Microbial Kinetics and Dependencies of Individual and Combined Antibiotic Inhibitors of Protein Biosynthesis

Abstract

The generation rate constants for the steady-state growth of antibiotic-inhibited Escherichia Although chloramphenicol and tetracycline may bind differently on the ribosomal complex (7,22,24,25,30), they have been shown (12,27) to be "kinetically equivalent" in their growthinhibitory action against Escherichia coli. Erythromycin and the lincosaminide antibiotics are also presumed to be different in the mechanistic details of their action at the ribosomal site (3, 31), yet they demonstrate "kinetic equivalence" except where allosteric effects at the binding sites may yield antagonistic reactions (13,20,21,27). This paper presents the results of studies to determine the effects of combinations chosen from tetracycline, chloramphenicol, erythromycin, and the lincosaminides on the generation rate of E. coli and rationalizes the microbial kinetic dependencies on the concentrations of the separate and combined antibiotics. The microbial kinetics of deoxylincomycin have been studied in detail.MATERIALS AND METHODS Growth medium. Antibiotic medium 3 (Difco Laboratories) was used as the growth medium. The medium was clarified by filtration through 22-jAm membrane filters (HA type; Millipore Corp.) followed by 0.45-Mm membrane filters, and then autoclaved. The pH was 7.05 ± 0.05.Bacteria and growth conditions. E. coli ATCC 12407, referred to as strain B/r in previous publications (12-15, 17, 18, 20, 21, 26), was used in all experiments. Slants were prepared from single-colony isolates and stored in a refrigerator at 4 C.Overnight cultures, grown aerobically at 37.5 C in a shaker, were diluted 1,000-fold into fresh medium and brought to exponential growth. Further dilutions were made to provide replicate exponential cultures of 50 ml with a cell density of about 106/ml at the time that antibiotics were added.Antibiotics. Assayed samples of lincomycin hydrochloride (895 gg base eq/mg), deoxylincomycin hydrochloride (893.4 gg base eq/mg), clindamycin hydrochloride (860 ug base eq/mg), U24729 A as the hydrochloride (906.1 gg base eq/mg), erythromycin lactobionate (670 yg base eq/mg), and tetracycline hydrochloride (USP) were used. The concentrations employed in all experiments refer to the salts of these antibiotics. Stock solutions were aseptically prepared by membrane filtration and stored at 4 C. Total-count method. Total counts of bacterial cultures were determined with a Coulter counter (14). Samples of 1 ml were withdrawn at 20-to 30-min intervals and diluted in Formol-saline to be within a range of 10,000 to 30,000 counts per 50 Mliters on a

Effect of Novobiocin and Its Combination with Tetracycline, Chloramphenicol, Erythromycin, and Lincomycin on the Microbial Generation of Escherichia coli

“…CHEMOTHER. The linearity of the kapp with drug concentration for novobiocin is similar to the concentration dependence found with chloramphenicol, tetracycline, and spectinomycin (16) and can be explained as described in the previous paper in this series (17).…”

“…The blockage of one ribosome near the terminus of the mRNA could, in effect, block the movement (and thereby the function) of all ribosomes proximal to it, whether they are inhibited or not (17). The slower process would determine the overall rate of protein biosynthesis and thus the dependent rate of microbial generation.…”

“…Tetracycline shows no antagonistic effects in binary combinations with chloramphenicol (16), erythromycin, or lincomycin (17), as well as with novobiocin (Fig. 8a, b).…”

“…4,1973 on May 12, 2018 by guest http://aac.asm.org/ Downloaded from and movement of messenger RNA (mRNA) (46). The indifferent effect (16) of tetracycline in combination with chloramphenicol, erythromycin, or lincomycin has been explained (16,17).…”

Comparison of Tetracycline Action on Staphylococcus aureus and Escherichia coli by Microbial Kinetics

“…Studies on the action of tetracycline against E. coli by the kinetics of microbial growth (2,(10)(11)(12)(13)(14)24) permitted not only the characterization of drug-receptor interactions in the biophase but also an elucidation of the possible mode of tetracycline action on the cells. Recently, comparative studies on the action of some drugs on S. aureus and E. coli by microbial growth kinetics (16) have revealed relative differences in the kinetics and dependencies related to modes of drug action on gram-positive and gram-negative organisms.…”