title: Enhancement of fluoroquinolone activity by C-8 halogen and methoxy moieties: action against a gyrase resistance mutant of Mycobacterium smegmatis and a gyrase-topoisomerase IV double mutant of Staphylococcus aureus.
abstract: The increasing prevalence of antibiotic resistance among bacterial pathogens prompted a microbiological study of fluoroquinolone structure-activity relationships with resistant mutants. Bacteriostatic and bactericidal activities for 12 fluoroquinolones were examined with a gyrase mutant of Mycobacterium smegmatis and a gyrase-topoisomerase IV double mutant of Staphylococcus aureus. For both organisms C-8 halogen and C-8 methoxy groups enhanced activity. The MIC at which 99% of the isolates tested were inhibited (MIC(99)) was reduced three- to fivefold for the M. smegmatis mutant and seven- to eightfold for the S. aureus mutant by C-8 bromine, chlorine, and methoxy groups. With both organisms a smaller reduction in the MIC(99) (two- to threefold) was associated with a C-8 fluorine moiety. In most comparisons with M. smegmatis the response to a C-8 substituent was similar (within twofold) for wild-type and mutant cells. In contrast, mutant S. aureus was affected more than the wild type by the addition of a C-8 substituent. C-8 halogen and methoxy groups also improved the ability to kill the two mutants and the respective wild-type cells when measured with various fluoroquinolone concentrations during an incubation period equivalent to four to five doubling times. Collectively these data help define a group of fluoroquinolones that can serve (i) as a base for structure refinement and (ii) as test compounds for slowing the development of fluoroquinolone resistance during infection of vertebrate hosts.
authors.affiliation: Public Health Research Institute, 455 First Ave., New York, NY 10016, USA.
authors.forename: T
authors.initials: T
authors.lastname: Lu
authors.forename: X
authors.initials: X
authors.lastname: Zhao
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.forename: A
authors.initials: A
authors.lastname: Drlica-Wagner
authors.forename: J Y
authors.initials: JY
authors.lastname: Wang
authors.forename: J
authors.initials: J
authors.lastname: Domagala
authors.forename: K
authors.initials: K
authors.lastname: Drlica
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000737:chemistry / Q000494:pharmacology; D027081:DNA Gyrase / Q000235:genetics / Q000378:metabolism; D027101:DNA Topoisomerase IV / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D006219:Halogens / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D020102:Mycobacterium smegmatis / Q000187:drug effects* / Q000201:enzymology; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000201:enzymology; D059005:Topoisomerase II Inhibitors
chemical_list: D000890:Anti-Infective Agents; D006219:Halogens; D059005:Topoisomerase II Inhibitors; D002939:Ciprofloxacin; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase