title: Effect of D240G substitution in a novel ESBL CTX-M-27.
abstract: Escherichia coli clinical strain Gre-1 collected in 2000 from a French hospital harboured a novel CTX-M-encoding gene, designated blaCTX-M-27. CTX-M-27 differed from CTX-M-14 only by the substitution D240G and was the third CTX-M enzyme harbouring this mutation after CTX-M-15 and CTX-M-16. The Gly-240-harbouring enzyme CTX-M-27 conferred to E. coli higher MICs of ceftazidime (MIC, 8 versus 1 mg/L) than did the Asp-240-harbouring CTX-M-14 enzyme. Comparison of CTX-M-14 and CTX-M-27 showed that residue Gly-240 decreased Km for ceftazidime (205 versus 940 microM), but decreased hydrolytic activity against good substrates, such as cefotaxime (kcat, 113 versus 415 s-1), probably owing to the alteration of beta3 strand positioning during the catalytic process.
authors.affiliation: Laboratoire de Bactériologie, Faculté de Médecine, Service de Bactériologie-Virologie, 28 Place Henri-Dunant, 63001 Clermont-Ferrand Cedex, France. Richard.Bonnet@u-clermont1.fr
authors.forename: R
authors.initials: R
authors.lastname: Bonnet
authors.forename: C
authors.initials: C
authors.lastname: Recule
authors.forename: R
authors.initials: R
authors.lastname: Baraduc
authors.forename: C
authors.initials: C
authors.lastname: Chanal
authors.forename: D
authors.initials: D
authors.lastname: Sirot
authors.forename: C
authors.initials: C
authors.lastname: De Champs
authors.forename: J
authors.initials: J
authors.lastname: Sirot
mesh_terms: D019943:Amino Acid Substitution; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D004927:Escherichia coli Infections / Q000382:microbiology; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007525:Isoelectric Focusing; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism*; D047090:beta-Lactams
chemical_list: D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D047090:beta-Lactams; C477098:CTX-M-27, E coli; D001618:beta-Lactamases