Plasmid curing effect of trovafloxacin

The effect of sub-inhibitory concentrations of trovafloxacin, a recently developed fluoroquinolone molecule, on the capability of Escherichia coli cells to maintain three different types of plasmids has been investigated by a number of approaches, including the quantification of the loss of plasmid-borne functions and of plasmid DNA by quantitative PCR. The results obtained demonstrate that at concentrations ranging from the MIC to 1/8 of the MIG, trovafloxacin induces a clear, albeit incomplete, 'episome-curing' effect which was observed with plasmids differing in copy number, size and nature of the replication origin of the episome. This effect was most likely not due to an alteration of DNA supercoiling. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.