Search PubMed⌕ Search

Biomedical subjects

J Dankert

Publications and source records attributed to J Dankert.

At least 145 records · Page 8Linked to original sources
PubMed1996

The interrelationship between cytotoxin-associated gene A, vacuolating cytotoxin, and Helicobacter pylori-related diseases.

The interrelationship between cytotoxin-associated gene A (CagA), vacuolating cytotoxin (VacA), and Helicobacter pylori-related diseases was investigated in 155 H. pylori-infected patients. Four (7%) of 60 subjects had mixed cagA+ and cagA- H. pylori infections. The H. pylori isolates from 98.3% of 121 patients with anti-CagA antibodies were cagA+. The occurrence of cagA+ H. pylori among 76 patients with peptic ulcer disease (PUD) was higher (93.4%) than among 79 patients with functional dyspepsia (FD; 64.6%) (odds ratio [OR] = 7.80; P < .001). VacA+ isolates were isolated from 56.6% of the PUD patients and 35.4% of the FD patients (OR = 2.37; P = .0132). For type I (cagA+VacA+) isolates, these numbers were 56.6% and 31.6%, respectively (P = .003). Only 4% of the 71 VacA+ isolates were cagA-. In addition, 37% of the patients with PUD were infected with cagA+VacA- H. pylori. Chi 2 results did not improve when VacA was entered into the model in the presence of cagA, indicating that only cagA is associated with PUD.

Adult↗
PubMed1996

Antimicrobial susceptibility of Haemophilus influenzae, Neisseria meningitidis and Streptococcus pneumoniae isolates causing meningitis in The Netherlands, 1993-1994.

The increasing antimicrobial resistance among pathogens frequently isolated from patients with bacterial meningitis formed the rationale to perform a surveillance study to determine the prevalence of resistance in The Netherlands. Haemophilus influenzae strains (n = 316) isolated from cerebrospinal fluid (CSF), 1125 meningococcal strains isolated from blood or CSF and 398 pneumococcal strains isolated from CSF in 1993 and 1994 were tested by the Etest for susceptibility to commonly prescribed antibiotics for the treatment of community-acquired meningitis. In H. influenzae strains ampicillin-resistance occurred in 7.0%, resistance to chloramphenicol in 2.2%, and resistance to both antibiotics in 0.9%. The prevalence of intermediate penicillin-resistance in meningococci was 3.3%. Resistance to rifampicin was rarely found (0.1%). Intermediate penicillin-resistance in pneumococci was found in only 0.5% of isolates. All 1839 isolates were susceptible to ceftriaxone. Based on these results, we conclude that empirical therapy of childhood community-acquired bacterial meningitis with amoxycillin and chloramphenicol is no longer justified in children who have not been vaccinated against H. influenzae type b. In vaccinated or older children and adults, amoxycillin is a rational choice for empirical treatment of meningitis. The prophylactic use of rifampicin in contacts of patients with meningococcal disease is still applicable.

Adolescent↗
PubMed1996

Prognostic indicators of the outcome of meningococcal disease: a study of 562 patients.

To assess prognostic indicators of a fatal outcome in patients with meningococcal disease, data from 562 patients with culture-proven meningococcal disease, reported in the Netherlands between 1 April 1989 and 30 April 1990, were collected prospectively by means of a questionnaire completed by the specialist in attendance. Analysis was done by the chi2 test and multiple logistic regression. During the study period 43 patients (7.7%) died. The risk of a fatal outcome was increased in patients aged 0-5 months, 10-19 years, and > or = 50 years, in female patients and in patients presenting with coma, temperature < or = 38.0 degrees C, mean arterial pressure < or = 70 mmHg, white blood cell count < or = 10 x 10(9)/L and platelet count < or = 100 x 10(9)/L. Predisposing factors and duration of disease before admission were significantly associated with outcome, but these associations disappeared in the multivariate analysis. Race, the administration of antibiotics prior to admission, seizures and haemorrhagic skin lesions were not associated with outcome. In conclusion age, gender, coma, temperature, mean arterial pressure, white blood cell count and platelet count were independent prognostic indicators of the outcome of meningococcal disease. The assessment of these characteristics may be helpful for the identification of high risk patients, whose prognosis might be improved by prompt transfer to an intensive care unit.

Adolescent↗
PubMed1996

Carrier detection by microsatellite haplotyping in 10 properdin type 1-deficient families.

Properdin deficiency carrier identification is relevant, because properdin-deficient persons have an increased risk of contracting meningococcal disease. Vaccination against meningococcal disease at a young age may provide protection. Accurate detection of this deficiency is needed. Microsatellite haplotyping with the PFCI and PFC2 markers closely linked to the properdin gene locus at Xp11.3-Xp11.23 may offer an easy and accurate identification of carriers of the properdin deficiency gene. The chance to study 91 relatives belonging to 10 families with complete (type 1) properdin deficiency offered a unique opportunity to assess whether properdin type 1 deficiency is associated with a distinct microsatellite haplotype. Haplotyping with the closely linked PFC1 and 2 markers yielded five different haplotypes, which did not support the concept of a founder effect. Among the 28 women carriers, two had normal properdin levels and in five the PFC1,2 polymorphism was not informative owing to homozygosity. Extending the microsatellite haplotyping with three additional markers (DXS1126, DXS426 and DXS7) yielded informative haplotypes in all meioses. We concluded that microsatellite haplo-typing using five markers in close proximity to the properdin gene locus is an accurate method of detecting carriers of the properdin deficiency gene and of properdin-deficient persons within a family at a young age.

Female↗
PubMed1996

Biliary excretion of ciprofloxacin and piperacillin in the obstructed biliary tract.

Biliary excretion of ciprofloxacin and piperacillin was determined in cholestatic patients who had undergone endoscopic cholangiography. The median concentration of ciprofloxacin (n = 9) was 2.36 micrograms/ml (range, 0.29 to 19.8 micrograms/ml) in bile compared with 1.66 micrograms/ml (range, 0.73 to 2.69 micrograms/ml) in serum. The median concentration of piperacillin (n = 7) was < 5 micrograms/ml (range, < 5 to 26) in bile compared with 14.3 micrograms/ml (range, 5.3 to 80) in serum. Ciprofloxacin, but not piperacillin, can be actively excreted into bile in the presence of a biliary tract obstruction.

Adult↗
PubMed1996

A simple procedure for isolation of cloning vectors and endogenous plasmids from viridans group streptococci and Staphylococcus aureus.

Isolation of plasmid DNA from viridans group streptococci is difficult, and preparations are often heavily contaminated with chromosomal DNA. We developed a simple protocol to isolate pure plasmid DNA for use in different molecular techniques, including automated sequencing. The protocol is also applicable for plasmid isolation from Staphylococcus aureus. In addition, the protocol allows isolation of pure endogenous plasmids from streptococci and S. aureus.

Cloning, Molecular↗
PubMed1996

Fine mapping of outer membrane protein P2 antigenic sites which vary during persistent infection by Haemophilus influenzae.

Antigenic drift of the major outer membrane protein (MOMP) P2 of nonencapsulated Haemophilus influenzae as observed during persistent infections in patients with chronic bronchitis was mimicked in a rabbit model in which H. influenzae persisted in subcutaneous cages. The antigenic drift resulted from amino acid substitutions in potentially surface-exposed loops of MOMP P2. Since in a rabbit model the appearance of antigenic variants was associated with the presence of strain-specific bactericidal antibodies (L. Vogel, B. Duim, F. Geluk, P. Eijk, H. Jansen, J. Dankert, and L. van Alphen, Infect. Immun. 64:980-986, 1996), we determined the epitope specificities of these bactericidal antibodies. The eight loops of MOMP P2 of H. influenzae d1 were separately expressed as fusion proteins with glutathione S-transferase. Sera of rabbits persistently infected with H. influenzae reacted with the loop 5 and loop 6 fusion proteins in immunoblotting and enzyme-linked immunosorbent assay. For fine mapping of the epitopes with pepscan analysis, overlapping synthetic peptides consisting of 12 amino acids were made. Rabbit sera contained antibodies reacting with peptides derived from loop 5 and peptides containing amino acids of the side of loop 6. In addition, MOMP P2 variant-specific reactions with the amino acids located at the tip of loop 6 were detected. The rabbit sera showed variant-specific complement-dependent bactericidal activities, which were eliminated by affinity chromatography with fusion proteins of loop 6 but not of loop 5. We conclude that, during persistence of H. influenzae in rabbits, variant-specific bactericidal antibodies are elicited to the variable tip of MOMP P2 loop 6.

Animals↗
PubMed1996

Immune selection for antigenic drift of major outer membrane protein P2 of Haemophilus influenzae during persistence in subcutaneous tissue cages in rabbits.

During persistence of nonencapsulated Haemophilus influenzae in the respiratory tracts of patients with chronic bronchitis, the major outer membrane proteins (MOMPs) P2 and P5 show antigenic drift. The hypothesis that appearance of antigenic variants is the consequence of antibody-dependent selection was tested in a rabbit model. Persistence of H. influenzae d1 was achieved in subcutaneous tissue cages for up to 948 days. During persistence in the rabbits, similar changes in MOMP P2 of H. influenzae occurred, as observed in isolates from chronic bronchitis patients. In rabbits vaccinated with strain d3 and in nonvaccinated rabbits, antigenic drift occurred later than in rabbits vaccinated with strain d1. High titers of antibodies against H. influenzae were measured in tissue cage fluid and serum. Vaccination of the rabbits with H. influenzae d1 or d3, an antigenic variant of strain d1, resulted neither in eradication of H. influenzae d1 nor in increased antibody titers in serum and tissue cage fluid. The sera of nonvaccinated rabbits during persistence had no strain d1-specific bactericidal activity in the presence of complement. Vaccination with H. influenzae d1 induced serum bactericidal activity against strain d1 in the presence of complement. However, a variant of strain d1 appearing in the tissue cages was not killed by this serum bactericidal activity. We conclude that immunological pressure leads to the selection of MOMP variants of H. influenzae and that these variants escape the antibody-mediated strain-specific bactericidal activity against H. influenzae.

Amino Acid Sequence↗
PubMed1996

Antibodies to Haemophilus influenzae type b polysaccharide affect bacterial adherence and multiplication.

Since immunization of infants with conjugated Haemophilus influenzae type b (Hib) capsular polysaccharide (PS) vaccines results in a reduction of colonization, we determined the inhibitory effect of anti-Hib PS on two steps in the colonization, i.e., adherence of H. influenzae to nasopharyngeal epithelium and bacterial growth. Monoclonal antibody (MAb) E117-5 specific for Hib PS inhibited at a concentration of at least 80 microg/ml in vitro the adherence of Hib strain 770235f+b+ to oropharyngeal epithelial cells by 50% (P <, 0.02), but this MAb and sera from children immunized with Hib PS conjugate vaccine (n = 10) were not inhibitory in final dilutions containing up to 20 microg of anti-Hib PS per ml. The growth of Hib strain 770235f+b+ did completely stop in the presence of 5 microg of anti-Hib PS MAb E117-5 per ml and human sera with an anti-Hib PS concentration of 2 microg/ml or more, in contrast to the growth of the nonencapsular variant strain 770235f+b0.

Agglutination↗
PubMed1996

Invasion of primary nasopharyngeal epithelial cells by Neisseria meningitidis is controlled by phase variation of multiple surface antigens.

We have investigated bacterial factors required for the entry of Neisseria meningitidis serogroup B into mucosal cells using a novel in vitro infection model of primary cultures of human nasopharyngeal epithelium. An invasive meningococcal phenotype was obtained after several cycles of selection for intracellular bacteria with gentamicin. Invasive bacteria differed from those in the initial inoculum in that they lacked a capsule and pili, exhibited a nonsialylated low-molecular-weight type of lipopolysaccharide (LPS), and produced a new 28-kDa opacity outer membrane protein. LPS revertants of the selected meningococci expressed a nonsialylated L3,(7,9) type of LPS and were also invasive, while after LPS sialylation bacterial entry was inhibited. Variants lacking the 28-kDa opacity protein were poorly invasive. Coexpression of the outer membrane protein Opc and the 28-kDa opacity protein strongly inhibited microbial invasion into the primary cultured nasopharyngeal cells. Conversely, meningococcal internalization by cells of various epithelia] cell lines was correlated with the expression of Opc rather than the 28-kDa opacity protein. Our data indicate that a concurrent phase switching of multiple phase-variable bacterial surface components may be a prerequisite for meningococcal invasion into nasopharyngeal epithelium and that meningococcal class 5 proteins (Opa and Opc) may promote tissue tropism.

Antigens, Bacterial↗
PubMed1996

Variation in metabolic enzyme activity of persistent Haemophilus influenzae in respiratory tracts of patients with cystic fibrosis.

Haemophilus influenzae organisms were isolated from sputum specimens prospectively collected from 40 patients with cystic fibrosis during 2 years to study variations in the metabolic enzyme activities of persistent H. influenzae strains as determined by biotyping. In total, 97 distinct H. influenzae strains without variations in their major outer membrane protein (MOMP) patterns and 73 MOMP variants derived from 30 of these distinct strains were obtained. Twelve distinct strains and 42 MOMP variant strains were isolated at multiple time points during the study period, indicating the persistence of these strains. Among the 54 persistent H. influenzae strains, 22 (41%) strains with stable MOMP compositions showed random variations in biotypes. In 39 of 103 (38%) H. influenzae strains, biotype changes coincided with MOMP variations. Biotype variations were the result of both the loss and the acquisition of enzyme activities. The results of the study indicate that changes in metabolic enzyme activity occur randomly during the persistence of H. influenzae organisms in cystic fibrosis patients, irrespective of MOMP variations.

Cystic Fibrosis↗
PubMed1996

Heterogeneity in susceptibility to metronidazole among Helicobacter pylori isolates from patients with gastritis or peptic ulcer disease.

Combination therapies that include metronidazole (MTZ) are the most successful therapies used in eradicating Helicobacter pylori. In this study, the prevalence and the relevance of heterogeneity in susceptibility to MTZ among H. pylori populations of 156 patients were evaluated. The results of this study show that 37 patients (24%) were infected with MTZ-resistant H. pylori (MIC > or = 8 micrograms/ml). Furthermore, 33% (52 of 156) of the patients were found to be infected with H. pylori populations heterogeneous for their susceptibility to MTZ. The reassessment of the MICs of MTZ for these 52 H. pylori populations revealed MTZ resistance in 28 of them, increasing the number of MTZ-resistant H. pylori populations among the 156 patients to 65 (42%). Out of 20 isolates, 2 (10%) heterogeneous in their susceptibility to MTZ also appeared to be heterogeneous at the genome level as determined by randomly amplified polymorphic DNA fingerprinting. In conclusion, the results show the limitations and risk of possible misinterpretations when only a single colony, picked from the primary H. pylori populations isolated from patients, is analyzed for its susceptibility to MTZ.

Drug Resistance, Microbial↗
PubMed1996

Clinical manifestations and course of meningococcal disease in 562 patients.

To describe the clinical manifestations and course of meningococcal disease (MD) data were collected on patients with culture-proven MD, reported in the Netherlands between April 1, 1989 and April 30, 1990 by means of a questionnaire completed by the specialist in attendance. During the study period, 562 patients (295 males, 267 females) were reported. The age of the patients ranged from 2 weeks to 88 years. Of the patients, 57.8% were classified as meningitic, 20.3% as bacteraemic and 21.9% as both meningitic and bacteraemic. In 4.6% of the patients a predisposing factor was present, and in 1.4% a previous episode of meningitis had occurred. A positive family history of meningitis was reported in 12.9% of the patients. On admission, 65.2% of the patients had haemorrhagic skin lesions, 7.9% coma and 4.2% seizures. During admission, 17.8% of the patients developed serious complications. The fatality rate was 7.7%. In 73.2% of the deceased, death occurred within 2 days after admission. Of the survivors, 8.5% recovered with serious sequelae. In conclusion, 16% of the patients with meningococcal disease either died or became severely disabled. Prevention of this putative life-threatening disease seems to be the only means of circumventing the problems caused by this serious condition.

Adolescent↗
PubMed1996

Immunoglobulin A antibodies against Pseudomonas aeruginosa in the tear fluid of contact lens wearers.

PURPOSE: Pseudomonas aeruginosa is the most important cause of contact lens-associated ulcerative keratitis, especially for those who use extended-wear lenses. Until now, the presence of specific anti-P. aeruginosa immunoglobulin A (IgA) antibodies in the tears of contact lens wearers has not been investigated and is the purpose of the current study. METHODS: The levels of specific IgA antibodies against P. aeruginosa and total secretory IgA (s-IgA) concentrations were measured in tears of various groups of contact lens and non-contact lens wearers using enzyme-linked immunosorbent assays. Contact lens groups were divided into the following categories: daily-wear rigid gas-permeable lenses (n = 23), daily-wear soft lenses (n = 22), extended-wear soft lenses (n = 17), and non-contact lens wearers (n = 23). As a positive control group, we tested tears obtained from patients with cystic fibrosis (n = 5) because the respiratory tract of these persons often are colonized by P. aeruginosa. RESULTS: The percentage of nonresponders (< 15 U/ml) varied between 9% in daily-wear rigid gas-permeable contact lens users to 23% in daily-wear soft contact lens users. The percentage of nonresponders in controls was 13%. The frequency of nonresponders was not significantly different among the different groups tested. All patients with cystic fibrosis showed a very high anti-P. aeruginosa IgA response in their tears. When analyzing the mean anti-P. aeruginosa IgA response, a significantly lower level was found in extended-wear contact lens users (38 U/ml) compared to non-contact lens wearers (82 U/ml). Total s-IgA levels in the tears of the various groups tested were not significantly different. CONCLUSIONS: A substantial number of persons in the population of contact lens wearers tested lack detectable IgA antibodies against P. aeruginosa in their tears and may be susceptible to P. aeruginosa keratitis if the physiological condition of their cornea is compromised.

Adolescent↗
PubMed1996

Therapeutic options after failed Helicobacter pylori eradication therapy.

OBJECTIVES: Many of the currently used Helicobacter pylori eradication regimens fail to cure 5-20% of the patients. Those patients will remain at risk of developing a potentially fatal complication of peptic ulcer disease. Therefore, a new attempt to cure H. pylori infection after initial failure of therapy is indicated. We studied the efficacy of three retreatment regimens after initial failure of omeprazole-amoxicillin dual therapy. METHODS: Fifty-three patients whose treatment failed were randomly assigned to receive retreatment with the same regimen of omeprazole 20 mg b.i.d. (group I) or omeprazole 40 mg t.i.d. (group II) plus amoxicillin 750 mg t.i.d. for 14 days. Forty patients in whom the omeprazole-amoxicillin retreatment failed were assigned to receive omeprazole 20 mg b.i.d., amoxicillin 750 mg t.i.d., and metronidazole 500 mg t.i.d. for 14 days (group III) or omeprazole 20 mg b.i.d. plus clarithromycin 500 mg t.i.d. for 14 days (group IV). H. pylori infection was assessed by culture and histology of gastric biopsies before and 4-6 wk after cessation of therapy. Susceptibility of H. pylori to amoxicillin, clarithromycin, and metronidazole was determined by the E test. RESULTS: In groups I (n = 28) and II (n = 25), cure of H. pylori infection was achieved in 21% and 28% of patients, respectively (not significant). In groups III (n = 20) and IV (n = 20), H. pylori infection was cured in 75% and 70%, respectively. CONCLUSIONS: Retreatment with an identical omeprazole-amoxicillin dual regimen is of limited benefit, a result that is independent of the omeprazole dose. In contrast, a third H. pylori eradication attempt with omeprazole-clarithromycin dual therapy or omeprazole-amoxicillin-metronidazole triple therapy provides reasonable cure rates after failure of omeprazole-amoxicillin dual therapy.

Adult↗