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The cascading of H-bridges, with different DC-link potentials and power devices, to implement modular hybrid binary, quasilinear and trinary multilevel inverters has been a recent research area. To achieve true modular implementation of a hybrid inverter, it is important to design each H-bridge as a stand-alone power bridge with its own integrated controller. Various three-level hysteresis controllers suitable for integrating with an H-bridge inverter to form a stand- alone power bridge are presented. The hysteresis current controllers on multiple power bridges can be coordinated to implement a modular hysteresis-controlled hybrid multilevel inverter with robust reference tracking and fast dynamic performance. Digital logic synthesised to ensure equal switch utilisation within each of the power bridges is also presented. Simulation and experimental results verify the performance and practicality of the proposed modular hysteresis control of hybrid multilevel inverters. [ABSTRACT FROM AUTHOR]

Numerous tests, both invasive and non-invasive, are available for the diagnosis of Helicobacter pylori infection. The aim of this study was to evaluate the extent and determinants of differences in serology and 13C-urea breath test (13C-UBT) in diagnosing H. pylori. Four-hundred-and-seventy-four asymptomatic blood donors aged 40 to 68 years (mean age 55.8 years) and of German nationality were recruited between October 1996 and November 1997. H. pylori infection was measured with 13C-UBT and with a commercial IgG-ELISA test (Medac; Hamburg, Germany). A standardized questionnaire was applied to identify factors which could explain discrepant results of 13C-UBT and serology. Prevalence of infection was similar according to both tests (33.1% for 13C-UBT and 30.8% for serology). From the 146 subjects with a positive serology, 121 (82.7%) had a positive 13C-UBT. Previous treatment of H. pylori infection was the strongest predictor of a negative 13C-UBT given positive IgG serology (odds ratio (OR)= 12.87, 95% CI=4.10-40.36). Coffee consumption of more than 3 cups/day was also associated with an increased odds of a negative 13C-UBT given positive serology (OR = 3.12, 95% CI=1.16-8.43). No significant determinants of positive 13C-UBT given negative serology could be identified. These findings suggest a delayed fall in serum antibodies following eradication of the infection to be a major source of differences in H. pylori diagnosis using non invasive 13C-UBT and serology. [ABSTRACT FROM AUTHOR]

Numerous tests, both invasive and non-invasive, are available for the diagnosis of Helicobacter pylori infection. The aim of this study was to evaluate the extent and determinants of differences in serology and [sup 13]C-urea breath test ([sup 13]C-UBT ) in diagnosing H. pylori. Four-hundred-and-seventy-four asymptomatic blood donors aged 40 to 68 years (mean age 55.8 years) and of German nationality were recruited between October 1996 and November 1997. H. pylori infection was measured with [sup 13]C-UBT and with a commercial IgG-ELISA test (Medac; Hamburg, Germany). A standardized questionnaire was applied to identify factors which could explain discrepant results of [sup 13]C-UBT and serology. Prevalence of infection was similar according to both tests (33.1% for [sup 13]C-UBT and 30.8[sup %] for serology). From the 146 subjects with a positive serology, 121 (82.7%) had a positive [sup 13]C-UBT. Previous treatment of H. pylori infection was the strongest predictor of a negative [sup 13]C-UBT given positive IgG serology (odds ratio (OR) = 12.87, 95% CI = 4.10-40.36). Coffee consumption of more than 3 cups/day was also associated with an increased odds of a negative serology (OR = 3.12, 95% CI = 1.16-8.43). No significant determinants of positive [sup 13]C-UBT given negative serology could be identified. These findings suggest a delayed fall in serum antibodies following eradication of the infection to be a major source of differences in H. pylori diagnosis using non invasive [sup 13]C-UBT and serology. [ABSTRACT FROM AUTHOR]

Background Knowledge about the possible role of phospholipase C (PLC) activity of microbial pathogens in the development of disease is increasing. Recently attention has focused on investigating PLC activity elaborated by Helicobacter pylori, but the role of this enzyme in H. pylori pathogenesis is still unknown. The aim of this study was to correlate PLC-activity of H. pylori on the basis of the cagA status with the clinical diagnosis of the patients. Materials and methods Helicobacter pylori was isolated from patients with gastritis (G; n = 38), duodenal ulcer (DU; n = 15), gastric ulcer (GU; n = 11) and gastric cancer (GC; n = 12). Polymerase chain reaction primers DZ3/R009 which amplified a 1350-bp fragment were used to detect the cagA gene. PLC activity was determined using p-nitrophenylphosphorylcholine as substrate. Results Of the strains, 60% were cagA[sup +] and 40% were cagA[sup -]. All strains showed PLC activity (2·20 ± 0·91 U mg[sup -1] protein). PLC activity showed no association with the cagA status: cagA[sup +] (2·21 ± 1·03 U mg[sup -1] protein), cagA[sup -] (2·18 ± 0·79 U mg[sup -1] protein). Patients with GU had the highest PLC activity (2·77 ± 1·26 U mg[sup -1] protein) and patients with GC had the lowest activity (1·8 ± 0·57 U mg[sup -1] protein). Conclusions Although PLC activity was present in all strains tested, it may only have pathological importance in patients with GU. However, the extent of PLC activity was independent of the presence of the cagA gene. [ABSTRACT FROM AUTHOR]

To test the hypothesis that Helicobacter pylori may be transmitted by the oral-oral route, we applied nested PCR and DNA sequencing to detect and analyze H. pylori DNA in the oral cavity of 20 adult patients undergoing endoscopy. Dental plaques of molars, premolars, and incisors and saliva were collected. Additional paraffin-embedded gastric biopsies were analyzed in four patients. Two sets of highly sensitive and specific primers, EHC-U/EHC-L and ET5-U/ET-5L directed to a 860-bp fragment of H. pylori DNA, were used in the nested PCR. Eight patients had an active infection in the stomach determined with the [13C]urea breath test and the other 12 were negative. Nested PCR showed that all 20 subjects (100%) were positive for H. pylori in the oral cavity. DNA sequencing demonstrated that all tested PCR products of the expected size from the oral samples have more than 97% identity with that from H. pylori type strain ATCC 43629. However, sequences differed in oral samples from different subjects as well as between different oral locations and gastric biopsies within the same individuals. In conclusion, the oral cavity may be a permanent reservoir for H. pylori and can harbor multiple H. pylori strains at the same time. [ABSTRACT FROM AUTHOR]

This study assessed the role of parental infection status in the transmission of Helicobacter pylori infection in a large population-based sample of preschool-aged children. The subjects, who lived in Ulm, Germany, and in two nearby communities, were screened for school fitness between January and July 1997. Their H. pylori infection status was determined by 13C-urea breath test. Of 1522 eligible children, 1221 (80.2%) participated in the study. Crude prevalence of H. pylori infection in children was 11.3% (95% confidence interval [CI], 9.5-13.3) and 36.4% in their parents (95% CI, 33.5-39.4). The crude odds ratio (OR) for H. pylori infection of children whose mothers were infected was 16.5 (95% CI, 8.9-30.8) and 7.9 after adjustment for potential confounders (95% CI, 4.0-15.7). The crude OR if the child's father was infected was 7.8 (95% CI, 2. 5-24.2) and 3.8 after adjustment for potential confounders (except maternal infection) (95% CI, 0.8-19.1). The results suggest that infected parents, especially infected mothers, may have a key role in transmission of H. pylori within families. Copyright © 1999 The University of Chicago [ABSTRACT FROM AUTHOR]

This study was designed to compare different primer sets for PCR analysis of H. pylori in the same series of 40 dental plaque samples. Three pairs of primers, HPU1/HPU2, HP1/HP2, and EHC-U/EHC-L, directed to the urease A gene, 16S rRNA gene, or 860-bp DNA of H. pylori, respectively, were used. Our results demonstrate that EHC-L/EHC-U were more specific and sensitive for H. pylori added to saliva or dental plaque than HPU1/HPU2 and HP1/HP2. The detection rates for H. pylori DNA in dental plaque samples from randomly selected adult patients from the Dental Clinic of the University of Ulm were 26.5% (9/34) for HPU1/HPU2, 78.9% (30/38) for HP1/HP2, and 100% (40/40) for EHC-U/EHC-L (P < 0.001). Nested PCR using primers directed to the 860-bp DNA of H. pylori further confirmed the presence of H. pylori DNA (40/40) in all these samples. Our results indicate that primers EHC-U/EHC-L are to be recommended for PCR detection of H. pylori in the oral cavity. [ABSTRACT FROM AUTHOR]

Background: The C-urea breath (C-UBT) test value is (semi-)quantitatively related to Helicobacter pylori density in the gastric antrum, and the value correlates with the grade of gastritis. The aim of this study was to assess variation of the C-urea breath test value by sociodemographic factors in H. pylori-positive children. Methods: The analysis was performed on 127 asymptomatic children (aged 5-7 years) who were identified as H. pylori-positive with the C-UBT test in a large population-based epidemiologic study in the city of Ulm (southern Germany). The parents of the children were asked to fill out a standardized questionnaire about sociodemographic data. Results: Forty-two infected children (33.1%) were of German nationality, 47 children (37.0%) were of Turkish and 38 children (29.9%) were of another nationality. Turkish children had a significantly higher C-UBT value (geometric mean = 27.2‰) than German children (16.7‰) or children with another nationality (19.3‰) (P < 0.001). Girls had a trend towards higher values than boys (P = 0.058 after adjustment for nationality). Body mass index, education of the parents, and prior use of antibiotics were unrelated to the extent of the C-UBT. Conclusions: This study identified significant variation in the extent of the C value by nationality among H. pylori-infected children. Further studies are needed to elucidate the causes and potential consequences of these variations. [ABSTRACT FROM AUTHOR]