Action of ampicillin and kanamicin on the electrophysical characteristics ofEscherichia colicells

We examined the effect of ampicillin and kanamycin on the electrophysical characteristics of ampicillin- and kanamycin-sensitive and ampicillin- and kanamycin-resistant Escherichia coli cells. Substantial changes in the orientational spectra (OS) of suspensions of cells incubated with various ampicillin and kanamycin concentrations took place only at the first five frequencies of the orienting electric field (10–1000 kHz). The maximal change in the magnitude of the electro-optical signal occurred at 50 µg mL−1 of ampicillin and 10 µg mL−1 of kanamycin. The suspension-OS changes did not depend on the antibiotic-action period. Under the action of ampicillin and kanamycin, sensitive and resistant E. coli strains gave different electro-optical (EO) effects. It follows that the sensitive and resistant E. coli strains exhibit different of the EO effect on the action of ampicillin and kanamycin. Thus, the suspension-OS changes occurring under the effect of ampicillin and kanamycin may be used as a test for resistance to this antibiotic in the cells studied.