

This study examined whether reinfection or recrudescence accounts for the reappearance of Helicobacter pylori infection after apparent successful eradication. In a prospective study, 173 patients cured from H. pylori infection underwent follow-up endoscopies, with biopsies for culture and histopathology, every 3 months during the first year after treatment. Subsequently, elective half-yearly endoscopies were performed in 124 patients; the remaining 49 underwent follow-up endoscopy only in 1995. At reappearing infection, DNA profiles of pretreatment and recurrent strains were compared. After 3.5 years (range, 1.0-9.2), H. pylori infection recurred in 9 patients (5.2%). Reappearing infections were classified as endoscopically transmitted reinfection (n = 2), unclassified because of loss of pretreatment isolate (n = 1), or recrudescence (identical DNA patterns before and after treatment; n = 6). The reappearance rate of infection, discarding endoscopic transmission, was 1.2% (7/601 H. pylori-negative patient-years). There was virtually no reinfection with H. pylori after eradication in this adult Western population. These data do not rule out acquisition of H. pylori.

Adult↗

PubMed1997

Equally high prevalences of infection with cagA-positive Helicobacter pylori in Chinese patients with peptic ulcer disease and those with chronic gastritis-associated dyspepsia.

Approximately 60% of Helicobacter pylori isolates in the Western world possess the cytotoxin-associated gene A (cagA). cagA-positive H. pylori is found to be associated with peptic ulcer disease (PUD) and gastric adenocarcinoma. To investigate the cagA status of H. pylori isolates from Chinese patients with PUD and chronic gastritis (CG), H. pylori populations from 83 patients, 48 with PUD and 35 with CG, were assessed by two different cagA-specific PCRs, Southern blotting, and colony hybridization. The combined results from PCR, Southern blotting, and colony hybridization indicate a prevalence of cagA-positive H. pylori isolates of 98% (47 of 48) among Chinese PUD patients and 100% (35 of 35) among Chinese CG patients. Amplification with primer sets 1 and 2 yielded 52 and 95% of the 82 cagA-positive Chinese H. pylori, respectively. In contrast, the sensitivity of cagA-specific PCR for cagA-positive H. pylori isolates from Dutch patients with primer set 1 was 92% (112 of 122) and that with primer set 2 was 91% (50 of 55). The prevalence of cagA-positive H. pylori populations in Chinese patients with PUD and CG is almost universally high. Therefore, cagA cannot be used as a marker for the presence of PUD in Chinese patients. Our data further suggest that allelic variation in cagA may exist and that distinct H. pylori genotypes may circulate in China and Western Europe.

Adult↗

PubMed1996

Treatment of Helicobacter pylori infection with low or high dose omeprazole combined with amoxycillin and the effect of early retreatment.

BACKGROUND: Cure rates of H. pylori infection, using dual therapy with omeprazole and amoxycillin, vary considerably and the efficacy of retreatment with this regimen in the case of initial failure is controversial. Therefore, we conducted a large prospective double-blind randomized trial, studying the efficacy of low vs. high dose omeprazole in dual therapy and of early retreatment with the same regimens. METHODS: One hundred and sixty-eight consecutive H. pylori-positive patients, suffering from either peptic ulcer disease or functional dyspepsia, were enrolled. Group I (n = 84) received omeprazole 20 mg b.d. plus amoxycillin 750 mg t.d.s., for 2 weeks. Group II (n = 84) received omeprazole 40 mg t.d.s. plus amoxicillin 750 mg t.d.s., for 2 weeks. RESULTS: The H. pylori eradication rate was 60.2% in group I and 64.3% in group II (P = 0.59). Cure of H. pylori infection was significantly better in patients with peptic ulcer disease, compared to non-ulcer dyspeptics (P = 0.016). Retreatment, given in 54 patients, was successful in 21.4% patients in group I and in 28% patients in group II (P = 0.58). CONCLUSIONS: High dose of omeprazole has no advantage compared to low dose in terms of eradication efficacy. Early retreatment with the same regimen offers limited improvement in cure rate. Presence of peptic ulcer disease influences cure rates significantly.

Adolescent↗

PubMed1996

Heterogeneous Helicobacter pylori isolates from members of a family with a history of peptic ulcer disease.

BACKGROUND & AIMS: Duodenal ulcer formation in persons infected with Helicobacter pylori correlates with the expression of the cytotoxin-associated gene A (cagA) and the vacuolating cytotoxin (VacA). The aim of this study was to assess the occurrence of cagA and VacA variants among H. pylori isolates. METHODS: H. pylori was isolated from 8 members of one family with a history of peptic ulcer disease (PUD). Each strain was characterized by random amplified polymorphic DNA (RAPD) fingerprinting. cagA was detected by polymerase chain reaction (PCR), Southern blotting, and colony hybridization. Viable H. pylori was added to mammalian cells to assess their cytotoxin activity. RESULTS: The RAPD patterns of the 8 patients' strains were similar. Analysis of 10 single colonies from the primary culture plates showed that all but 1 subject harbored multiple H. pylori subtypes. The proportion of cagA-positive colonies on the primary culture plates ranged from 0% to 90% between the isolates from all patients. In addition, the different H. pylori subtypes showed no cytotoxin activity in mammalian cells. CONCLUSIONS: Genotypic comparison of H. pylori isolated from different patients requires analysis of multiple colonies selected from the primary culture plate. In addition, infection by cagA-positive H. pylori in the family members with PUD (subjects 2-8) is consistent with the observed association between cagA positivity and PUD.

Adult↗

PubMed1996

Gastric non-Hodgkin lymphomas of mucosa-associated lymphoid tissue are not associated with more aggressive Helicobacter pylori strains as identified by CagA.

Primary gastric non-Hodgkin lymphoma of mucosa-associated lymphoid tissue (MALT-NHL) is strongly related to Helicobacter pylori (H pylori) infection. CagA positive H pylori strains appear to be more aggressive, as reflected by a greater degree of gastric inflammation and higher levels of Il-8 production. Using a polymerase chain reaction-based assay, cagA status was determined in H pylori strains of 12 patients with gastric MALT-NHL, 38 patients with peptic ulcer disease, and 39 patients with non-ulcer dyspepsia. CagA-positive H pylori strains were significantly more frequent in peptic ulcer disease than in non-ulcer dyspepsia (Fisher's exact test p <0.001). An increased frequency of CagA-positive strains was not identified in gastric MALT-NHL compared to non-ulcer dyspepsia patients (Fisher's exact test P <.3). Therefore, it can be concluded that infection with more aggressive strains is associated with the development of peptic ulcer disease, but plays a minor role, if any, in the development of gastric MALT-NHL.

Adult↗