Biomedical subjects
Publications and source records attributed to M J Wolfhagen.
This is the first report of a patient with a syndrome resembling thrombotic thrombocytopenic purpura associated with a recent human parvovirus B19 infection.
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OBJECTIVE: this study compares the efficacy and side effects of the two commonly used treatment regimens for Helicobacter pylori infection. METHODS: 118 patients with culture-proven H. pylori infection (61 with duodenal ulcer, 19 with gastric ulcer, three with both duodenal and gastric ulcer, and 35 with non-ulcer dyspepsia) were randomized to receive either triple therapy (tetracycline 250 mg, metronidazole 250 mg, colloidal bismuth subcitrate 120 mg, four times daily) for 14 days or amoxicillin 1000 mg and omeprazole 40 mg both twice daily for 14 days. The isolated H. pylori strain was metronidazole susceptible in 93%. Antral biopsy samples were taken for culture, urease testing, histology and, in most patients, for PCR at least 6 wk after treatment. A separate corpus sample was taken for culture. Eradication was defined as the absence of H. pylori in all specimens. In seven cases, when only histology was doubtfully positive, and all other tests including PCR were negative, a 13C-urea breath test was performed, the result of which was recorded by the patient on a semi-quantitative scale. RESULTS: H. pylori was eradicated by triple therapy in 96.3% and by amoxicillin/omeprazole in 77.2% of the patients (p = 0.008). Side effects occurred more often with triple therapy (72.7% vs. 50.8%; p< 0.05) but were mild in most cases. Severe side effects occurred equally in both treatment groups. CONCLUSIONS: When the prevalence of metronidazole resistance is low, triple therapy is more effective than amoxicillin/omeprazole. Side effects occur more often in triple therapy but are mild in most cases.
A specific monoclonal antibody against toxin A from Clostridium difficile was generated that did not show thermolabile binding. Nonspecific murine monoclonal antibodies bound toxin A at 4 degrees C, but less effectively at 37 degrees C. Nonspecific human monoclonal antibodies did not bind to toxin A at 4 degrees C. Cytotoxic properties of purified toxin A were not inhibited by Bandeiraea simplicifolia lectin. This points to a carbohydrate moiety on the cell surface and a multivalent nonspecific carbohydrate binding ligand on toxin A.
The toxins produced by Clostridium difficile share several functional properties with other bacterial toxins, like the heat-labile enterotoxin of Escherichia coli and cholera toxin. However, functional and structural differences also exist. Like cholera toxin, their main target is the disruption of the microfilaments in the cell. However, since these effects are not reversible, as found with cholera toxin, additional mechanisms add to the cytotoxic potential of these toxins. Unlike most bacterial toxins, which are built from two structurally and functionally different small polypeptide chains, the functional and binding properties of the toxins of C. difficile are confined within one large polypeptide chain, making them the largest bacterial toxins known so far.
Rapid detection of toxigenic Clostridium difficile in fecal samples was accomplished with the magnetic immuno PCR assay (MIPA). Elaborate DNA extraction techniques were unnecessary. First, we generated a mouse monoclonal antibody (MAb) reactive with only C. difficile, Clostridium sordellii, and Clostridium bifermentans. Then, magnetic beads were coated with the MAb, incubated with fecal samples to allow binding with C. difficile, extracted from the stool with a magnet, and processed in the PCR with primers specific for the toxin B gene. After optimizing MIPA by raising the number of PCR cycles from 35 to 40 and adding Chelex 100 to the PCR mixture, we found a sensitivity of 96.7%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 94.1% when compared with the culture of cytotoxic C. difficile from fecal samples. MIPA is a rapid, easy, and sensitive PCR method for demonstrating the presence of toxigenic C. difficile in stool samples and avoids the disadvantage of elaborate extraction of DNA from fecal samples.
In this study, clinical and laboratory findings were tested for correlation with the presence of Clostridium difficile. The toxigenicity of the isolated strains and the toxins were determined in faecal samples of immunocompromised children admitted to a single room for protective isolation. Using the toxin assay as the gold standard, the culture sensitivity of toxigenic C difficile was 94.1%, the specificity 93.8%, the positive predictive value 62.8%, and the negative predictive value 99.3%. Correction for stools with a positive culture of toxigenic C difficile preceding detection of toxin, resulted in a positive prediction value of 78.4%. A statistically significant association was found between a positive faecal toxin assay and fever, and between a positive culture of toxigenic C difficile and abdominal pain: 42% of the patients with positive toxin assays had fever versus 21% with negative toxin assays, and 66% of the patients with a positive culture for toxigenic C difficile had abdominal pain, versus 22% with negative cultures. Further analysis of the cultures and toxin assays showed no statistically significant association with diarrhoea, fever, white blood cell count, C reactive protein concentrations, or abdominal pain. Based on these findings, it is suggested that immunocompromised children should be treated when toxigenic C difficile is cultured or when toxin is detected in stool samples.
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A hybridization assay for detection of toxigenic Clostridium difficile in fecal samples was developed and compared with the classical tissue culture cytotoxicity assay. A DNA fragment probe specific for the toxin B gene of Clostridium difficile was synthesized by the polymerase chain reaction and labelled with digoxigenin. Fecal samples were cultured for 24 hours, replica-plated and hybridized with the probe. The hybridization assay had a sensitivity of 100%, specificity of 96.7%, positive predictive value of 86.7% and negative predictive value of 100% compared with the cytotoxicity assay.
A simple discriminative typing method for Clostridium difficile has been developed. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell proteins and restriction enzyme analysis are relatively simple techniques but are difficult to evaluate, especially the restriction enzyme analysis. Immunoblotting and restriction fragment length polymorphism typing facilitate simple discrimination of patterns.
To assess the role of enterovirulent Escherichia coli at home and abroad, faeces samples of patients with diarrhoea and of healthy controls in Tunisia, Seville (southern Spain) and the Netherlands were investigated. Enterovirulent E. coli were identified by hybridization with five different non-radioactively labelled DNA probes specific for enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC) and verocytotoxin producing E. coli (VTEC). ETEC was the main causative agent of travellers' diarrhoea in Tunisia. The isolation of ETEC in the Netherlands was shown to be related to travel in endemic areas. EPEC probe positive strains were isolated in children and in adults, but were not in all cases associated with intestinal disease. During this study no VTEC were detected. From an immunocompromised kidney transplantation patient with sepsis and diarrhoea ETEC were isolated from blood.
A total of 39 toxigenic and 20 nontoxigenic strains of Clostridium difficile were tested for the presence of either toxin A or toxin B by the polymerase chain reaction (PCR). All toxigenic strains produced cytotoxin as assayed by using highly sensitive fetal lung fibroblasts and were positive for toxin A as well as toxin B in the PCR assay. All nontoxigenic strains failed to produce toxin and were negative in the PCR assay. This study shows that nontoxigenic strains of Clostridium difficile lack the toxin A as well as the toxin B gene.
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In a double-blind randomized trial, we evaluated the efficacy and safety of three oral dosage regimens of fleroxacin, a new fluoroquinolone, once daily in 62 patients for the treatment of complicated urinary tract infections. The regimens compared were 200 mg for 10 days (n = 20), 400 mg for 10 days (n = 21), and 600 mg for 10 days (n = 21). Forty-five patients were evaluable for efficacy. A clinical cure was reached in 78% of the patients. Overall, a favorable bacteriological response (negative culture or reinfection at 4 to 6 weeks) was obtained in 36 of 45 (80%) patients. No significant difference could be found among the three dosage groups. During therapy, one Klebsiella ozaenae strain became resistant and one Pseudomonas aeruginosa strain became less susceptible to fleroxacin. In 13 patients, therapy had to be discontinued due to major adverse events (oliguria [n = 1], psychosis [n = 1], photosensitivity [n = 1], insomnia [n = 1], and nausea [n = 9]). Minor side effects were seen in 13 other patients. Increased dosage correlated significantly (P less than 0.01) with total number of adverse events.
To determine the efficacy, safety and effect on fecal flora of ciprofloxacin in the prevention of travelers' diarrhea, 54 volunteers traveling to Tunisia were randomized in a double-blind manner to receive either 500 mg ciprofloxacin or a placebo once daily for one week. Results of 53 volunteers were available for evaluation of efficacy. One of 25 subjects (4%) receiving ciprofloxacin versus 18 of 28 subjects (64%) in the placebo group experienced travelers' diarrhea (p less than 0.0001). The protection offered by ciprofloxacin was 94%. In one volunteer taking ciprofloxacin, prophylaxis was terminated due to sunburn with blistering. Among 41 subjects reporting sunburn, no statistical difference was observed between the two treatment groups in the percentage of body surface area of sunburn. Quantitative feces cultures revealed a marked decrease in the number of gram-negative organisms in volunteers receiving ciprofloxacin and a significant increase in the number of Escherichia coli in the placebo group. Five weeks after return, the aerobic bacterial flora of both treatment groups showed the pre-travel pattern.
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