We thank Professor J. Poupaert for fruitful discussions, and Professors F. Van Bambeke and P. M. Tulkens for supporting the project.
R.B., E.G., L.L., M.D., and Y.D. are, respectively, Research Directors and Research Associates of the National Foundation for Scientific Research. H.B. is an assistant and doctoral fellow of the Université Catholique de Louvain. The support of the Région Wallonne, of the National Foundation for Scientific Research, of the Université Catholique de Louvain (Fonds Spéciaux de Recherche, Actions de Recherche Concertées), and of the Federal Office for Scientific, Technical and Cultural Affairs (Interuniversity Poles of Attraction Program), is gratefully acknowledged. We also thank Bayer Healthcare AG for providing us fluoroquinolone antibiotics.
Hayet Bensikaddour and Nathalie Fa contributed equally to the work.
Nathalie Fa's present address is Campden & Chorleywood Food Research Association Group, Chipping Campden, Gloucestershire, GL55 6LD, UK.
Editor: Petra Schwille.
Submitted on June 15, 2007; accepted for publication October 3, 2007.