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  • 1
    Online Resource
    Online Resource
    Assessment of Helicobacter pylori vacA and cagA Genotypes and Host Serological Response
    American Society for Microbiology ; 2001
    In:  Journal of Clinical Microbiology Vol. 39, No. 4 ( 2001-04), p. 1339-1344
    Details
    In: Journal of Clinical Microbiology, American Society for Microbiology, Vol. 39, No. 4 ( 2001-04), p. 1339-1344
    Abstract: Helicobacter pylori strains can be distinguished by genotyping of virulence-associated genes, such as vacA and cagA . Because serological discrimination between strain types would reduce the need for endoscopy, 61 patients carrying H. pylori were studied by vacA and cagA genotyping of H. pylori in gastric biopsy specimens and by detection of specific serum antibodies. Serological responses to H. pylori were determined by Helicoblot (versions 2.0 and 2.1). Antibodies to CagA also were determined by a rapid anti-CagA assay (Pyloriset screen CagA) as well as by two noncommercially developed enzyme immunoassays, each using a recombinant CagA protein. Assessment of performance of the Helicoblot assays indicated substantial interobserver variation, with kappa values between 0.20 and 0.93. There was no relationship between the serological profiles on the Helicoblot and the genotypes from the same patients, except for strong associations between the presence of anti-CagA and the cagA -positive and vacA s1 H. pylori genotypes. Detection of anti-CagA by the five different assays varied considerably, with kappa values ranging from 0.21 to 0.78. Using the cagA genotype as the “gold standard,” the sensitivity and specificity of the anti-CagA assays varied from 71.4 to 85.7% and from 54.2 to 100%, respectively. Thus, serological profiles of antibodies to H. pylori are heterogeneous and, with the exception of anti-CagA antibodies, show no relation to the H. pylori vacA and cagA genotypes. Detection of anti-CagA antibodies is strongly dependent on the test used.
    Type of Medium: Online Resource
    ISSN: 0095-1137 , 1098-660X
    URL: Article
    DOI: 10.1128/JCM.39.4.1339-1344.2001
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2001
    detail.hit.zdb_id: 1498353-9
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Accurate Prediction of Macrolide Resistance in Helicobacter pylori by a PCR Line Probe Assay for Detection of Mutations in the 23S rRNA Gene: Multicenter Validation Study
    American Society for Microbiology ; 2001
    In:  Antimicrobial Agents and Chemotherapy Vol. 45, No. 5 ( 2001-05), p. 1500-1504
    Details
    In: Antimicrobial Agents and Chemotherapy, American Society for Microbiology, Vol. 45, No. 5 ( 2001-05), p. 1500-1504
    Abstract: Helicobacter pylori strains from 299 patients were tested in six laboratories in different countries. Macrolide susceptibility of the strains was determined by agar dilution (17.4%) or the epsilometer test (82.6%). Mutations in the 23S ribosomal DNA (rDNA) that are associated with macrolide resistance were analyzed by PCR and reverse hybridization (PCR-line probe assay [LiPA]). This method identifies A2115G, G2141A, A2142G, A2142C, A2142T, A2143G, and A2143C mutations in the 23S rDNA. vacA s-region (s1a, s1b, s1c, and s2) and m-region (m1, m2a, and m2b) genotypes and cagA status were also determined using another PCR-LiPA system. Of the 299 strains investigated by MIC testing, 130 (43.5%) were resistant and 169 (56.5%) were susceptible to clarithromycin. Of the 130 resistant strains, 127 (97.7%) contained 23S rDNA mutations, whereas 167 (98.8%) of the 169 susceptible strains contained wild-type sequences. The predominant mutations were A2143G (45.2%) and A2142G (33.3%). Twenty-eight (19.8%) strains contained multiple 23S rDNA mutations. Only five resistant strains contained the A2142C mutation (three of these in combination with the A2142G mutation), and the A2115G, G2141A, A2142T, and A2143C mutations were not found. MICs of clarithromycin for the A2142G mutant strains were significantly higher than MICs for the A2143G strains. Although there was no significant association between 23S rDNA mutations and the vacA and cagA status, clarithromycin-susceptible strains more often contained mixed vacA genotypes, indicating the presence of multiple H. pylori strains. In conclusion, our data confirmed the very strong association between 23S rDNA mutations and macrolide resistance and showed that the PCR-LiPA permits accurate and reliable diagnosis of macrolide resistance in H. pylori .
    Type of Medium: Online Resource
    ISSN: 0066-4804 , 1098-6596
    URL: Article
    DOI: 10.1128/AAC.45.5.1500-1504.2001
    RVK:
    XA 24552
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2001
    detail.hit.zdb_id: 1496156-8
    SSG: 12
    SSG: 15,3
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  • 3
    Online Resource
    Online Resource
    The Efficacy of Laboratory Diagnosis of Helicobacter pylori Infections in Gastric Biopsy Specimens Is Related to Bacterial Density and vacA , cagA , and iceA Genotypes
    American Society for Microbiology ; 2000
    In:  Journal of Clinical Microbiology Vol. 38, No. 1 ( 2000-01), p. 13-17
    Details
    In: Journal of Clinical Microbiology, American Society for Microbiology, Vol. 38, No. 1 ( 2000-01), p. 13-17
    Abstract: A total of 500 consecutive patients undergoing upper endoscopy were biopsied and tested for H. pylori infection by the Campylobacter -like organism (CLO) test, culture, histology, and PCR. Serum samples were tested by two different serological assays. Patients were considered H. pylori positive if at least two of the four biopsy specimen-based methods yielded positive results. PCR had the highest diagnostic sensitivity (99.4%), followed by histology (92.2%), culture (89.5%), and the CLO test (89.0%). The specificities of all methods were higher than 98%. Of the organisms from the 181 PCR-positive patients, the vacA (s and m regions), cagA , and iceA genotypes were determined by reverse hybridization (line probe assay) or an allele-specific PCR. Organisms that were detected by PCR but that remained undetected by the CLO test were significantly more often vacA s1 ( P = 0.006), m1 ( P = 0.028), and cagA positive ( P = 0.029) than vacA s2, m2, and cagA negative, respectively. Organisms that were detected by PCR but that remained undetected by culture or histology more often contained iceA1 ( P = 0.034 and P = 0.029, respectively) than iceA2 . Higher H. pylori density was associated with vacA s2 ( P = 0.024), vacA m2 ( P = 0.050), and cagA -negative ( P = 0.035) genotypes. Also, the diagnostic results of the CLO test ( P = 0.001) and culture ( P = 0.031) but not those of the PCR ( P = 0.130) were significantly associated with the H. pylori density. The rate of detection by the four biopsy specimen-based tests was lower for patients who used proton pump inhibitors, but this was independent of the H. pylori genotypes. These observations may be explained by different bacterial densities, as established by the distinct genotypes of H. pylori , and confirm that the biologies of strains with such genotypes are considerably different.
    Type of Medium: Online Resource
    ISSN: 0095-1137 , 1098-660X
    URL: Article
    DOI: 10.1128/JCM.38.1.13-17.2000
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2000
    detail.hit.zdb_id: 1498353-9
    SSG: 12
    Library Location Call Number Volume/Issue/Year Availability
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