Search PubMed⌕ Search

Biomedical subjects

J Dankert

Publications and source records attributed to J Dankert.

At least 37 records · Page 2Linked to original sources
PubMed2001

Clarithromycin-susceptible and -resistant Helicobacter pylori isolates with identical randomly amplified polymorphic DNA-PCR genotypes cultured from single gastric biopsy specimens prior to antibiotic therapy.

Of the Helicobacter pylori populations from 976 patients, six contained clarithromycin-resistant as well as -susceptible colonies. In each heterogeneous H. pylori population, resistant H. pylori colonies harbored identical 23S ribosomal DNA (rDNA) mutations associated with clarithromycin resistance, while the susceptible H. pylori colonies all had wild-type 23S rDNA. The resistant and susceptible colonies of each of the heterogeneous H. pylori populations had identical randomly amplified polymorphic DNA-PCR genotypes. In conclusion, evaluation of antimicrobial susceptibility can be misinterpreted if only a single colony from the primary H. pylori population is used to test for clarithromycin susceptibility.

Anti-Bacterial Agents↗
PubMed2001

[Sterilization of dental instruments].

Instruments used by dentists are often sterilized with steam sterilization. At this moment three types of processes are described in the European norms: Type N, S and B. According to the norms type N can be used for non-wrapped non-hollow instruments and non-porous instruments, type S can be used for instruments specified by the manufacturer and type B can be used for wrapped, hollow and porous instruments. The principles on which the sterilizors are based are described. It is concluded that before purchasing the sterilizor the method of working and instruments to be sterilized must specified. In most cases a type B process is preferable in order to gaurantee to be certain to have an effective and reproducible process.

Dental Instruments↗
PubMed2000

Results of molecular detection of Mycoplasma pneumoniae among patients with acute respiratory infection and in their household contacts reveals children as human reservoirs.

During a 30-month prospective study in The Netherlands, the distribution of Mycoplasma pneumoniae and respiratory viruses among 1172 patients with acute respiratory infection (ARI) who were treated in the outpatient general practitioner setting was studied. M. pneumoniae, as detected by polymerase chain reaction analysis, was present in 39 (3.3%) patients. The infection rate was similar in all age groups. Nose and throat samples collected from 79 household contacts of M. pneumoniae-positive index patients revealed M. pneumoniae in 12 (15%) cases. The frequency of M. pneumoniae among household contacts of index patients treated with appropriate antibiotics and untreated index patients was similar. Nine of the 12 M. pneumoniae-positive household contacts were <16 years old (P=.02), and 4 (44%) of them did not develop ARI. Apparently, children are a relevant reservoir for M. pneumoniae.

Acute Disease↗
PubMed2000

Representational difference analysis of Neisseria meningitidis identifies sequences that are specific for the hyper-virulent lineage III clone.

Neisseria meningitidis may cause meningitis and septicemia. Since the early 1980s, an increased incidence of meningococcal disease has been caused by the lineage III clone in many countries in Europe and in New Zealand. We hypothesized that lineage III meningococci have specific DNA sequences, providing an opportunity to facilitate epidemiological studies by detecting lineage III isolates rapidly. Applying representational difference analysis on one lineage III tester strain and two non-lineage III driver strains, we identified three lineage III-specific sequences, probably part of a single locus encoding a restriction modification system. A PCR based on one of these sequences identified lineage III meningococcal isolates with a sensitivity of 100% and a specificity of 93%, which is superior to the serological identification of lineage III isolates.

Blotting, Southern↗
PubMed2000

Thrombocidins, microbicidal proteins from human blood platelets, are C-terminal deletion products of CXC chemokines.

Antibacterial proteins are components of the innate immune system found in many organisms and produced by a variety of cell types. Human blood platelets contain a number of antibacterial proteins in their alpha-granules that are released upon thrombin activation. The present study was designed to purify these proteins obtained from human platelets and to characterize them chemically and biologically. Two antibacterial proteins were purified from platelet granules in a two-step protocol using cation exchange chromatography and continuous acid urea polyacrylamide gel electrophoresis and were designated thrombocidin (TC)-1 and TC-2. Characterization of these proteins using mass spectrometry and N-terminal sequencing revealed that TC-1 and TC-2 are variants of the CXC chemokines neutrophil-activating peptide-2 and connective tissue-activating peptide-III, respectively. TC-1 and TC-2 differ from these chemokines by a C-terminal truncation of 2 amino acids. Both TCs, but not neutrophil-activating peptide-2 and connective tissue-activating peptide-III, were bactericidal for Bacillus subtilis, Escherichia coli, Staphylococcus aureus, and Lactococcus lactis and fungicidal for Cryptococcus neoformans. Killing of B. subtilis by either TC appeared to be very rapid. Because TCs were unable to dissipate the membrane potential of L. lactis, the mechanism of TC-mediated killing most probably does not involve pore formation.

Amino Acid Sequence↗
PubMed2000

In vivo and in vitro release of lysozyme from cross-linked gelatin hydrogels: a model system for the delivery of antibacterial proteins from prosthetic heart valves.

Prosthetic valve endocarditis may be reduced by the local delivery of antibacterial proteins from the Dacron sewing ring of a prosthetic heart valve. Dacron discs were treated with a carbon dioxide gas plasma to improve the hydrophilicity and thereby enabling homogeneous impregnation with gelatin type B. The gelatin samples were cross-linked to different degrees using various amounts of water-soluble carbodiimide (EDC) and N-hydroxysuccinimide (NHS). Lysozyme, a model protein for antibacterial proteins, was loaded into (non)-cross-linked gelatin gels incorporated in Dacron, or adsorbed onto non-treated and gas plasma-treated Dacron. The in vivo lysozyme release was measured after subcutaneous implantation of lysozyme-loaded samples in rats. The lysozyme content of the samples, and the lysozyme level of the surrounding tissue were determined at different explantation times (ranging from 6 h up to 1 week). For cross-linked gelatin gels, the lysozyme tissue level was elevated up to 2 days after implantation. In vitro release was measured using agarose medium or phosphate buffer. Lysozyme release in buffer solution under sink conditions was in good agreement with the in vivo lysozyme release profiles, and therefore considered a good model to describe in vivo release characteristics. The release was modelled with a solution of Fick's second law of diffusion using the appropriate boundary conditions. In this way the lysozyme concentration in the gel and the surrounding tissue as a function of time and distance was obtained. The presence of cross-linked gelatin in Dacron did lead to an increased uptake of lysozyme and a delayed release during 30 h after implantation, whereas a burst release took place from Dacron, gas plasma-treated Dacron, or Dacron containing non-cross-linked gelatin.

Algorithms↗
PubMed2000

Subcutaneous abscess formation around catheters induced by viable and nonviable Staphylococcus epidermidis as well as by small amounts of bacterial cell wall components.

The use of catheters is often complicated by infection, mainly due to Staphylococcus epidermidis. Recently, a novel poly(vinylpyrrolidone)-grafted silicone elastomer catheter (SEpvp) was introduced. Less bacteria adhered to SEpvp than to conventional SE catheters in vitro. The frequency of S. epidermidis infection associated with SEpvp and SE was assessed in a rabbit model. Unexpectedly, abscesses were induced by the injection of low numbers of S. epidermidis along subcutaneously inserted SEpvp. No abscesses were seen around SE, even when very high numbers of S. epidermidis were injected. This bioincompatibility reaction observed around the SEpvp was independent of the host, bacterial strain, and method of inoculation. Abscesses were also induced by nonviable S. epidermidis and by bacterial cell wall components. Because these incompatibility reactions were not observed in the absence of bacteria, biocompatibility testing should include experiments in which the inflammatory effects of the combination of catheter and (non)viable bacteria are tested.

Abscess↗
PubMed2000

Biomaterial-associated persistence of Staphylococcus epidermidis in pericatheter macrophages.

Biomaterial surfaces may be modified to reduce bacterial adhesion. The susceptibility in mice to Staphylococcus epidermidis infection in tissue surrounding the commonly used catheter materials-silicon elastomer (SE), polyamide (PA), and their surface-modified polyvinylpyrrolidone (PVP)-grafted derivatives, SE-PVP and PA-PVP, respectively-was assessed. Abscesses developed around SE-PVP. Around SE, PA, and PA-PVP catheters, no signs of infection were observed, although mice carrying PA-PVP developed septicemia after 14-21 days. S. epidermidis was cultured from the tissue surrounding PA-PVP segments. Cells around PA-PVP segments containing large numbers of bacteria were identified as macrophages by use of immunohistochemistry and electron microscopy. This persistence of intracellular bacteria was also observed around SE-PVP, SE, and PA catheters, although to a lesser extent. The cytokine profiles around the 4 materials were different. Implanted biomaterial induces an inflammatory response favorable to the persistence of S. epidermidis. Intracellular persistence of bacteria inside macrophages may be a pivotal process in the pathogenesis of biomaterial-associated infection.

Animals↗
PubMed2000

In vivo compatibility and degradation of crosslinked gelatin gels incorporated in knitted Dacron.

Gelatin gels were applied to porous Dacron meshes with the aim of using these gels for local drug delivery. In this article, the biocompatibility and degradation of gelatin gels with different crosslink densities applied in Dacron were studied in vivo by subcutaneous implantation in rats. Dacron discs were treated with carbon dioxide gas plasma to improve hydrophilicity, and subsequently impregnated with gelatin type B. The gelatin samples were crosslinked to different extents using various amounts of water-soluble carbodiimide (EDC) and N-hydroxysuccinimide (NHS). After 6 h, 2, 5, and 10 days, and 3, 6, and 10 weeks of postimplantation, the tissue reactions and biodegradation were studied by light microscopy. The early reaction of macrophages and polymorphonuclear cells to crosslinked gelatin was similar to or milder than Dacron. Giant cell formation was predominantly aimed at Dacron fibers and was markedly reduced in the presence of a crosslinked gelatin coating. At week 10 of implantation, the crosslinked gelatin gels were still present in the Dacron matrix. The gelatin degradation was less for samples with the highest crosslink density. The gelatin gel with the lowest crosslink density showed clear cellular ingrowth, starting after 6 weeks of implantation. The intermediate and high crosslinked gelatin gels showed little or no ingrowth. In these gels, giant cells were involved in the phagocytosis of gelatin parts at week 10. Application of carbodiimide crosslinked gelatin gels in Dacron is suitable for medical applications because of the good biocompatibility of the gels and the possibility of adapting the degradation rate of gelatin to a specific application.

Amines↗
PubMed2000

Clinical comparison of two commercial blood culture systems.

A prospective, volume-controlled comparison of the BacT/Alert FAN (Organon Teknika, USA) and Vital (bioMérieux, France) blood culture systems was performed in a university hospital during a period of 11 months. Twenty to 40 ml of blood drawn from an adult patient was distributed equally between a BacT/Alert FAN and a Vital blood culture set, both consisting of an aerobic and an anaerobic bottle. Bottles were weighed prior to use and after incubation to calculate the blood volume. A compliant pair of aerobic, or anaerobic, bottles of a blood culture was defined as follows: blood volumes were 4-11 ml and the blood volumes in the two bottles differed by < or =20%. From 120 compliant pairs of aerobic bottles, 135 organisms were recovered, of which 78 were isolated in both bottles, 44 in the BacT/Alert FAN bottle only and 13 in the Vital bottle only (P<0.0005). In particular, aerobic BacT/Alert FAN bottles yielded more members of the family Enterobacteriaceae (P<0.01). The BacT/Alert FAN system also performed significantly better when comparing anaerobic bottles, and the yield was greater during septic episodes. Both culture systems were similar regarding detection time, recovery during antimicrobial therapy, and the occurrence of false-positive and false-negative bottles. The overall performance of the BacT/Alert FAN system was better than that of the Vital system.

Adult↗
PubMed2000

In vitro and in vivo evaluation of gelatin-chondroitin sulphate hydrogels for controlled release of antibacterial proteins.

Chemically cross-linked gelatin-chondroitin sulphate (ChS) hydrogels, impregnated in Dacron, were evaluated as drug delivery systems for antibacterial proteins. The gelatin-chondroitin sulphate gels, plain or impregnated in Dacron, were cross-linked with a water-soluble carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The release of lysozyme and recombinant thrombocidin (rTC-1), an antibacterial protein derived from human blood platelets, from the gelatin-ChS gels in Dacron in phosphate-buffered saline at 37 degrees C was determined, and compared to the release from gelatin gels in Dacron and plain gelatin-ChS gels. The incorporation of chondroitin sulphate into gelatin gels, caused a marked increase in lysozyme loading capacity, and a slower release rate. The relative release profiles for rTC-1 and lysozyme were equal for cross-linked gelatin as well as for cross-linked gelatin-ChS gels. Furthermore, rTC-1 showed no loss of antibacterial activity after 1 week of release. The lysozyme concentration profiles in the samples and in the surrounding medium as a function of time were calculated using mathematical solutions for Ficks second law of diffusion for a semi-infinite composite medium, which is a schematic representation of a slab in a surrounding medium. The biocompatibility and degradation of the Dacron matrices impregnated with gelatin-ChS gels was studied after implantation in subcutaneous pockets in rats. Chemically cross-linked gelatin-Ch5 gels showed a mild tissue reaction, and almost complete degradation within 18 weeks of implantation.

Animals↗
PubMed2000

Two distinct ospA genes among Borrelia valaisiana strains.

Borrelia valaisiana is a recently described bacterial species in the Borrelia burgdorferi sensu lato complex. To further characterize this bacterium, the plasmid-encoded ospA genes from eight B. valaisiana isolates were amplified by PCR, cloned and sequenced. All B. valaisiana isolates studied possessed an ospA gene with a size of 822-825 bp. The identity of the predicted amino acid sequences of the OspA proteins among B. valaisiana isolates was 69.1-100%, and ranged from 68.2 to 79.1% between B. valaisiana and other B. burgdorferi sensu lato species. Based on the OspA protein sequences, the eight B. valaisiana isolates could be distinguished into two subgroups. Subgroup I contained six B. valaisiana isolates of which OspA sequences were almost identical, but clearly differed from other LB spirochetes. Subgroup II consisted of two isolates with identical OspA sequences which were only 70% identical to subgroup I B. valaisiana isolates and similarly distant from the OspA sequences of other B. burgdorferi sensu lato genospecies. Phylogenetic analysis indicates that B. valaisiana isolates belonging to subgroups I and II possibly evolved from two distinct ancestors. Our data showed for the first time a major difference in OspA proteins within a well-defined B. burgdorferi sensu lato species at the evolutionary level, suggesting that it is not always reliable to assign Borrelia isolates to a definite species solely based on data from ospA gene sequence analysis.

Amino Acid Sequence↗
PubMed2000

Development of antibodies against tetravalent meningococcal polysaccharides in revaccinated complement-deficient patients.

Individuals deficient in C3 or a late complement component are susceptible to recurrent meningococcal infections. Since they experience meningococcal episodes mostly with uncommon meningococcal serogroups, vaccination with a tetravalent vaccine containing A, C, Y and W135 polysaccharides has been suggested. We vaccinated a cohort of two C3 and 17 late complement component-deficient (LCCD) patients, revaccinated them 7 years later and investigated the development of their IgG antibodies to the capsular polysaccharides of the meningococcal vaccine. Seven years after the first vaccination levels of IgG antibodies declined compared with the levels present at 6 months after the first vaccination, but were still at least four times higher than before vaccination. Levels of antibodies to Y polysaccharide in serum of complement-deficient patients were rather low but they did not differ significantly from those in serum of healthy non-related controls (P = 0.07). Three months after the second vaccination IgG antibodies against all polysaccharides increased, exceeding those measured at 6 months after the first vaccination. In the 8 years of observation after the first vaccination two new meningococcal infections with strains related to the vaccine (serogroup Y strains) occurred in two patients, 3.5 and 5 years after the first vaccination. Our findings show that high IgG antibody levels against the tetravalent meningococcal polysaccharide vaccine were reached after revaccination of two C3 and 17 LCCD individuals 7 years after the first vaccination. Whether revaccination should be required within a period shorter than 7 years is discussed, since two vaccinees developed meningococcal disease to vaccine serogroup Y.

Adolescent↗
PubMed2000

Interferon-gamma protects against biomaterial-associated Staphylococcus epidermidis infection in mice.

Survival of Staphylococcus epidermidis inside macrophages has been recognized as a pivotal process in the pathogenesis of biomaterial-associated infection (BAI). Interferon (IFN)-gamma is a potent activator of macrophages. This study examined whether subcutaneous injections of IFN-gamma can reverse macrophage deactivation induced by implanted biomaterials. Mice received subcutaneous implants combined with an injection of 106 S. epidermidis to induce an experimental BAI. Subsequently, 3 groups of mice received subcutaneous injections of 25,000 IU IFN-gamma 3 times weekly, 10,000 IU IFN-gamma 3 times in 2 weeks, or saline 3 times weekly (saline control), respectively. A fourth group received no injections (control). Segments and tissues of the IFN-gamma-treated mice were significantly less (P<.05) culture positive than those of the control groups. Histologically, the high numbers of intracellularly persisting gram-positive cocci observed in the control mice were absent in the IFN-gamma-treated mice. These data indicate that IFN-gamma protects against experimental BAI.

Animals↗
PubMed2000

Antibacterial activity of antibiotic-soaked polyvinylpyrrolidone-grafted silicon elastomer hydrocephalus shunts.

If shunts, inserted for the relief of hydrocephalus, are pretreated with antimicrobials, the incidence of shunt-associated infections (SAI) may be reduced. The duration of the antibacterial activity of shunts, made from conventional silicon elastomer (SE) or from SE grafted with the hydrogel polyvinylpyrrolidone (SEpvp), which had been soaked in various antibiotics, was assessed in vitro. For any antibiotic or combination, using an arbitrary breakpoint (aBP), SEpvp remained antibacterially active for longer periods than SE. Bacterial adherence to either shunt was prevented during the period of antibacterial activity. Thus, the aBP is a good indicator of the capacity of antimicrobial-treated shunts to prevent bacterial colonization in vitro. Hydrogel-grafting of shunts may be useful in preventing SAI.

Anti-Bacterial Agents↗
PubMed2000

Flucytosine: a review of its pharmacology, clinical indications, pharmacokinetics, toxicity and drug interactions.

Flucytosine (5-FC) is a synthetic antimycotic compound, first synthesized in 1957. It has no intrinsic antifungal capacity, but after it has been taken up by susceptible fungal cells, it is converted into 5-fluorouracil (5-FU), which is further converted to metabolites that inhibit fungal RNA and DNA synthesis. Monotherapy with 5-FC is limited because of the frequent development of resistance. In combination with amphotericin B, 5-FC can be used to treat severe systemic mycoses, such as cryptococcosis, candidosis, chromoblastomycosis and aspergillosis. Recently, 5-FC has been combined with newer azole antifungal agents; it also plays an important role in a new approach to the treatment of cancer. The severe side effects of 5-FC include hepatotoxicity and bone-marrow depression. In most patients, these side effects are concentration dependent, predictable, possibly avoidable with close monitoring to maintain 5-FC concentrations at <100 mg/L, and reversible with drug discontinuation or reduction of dose. 5-FC is well absorbed after oral administration, penetrates into body tissues well and is excreted mainly by the kidneys. In renal failure, major dose adjustments have to be made. The most important drug interaction of 5-FC occurs with concomitant administration of 5-FC and nephrotoxic drugs, especially amphotericin B. Owing to the crucial role of glomerular filtration in 5-FC elimination, drugs that impair this mechanism will decrease the elimination of 5-FC and thus prolong its half-life.

Animals↗
PubMed2000

Population pharmacokinetics of flucytosine: comparison and validation of three models using STS, NPEM, and NONMEM.

The objective of this study is to compare and validate three models of flucytosine (5-FC) population pharmacokinetics using three methods of analysis to elucidate which model describes 5-FC pharmacokinetics most accurately and which method is the most suitable for this purpose. Retrospectively, demographic and clinical data of two similar sets of a total of 88 intensive care unit (ICU) patients were gathered for calculation and validation of 5-FC pharmacokinetics respectively. Three pharmacokinetic models were analyzed: a one-compartment with renal elimination (renal model), a one-compartment with renal and metabolic elimination (mixed model), and a two-compartment with renal elimination (two-compartment model). Population pharmacokinetic parameters were calculated using the standard two-stage method (STS), NONMEM, and NPEM. Furthermore, a covariate model was built by NONMEM. Validation of the 10 calculated pharmacokinetic models showed that NONMEM is most suitable for predicting 5-FC population pharmacokinetics. Based upon AIC values, bias and precision, the best results are obtained using a two-compartment model with renal elimination (k(elr) = 0.000858 +/- 0.000143 l/h per mL per min, k12 = 0.0313 +/- 0.0168 h(-1), k21 = 0.0353 +/- 0.0145 h(-1), and Vd = 0.541 +/- 0.084 L/kg; bias = -13.16; 95% CI = -16.77; -9.55; precision = 30.50; 95% CI = 27.47; 33.26) or a two-compartment covariate model as built by NONMEM [Vd (L) = 0.572 x WT, Cl(5FC) (L/h) = 1.69 + 0.0273 x (Cl(cr) (mL/min) - 52.5), k12 = 0.0235 +/- 0.0107 h(-1), and k21 = 0.0375 +/- 0.0147 h(-1); bias = -8.29; 95% CI = -11.63; -4.95; precision = 26.77; 95% CI = 24.24; 29.07]. In conclusion, this study shows that a two-compartment model with renal elimination best describes 5-FC population pharmacokinetics and NONMEM is able to build a two-compartment covariate model that predicts 5-FC levels equally well in our population of ICU patients. Furthermore, NONMEM appeared to be the most suitable method of population pharmacokinetics in our population and for this purpose it offers more reliable and accurate results than NPEM or the STS method.

Adult↗