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Biomedical subjects

I Steinmetz

Publications and source records attributed to I Steinmetz.

At least 19 recordsLinked to original sources
PubMed2006

Bacterial colonisation of interior implant threads with and without sealing.

Premature loss of dental implants is due, apart from mechanical factors, to germrelated inflammation. Gaps and hollow spaces within the implant system, for example the gap between implant and abutment in the two-part implant system, may provide a bacterial reservoir causing or maintaining inflammation. The bacterial spectrum involved is similar to that found in periodontitis. This in vitro study aimed to scrutinise the capability of Porphyromonas gingivalis (DSM 20709), the bacterium blamed for inducing peri-implantitis, to pass the implant/abutment gap in titanium implant systems used for orthodontic anchorage and to remain vital in the interior. Additionally, the in vitro effectiveness of gutta percha for gap sealing was examined. Twelve titanium implants (Straumann, diameter: 3.3 mm, length 5.5 mm) were provided with abutments at a defined torque (20 Ncm), six of which were sealed with gutta percha before screwing in the abutment. Subsequently the implants were placed in a nutrient solution (thioglycolate boullion with haemin-menadione solution) that contained Porphyromonas gingivalis. Microbiological specimens were sampled from the implant interiors after 24 and 72 hours and analysed using culture methods. There was evidence that penetration of the periodontal pathogen Porphyromonas gingivalis to the implant interior may occur as early as after 24 hours. Microbes were also detected in the interior of implants sealed with gutta percha. The abutment/implant interface in vitro provides a microbiological leakage for the prospective peri-implantitis-inducing bacterium Porphyromonas gingivalis. Survival of the bacterium is possible in the interior, so that development of a bacterial reservoir is assumed. This in vitro trial produced no evidence that sealing with gutta percha is an effective means to prevent secondary bacterial colonisation in the implant interior.

Colony Count, Microbial↗
PubMed2003

Fatal outcome of lung transplantation in cystic fibrosis patients due to small-colony variants of the Burkholderia cepacia complex.

The aim of this study was to investigate the possible role of small-colony variant morphotypes of Burkholderia cepacia-like organisms in infectious complications in cystic fibrosis patients following lung transplantation. Respiratory tract specimens from 470 cystic fibrosis patients were screened over a 22-month period for Burkholderia cepacia-like organisms. Nineteen patients were positive for these organisms, eight of whom harboured small-colony-variant morphotypes. Three patients underwent bilateral lung transplantation during the study, two of whom harboured small-colony variants in addition to clonally identical wildtypes of Burkholderia multivorans and Burkholderia cepacia genomovar III prior to lung transplantation. Both patients developed fatal systemic infections post transplantation due to small-colony variants. In vitro testing revealed that small-colony variants exhibited increased serum resistance in comparison to wildtypes. The results of this study indicate that diagnostic efforts should be undertaken to carefully identify small-colony variants of Burkholderia cepacia complex, since they might be an indicator of poor post-transplantation outcome in patients with cystic fibrosis.

Adolescent↗
PubMed2003

Structural and functional cellular changes induced by Burkholderia pseudomallei rhamnolipid.

In this study we report that extracellular Burkholderia pseudomallei rhamnolipid induced cytopathic changes characterized by retraction, rounding up, and, finally, detachment in phagocytic and nonphagocytic cell lines. These changes were due to a progressive reorganization of the F-actin network resulting in impaired cell cycle progression and a reduced phagocytic function of macrophages.

Actins↗
PubMed2001

Chronic melioidosis in a patient with cystic fibrosis.

Burkholderia pseudomallei, the causative agent of melioidosis, is endemic in Southeast Asia and northern Australia, where it can be found in soil and surface water. We report a case of chronic pulmonary melioidosis in a patient with cystic fibrosis who had traveled to an area where B. pseudomallei is endemic.

Adult↗
PubMed2000

Economic and clinical outcomes of microlaparoscopic and standard laparoscopic sterilization. A comparison.

OBJECTIVE: To compare micro-laparoscopic surgical sterilization and standard laparoscopic sterilization with respect to cost effectiveness and patient preferences. STUDY DESIGN: A retrospective study of all laparoscopic surgical sterilizations performed under general anesthesia at Johns Hopkins Bayview Medical Center--16 micro-laparoscopies and 34 standard laparoscopies. Cases selected for review were limited to patients undergoing surgical contraception and not requiring additional, concurrent procedures. Laparoscopic surgical sterilization was performed using a double-puncture technique with silicone band application. In each case either a standard, 10-mm laparoscope or a 2-mm micro-laparoscope was used, and the procedure was performed under general anesthesia. Postoperative pain management was achieved by nonsteroidal antiinflammatory drugs and/or narcotic analgesia. All cases were performed by residents under faculty supervision. Medical records and hospital billing records were reviewed, and a standardized telephone interview was conducted to assess postoperative quality of life and patient satisfaction. RESULTS: Both techniques were comparable in cost effectiveness. There was no significant difference in operating room time, average operating room costs, average ancillary department costs, instrument and supply costs, or length of stay. Postoperative discomfort was significantly less with microlaparoscopy (P = .05), and patient satisfaction was higher in the microlaparoscopy group. CONCLUSION: Microlaparoscopy and the standard laparoscopic approach for surgical sterilization are associated with similar hospital charges. Postoperative pain and overall patient satisfaction were significantly better with microlaparoscopy than standard laparoscopy.

Arizona↗
PubMed1999

Discordancy between clinical predictions vs lymphoscintigraphic and intraoperative mapping of sentinel lymph node drainage of primary melanoma.

OBJECTIVE: To evaluate discordancy between clinical predictions and lymphatic drainage patterns of primary cutaneous melanoma as determined by preoperative lymphoscintigraphy and intraoperative lymphatic mapping of sentinel lymph nodes (SLNs). DESIGN: Before selective SLN dissection, 226 consecutive patients with melanoma underwent preoperative lymphoscintigraphy. SETTING: Teaching hospital tertiary care center. MAIN OUTCOME MEASURE: Correlation of lymphatic drainage patterns from the following 3 data sources: clinical predictions preoperatively based on anatomical location of primary melanoma, lymphatic drainage patterns as determined by preoperative lymphoscintigraphy, and identification of SLNs during surgery. RESULTS: Preoperative lymphoscintigraphy was successful in identifying at least 1 SLN in all 226 patients. In head and neck melanomas, at least 1 SLN was identified in an area outside what would have been clinically predicted in 11 (36.7%) of 30 cases. Discordancy for trunk melanomas was seen in 24 (25.3%) of 95 cases. Extremity melanomas showed drainage to unexpected SLNs in 6 (13.6%) of 44 and 3 (5.3%) of 57 patients for the upper and lower extremities, respectively. The overall rate of discordancy was 44 (19.5%) of 226. The SLNs were identified in surgery in all but 4 cases. CONCLUSIONS: Discordancy is most frequent in melanomas of the head and neck region, followed by that of the trunk. Preoperative lymphoscintigraphy identifies the occasional cases in the upper and lower extremities where drainage occurs to a basin that is not clinically predictable. Preoperative lymphoscintigraphy is a prerequisite for characterizing the lymphatic drainage pattern in patients with primary melanoma, especially for sites such as head and neck as well as trunk, before selective SLN dissection.

Adolescent↗
PubMed1999

Highly resistant Burkholderia pseudomallei small colony variants isolated in vitro and in experimental melioidosis.

Burkhloderia pseudomallei is the causative agent of melioidosis, a disease in which treatment failures and relapses are common. This study reports on slow growing B. pseudomallei 'small colony variants' (SCVs), isolated either in vitro after exposure to ceftazidime, ciprofloxacin or gentamicin or from the spleen and liver in a mouse model of melioidosis after treatment with ceftazidime. Interestingly, SCVs isolated by either method or antimicrobial agent showed a significant increase in the minimal inhibitory concentrations of various unrelated classes of antimicrobial agents. B. pseudomallei SCVs did not differ from their parental strains in standard biochemical profiles, nor by pulsed field gel electrophoresis or electron microscopy. Although the SCV phenotype was stable throughout numerous passages on antibiotic-free solid media, revertants with the parental colony morphology and, most importantly, with the parental susceptibility pattern occurred. These revertants led to rapid overgrowth of SCVs in liquid media without added antibiotics. Future studies will have to determine the clinical relevance of B. pseudomallei SCVs especially in treatment failure and relapse of infection.

Animals↗
PubMed1999

Small-colony variants of Pseudomonas aeruginosa in cystic fibrosis.

In the context of chronic lung infection due to Pseudomonas aeruginosa in cystic fibrosis (CF), attention has been focused on the presence of the most common mucoid phenotype. In this study, the presence of small-colony variants (SCVs) of P. aeruginosa in respiratory tract specimens from patients with CF was investigated, and the clinical conditions predisposing to SCVs were analyzed. P. aeruginosa SCVs were isolated from 33 of 86 P. aeruginosa-positive CF patients over a 2-year period. Fast-growing revertants with larger surface colonies could be isolated from SCV populations. Electron microscopy revealed no significant difference in cell size or morphology. MICs of a broad range of antipseudomonas agents for SCVs were two- to eightfold higher than values for revertants. Recovery of SCVs was correlated with parameters revealing poor lung function and was significantly associated with daily inhalation of tobramycin or colistin.

Adolescent↗
PubMed1999

Characterization of a murine model of melioidosis: comparison of different strains of mice.

Melioidosis is an infectious disease caused by the saprophytic gram-negative rod Burkholderia pseudomallei. The aim of this study was to establish and characterize a murine model of melioidosis to provide a basis for further investigations on the pathogenesis of the disease. After intravenous infection with B. pseudomallei, C57BL/6 mice were found to be significantly more resistant than BALB/c mice. There was a marked organotropism of B. pseudomallei for the spleen and liver in both strains of mice, with the highest bacterial load in the spleen. Electron microscopic investigations of the spleen clearly demonstrated intracellular replication within membrane-bound phagosomes. Electron micrographs of the liver provided evidence that B. pseudomallei-containing phagosomes in hepatocytes fuse with lysosomes, leading to degradation of bacteria. In both strains of mice, the course of infection was highly dependent on the infective dose and the bacterial strain used, ranging from death within a few days to death after several weeks. In comparison with BALB/c mice, the bacterial counts in C57BL/6 mice were decreased 12 h after infection, which is suggestive of an innate immune mechanism against B. pseudomallei in this early phase of infection contributing to the lower susceptibility of C57BL/6 mice. BALB/c mice developed a more pronounced lymphopenia, granulocytosis, and splenomegaly at a lower infective dose compared to C57BL/6 mice. Analysis of the antibody response against B. pseudomallei 11 days after infection revealed a significantly higher immunoglobulin G2A (IgG2a)/IgG1 ratio in C57BL/6 mice than in BALB/c mice, indicating that a T helper type 1 immune response is associated with resistance to infection with B. pseudomallei.

Animals↗
PubMed1999

Rapid identification of Burkholderia pseudomallei by latex agglutination based on an exopolysaccharide-specific monoclonal antibody.

We recently identified a constitutively expressed exopolysaccharide of Burkholderia pseudomallei which is composed of a unique linear tetrasaccharide repeating unit consisting of three galactose residues and one 3-deoxy-D-manno-2-octulosonic acid residue. In this study we developed a latex agglutination test based on monoclonal antibody 3015, which is specific for this exopolysaccharide, and evaluated this test for rapid identification of B. pseudomallei grown on agar plates. All 74 environmental and clinical B. pseudomallei strains tested, originating from different areas of Southeast Asia, northern Australia, and Africa, showed a strong and specific agglutination. B. pseudomallei-like organisms and a variety of other bacteria did not react. In conclusion this monoclonal antibody-based test is a simple, rapid, and highly specific method for identifying B. pseudomallei culture isolates from different geographic areas.

Antibodies, Bacterial↗
PubMed1999

Immunohistological characterization of leukocytes in the lungs of healthy mice and after bacterial intratracheal infection.

Leukocytes in the peripheral lung parenchyma of mice have not been characterized histologically during bacterial infection. The aim of this study was to investigate (a) the immunohistological characteristics of healthy murine lungs and (b) the cell kinetics during acute inflammation. BALB/c and MF1 mice were examined; as well as transgenic mice with the gene defect of cystic fibrosis (CF) in the airways as an animal model for this disease. MF1 mice served as controls for the transgenic animals. Lavaged and perfused lungs were snap frozen. B and T lymphocytes, CD4+ and CD8+ cells, dendritic cells, neutrophils and a subset of macrophages were enumerated on cryostat lung sections. The lung tissue and bronchoalveolar lavage (BAL) of BALB/c mice, infected intratracheally with Haemophilus influenzae type b (Hib), were studied at different time points after infection. In the lungs of healthy mice, including CF mice, the largest population was that of T cells, CD4+ cells being always more frequent than CD8+ cells. During acute inflammation the number of neutrophils in the lung parenchyma and BAL increased strongly within the first hours after bacterial instillation and reached baseline levels within one week. This study provides a semi-quantitative analysis of immunocompetent cells in normal and infected murine lung tissue. Differences in cell numbers are found between different strains. Moreover, the cellular reaction during Hib infection in mouse lungs is dominated by neutrophils, as expected in a primary immune response. In uninfected CF mice the numbers and distribution of immune cells in the lung tissue are normal, indicating that the cellular defense is adequate.

Animals↗
PubMed1998

Impairment of peroxisomal structure and function in rat liver allograft rejection: prevention by cyclosporine.

BACKGROUND: During allograft rejection, cytokines and lipid mediators contribute to cell injury and organ failure. Peroxisomes play a crucial role in lipid metabolism, including the degradation of lipid mediators by peroxisomal beta-oxidation. Therefore, we investigated the alterations of hepatic peroxisomes after allogeneic rat liver transplantation. METHODS: MHC-incompatible Dark Agouti (RT1a) donor rats and Lewis (RT1(1)) recipient rats were used for allogeneic transplantation. For immunosuppression, a group of these animals received cyclosporine (CsA) intraperitoneally (1 mg/kg body weight per day). Lewis rats were used for isogeneic transplant combination. Ten days after transplantation, livers were investigated using morphometrical methods for determination of peroxisomal diameter and volume density. The activities of peroxisomal catalase (CAT) and acyl-coenzyme A oxidase (AOX) were determined, and the corresponding proteins were evaluated by quantitative immunocytochemistry and immunoblotting. The expressions of mRNAs encoding CAT and AOX were investigated by Northern blotting. RESULTS: The volume density and diameter of peroxisomes were significantly decreased in allogeneic transplanted livers but were unchanged in CsA-treated animals. Both the activities of CAT and AOX and their protein levels were significantly reduced in liver allografts. Moreover, the corresponding mRNA levels of CAT and AOX were decreased significantly in liver allografts, whereas CsA treatment led to an increase of those mRNAs. Isogeneic transplanted livers showed only a slight reduction of the corresponding enzyme values. CONCLUSIONS: Peroxisomes are severely affected both morphologically and functionally after allogeneic liver transplantation. These results suggest that impairment of peroxisomal lipid beta-oxidation could contribute to the pathogenesis of the rejection process by decreased catabolism of lipid mediators involved in the regulation of the inflammatory response. CsA, in addition to its immunosuppressive effects, may contribute to allograft survival by maintenance of those important peroxisomal functions.

Acyl-CoA Oxidase↗
PubMed1998

Phase-variable expression of lipopolysaccharide contributes to the virulence of legionella pneumophila.

With the aid of monoclonal antibody (mAb) 2625, raised against the lipopolysaccharide (LPS) of Legionella pneumophila serogroup 1, subgroup OLDA, we isolated mutant 811 from the virulent wild-type strain RC1. This mutant was not reactive with mAb 2625 and exhibited an unstable phenotype, since we observed an in vitro and in vivo switch of mutant 811 to the mAb 2625-positive phenotype, thus restoring the wild-type LPS. Bactericidal assays revealed that mutant 811 was lysed by serum complement components, whereas the parental strain RC1 was almost serum resistant. Moreover, mutant 811 was not able to replicate intracellularly in macrophage-like cell line HL-60. In the guinea pig animal model, mutant 811 exhibited significantly reduced ability to replicate. Among recovered bacteria, mAb 2625-positive revertants were increased by fourfold. The relevance of LPS phase switch for pathogenesis of Legionella infection was further corroborated by the observation that 5% of the bacteria recovered from the lungs of guinea pigs infected with the wild-type strain RC1 were negative for mAb 2625 binding. These findings strongly indicate that under in vivo conditions switching between two LPS phenotypes occurs and may promote adaptation and replication of L. pneumophila. This is the first description of phase-variable expression of Legionella LPS.

Animals↗
PubMed1998

Purification and characterization of a cytotoxic exolipid of Burkholderia pseudomallei.

Burkholderia pseudomallei is the causative agent of melioidosis, an infectious disease, which is increasingly recognized as an important public health problem in various tropical regions. This study describes the identification and characterization of a heat-stable extracellular toxin of B. pseudomallei. After cultivation of B. pseudomallei in liquid media, the heated cell-free supernatant was concentrated by ultrafiltration. The concentrate exhibited a cytotoxic and hemolytic activity which showed remarkable resistance against alkaline and acidic treatments. For further purification, reversed-phase chromatography using a fast-performance liquid chromatography system was performed. After elution with an acetonitrile gradient, a single cytotoxic and hemolytic peak was detected. Structural characterization of the toxin was performed by a combination of mass spectrometric and nuclear magnetic resonance spectroscopic techniques. A highly purified glycolipid, 2-O-alpha-L-rhamnopyranosyl-alpha-L-rhamnopyranosyl-beta-hydroxytetradec anoyl-beta-hydroxytetradecanoate (Rha-Rha-C14-C14), with a molecular mass of 762 Da was identified. The purified exolipid showed a time- and dose-dependent cytotoxic effect on phagocytic (HL60) and nonphagocytic (HeLa) cell lines. In addition, a time- and dose-dependent hemolysis of erythrocytes from various species was observed. The toxin structure makes a detergentlike action most probable. Interestingly, the cytotoxic and hemolytic activities of the glycolipid could be neutralized by albumin. Future studies will concentrate on the role of this exolipid as a virulence factor in the pathogenesis of melioidosis.

Animals↗
PubMed1997

Structure of an acidic exopolysaccharide of Burkholderia pseudomallei.

A recently described water-soluble exopolysaccharide of Burkholderia pseudomallei recognized by the IgG 1 monoclonal antibody 3015 [Steinmetz, I., Rohde, M. & Brenneke, B. (1995) Infect. Immun. 63, 3959-3965] was isolated by repetitive ethanol-precipitation steps and by anion-exchange chromatography. The structure of the polysaccharide was determined by a combination of chemical-derivatization and mass-spectrometric techniques (compositional and methylation analysis, GC/MS, and electrospray-ionization-MS/MS of reduced and permethylated hydrolytic fragments), and two-dimensional 1H-NMR methods (COSY, TOCSY and NOESY) and confirmed by isolation and structural characterization of the depolymerized repeating unit of the polysaccharide. The combined structural data established a linear tetrasaccharide repeating unit consisting of three galactose residues, one bearing a 2-linked O-acetyl group, and a 3-deoxy-D-manno-2-octulosonic acid residue. [-->3)-beta-D-Galp2Ac-(1-->4)-alpha-D-Galp-(1-->3)-beta-D-Galp-(1- ->5)-beta-Kdo-(2-->]n

Burkholderia pseudomallei↗
PubMed1997

Monoclonal antibody against species-specific epitope of Pseudomonas aeruginosa Hsp60 protein cross-reacts with Pseudomonas stutzeri and other Pseudomonas species.

In a previous study, we determined the epitope of the Pseudomonas aeruginosa Hsp60 heat shock protein which is recognized by the specific monoclonal antibody (MAb) 2528. Subsequent investigations revealed a weak cross-reactivity of MAb 2528 with P. stutzeri, P. alcaligenes, P. mendocina and P. pseudoalcaligenes. To elucidate the molecular structure for these cross-reactions, we cloned the P. stutzeri hsp60 gene in Escherichia coli and determined the nucleotide sequence of the gene. In addition, the hsp60 gene of further Pseudomonas species was amplified and sequenced and amino acid substitutions within the epitope recognized by MAb 2528 were determined. The decapeptide QADIEARVLQ is unique to the P. aeruginosa Hsp60 protein, and cross-reaction of MAb 2528 reflects the phylogenetic relationship of Pseudomonas species as P. aeruginosa and all four cross-reacting species constitute a DNA homology group within the rRNA group I of the family Pseudomonadaceae, which belong to the gamma-subclass of the Proteobacteria.

Amino Acid Sequence↗
PubMed1997

Significant increase of Kuppfer cells associated with loss of Na+,K+-ATPase activity in rat hepatic allograft rejection.

BACKGROUND: Cholestasis is a complication that occurs during the rejection of liver transplants. The aim of this study was to investigate the association of activated Kupffer cells (KCs) and Na+,K+-ATPase activity for taurocholate cotransport and bile canalicular (BC) Mg++-ATPase activity for hepatobiliary excretion in rat liver allograft. METHODS: Quantitative analyses of KC number and size in relationship to enzyme activity of Na+,K+-ATPase and of BC Mg++-ATPase were conducted in rejected liver after allogenic transplantation and after prevention of rejection using cyclosporine. RESULTS: The animals were examined on the 10th postoperative day. In the rejection group, the number of KCs significantly increased more than fourfold in comparison with the number of KCs in the control livers. Some KCs were found in the sinusoids, but the majority were located in the space of Disse. Na+,K+-ATPase activity vanished from the basolateral plasma membrane, whereas BC Mg++-ATPase activity was restored in the apical domain. With immunosuppression, KCs showed the same behavior as in the control group, and activity of both ATPases was observed as strong electron-dense precipitates in basolateral and apical plasma membrane domains. CONCLUSIONS: In this study, we demonstrate that activated KCs migrate into the donor liver and release cytokines, which leads to the loss of Na+,K+-ATPase activity in the rejection group. BC Mg++-ATPase activity was not influenced by these mediators of activated macrophages. Since Na+,K+-ATPase is the cotransporter for hepatocyte taurocholate uptake, these data may contribute to understanding the mechanisms for cholestasis during hepatic allograft rejection.

Animals↗