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Lars Engstrand

Publications and source records attributed to Lars Engstrand.

46 records · Page 3Linked to original sources
PubMed2003

DNA-level characterization of Helicobacter pylori strains from patients with overt disease and with benign infections in Bangladesh.

The complex relation between the genotype of Helicobacter pylori and its association with clinical outcome is not well understood. Studies in the West have showed that strains expressing certain virulence factors (vacAs1, vacAm1, and cagA) are associated with duodenal ulcer disease. However, the H. pylori genotype is known to vary with geographic region. In the present study, we compared several virulence markers (cagA, vacA, and iceA) and neutral markers (IS605, IS606, and IS608) in H. pylori strains isolated from 65 adult patients with peptic ulcer (PU) and 50 patients with nonulcer dyspepsia (NUD). PCR tests indicated that cagA is present in 75% of the strains from patients with PU compared to 55% in patients with NUD, and 80% of the isolates from patients with PU carried potentially toxigenic vacAs1 alleles of the vacuolating cytotoxin gene (vacA) compared to 60% in isolates from patients with NUD. However, no significant difference in any other virulence marker was observed in isolates from both groups. Phylogenetic analysis of the vacA middle region and the 5' end of the cagA gene indicates that Bangladeshi isolates are more closely related to H. pylori isolates from India and are different from isolates from East Asia.

Adult↗
PubMed2002

Cultured human gastric explants: a model for studies of bacteria-host interaction during conditions of experimental Helicobacter pylori infection.

The unique environment of the human stomach makes it difficult to establish representative in vitro models for Helicobacter pylori that mimic the natural infection. The in vitro explant culture (IVEC) technique is based on coculture of human gastric explants with H. pylori, where bacteria-host interaction is studied on the basis of interleukin (IL)-8 secretion of the explant tissue in response to infection. In this study, it was shown that H. pylori attachment to gastric epithelial tissue was required for induction of representative inflammatory responses, assessed here by IL-8 production. Furthermore, IL-8 production by the explant tissue in response to H. pylori infection demonstrated that the explants were adequately responsive. The IVEC technique for studies of the interplay between H. pylori and the human gastric mucosa during conditions of experimental infections in vitro could add knowledge to our understanding of the complex bacteria-host cross-talk in vivo.

Adult↗
PubMed2002

Colonization of germ-free transgenic mice with genotyped Helicobacter pylori strains from a case-control study of gastric cancer reveals a correlation between host responses and HsdS components of type I restriction-modification systems.

Helicobacter pylori infects the stomachs of half of all humans. It has a relatively benign relationship with most hosts but produces severe pathology, including gastric cancer, in others. Identifying the relative contributions of host, microbial, and environmental factors to the outcome of infection has been challenging. Here we describe one approach for identifying microbial genes that affect the magnitude of host responses to infection. Single colony purified H. pylori isolates were obtained from 25 cases and 71 controls in a Swedish case-control study of gastric cancer. Strains were first phenotyped based on their ability to produce adhesins that recognize two classes of human gastric epithelial receptors. Thirteen binding strains and two non-binding controls were then subjected to whole genome genotyping using H. pylori DNA microarrays. A cohort of "variable" genes was identified based on a microarray-determined call of "absent" in at least one member of the strain panel. Each strain was subsequently introduced into two types of germ-free transgenic mice, each programmed to express a different host factor postulated to pose increased risk for development of severe pathology. Expression of biomarkers of host defense was quantitated 4 weeks after inoculation, and the magnitude of the response correlated with bacterial genotype. The proportion of genes encoding HsdS homologs (specificity subunit of hetero-oligomeric type I restriction-modification systems) was significantly higher in the pool of 18 variable genes whose presence directly correlated with a robust host response than their proportion in the remaining 352 members of the variable gene pool. This suggests that the functions of these HsdS homologs may include control of expression of microbial determinants that affect the extent of gastric responses to this potentially virulent pathogen.

Animals↗
PubMed2002

An anthroposophic lifestyle and intestinal microflora in infancy.

The intestinal flora is considered to have an impact on the development of the immune system. In the anthroposophic lifestyle, a diet comprising vegetables spontaneously fermented by lactobacilli, and a restrictive use of antibiotics, anti-pyretics and vaccinations, is typical. The aim of this study was to assess the gut flora in infants in relation to certain lifestyle characteristics associated with anthroposophy. Sixty-nine children < 2 years of age with an anthroposophic lifestyle, and 59 infants of a similar age with a traditional lifestyle, were clinically examined and questionnaire replies assessed. Fecal samples were analyzed by bacterial enumeration, bacterial typing through biochemical fingerprinting and by measuring microflora-associated characteristics (MACs). The numbers of colony-forming units (CFU)/g of feces were significantly higher for enterococci and lactic acid bacteria in children who had never been exposed to antibiotics (5.5 x 107 vs. 2.1 x 107; p < 0.001 and 10 x 107 vs. 4.1 x 107; p < 0.01, respectively). Furthermore, the number of enterococci was significantly higher in breastfed and vegetarian infants (p < 0.01). The diversity (Simpson's diversity index) of lactobacilli, as determined by biochemical fingerprinting, was higher in infants born at home than in those born in hospital (p < 0.01). Several MACs were related to specific lifestyle features, and infants with an anthroposophic lifestyle had a higher proportion of acetic acid and a lower proportion of propionic acid in their stool as compared to the control children. In conclusion, lifestyle factors related to the anthroposophic way of life influenced the composition of the gut flora in the infants. These differences may contribute to the lower prevalence of atopic disease previously observed in children in anthroposophic families.

Age Factors↗
PubMed2002

Free-living amoebae promote growth and survival of Helicobacter pylori.

Transmission routes of Helicobacter pylori remain poorly understood. The finding of bacterial DNA in water suggests the involvement of environmental factors. Here we report successful co-cultivation of H. pylori with Acanthamoeba castellanii, which circumvents the requirement of this bacterium for precise microaerobic conditions and a large supply of nutrients in order to grow. H. pylori was able to propagate and remain viable for several weeks in the presence of amoebae under experimental conditions. Intact, metabolically active bacteria could be demonstrated in vacuoles. The putative dependence of H. pylori on free-living amoebae in nature could be important with respect to transmission and prevalence, as shown for some other pathogenic bacteria.

Acanthamoeba↗
PubMed2002

Phenotypic variation of Helicobacter pylori isolates from geographically distinct regions detected by lectin typing.

A total of 309 Helicobacter pylori isolates from 18 different countries were analyzed with a previously developed lectin typing system. The system was developed by using a proteolytic pretreatment to enhance the carbohydrate fraction of the sample. Four lectins from Ulex europaeus, Lotus tetragonolobus, Erythrina cristigali, and Triticum vulgaris were used to type the strains. The lectins were chosen for their specificities for sugars commonly encountered in the lipopolysaccharide of H. pylori. The isolates were received from their parent institutions as pellets of biomass and were typed at one of three centers (in Ireland, Sweden, and Estonia). All 16 possible lectin reaction patterns were observed in the study, with the isolates with the predominant pattern exhibiting reactions with all the lectins in the panel. For European patients suffering from gastritis, an association was noted between lectin reaction pattern MH4 and atrophic chronic gastritis; isolates with lectin reaction pattern MH4 were isolated from patients with atrophic chronic gastritis, whereas isolates with this pattern were not isolated from patients with chronic gastritis (P = 0.0006). In addition, statistically significant relationships were noted between the lectin reaction pattern and the associated pathology of isolates from the Swedish population. Isolates with patterns MH13 and MH16, which had low lectin reactivities, correlated with nonulcer disease (P = 0.0025 and P = 0.0002, respectively), and all four isolates from adenocarcinoma patients were characterized as possessing reaction pattern MH16. In contrast, isolates with lectin reaction patterns MH1 and MH10, which had high lectin reactivities, were associated with ulcer disease (P = 0.046 and P = 0.0022, respectively).

Bacterial Typing Techniques↗
PubMed2002

Determining antibiotic resistance in Helicobacter pylori.

Resistance development is a significant clinical problem in Helicobacter pylori and represents the major cause of treatment failure. Today the problem is most focused on the macrolide clarithromycin that is an essential component of the H. pylori treatment. Traditional methods for resistance determination, e.g., disc diffusion tests or E-tests, could in the next 5 years be replaced by DNA-based methods. The most commonly used molecular methods available today are not used in the daily routine work. Rapid and reliable DNA-based methods for prediction of antimicrobial resistance phenotype are currently available within research. As fabrication costs reduce and validated targeted assays are developed with easy hands-on procedures, it is most likely that such assays will become important tools for clinical diagnosis of resistant H. pylori strains.

Anti-Bacterial Agents↗
PubMedDate not supplied

Expression of tumor-associated Thomsen-Friedenreich antigen (T Ag) in Helicobacter pylori and modulation of T Ag specific immune response in infected individuals.

We tested the hypothesis that the gastric cancer associated bacteria, Helicobacter pylori (H. pylori) express the cancer-related Thomsen-Friedenreich (T) antigen. We also analysed whether infection with H. pylori alters the amount of natural anti-T antibodies in the patients' sera. Cell surface membrane extracts of H. pylori NCTC 11637 strain and clinical isolates of H. pylori (n = 13) were analysed by immunoblotting and cell-ELISA with five different T antigen-specific monoclonal antibodies (MAbs). Two major protein bands of approximately 68 kDa and 58 kDa were immunostained on blots of H. pylori extracts with T specific MAbs but not immunostained with unrelated MAb. The specificity was shown in that immunostaining was blocked with peanut agglutinin (PNA) and rabbit antiserum to T antigen. The binding of T specific MAb to the 58 kDa protein band was also blocked by rabbit antiserum against heat shock proteins of H. pylori. The relative expression of T antigen-related proteins differed among H. pylori strains, with 68 kD associated T antigen expression higher in patients with more severe pathology. The level of IgG antibody to T epitope in patients with gastric cancer (n = 66) and normal blood donors (n = 62) were compared and the level of anti-T Ab in gastric cancer patients was significantly lower than that in normal blood donors. A significant positive correlation between T specific antibody in serum and H. pylori IgG antibody level was found in H. pylori-infected normal blood donors (P < 0.001), but this correlation was not found in H. pylori-infected cancer patients. In summary, the cancer related T epitope is expressed in H. pylori and modulation of T antigen-specific immune response in H. pylori-infected individuals suggests that H. pylori infection may alter natural immune mechanisms against cancer.

Animals↗