title: Decreased production of AmpC-type beta-lactamases associated with the development of resistance to quinolones in Citrobacter freundii strains.
abstract: The effect of fluoroquinolones in Citrobacter freundii strains that results in a decreased expression of cephalosporin-hydrolysing beta-lactamases was studied. Resistance to broad-spectrum cephalosporins and penicillins in two C. freundii clinical isolates was associated with moderate production of chromosomal AmpC-type-beta-lactamase in addition to changes in the outer membrane proteins profile with respect to wild-type C. freundii strains. Ten quinolone-resistant mutants were derived from the two clinical isolates using increasing fluoroquinolone concentrations. The level of susceptibility to cephalosporins and meropenem of these 10 mutants was increased and was associated with a 3.6-32% diminution in the hydrolyzing activity of their periplasmic extracts containing beta-lactamases on cephaloridine as compared with those from their parent strains. Susceptibility to cephalosporins and meropenem, as well as the expression of chromosomal AmpC-type-beta-lactamase in C. freundii strains, was influenced by the exposure to quinolones.
authors.affiliation: Department of Clinical Sciences, School of Medicine, University of Las Palmas de G.C., Spain.
authors.forename: M M
authors.initials: MM
authors.lastname: Tavío  Pérez
authors.forename: G
authors.initials: G
authors.lastname: Amicosante
authors.forename: N
authors.initials: N
authors.lastname: Franceschini
authors.forename: J
authors.initials: J
authors.lastname: Vila
authors.forename: J
authors.initials: J
authors.lastname: Ruiz
authors.forename: A
authors.initials: A
authors.lastname: Oratore
authors.forename: A M
authors.initials: AM
authors.lastname: Martín-Sánchez
authors.forename: M T
authors.initials: MT
authors.lastname: Jiménez de Anta
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D001426:Bacterial Proteins; D016971:Citrobacter freundii / Q000187:drug effects* / Q000201:enzymology; D004352:Drug Resistance, Microbial; D024841:Fluoroquinolones; D006868:Hydrolysis; D007525:Isoelectric Focusing; D008826:Microbial Sensitivity Tests; D001618:beta-Lactamases / Q000096:biosynthesis* / Q000378:metabolism
chemical_list: D000890:Anti-Infective Agents; D001426:Bacterial Proteins; D024841:Fluoroquinolones; C048795:AmpC beta-lactamases; D001618:beta-Lactamases