Abstract
Electronmicroscopic study was carried out to examine the in vitro antimicrobial activity of enramycin (ERM) against Staphylococcus aureus and Corynebacterium diphtheriae. Exposure of Staphylococcus aureus to ERM rapidly caused morphological changes in the cell membrane such as fold formation, inward incarceration and formation of many mesosomes followed by transudation of the cellular contents which appeared to result from the impaired permeability of the cell membrane, and this proceeded rapidly to bacteriolysis. The bacteriolytic action is characterized in that it takes place in a very short time at such low concentrations of ERM as are lower than the in vitro minimum inhibitory concentration (MIC) of the antibiotic. In this case, neither hypertrophy of the septum nor formation of protoplast has been observed with Staphylococcus aureus. On the other hand, the antibacterial pattern of ERM against Corynebacterium diphtheriae has been found to be similar to that against Staphylococcus aureus. Namely, morphological changes, such as formation of folds in the cell membrane and inward incarceration of the membrane, took place immediately followed by bacteriolysis. No elongation of the cells of Corynebacterium diphtheriae has been found.
