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Biomedical subjects

W Ehret

Publications and source records attributed to W Ehret.

50 records · Page 3Linked to original sources
PubMed1987

Determination of aztreonam in faeces of human volunteers: a comparison of reversed-phase high pressure liquid chromatography and bioassay.

Aztreonam was given orally to eight healthy volunteers in two different dosage regimens. To determine the concentration of aztreonam in faecal specimens a method was established using reversed-phase high pressure liquid chromatography (HPLC). Comparison of microbiological and HPLC assays showed a linear relationship between both techniques which, however, was not 1:1. The microbiological assay tended to yield higher aztreonam levels than the HPLC method. The HPLC assay for aztreonam proved to be five-fold less sensitive than the bioassay; however, since in most cases high aztreonam levels were found in the faeces of the test subjects, this was not a disadvantage. The HPLC assay was much easier to perform than the bioassay and yielded easily quantifiable results in a wider concentration range. In the stool specimens of one volunteer no aztreonam could be detected by either method, indicating inactivation and/or degradation of the compound.

Adolescent↗
PubMed1986

Discrimination between clinical and environmental strains of Legionella pneumophila by a monoclonal antibody.

Legionellae are widely spread in natural and man-made habitats. In many instances contaminated tap water has been linked to sporadic or endemic cases of human pulmonary infections, but it is not known why, in spite of frequent occurrence, legionellae only rarely cause disease. Monoclonal antibodies against Legionella pneumophila serogroup 1 (Philadelphia 1) were prepared in order to distinguish between subtypes of this serogroup. Balb/c mice were immunized i.v. three times with heat inactivated bacteria. Antibody formation was detected by an enzyme-linked immunosorbent assay (ELISA) technique using peroxidase-conjugated antimouse IgG. Spleen cells were then fused with NS-1 myeloma cells and cloned by limiting dilution. Four monoclonal antibodies were studied in detail. The study included 47 strains of L. pneumophila: 19 strains were of human origin and 28 were isolated from different environmental sources. Most were from tap water, but none from natural habitats. All strains belonged to serogroup 1 as defined by direct immunofluorescence (DFA) using monospecific FITC-labelled polyclonal antisera from rabbits. The strains were further characterized by beta-lactamase production, activity of catalase, oxidase and proteases, analysis of ubiquinones, and demonstration of membrane protein patterns by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. A strong homogenicity between all the strains could be revealed by these methods independent of their origin. One of the monoclonal antibodies (B-1) was able to distinguish between human and environmental isolates. Eighteen of the 19 human strains reacted very strongly in DFA using antimouse immunoglobulin. No reaction, however, was seen with all of the environmental strains. Immunoblots were performed for characterization of the distinguishing feature using membrane complexes of all strains on nitrocellulose strips. The blots were incubated with antibody B-1, and immune complexes were detected by 125I-protein A. Broad intense blackening was seen between 22 and 70 kilodalton. This result suggests that no single protein, but rather a smaller component such as an oligosaccharide attached to constituents of different molecular weights, might be responsible for the discriminating reaction.

Animals↗
PubMed1985

Membrane proteins of legionellaceae. I. Membrane proteins of different strains and serogroups of Legionella pneumophila.

The protein composition of the outer membranes of eight serogroups of Legionella pneumophila has been determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Outer membranes were prepared by detergent extraction using sodium lauryl sarcosinate or by isopycnic sucrose gradient centrifugation. With both techniques one major outer membrane protein of about 29,000 daltons was found to be characteristic for the species L. pneumophila. It was the predominating feature in all 22 strains of L. pneumophila studied, regardless of serogroup. SDS-PAGE patterns of non inactivated L. pneumophila strains were compared with those following formaldehyde-, heat- or ether inactivation. Formaldehyde inactivation gave the fewest protein bands while the outer membrane protein profiles of non inactivated as well as of heat- or ether-inactivated strains revealed some additional minor components. With the exception of a 46,000 dalton band that showed, in some strains, an altered electrophoretic mobility of ca. 48,000 dalton, all strains and serogroups of L. pneumophila presented with the same outer membrane protein pattern. Analysis of outer membrane protein profiles by SDS-PAGE should therefore be a valuable tool for the identification of L. pneumophila. Comparing total membrane preparations the 29,000 dalton component was also the predominant feature, an appreciable number of additional bands, however, allow a clear discrimination between different strains. The protein profiles of outer and total membranes of L. pneumophila as determined by SDS-PAGE therefore may be used for taxonomical and epidemiological studies.

Bacterial Outer Membrane Proteins↗
PubMed1985

Membrane proteins of Legionellaceae. II. Serogroup- and species-specific antigens in the outer membrane of Legionella pneumophila.

Antigens of the outer membrane of Legionella pneumophila were investigated by means of the immunoblotting-technique using rabbit antisera against three different formaldehyde-inactivated strains, and one heat-inactivated strain of L. pneumophila serogroup 1. Nitrocellulose blots were prepared from membrane fractions extracted with sodium-N-lauryl-sarcosinate from 14 strains of L. pneumophila (eight strains of serogroup 1, and one strain each of serogroups 2-7) and 12 strains of gram-negative rods of various species. After incubation with 125I-protein A or 125I-anti-rabbit IgG immune complexes were identified. These results were compared with Coomassie-stained and silver-stained SDS gels. There was a diffuse reaction in the homologous system between 20 and 80 kilodalton (kDal) after incubation with 125I-protein A, and an intense reaction between 22 and 29 kDal after incubation with 125I-anti-rabbit IgG. Membrane preparations of the different strains of serogroup 1 exhibited clearly discernible patterns. Immunoblots of formaldehyde-inactivated strains when reacted with antiserum against heat-inactivated immunogen showed a single species-specific antigen of approximately 22.5 kDal which could not be assigned to a major protein. Immunoblots of the same antiserum but with heat-inactivated cell wall preparations gave a second species-specific band of approximately 65 kDal. Antisera against formaldehyde-inactivated bacteria demonstrated more complex characteristic patterns, with protein-associated components occurring at 29, 44, 46, 48, 65 and 80 kDal; in addition, cross-reacting fractions were present at 15.5, 17.5 and 22.5 kDal. The 29 kDal major outer membrane protein was immunogenic in most but not all cases.

Animals↗
PubMed1984

Susceptibility of Legionella spp. to imipenem and 27 other beta-lactam antibiotics.

With 28 beta-lactam antibiotics the susceptibilities of 60 strains of Legionella spp. (49 Legionella pneumophila and 11 ATCC type strains of other Legionella species) were determined. Agar dilution testing was used on buffered charcoal-yeast extract agar to which 0.1% alpha-ketoglutarate was added. The most active of the penicillins tested were ampicillin (MIC = 0.06-8 mg/l) and temocilin (MIC = 0.125 - 16 mg/l); the most active cephalosporins were ceftazidime (MIC = 0.03 - 0.5 mg/l), HR 810 (MIC = 0.06 - 1 mg/l) and cefoxitin (MIC = 0.125 - 2 mg/l). Of all the drugs tested imipenem had the most pronounced activity (MIC = .0075 - 0.06 mg/l).

Anti-Bacterial Agents↗
PubMed1983

Species specific membrane proteins of Legionellaceae.

The protein composition of the outer membrane and the whole cell wall of 21 strains representing 14 different serotypes of seven different Legionella species has been determined by sodium dodecylsulfate-polyacrylamide gel electrophoresis. The insoluble residue after extraction of cell envelopes with sodium laurylsarcosinate was considered to represent the outer membrane. Alternatively isopycnic sucrose density gradient centrifugation could be used; this approach gave similar results to the detergent method. Furthermore the effect of different methods of inactivation, e.g. treatment of the organisms with formaldehyde, heat or either on the outer membrane proteins was investigated. Each of 14 strains from seven serogroups of Legionella pneumophila yielded identical patterns of outer membrane proteins. The most prominent feature is a L. pneumophila specific major outer-membrane protein with a molecular weight of 29,000 dalton. This characteristic component was present after every method of inactivation and could also be found as a prominent protein band in total membrane preparations of non-inactivated L. pneumophila. More protein bands were observed after heat or ether inactivation than after formaldehyde inactivation. None of the other Legionella species under investigation contained the characteristic 29,000 dalton major outer membrane protein of Legionella pneumophila. Under all preparation conditions Legionella micdadei showed a characteristic intensively staining protein of 39,000 dalton. Neither the 29,000 dalton protein of L. pneumophila nor the 39,000 dalton component of L. micdadei were present in any of the other Legionella species. These other Legionella species exhibited on the contrary no single dominant membrane component but some weaker staining protein bands were observed and these were characteristic for each species. Both serogroups of Legionella longbeachae yielded identical patterns. (ABSTRACT TRUNCATED AT 250 WORDS)

Electrophoresis, Polyacrylamide Gel↗
PubMed1977

Transitory impairment of vision after light head trauma in childhood.

From a group of 101 children, eleven (10.9 p.c. ranging in age from 4--12) reported transient visual disturbances such as blurred vision, grey vision or photopsias immediately after a light head trauma. As to the origin of these impediments all evidence points to the occipital areas. Oculopupillary defects or pathological nystagmus phenomena were in no case associated. The frequency of pathological EEG recording over the occipital area was statistically significant (chi-quadrat = 4.27; p less than or equal to 0.05). The pathogenetic mechanism may be explained by means of a local oedematous reaction.

Adolescent↗
PubMedDate not supplied

Nosocomial outbreak of legionellosis in a rehabilitation center. Demonstration of potable water as a source.

Ten patients from a rehabilitation center were admitted to hospital with serious respiratory infections within ten weeks. An outbreak of Legionnaire's disease was suspected based on the epidemic and atypical manifestation of pneumonia and could be proven microbiologically. Pulmonary and extrapulmonary complications included respiratory failure, lung abscess, transitory renal impairment in five patients and acute renal failure requiring dialysis in one, tetraparesis caused by peripheral neuropathy and acute psychosis. Three patients died despite immediate institution of therapy with erythromycin. Legionella pneumophila serogroup 1 subtype Pontiac was isolated from a bronchial lavage sample of one patient and from the water supply of the rehabilitation center. Monoclonal antibody subtyping and restriction endonuclease analysis were performed on both environmental and patient isolates. Potable water was identified as the source of the outbreak based on identical patterns on restriction endonuclease analysis. Despite thermic and chemical disinfection with chlorination (up to 15 ppm) in the rehabilitation clinic, an eleventh case of Legionnaire's disease was detected 11 months later.

Acute Disease↗