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J Dankert

Publications and source records attributed to J Dankert.

At least 73 records · Page 4Linked to original sources
PubMed1999

Evidence for frequent OspC gene transfer between Borrelia valaisiana sp. nov. and other Lyme disease spirochetes.

Molecular polymorphism of the ospC gene has been reported in Borrelia burgdorferi sensu stricto, Borrelia garinii and Borrelia afzelii, the spirochetes causing human Lyme borreliosis. To assess the genetic relationship between ospC genes from the recently described Borrelia valaisiana sp. nov. and other B. burgdorferi sensu lato species, the ospC genes from eight B. valaisiana isolates were amplified by PCR, cloned and sequenced. The ospC genes of three B. valaisiana isolates were identical, but clearly distinct from ospC genes from other Borrelia species. Four B. valaisiana isolates possessed ospC genes more related to those of B. garinii, and fell into a cluster representing B. garinii species in the phylogenetic tree. One isolate had an ospC gene encoding a protein identical to that of B. afzelii strain. Since five of the eight (62.5%) B. valaisiana isolates contained a gene highly homologous or even identical to ospC genes found among B. garinii and B. afzelii strains, our findings indicate that ospC gene transfer occurs between B. valaisiana and other Lyme disease spirochetes.

Amino Acid Sequence↗
PubMed1999

[Pathophysiology of Helicobacter pylori infections].

Helicobacter pylori is the causative factor of chronic gastritis and ulcers of duodenum and stomach and relates to mucosa-associated lymphoid tissue (MALT) lymphomas. Host factors, bacterial factors and dietary habits conceivably play a part in the more severe mucosal lesions induced by H. pylori. H. pylori is a heterogeneous bacterial species, the various types differing in possession of a locus with genes coding for products that may intensify the inflammatory reaction. The cytotoxin-associated gene (cagA) protein is a marker for this locus; this protein and the vacuolating-associated cytotoxin A are clearly related to the ulcerative disease. Patients may be colonized by a mixed population of H. pylori consisting of cagA-positive and cagA-negative H. pylori. Also, a patient may be infected by a mixed population of H. pylori sensitive and resistant to metronidazole. Accordingly, a substantial part of the H. pylori population in a patient should be examined to arrive at an adequate conclusion concerning the production of H. pylori factors that may relate to a particular clinical picture and to the sensitivity to antibiotics of the H. pylori.

Duodenal Ulcer↗
PubMed1999

Haemophilus influenzae localized in epithelial cell layers is shielded from antibiotics and antibody-mediated bactericidal activity.

Nonencapsulated Haemophilus influenzae frequently persists in the lungs of chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF) patients for prolonged periods of time. The bacteria are not eradicated by antibiotic treatment of the patients or by specific antibodies that are found in the sputum and sera of these patients. We investigated whether H. influenzae, when localized in lung epithelial cell layers, is shielded from antibiotics and from antibody-mediated bactericidal activity of specific antibodies. An in vitro model system consisting of lung epithelial NCI-H292 cells on permeable supports was developed to allow long term association of H. influenzae with the cells. Microscopic examination showed increasing numbers of H. influenzae bacteria between the epithelial cells up to 24 h of incubation. Coinciding with the microscopic observations the maximum number of cell-associated bacteria surviving gentamicin treatment of the cell layers was obtained after 24 h of incubation. All H. influenzae strains, and one Haemophilus parainfluenzae strain tested penetrated into the cell layer as determined by gentamicin killing. Cell-associated bacteria were shielded from the bactericidal activity of several antibiotics and from antibody-mediated bactericidal activity. After prolonged incubation in the cell system in the presence of a specific bactericidal antibody against major outer membrane protein (MOMP) P2, antigenic variation occurred due to a point mutation in the MOMP P2 gene, similar to point mutations observed in vivo. We conclude that penetration of H. influenzae between lung epithelial cells results in shielding the bacteria from killing by antibody dependent defense mechanisms and by antibiotics. Therefore, penetration of H. influenzae between epithelial cells may contribute to the persistence of this microorganism in COPD and CF patients.

Anti-Bacterial Agents↗
PubMed1999

Isolation and characterization of promoter regions from Streptococcus gordonii CH1.

We aimed to identify transcription signal sequences from Streptococcus gordonii strain CH1 by random chromosomal cloning. Five genomic fragments from a Sau3A digest, which constitutively activated transcription of a promoterless spectinomycin resistance gene in this strain, were isolated and characterized. Additionally, one promoter fragment was isolated that was specifically activated under iron-limiting conditions. A sequence motif with similarity to the consensus for Fur-binding regulatory DNA sequences (Fur box) in Escherichia coli was detected within the putative promoter region. The open reading frame downstream of this region possibly encodes a transmembrane protein involved in iron uptake.

Amino Acid Sequence↗
PubMed1999

The intestinal mucus layer from patients with inflammatory bowel disease harbors high numbers of bacteria compared with controls.

BACKGROUND & AIMS: Whether the bacterial flora contributes to the pathogenesis of inflammatory bowel disease (IBD) by increased penetration in mucus, increased adherence to epithelial cells, or invasion of the epithelium is unknown. We therefore studied the spatial distribution of bacteria in the mucosa of rectal biopsy specimens from patients with IBD and from controls. METHODS: Rectal biopsy specimens from 19 patients with IBD and from 14 controls were studied by using nonradioactive ribosomal RNA in situ hybridization. Total mucosal surface length examined for each patient was measured, and the number of bacteria visualized was estimated semiquantitatively. RESULTS: No bacteria were observed in biopsy specimens from 10 controls (71%) and 6 IBD patients (32%) (P = 0.04; odds ratio, 5.42; 95% confidence interval, 1.23-23.9). IBD rectal specimens contained significantly more bacteria than control samples (P = 0.004). Bacteria were localized within the mucus layer but did not adhere to the epithelial cells and were not present within the lamina propria. There was no correlation between the numbers of bacteria present and either the degree of inflammation or the use of anti-inflammatory agents or sulfasalazine compounds. CONCLUSIONS: The intestinal mucus in IBD patients is less protective against the endogenous microflora than in controls, resulting in increased association of luminal bacteria with the mucus layer.

Bacteria↗
PubMed1999

Assessment of complement deficiency in patients with meningococcal disease in The Netherlands.

The frequency of complement deficiency in 176 of 7,732 patients with meningococcal disease in the Netherlands from 1959 through 1992 was assessed. Complement deficiency was found in six patients (3%): 3 (7%) of the patients with Neisseria meningitidis serogroup C disease, 1 (2%) of the patients with N. meningitidis serogroup A disease, and 2 (33%) of the patients with infections due to uncommon serogroups and nongroupable strains of N. meningitidis. Of 91 additional patients with meningococcal infections due to uncommon serogroups, 33% also had complement deficiency. Thirty-four of the 36 complement-deficient patients with meningococcal disease who were from 33 families were 5 years of age or older. Twenty-six additional complement-deficient relatives were found. Screening individuals with meningococcal disease due to uncommon serogroups who were 5 years of age or older identified 30 of the 33 complement-deficient families. Only 27% of the complement-deficient relatives had had meningococcal disease. This risk was lower for relatives with properdin deficiency (18%) than for those deficient in the late component of complement (38%). Therefore, pedigree studies are warranted for identifying those complement-deficient persons who require vaccination for meningococcal disease.

Adolescent↗
PubMed1999

Early switch from intravenous to oral antibiotics: guidelines and implementation in a large teaching hospital.

In recent years 'switch therapy' has been advocated: short intravenous antibiotic therapy, for 2-3 days, followed by oral treatment for the remainder of the course. Little is known about the number of patients that could benefit from early switch therapy and the consequences of introducing this strategy in everyday practice. We prospectively registered all antibiotic courses on wards for Internal Medicine, Surgery, and Pulmonology during a 2 month period, before (n = 362, inventorial phase) and after (n = 281, implementation phase) the introduction of guidelines for switching therapy. Approximately 40% of all patients who started on iv antibiotics were candidates for an early iv-oral switch. During the inventorial phase, 54% (52/97) of eligible patients were switched to oral treatment, after a median of 6 days (range 2-28 days). After implementation of the guidelines, this percentage rose to 83% (66/80) (difference 29%, 95% CI 16-42%; P < 0.001). Therapy was also switched earlier, after a median of 4 days (range 2 to 16 days). In the 6 weeks after completion of the oral course, recurrence of infections, or readmissions due to reinfections did not occur. Compared with the inventorial phase, 43% of iv administrations could be avoided, that is >6000 per year. This means a potential annual reduction of dfl.60,000 (c. US$30,000) of administration costs. The potential savings in purchase costs of the antibiotics were dfl.54,000 (US$27,000) annually. In conclusion, a substantial number of patients starting on iv antibiotics were candidates for an early iv-oral switch. The guidelines were well accepted by the physicians and substantial savings in costs and nursing time were achieved.

Administration, Oral↗
PubMed1999

Thoracic duct in patients with multiple organ failure: no major route of bacterial translocation.

OBJECTIVE: To determine whether translocation of bacteria or endotoxin occurred into the thoracic duct in patients with multiple organ failure (MOF). SUMMARY BACKGROUND DATA: Translocation of bacteria or endotoxin has been proposed as a causative factor for MOF in patients without an infectious focus, although it has rarely been demonstrated in patients at risk for MOF. Most studies have investigated the hematogenic route of translocation, but it has been argued that lymphatic translocation of bacteria or endotoxin by the thoracic duct is the major route of translocation. METHODS: The thoracic duct was drained for 5 days in patients with MOF caused either by generalized fecal peritonitis (n = 4) or by an event without clinical and microbiologic evidence of infection (n = 4). Patients without MOF who were undergoing a transthoracic esophageal resection served as controls. In lymph and blood, concentrations of endotoxin, proinflammatory cytokines, and antiinflammatory cytokines were measured. RESULTS: Endotoxin concentrations in lymph and blood of patients with MOF ranged from 39 to 63 units per liter and were not significantly different from concentrations in patients without MOF. The quantity of endotoxin transported by the thoracic duct in the study group was small. In patients with MOF, low levels of proinflammatory cytokines and high levels of antagonists of these cytokines were found. CONCLUSION: This study provides evidence that translocation (especially of endotoxin) occurs into the thoracic duct. However, these data do not support the concept that the thoracic duct is a major route of bacterial translocation in patients with MOF.

Aged↗
PubMed1999

Upper respiratory tract infection, heterologous immunisation and meningococcal disease.

To test the hypothesis that an episode of upper respiratory tract infection or heterologous immunisation is a predisposing factor for the occurrence of meningococcal disease, data from 377 cases of meningococcal disease and their household contacts (n = 1124) were analysed by conditional logistic regression analysis with stratification for household. The odds ratio for a recent upper respiratory tract infection for patients versus household contacts, adjusted for age and the presence of an underlying predisposing disease, was 2.8 and that for recent heterologous immunisation 1.0. These results support previous observations regarding the association between a preceding upper respiratory tract infection and the occurrence of meningococcal disease; however, no association was found between preceding heterologous immunisation and meningococcal disease. Therefore, increased alertness after heterologous immunisation does not seem warranted.

Adolescent↗
PubMed1999

Relation between vacA subtypes, cytotoxin activity, and disease in Helicobacter pylori-infected patients from The Netherlands.

OBJECTIVE: The vacuolating cytotoxin of Helicobacter pylori (H. pylori) is encoded by vacA, of which allelic variation has been described. In the U.S., H. pylori strains with the signal sequence allele s1a are associated with enhanced gastric inflammation and with peptic ulcer disease (PUD). The m1 middle region allele is linked with more severe gastric epithelial damage. However, the distribution of H. pylori genotypes and the association with disease may be different in other geographical areas. The aim of this study was to establish whether vacA types among H. pylori isolates from Dutch patients are associated with disease. METHODS: The cytotoxin activity of the H. pylori isolates from 34 PUD patients and 46 patients with functional dyspepsia (FD) was assessed by an in vitro assay using HeLa cells as indicator cells. The vacA types and cagA status of the isolates were assessed by polymerase chain reaction (PCR). RESULTS: vacA s1-type H. pylori displayed cytotoxin activity more frequently than s2 vacA-type H. pylori (p = 0.003). This difference was not significant when only cagA+ H. pylori were considered. H. pylori isolates with the m1 vacA type exhibited a higher cytotoxin activity, independent of cagA (p = 0.006). Ninety-four percent (32/34) of the PUD patients and 74% (34/46) of the FD patients were infected with s1 vacA-type H. pylori (p = 0.04). When only cagA+ H. pylori were considered, s1 vacA type was not associated with disease. In addition, neither the s1a nor s1b subtypes correlated with disease. CONCLUSIONS: An association between vacA subtypes and disease could not be established in this patient population, due to the strong linkage between vacA s1 type and cagA.

Antigens, Bacterial↗
PubMed1999

Variation in the composition and pore function of major outer membrane pore protein P2 of Haemophilus influenzae from cystic fibrosis patients.

We investigated the relationship between susceptibility to beta-lactam antibiotics and variation in the major outer membrane protein P2 (OmpP2; also called porin) of persistent nonencapsulated Haemophilus influenzae isolated from cystic fibrosis patients. Nine OmpP2 variants were selected from two distinct H. influenzae strains from two patients extensively treated with beta-lactam antibiotics. The variants differed in their susceptibilities to at least two beta-lactam antibiotics. By detergent extraction and column chromatography, OmpP2 was purified from two variants that were derived from strain 70 and that differed notably in their susceptibilities to beta-lactam antibiotics. The proteins were reconstituted into black lipid membranes for measurement of porin function. OmpP2 from the more resistant isolate (isolate 70b) had a smaller channel conductance than OmpP2 of the more susceptible isolate (isolate 70f). DNA sequencing of ompP2 of these isolates revealed single nonsynonymous base differences; there were changes in the amino acid sequence corresponding to surface-exposed loops 4, 5, 6, and 8. Changes in loops 4, 5, and 6 were previously shown to result in antigenic differences. Beside these mutations, variants of strain 70 showed additional mutations in loop 1 and nonexposed loop 3. Taken together, our results suggest that in variants of strain 70, nonsynonymous point mutations accumulated both in the sequences of ompP2 coding for antigen-variable loops and in other loops, notably, loops 1 and 3. The latter changes are suggested to affect the permeability of the porin channel.

Amino Acid Sequence↗
PubMed1999

Molecular typing of Borrelia burgdorferi sensu lato: taxonomic, epidemiological, and clinical implications.

Borrelia burgdorferi sensu lato, the spirochete that causes human Lyme borreliosis (LB), is a genetically and phenotypically divergent species. In the past several years, various molecular approaches have been developed and used to determine the phenotypic and genetic heterogeneity within the LB-related spirochetes and their potential association with distinct clinical syndromes. These methods include serotyping, multilocus enzyme electrophoresis, DNA-DNA reassociation analysis, rRNA gene restriction analysis (ribotyping), pulsed-field gel electrophoresis, plasmid fingerprinting, randomly amplified polymorphic DNA fingerprinting analysis, species-specific PCR and PCR-based restriction fragment length polymorphism (RFLP) analysis, and sequence analysis of 16S rRNA and other conserved genes. On the basis of DNA-DNA reassociation analysis, 10 different Borrelia species have been described within the B. burgdorferi sensu lato complex: B. burgdorferi sensu stricto, Borrelia garinii, Borrelia afzelii, Borrelia japonica, Borrelia andersonii, Borrelia valaisiana, Borrelia lusitaniae, Borrelia tanukii, Borrelia turdi, and Borrelia bissettii sp. nov. To date, only B. burgdorferi sensu stricto, B. garinii, and B. afzelii are well known to be responsible for causing human disease. Different Borrelia species have been associated with distinct clinical manifestations of LB. In addition, Borrelia species are differentially distributed worldwide and may be maintained through different transmission cycles in nature. In this paper, the molecular methods used for typing of B. burgdorferi sensu lato are reviewed. The current taxonomic status of B. burgdorferi sensu lato and its epidemiological and clinical implications, especiallly correlation between the variable clinical presentations and the infecting Borrelia species, are discussed in detail.

Bacterial Typing Techniques↗
PubMed1999

Deletion of porA by recombination between clusters of repetitive extragenic palindromic sequences in Neisseria meningitidis.

PorA is an important component in a vaccine against infection with Neisseria meningitidis. However, porA-negative meningococci were isolated from patients, thereby potentially limiting the role of PorA-mediated immunity. To analyze the mechanism by which the porA deletion occurred, the regions upstream and downstream of porA from three meningococcal strains (H44/76, H355, and 860183) were sequenced. The porA upstream region in strain 860183 contains a cluster of 22 repetitive palindromic RS3 core sequences (ATTCCC-N8-GGGAAT) and 10 RS3 core sequences (ATTCCC) in direct orientation. The cluster is flanked by neisserial repeats, so-called Correia elements, and can be subdivided into three repeats of 518 bp followed by a truncated repeat. The porA upstream region of the other two strains showed deletions, probably caused by a recombination between RS3 core sequences. The porA downstream region of H44/76 and H355 contains the IS1106 element followed by a cluster of 10 palindromic RS3 core sequences, 4 RS3 core sequences, and 1 other RS3 core sequence (GGGAAT) and is followed by a Correia element. This cluster can be subdivided into four direct repeats of 370 bp. Strain 860183 had two such repeats instead of four. Sequence analysis of the porA-negative variants indicated that the deletion of porA occurred via a recombination between two copies of the 116-bp region, containing two palindromic RS3 core sequences and a single RS3 core sequence. This region is homologous in the upstream and downstream clusters.

Base Sequence↗
PubMed1999

Antigenic variation of the class I outer membrane protein in hyperendemic Neisseria meningitidis strains in the netherlands.

Since 1980, the number of cases of meningococcal disease caused by serogroup B isolates with the P1.4 serosubtype has greatly increased in The Netherlands. Screening for this serosubtype in the strain collection of The Netherlands Reference Laboratory for Bacterial Meningitis revealed that a low number of P1.4 strains had been present in the Dutch meningococcal population since 1965. Genotyping of P1.4 strains showed that one cluster of strains, the hyperendemic lineage III (D. A. Caugant et al., J. Infect. Dis. 162:867-874, 1990), is responsible for the increase since 1980. The diversity of the porA genes, which encode the P1 protein on which serosubtyping is based, was studied for genotypically different P1.4 strains and for lineage III strains expressing antigenically different P1 proteins. Sequence analysis showed that porA genes of genotypically distinct strains that express antigenically indistinguishable P1 proteins are identical only in the epitope-encoding region, suggesting that this region has spread through the meningococcal population via horizontal gene transfer. Analysis of porA genes of lineage III strains showed that both horizontal gene transfer and partial deletion of the epitope-encoding region may contribute to the different antigenic properties for P1 of these strains. Phase variation of expression of the porA gene seems to account for most nonreacting strains. These results show that serosubtyping may underestimate the rise of a hyperendemic clone.

Amino Acid Sequence↗