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Biomedical subjects

G Seltmann

Publications and source records attributed to G Seltmann.

At least 19 recordsLinked to original sources
PubMed1992

Resistance of Escherichia coli to nourseothricin (streptothricin): sensitization of resistant strains by abolition of its outer membrane resistance.

The polycationic antibiotic, nourseothricin, represents a mixture of several streptothricins, mainly D and F. The molecular weight of the latter compound amounts to 486. Obviously, although very slowly, it can pass the outer membrane via the porin pores. It has been shown earlier that nourseothricin is able to generate some kind of channels into the outer membrane through which it can pass the cell wall. On the other hand, there were indications that resistant strains containing a streptothricin-inactivating acetyl transferase possess an additional protecting system, namely a reduced penetrability of the outer membrane. In this study, it could be shown that such strains indeed could be rendered sensitive by damaging the barrier function of the outer membrane.

Cell Membrane↗
PubMed1992

Characterization of a lipopolysaccharide encoded by a recombinant Shigella sonnei plasmid in Escherichia coli K-12.

The genetic information to synthesize the S-specific region of Shigella sonnei phase I lipopolysaccharide (LPS) is localized on a 180 kb plasmid which is lost quite readily. A recombinant plasmid derivative remaining stable in the bacteria was shown to determine the S-specific region of the LPS which is completely identical with that of a S. sonnei phase I strain following transfer in Escherichia coli K-12. However, the length control in polysaccharide biosynthesis is lost at least partially.

Carbohydrate Sequence↗
PubMed1991

[Determining the pattern of outer membrane proteins of gram-negative bacteria as a contribution to complex typing].

The aim of these investigations was to study relations between the serotype of E. coli strains and the pattern of their outer membrane proteins ("OMP") in sodium dodecylsulfate polyacrylamide gel electrophoresis. Three groups of strains being well characterized at least serologically (01, 02, 018ac containing different K, H, and in part F antigens) were submitted to this analysis. In all cases a nearly complete paralellity between OMP pattern and O:K:H(F:) type was observed, provided that the strains were epidemiologically related. The possibility is discussed that the OMP type could be used as a guide marker for the complex typing of E. coli strains.

Bacterial Outer Membrane Proteins↗
PubMed1989

Resistance of Escherichia coli to nourseothricin (streptothricin): reduced penetrability of the cell wall as an additional, possibly unspecific mechanism.

The resistance of E. coli strains to the antibiotic nourseothricin is known to be caused by an acetyltransferase acetylating the beta-lysine chain of the antibiotic. In addition, most of the resistant strains exhibit reduced penetrability of the outer membrane, presumably caused by a reduced amount of available negative charges. This was shown using crystal violet, Congo red, or the hydrophobic antibiotic novobiocin as indicators.

Absorption↗
PubMed1989

Biochemical aspects of the resistance to nourseothricin (streptothricin) of Escherichia coli strains.

In most cases Escherichia coli strains phenotypically resistant against nourseothricin (streptothricin) harbour a plasmid which codes for an acetyltransferase. This enzyme transfers an acetyl group from acetyl-coenzyme A to an amino group of the beta-lysine (peptide) chain of the antibiotic, thus inactivating it. Additionally, the penetrability for nourseothricin of the cell wall is drastically reduced in a high percentage of the resistant strains. Both resistance mechanisms seem to be independent of each other.

Aminoglycosides↗
PubMed1987

Effect of nourseothricin (streptothricin) on the outer membrane of sensitive and resistant Escherichia coli strains.

Nourseothricin (streptothricin) causes disturbances (perforations) in the outer membrane of sensitive E. coli strains allowing lysozyme and deoxycholate, but not the periplasmic alkaline phosphatase to penetrate. EDTA slightly increases, but Mg++ ions slightly decrease this effect. The cell walls of three from four nourseothricin-resistant strains do not become permeable under these conditions, but remain sensitive against TRIS/EDTA. Nourseothricin is supposed to pass the outer membrane of sensitive bacteria via some kind of "self-promoting" pathway. This way can (but need not) be blocked in resistant strains.

Anti-Bacterial Agents↗
PubMed1987

Studies on clonal assignment of urinary Escherichia coli O1:K1 strains.

Fifty-nine Escherichia coli strains belonging to two clonal groupings were investigated for major outer membrane proteins, colicin production, and partly for plasmid DNA content. The membrane protein patterns of the 01:K1:H7(H-):F11 and O1:K1:H-:F9 strains obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were distinctly different from each other and, therefore, are useful for clonal assignment. All of the F11 isolates had one plasmid of about 85 Md in common which is suggested to be characteristic for the clone. Their content of smaller plasmid DNA was heterogeneous and showed geographical differences. The F9 strains showed a plasmid pattern different from the F11 strains. A plasmid of 2.6 Md was found in all of these isolates. Colicin production was found to be useful for clonal assignment only in two thirds of the F9 and not in the F11 strains. Some strains with identical properties seem to be of epidemic importance.

Bacterial Outer Membrane Proteins↗
PubMed1987

Nourseothricin (streptothricin) inactivated by a plasmid pIE636 encoded acetyl transferase: nature of the inactivated nourseothricin.

Nourseothricin, a mixture of several streptothricins, is inactivated by an acetyl transferase produced by Escherichia coli containing the plasmid pIE636. Nourseothricin inactivated in the presence of 14C-acetate was purified and submitted to partial hydrolysis. In the hydrolysate besides others a radioactive and ninhydrin-reactive substance moving only slightly towards the cathode was found. It proved to be [14C]-acetyl beta-lysine.

Acetylation↗
PubMed1986

Monosaccharide composition of lipopolysaccharides from Campylobacter jejuni and Campylobacter coli.

The monosaccharide composition of the LPS from 5 Campylobacter jejuni strains and 7 Campylobacter coli strains has been studied. All LPS's contained KDO, heptose, glucosamine, glucose, and (with one exception) galactose. All C. jejuni and 3 C. coli LPS's contained greater than 1% galactosamine. 3-Amino-3.6-dideoxyglucose was present in all but one C. coli LPS and in only one C. jejuni LPS.

Campylobacter↗
PubMed1986

Surface hydrophobicity of plasmid-carrying virulent Shigella flexneri and their avirulent variants.

Five pairs of strains of S. flexneri each differing in the colour of their colonies after growth on Congo red agar have been tested for their ability to cause keratoconjunctivitis in the guinea pig eye, for the presence of the 140 Md virulence plasmid, for the presence of the virulence marker antigen, and for their ability to adsorb to hydrophobic surfaces (cellulose nitrate filters and Phenyl Sepharose). The results suggest that the presence of the 140 Md virulence plasmid provides the bacterial surface with a rather high degree of hydrophobicity; exceptions have been found.

Animals↗
PubMed1985

[Cell wall proteins of Escherichia coli: a substance resembling the thermolabile enterotoxin (LT)].

In ultrasonic extracts of all 19 investigated non-enterotoxigenic E. coli strains a substance (LTLS) could be detected reacting positively in all tests which are commonly used to detect specifically E. coli thermolabile enterotoxin (LT). Culture supernatants of these strains in general did not contain LTLS in detectable amounts. LTLS can be found in the whole cell, however, the membrane fraction contains the highest quantities. Released LTLS appears mainly aggregated with components of the cell wall, especially with lipopolysaccharides. This fact in combination with the very low quantities produced by the bacteria renders very difficult purification of LTLS.

Animals↗
PubMed1985

[Nourseothricin (streptothricin) inactivated by plasmid pIE 636-encoded acetyltransferase: detection of N-acetyl-beta-lysine in the inactivated product].

Nourseothricin (streptothricin) can be inactivated by an acetyl transferase synthesized by E. coli strains containing plasmid pIE 636. Nourseothricin inactivated in the presence of 14C-acetyl-coenzyme A was purified and submitted to partial acidic hydrolysis. By electrophoresis of the hydrolysate a 14C-containing substance moving only slowly towards the cathode could be isolated. This substance after complete hydrolysis yields only unlabelled beta-lysine.

Acetyltransferases↗
PubMed1985

Pathogenicity and virulence of methicillin resistant Staphylococcus aureus: slime layer production.

Nine methicillin-resistant (MR) mutants and three methicillin-sensitive (MS) substrains, all derived from naturally occurring heteroresistant isolates of Staphylococcus aureus were examined for slime production. All strains showed an increased mucoid character when cultured on a modified Staphylococcus Medium No. 110. The uranic acid content of the slime layer ranged from 2% to 6% in the MR mutants and from 1.3% to 5.1% in the MS substrains. The amount of uronic acid per g of dry bacteria ranged from 82.5 mg to 143.8 mg in the MR mutants, and between 51.4 mg and 98.8 mg in the MS substrains. In 3 pairs of MR mutants and MS substrains originating from the same parents, the MR cells possessed more of uronic acid than their MS counterparts. The partially purified polysaccharide part of the slime contained D-galactose, D-mannose, D-xylose, D-galacturonic acid, D-galactosamine and D-glucuronic acid in all strains studied. Its quantitative composition was identical in each pair of the MR mutant and MS substrain; there were, however, considerable differences among the strains and between the pairs. Methicillin resistance and slime formation seem to be independent properties in S. aureus. The presumable significance of the readiness of slime production by MR cocci during infections is discussed.

Anti-Bacterial Agents↗