Abstract
The stereoisomer (trans-isomer) of benzylpenicillin was examined for its antibacterial activity and properties as a substrate and inducer of β-lactamases in comparison with benzylpenicillin. The minimum inhibitory concentrations of the trans-isomer against Staphylococcus aureus FDA 209P and Bacillus subtilis PCI 219 were 1.6 and 12.5 μg/ml, respectively, which were about twenty-five times higher than those of benzylpenicillin. However, the transisomer was very stable to the penicillinases prepared from both S. aureus and Escherichia coli carrying an ampicillin-resistant R factor. The rates of hydrolysis of the trans-isomer by these pencillinases were less than 3 % of the corresponding rates with benzylpenicillin as a substrate. The trans-isomer was a powerful inducer of the penicillinase synthesis by S. aureus and of the cephalosporinase synthesis by Proteus vulgaris.
