Search PubMed⌕ Search

Biomedical subjects

J Dankert

Publications and source records attributed to J Dankert.

At least 109 records · Page 6Linked to original sources
PubMed1998

Molecular typing of Borrelia burgdorferi sensu lato by randomly amplified polymorphic DNA fingerprinting analysis.

To study whether pathogenic clusters of Borrelia burgdorferi sensu lato strains occur, we typed 136 isolates, cultured from specimens from patients (n = 49) with various clinical entities and from ticks (n = 83) or dogs (n = 4) from different geographic regions, by randomly amplified polymorphic DNA (RAPD) fingerprinting with four arbitrary primers. The RAPD patterns were reproducible up to the 95% similarity level as shown in duplicate experiments. In these experiments the purified DNAs prepared on different days, from different colonies, and after various passages were used as templates. With an intergroup difference of 55%, the 136 strains could be divided into seven genetic clusters. Six clusters comprised and corresponded to the established species B. burgdorferi sensu stricto (n = 23), Borrelia garinii (n = 39), Borrelia afzelii (n = 59), Borrelia japonica (n = 1), Borrelia valaisiana (n = 12), and genomic group DN127 (n = 1). One strain from a patient with erythema migrans (EM) did not belong to any of the species or genomic groups known up to now. The RAPD types of B. burgdorferi sensu stricto, B. garinii, and B. afzelii isolates, which may give rise to human Lyme borreliosis (LB), were associated with their geographic origins. A high degree of genetic diversity was observed among the 39 B. garinii strains, and six subgroups could be recognized. One of these comprised eight isolates from patients with disseminated LB only and no tick isolates. B. afzelii strains from patients with EM or acrodermatitis chronica atrophicans were not clustered in particular branches. Our study showed that RAPD analysis is a powerful tool for discriminating different Borrelia species as well as Borrelia isolates within species.

Animals↗
PubMed1998

Randomly amplified polymorphic DNA genotyping of serogroup A meningococci yields results similar to those obtained by multilocus enzyme electrophoresis and reveals new genotypes.

Randomly amplified polymorphic DNA (RAPD) genotyping was applied to one representative strain of each of the 84 electrophoretic types (ETs) of Neisseria meningitidis serogroup A previously defined by multilocus enzyme electrophoresis (MEE) (J.-F. Wang et al., Infect. Immun. 60:5267-5282, 1992). Twenty-seven additional isolates comprising six ETs were also tested. MEE and RAPD genotyping yielded similar dendrograms at the subgroup level. Similar results were obtained by both methods for 18 serogroup A meningococci isolated in The Netherlands between 1989 and 1993. Ten of these isolates defined a new subgroup, designated subgroup IX. One isolate belonged to the ET-5 complex, normally associated with serogroup B strains (D. A. Caugant et al., Proc. Natl. Acad. Sci. USA 83:4927-4931, 1986). By RAPD genotyping, meningococci can be linked to previously characterized genotypes by using a computerized database, and dendrograms based on cluster analyses can easily be generated. RAPD analysis offers advantages over MEE since intermediate numbers of isolates of serogroup A meningococci can quickly be assigned to known subgroups and new subgroups can be defined.

Bacterial Typing Techniques↗
PubMed1998

Characterization of Neisseria meningitidis strains causing disease in complement-deficient and complement-sufficient patients.

Serotyping and serosubtyping of meningococci showed no difference between isolates from 44 complement-deficient persons and from 50 complement-sufficient persons with meningococcal disease. Multilocus enzyme electrophoretic typing of the meningococci revealed 54 electrophoretic types that were equally distributed among isolates from complement-deficient and complement-sufficient patients. Analysis of strains isolated from eight complement-deficient persons with 11 recurrences of meningococcal disease showed that one strain was identical to the strain previously isolated from the same individual. Our results indicate that there are no differences between the clonal distributions of strains infecting complement-deficient and complement-sufficient patients. Most recurrences were infections caused by different strains.

Adolescent↗
PubMed1998

Influence of metronidazole resistance on efficacy of quadruple therapy for Helicobacter pylori eradication.

BACKGROUND: Metronidazole-containing eradication therapies are less effective for metronidazole resistant Helicobacter pylori. Although early data suggested improvement of the efficacy of bismuth triple therapy after the addition of acid suppressives, these findings were based on studies with small numbers of patients, incomplete post-eradication follow up, or omission of pretreatment susceptibility testing. AIMS: To study the efficacy of quadruple therapy in the Amsterdam area, where the efficacy of bismuth triple therapy has been proved to be affected by metronidazole resistance. PATIENTS AND METHODS: Eighty two consecutive dyspeptic H pylori positive patients with either metronidazole susceptible (group I) or metronidazole resistant H pylori strains (group II) received quadruple therapy for one week: omeprazole 20 mg twice daily; colloidal bismuth subcitrate 120 mg four times a day; tetracycline 500 mg four times a day; metronidazole 500 mg three times a day. Susceptibility to metronidazole was determined by the E-test. RESULTS: Intention to treat analysis showed that H pylori infection had been cured in 42/43 patients (98%) in group I and 32/39 patients (82%) in group II (p = 0.02). CONCLUSION: The efficacy of quadruple therapy is significantly impaired in patients infected with metronidazole resistant H pylori. Therefore a non-metronidazole-containing regimen should preferably be used in areas known to have a high prevalence of pretreatment metronidazole resistance.

Adult↗
PubMed1998

Haemophilus influenzae in lung explants of patients with end-stage pulmonary disease.

In order to determine the presence and distribution of Haemophilus influenzae in lung tissue sections, we obtained lung explants from 49 lung transplant recipients with cystic fibrosis (CF) (n = 16), chronic obstructive pulmonary disease (COPD) including emphysema (n = 16), bronchiectasis (n = 5), pulmonary hypertension (n = 9), Langerhans cell histiocytosis (n = 1), and idiopathic pulmonary fibrosis (n = 2). Analysis was done by selective culturing, immunoperoxidase (IP) staining, and by polymerase chain reaction (PCR). H. influenzae was cultured from specimens of the lung explants from one CF and one COPD patient. IP staining of tissue sections was positive in 24 patients (10 CF patients, eight COPD patients, two bronchiectasis patients, and four patients with noninfectious pulmonary diseases). IP-positive tissue sections were PCR-positive, and IP-negative sections were PCR-negative. H. influenzae was more frequently detected in tissue sections of lung explants from CF and COPD patients than from patients with bronchiectasis or noninfectious pulmonary diseases. H. influenzae was diffusely present in the epithelium, the submucosa of the bronchi, the bronchioles, the interstitium, and the alveolar epithelium. H. influenzae was localized extracellularly alone and in bacterial clusters, and was also associated with macrophages in CF patients. The results of this study demonstrate that H. influenzae is often present in the lungs of patients with end-stage pulmonary disease, especially CF and COPD patients. H. influenzae is diffusely present in the respiratory epithelium and subepithelial layers of the lungs of these patients.

Adolescent↗
PubMed1998

Duplex (thermotroph-psychrotroph) quadrant plates: convenient, error-avoiding tools for monitoring of HACCP-contained food lines and for epidemiological investigations under conditions of military or other constraints.

A set of two "two-tier" (thermotroph-psychrotroph) single quadrant plates (QPs) was developed previously to allow convenient enumeration of numbers of colony-forming units of most pertinent pathogenic bacteria or marker bacteria in foods. These include Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, thermotrophic and psychrotrophic Enterobacteriaceae, Clostridium spp., and Enterococcus spp. As the QPs had given excellent results in monitoring samples of marketed food products potentially involved in food-transmitted illnesses, the approach was tested for practicability under military deployment and other constraints. Three approaches were envisaged: (i) validating lapse-free adherence to meticulously codified good military catering practices; (ii) acceptance/rejection testing of locally procured foods or meals; and (iii) employing rapid culture in support of evidence obtained by microscopy in attempts to identify foods involved in infectious or toxic disease outbreaks occurring in the field. The method was found to be elegant, avoiding confusion when larger number of specimens were to be screened, as well as easy to teach to staff with little or no training in microbiology, and it provided entirely reliable results. For use outside the laboratory, preparation of food macerates by use of shake flasks containing glass or plastic beads and peptone saline as a substitute for stomaching was found acceptable, though the shake flask technique led to slightly diminished colony counts. Results obtained with incubation times shortened to ca. 12 h could be relied on only when the results were alarmingly positive, but not when the colony counts at the 12-h point did not yet indicate a reason for concern.

Cheese↗
PubMed1997

Human lactoferrin receptor activity in non-encapsulated Haemophilus influenzae.

Since the ability of bacteria to compete with lactoferrin for iron contributes to the pathogenesis of mucosal infections, the presence of lactoferrin receptor activity in non-encapsulated Haemophilus influenzae was investigated. The growth of 18 H. influenzae isolates from the sputum samples of chronic bronchitis patients and of six of seven H. influenzae throat isolates from healthy adults was stimulated by iron saturated human lactoferrin. Apo-lactoferrin did not stimulate the growth of H. influenzae. Human lactoferrin binding to iron limited bacteria was detected for 16 H. influenzae strains from chronic bronchitis patients and for five of seven isolates from healthy adults. We conclude that the majority of H. influenzae isolates tested bind human lactoferrin and that the iron from lactoferrin is used for growth.

Adult↗
PubMed1997

Sequence variation in the hpd gene of nonencapsulated Haemophilus influenzae isolated from patients with chronic bronchitis.

The molecular diversity of protein D of nonencapsulated Haemophilus influenzae strains isolated from persistently infected patients with chronic bronchitis was studied by sequencing the hpd gene of four independently obtained isolates. The nucleotide (nt) sequences of the hpd genes of two strains were identical. The other two hpd sequences showed nt substitutions which were mostly synonymous. As a consequence the deduced amino acid (aa) sequences differed from the consensus sequence only by a few aa. No changes in the hpd genes were observed among the four variants of the four strains persisting in chronic bronchitis patients for 9, 11, 8 and 3 months, respectively, although variation in their major outer membrane proteins P2 and P5 occurred. We conclude that the hpd gene is conserved during chronic infections of nonencapsulated H. influenzae.

Amino Acid Sequence↗
PubMed1997

Effect of Helicobacter pylori eradication on gastritis in relation to cagA: a prospective 1-year follow-up study.

BACKGROUND & AIMS: Whether Helicobacter pylori eradication resolves intestinal metaplasia and atrophy and whether infection with cagA+ H. pylori is related to a specific clinical outcome are not known. The aim of this study was to investigate the role of H. pylori eradication on the course of intestinal metaplasia (IM) and atrophy in relation to cagA. METHODS: In a large prospective study, the cagA status of H. pylori isolated from consecutive dyspeptic patients was related to clinical outcome before and 1 year after successful eradication of H. pylori. At pretreatment and 4-6 weeks and on average 1 year after eradication therapy, the degree of gastritis and the status of H. pylori were assessed by culture and histopathology. RESULTS: Specimens of cagA+ H. pylori were recovered from 122 of 155 (79%) patients infected with H. pylori. Pretreatment degrees of gastritis activity, superficial epithelial damage, IM, and atrophy were significantly greater in patients infected with cagA+ H. pylori (P < 0.001). After successful eradication of H. pylori, a significant improvement of activity of gastritis and superficial epithelial damage occurred (P < 0.001), but the degree of IM and atrophy did not change, irrespective of the cagA status. CONCLUSIONS: The usefulness of H. pylori eradication to revert precancerous lesions such as IM and atrophy after 1-year follow-up is questionable.

Amoxicillin↗
PubMed1997

Effect of nationwide vaccination of 3-month-old infants in The Netherlands with conjugate Haemophilus influenzae type b vaccine: high efficacy and lack of herd immunity.

OBJECTIVE: The effect of nationwide vaccination in The Netherlands with conjugate Haemophilus influenzae type b vaccine on the incidence of H. influenzae meningitis was assessed in the first 3 years after the introduction of vaccination to the birth cohort at 3 months of age. STUDY DESIGN: Children in The Netherlands born after April 1, 1993, were vaccinated at the age of 3, 4, 5, and 11 months. Children older than 3 months at the inception of the H. influenzae type b vaccination program were not immunized. The number of cases among the vaccine cohort was compared with the number in a historical control group of children born in the period April 1, 1990, and April 1, 1993. RESULTS: The total number of patients with meningitis caused by H. influenzae type b reached a low, but constant level, that was expected for absence of herd immunity. Among children in the vaccine era group 22 cases occurred, whereas among the historical control group (prevaccine era) 342 cases were found. In the vaccine era cohort, 2 patients with H. influenzae type b meningitis had been vaccinated three times, 13 received one or no vaccine dose because of their age, and 7 were not vaccinated for religious or logistic reasons. The number of cases among nonvaccinated children older than 3 years and the number of H. influenzae meningitis cases caused by strains other than type b did not change. CONCLUSIONS: Conjugate H. influenzae type b vaccine prevents H. influenzae type b meningitis very effectively (99.4%) in children vaccinated twice or more. To reach rapid prevention of all H. influenzae type b disease simultaneous introduction of H. influenzae type b vaccination of children at various ages is recommended.

Cohort Studies↗
PubMed1997

The effect of mannan-binding lectin on opsonophagocytosis of Neisseria meningitidis.

Mannan-binding lectin (MBL), an acute phase protein with a structure and a function very similar to that of C1q, is known to act as an opsonin binding to a number of microorganisms. In order to investigate the effect of MBL on the phagocytic killing of meningococci, a serogroup B meningococcal strain (H44/76) and its unencapsulated variant v24, as well as a serogroup A meningococcal strain were opsonized with MBL (purified from normal human plasma at the State Serum Institute, Denmark) and used in a phagocytic killing assay at a density of 7 x 10(3) CFU/ml. Polymorphonuclear cells (PMNs) from one healthy donor were isolated by density gradient centrifugation over Percoll and added to the system (7 x 10(6) cells/ml). In a first set of experiments without addition of serum or complement, no influence of MBL was observed on the killing of any of these strains. Addition of MBL to non-opsonized bacteria of the serogroup A strain did not result in enhanced killing either; on the contrary, the growth of this strain increased significantly when a high MBL concentration (40 micrograms/ml) was used in the presence of PMNs. Further investigations were performed using sera of five individuals with late complement component deficiency (LCCD) and a concomitant MBL deficiency, vaccinated with a tetra-valent (ACYW135) meningococcal capsular polysaccharide vaccine. Pre- and post-vaccination sera (50% final concentration) were tested against a group A strain opsonized or not with MBL. In only one patient was there a moderate increase of killing of the opsonized bacteria after vaccination compared to pre-vaccination serum. Our results suggest that MBL may not play a significant role in the opsonophagocytosis of meningococci, irrespective of its binding to unencapsulated and serogroup A strains.

Bacterial Vaccines↗
PubMed1997

Photodynamic destruction of Haemophilus parainfluenzae by endogenously produced porphyrins.

Bacterial resistance against antibiotic treatment is becoming an increasing problem in medicine. Therefore methods to destroy microorganisms by other means are being investigated, one of which is photodynamic therapy (PDT). It has already been shown that a variety of Gram-positive and Gram-negative bacteria can be killed in vitro by PDT using exogenous sensitizers. An alternative method of photosensitizing cells is to stimulate the production of endogenous sensitizers. The purpose of this study was to investigate the bactericidal efficacy of PDT for Haemophilus parainfluenzae with endogenously produced porphyrins, synthesized in the presence of delta-aminolaevulinic acid (delta-ALA). H. parainfluenzae incubated with increasing amounts of delta-ALA showed decreased survival after illumination with 630 nm light. No photodynamic effect on the bacterial viability was found when H. parainfluenzae was grown without added delta-ALA. H. influenzae, grown in the presence of delta-ALA, but not capable of synthesizing porphyrins from delta-ALA, was not affected by PDT. Of the range of incident wavelengths, 617 nm appeared to be the most efficient in killing the bacteria. Spectrophotometry of the bacterial porphyrins demonstrated that the maximum fluorescence occurred at approximately 617 nm, with a much lower peak around 680 nm. We conclude that a substantial killing of H. parainfluenzae by PDT in vitro after endogenous sensitization with delta-ALA can be achieved.

Aminolevulinic Acid↗
PubMed1997

Reinfection versus recrudescence in Helicobacter pylori infection.

Antimicrobial treatment of Helicobacter pylori is the proper management strategy in patients with ulcers. A high rate of H. pylori reinfection after successful eradication therapy however, may give rise to ulcer recurrence. The risk of reinfection, depending on the prevalence and the rate of acquisition of H. pylori infection, varies with socioeconomic status, age and geographical location. The rate of reinfection may vary in a similar way. The available data in the literature reveal that reinfection by H. pylori is low or absent in developed countries and may be lower than the initial rate of acquisition. In addition, reported cases of H. pylori reinfection are often cases of recrudescent H. pylori infection. Acquisition rate in developing countries is high, so the reinfection rate is expected to be higher than in developed countries. However, studies discriminating reinfection from recrudescence are lacking and therefore more data from developing regions are needed to settle if 'cured once, cured forever' holds true.

Age Factors↗
PubMed1997

Prevalence of Campylobacter-associated diarrhea among patients infected with human immunodeficiency virus.

We performed a cross-sectional study at an outpatient AIDS clinic to assess the prevalence of Campylobacter species in stool specimens from 201 consecutive patients infected with human immunodeficiency virus (HIV). We characterized campylobacters phenotypically and genetically by using primers for the group of common species (i.e., C. jejuni, C. coli, C. lari, and C. upsaliensis) and for most individual uncommon species. We performed cultures with use of a membrane filter technique on nonselective blood agar and found that Campylobacter species were the most frequent enteropathogenic bacteria: the organisms were recovered from 7 (16%) of 43 patients with diarrhea and 5 (3%) of 158 patients without diarrhea (P = .001). We isolated only one campylobacter with use of conventional culture techniques on selective media. Phenotypic characterization of 10 campylobacter strains resulted in the misidentification of four isolates. C. upsaliensis was the most frequently isolated species, followed by C. jejuni and C. coli. Two strains could not be identified with the available primers. Two of 12 Campylobacter strains were resistant to erythromycin, and two were resistant to ciprofloxacin. We conclude that Campylobacter species other than C. jejuni can frequently be detected in the stools of HIV-infected patients and that these organisms could be associated with diarrhea.

Adult↗
PubMed1997

High seroprevalence of Encephalitozoon species in immunocompetent subjects.

Encephalitozoon species are important pathogens in human immunodeficiency virus-infected patients. However, in immunocompetent persons, little is known about Encephalitozoon infections, mainly because of the lack of reliable diagnostic tests. To improve diagnosis, three serologic techniques that use Encephalitozoon intestinalis as antigen were developed: an ELISA, an immunofluorescence technique (IFAT), and a counterimmunoelectrophoresis (CIE) method. The serologic response against E. intestinalis was studied in sera from 300 Dutch blood donors and 276 pregnant French women. For confirmation of specificity, sera from 150 subjects with various infectious and noninfectious diseases were examined. ELISA, IFAT, and CIE were specific for microsporidia infections, and IFAT and CIE were specific for Encephalitozoon infections. High antibody titers against Encephalitozoon organisms were found in 24 (8%) of 300 Dutch blood donors and in 13 (5%) of 276 pregnant French women. The high seroprevalence against Encephalitozoon species in Dutch blood donors and French women suggests that Encephalitozoon infection is common in immunocompetent subjects.

Adolescent↗