SEPARATION AND QUANTIFICATION OF MUREIN AND PRECURSORS FROM ENTEROBACTER-CLOACAE AFTER TREATMENT WITH TRIMETHOPRIM AND SULFADIAZINE

The intracellular concentrations of the soluble murein precursors UDP- Mur-NAc-penta-peptide in the cytoplasm, the membrane-bound lipid precu rsor disaccharide pentapeptide and the muropeptides of Enterobacter cl oacae cultures treated with trimethoprim (12.5 mu g mL(-1)) and sulpha diazine (250 mu g mL(-1)) were determined by using capillary zone elec trophoresis analysis. In the presence of trimethoprim, UDP-Mur-NAc-pen tapeptide as well as disaccharide pentapeptide accumulated. In the cas e of sulphadiazine-treated cells, the concentration of UDP-Mur-NAc-pen tapeptide roughly paralleled the control cells but sulphadiazine cause d a slow incremental accumulation of disaccharide pentapeptide. The mu ropeptide composition of the murein indicated that the differences bet ween the peptidoglycans produced by the control cells and the cells gr own in the presence of either trimethoprim or sulphadiazine alone or i n combination were quite marked. The results suggest that the enhanced activity of trimethoprim plus sulphadiazine against E. cloacae is cau sed by an additional effect on the inhibition of the bacterial peptido glycan biosynthesis and that this additional effect is a fundamental p art of the antibacterial action of the antimetabolites. This effect le ads to changes of cell morphology and resultant changes in bacterial c ell permeability.