Accumulation of Oxytetracycline Relevant to its Bactericidal Action in the Cells of Escherichia coli

Abstract

IN the course of work on the effect of oxytetracycline on the growth of E. coli B-151-1 using a nepherometer, we observed a remarkable increase in turbidity when the cells were incubated at high concentration of oxytetracycline over 100 µg/ml, in nutrient broth. Results showed that this increase in turbidity was not caused by the increase of number of cells, but was due to a remarkable accumulation of Oxytetracycline in the cells of E. coli. Cells of E. coli B-151-1 or E. coli K-12 were collected from 1516 h culture by shaking at 30° C in nutrient broth (pH 7.2), and were washed twice with distilled water. Usually Monod's test tube was used for both growth and accumulation tests unless otherwise indicated. Usually, cells of E. coli (about 1 mg dry weight) were suspended in 10 ml. of medium in 30 ml. Monod's test tube, and the tube was shaken at 30° C on a shaking machine. The resting cells were incubated with various concentrations of oxytetracycline in nutrient broth (pH 7.2) at 30° C, and the growth was measured using a Kotaki nepherometer. The amount of oxytetracycline was expressed as that of its hydrochloride.