title: Active efflux as a mechanism of resistance to ciprofloxacin in Streptococcus pneumoniae.
abstract: The accumulation of fluoroquinolones (FQs) was studied in a FQ-susceptible laboratory strain of Streptococcus pneumoniae (strain R6). Uptake of FQs was not saturable, was rapidly reversible, and appeared to occur by passive diffusion. In the presence of glucose, which energizes bacteria, the uptake of FQs decreased. Inhibitors of the proton motive force and ATP synthesis increased the uptake of FQs in previously energized bacteria. Similar results were observed with the various FQs tested and may be explained to be a consequence simply of the pH gradient that exists across the cytoplasmic membrane. From a clinical susceptible strain (strain SPn5907) we isolated in vitro on ciprofloxacin an FQ-resistant mutant (strain SPn5929) for which the MICs of hydrophilic molecules were greater than those of hydrophobic molecules, and the mutant was resistant to acriflavine, cetrimide, and ethidium bromide. Strain SPn5929 showed a significantly decreased uptake of ciprofloxacin, and its determinant of resistance to ciprofloxacin was transferred by transformation to susceptible laboratory strain R6 (strain R6tr5929). No mutations in the quinolone resistance-determining regions of the gyrA and parC genes were found. In the presence of arsenate or carbonyl cyanide m-chlorophenylhydrazone, the levels of uptake of ciprofloxacin by the two resistant strains, SPn5929 and R6tr5929, reached the levels of uptake of their susceptible parents. These results suggest an active efflux of ciprofloxacin in strain SPn5929.
authors.affiliation: Laboratoire de Recherche Moléculaire sur les Antibiotiques, Université Paris VI, France.
authors.forename: V
authors.initials: V
authors.lastname: Zeller
authors.forename: C
authors.initials: C
authors.lastname: Janoir
authors.forename: M D
authors.initials: MD
authors.lastname: Kitzis
authors.forename: L
authors.initials: L
authors.lastname: Gutmann
authors.forename: N J
authors.initials: NJ
authors.lastname: Moreau
mesh_terms: D042462:4-Quinolones; D000167:Acriflavine / Q000493:pharmacokinetics / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000890:Anti-Infective Agents / Q000493:pharmacokinetics* / Q000494:pharmacology*; D000891:Anti-Infective Agents, Local / Q000494:pharmacology; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000493:pharmacokinetics / Q000494:pharmacology; D002939:Ciprofloxacin / Q000493:pharmacokinetics* / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D004996:Ethidium / Q000493:pharmacokinetics / Q000494:pharmacology; D024841:Fluoroquinolones; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D015363:Quinolones / Q000493:pharmacokinetics; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D014169:Transformation, Bacterial; D015366:Pefloxacin
chemical_list: D042462:4-Quinolones; D000167:Acriflavine; D000255:Adenosine Triphosphate; D000890:Anti-Infective Agents; D000891:Anti-Infective Agents, Local; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D000077286:Cetrimonium; D002593:Cetrimonium Compounds; D002939:Ciprofloxacin; D004996:Ethidium; D024841:Fluoroquinolones; D015363:Quinolones; D015366:Pefloxacin