ABSTRACT
In 3 from 19 clinical isolates of Pseudomonas aeruginosa imipenem-resistant subpopulations could be detected in vitro. In comparison to their wild strains these imipenem-resistant cells were lacking an outer-membrane-protein of 50 kD. In the subpopulation derived from Pseudomonas aeruginosa 76 resistance to imipenem was found to be instable. It could be lost within a short period of time after subcultivation in the absence of imipenem. Cells with restored sensitivity to imipenem possess the outer membrane protein of 50 kD as the wild strain does.
Subject(s)
Imipenem/pharmacology , Pseudomonas aeruginosa/drug effects , Azlocillin/pharmacology , Aztreonam/pharmacology , Bacterial Outer Membrane Proteins/analysis , Ciprofloxacin/pharmacology , Drug Resistance, Microbial , Humans , Pseudomonas aeruginosa/analysisABSTRACT
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.
Subject(s)
Anti-Bacterial Agents/pharmacology , Escherichia coli/drug effects , Streptothricins/pharmacology , Cell Membrane/drug effects , Drug Resistance, Microbial , Escherichia coli/genetics , Species SpecificityABSTRACT
Streptothricin acetyl transferase coded for by plasmids pIE636 and pIE637 in Escherichia coli K-12 was found to be located at the inner side of the cytoplasmic membrane.
Subject(s)
Acetyltransferases/metabolism , Escherichia coli/enzymology , Acetyltransferases/isolation & purification , Alkaline Phosphatase/isolation & purification , Cytoplasm/enzymology , Escherichia coli/genetics , Osmotic Pressure , Peptide Hydrolases/isolation & purification , R Factors , Sonication , Streptothricins/pharmacology , beta-Galactosidase/isolation & purificationABSTRACT
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.
