[Electron microscopic study of the combined action of ampicillin and cephalexin on E. coli].

The data of electron microscopy study of morphological variation of E. coli, strain 423 in the logarithmic phase after exposure to ampicillin (2 gamma/ml) and cephalexin (4 gamma/ml) are presented. Pronounced ultrastructural changes not only in the cell wall but also in the cytoplasm were found. After exposure to ampicillin alone changes of the same type were observed. However, after exposure to the combination of the 2 antibiotics these changes were more pronounced and observed in the predominating part of the cells. Examination of ultrathin slices of the strain treated with cephalexin revealed no ultrastructural changes. The morphological changes in the cells of E. coli, strain 423 after its treatment with ampicillin and cephalexin combination were due mainly to ampicillin effect, while cephalexin increased the level of the changes.