title: Intracellular concentrations of enrofloxacin in quinolone-resistant Salmonella enterica subspecies enterica serovar Choleraesuis.
abstract: The emergence of fluoroquinolone-resistant strains of Salmonella enterica subspecies enterica serovar Choleraesuis is an important concern in several countries, including Japan. We examined the intracellular concentration of enrofloxacin in S. Choleraesuis to determine the existence of a relationship with the emergence of quinolone resistance. The intracellular concentration of enrofloxacin was significantly lower in nalidixic acid-resistant isolates compared with nalidixic acid-susceptible isolates. In the presence of carbonyl cyanide m-chlorophenylhydrazone, the intracellular concentration of enrofloxacin increased in all isolates, with no significant difference in the intracellular concentration between nalidixic acid-susceptible and -resistant isolates. The frequency of emergence of fluoroquinolone-resistant mutants was higher in susceptible isolates with a low intracellular concentration of enrofloxacin. The results presented suggest that a decrease in the intracellular concentration of enrofloxacin is related to active efflux pumps and contributes to the emergence of fluoroquinolone resistance.
authors.affiliation: National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, Kokubunji, Tokyo, Japan. usuima@nval.go.jp
authors.forename: Masaru
authors.initials: M
authors.lastname: Usui
authors.forename: Mariko
authors.initials: M
authors.lastname: Uchiyama
authors.forename: Mari
authors.initials: M
authors.lastname: Iwanaka
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Nagai
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Asai
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000032:analysis* / Q000494:pharmacology*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D003600:Cytosol / Q000737:chemistry; D024881:Drug Resistance, Bacterial; D000077422:Enrofloxacin; D024841:Fluoroquinolones / Q000032:analysis* / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007564:Japan; D008826:Microbial Sensitivity Tests; D012481:Salmonella Infections, Animal / Q000382:microbiology; D019779:Salmonella enterica / Q000737:chemistry* / Q000187:drug effects*; D013553:Swine Diseases / Q000382:microbiology; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D014475:Uncoupling Agents; D000077422:Enrofloxacin; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone