Electron-microscopic studies on the filamentous E. coli induced by the treatment with cephalexin in-vitro as well as in a clinical case revealed following findings:
The ultrastructures of cell-wall, cell-membrane and cytoplasma of the filamentous E. coli capable to revert into the conventional form did not differ very much from those of normal E. coli.
Some of the filamentous E. coli demonstrating findings of aggregated ribosome and sparse cytoplasma seemed to be non-viable.
The frequent findings of vacuole formation in the filaments seemed to originate from a gap of growth between the cell-wall and the cell-membrane, so it was most frequently observed when filaments began to revert in antibiotic-free media. Among cephalexin, cephalothin, cephaloridine and ampicillin the latter two demonstrated stronger effect on vacuole formation, meaning their stronger damages upon cell-walls.
The electron microscopic finfings of E. coli found in the urine of a patient treated with cephalexin were quite same as those observed in in-vitro experiments with respect to filamentous form and spheroplast. E. coli inphagocytes in the urines of a pyelonephritis patient were followed up during the course of cephalexin treatment. Every form of E. coli was observable after the initiation of cephalexin treatment. But contrary to the relatively rapid disappearance of extracellular E. coli in the urines phagocytes containing filaments and/or spheroplasts could be observed for a longer period. This will give a suggestion on dosage schedule of cephalexin treatment.