title: Characterization of the new AmpC β-lactamase FOX-8 reveals a single mutation, Phe313Leu, located in the R2 loop that affects ceftazidime hydrolysis.
abstract: A novel class C β-lactamase (FOX-8) was isolated from a clinical strain of Escherichia coli. The FOX-8 enzyme possessed a unique substitution (Phe313Leu) compared to FOX-3. Isogenic E. coli strains carrying FOX-8 showed an 8-fold reduction in resistance to ceftazidime relative to FOX-3. In a kinetic analysis, FOX-8 displayed a 33-fold reduction in kcat/Km for ceftazidime compared to FOX-3. In the FOX family of β-lactamases, the Phe313 residue located in the R2 loop affects ceftazidime hydrolysis and alters the phenotype of E. coli strains carrying this variant.
authors.affiliation: Servicio de Microbiología-INIBIC, Complejo Hospitalario Universitario A Coruña, A Coruña, Spain.
authors.forename: Francisco José
authors.initials: FJ
authors.lastname: Pérez-Llarena
authors.forename: Frédéric
authors.initials: F
authors.lastname: Kerff
authors.forename: Laura
authors.initials: L
authors.lastname: Zamorano
authors.forename: María Carmen
authors.initials: MC
authors.lastname: Fernández
authors.forename: Maria Luz
authors.initials: ML
authors.lastname: Nuñez
authors.forename: Elisenda
authors.initials: E
authors.lastname: Miró
authors.forename: Antonio
authors.initials: A
authors.lastname: Oliver
authors.forename: Ferran
authors.initials: F
authors.lastname: Navarro
authors.forename: Germán
authors.initials: G
authors.lastname: Bou
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002442:Ceftazidime / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D006868:Hydrolysis; D009154:Mutation; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D002442:Ceftazidime; C048795:AmpC beta-lactamases; D001618:beta-Lactamases