title: Characterization of a new plasmid-mediated extended-spectrum beta-lactamase from Serratia marcescens.
abstract: A new extended spectrum beta-lactamase was detected in Serratia marcescens 42039 that was isolated from urine of patients with complicated urinary tract infection in Japan. This stain produced three different beta-lactamase types (TEM-1, a cephalosporinase, and a new beta-lactamase: CKH-1). The TEM-1 and CKH-1 encoding genes were conjugated from S. marcescens 42039 to Escherichia coli K-12 at frequencies of 10(-5) to 10(-6). The MICs of beta-lactams against the transconjugant were: ampicillin > 1600, piperacillin 800, cephalothin 1600, ceftazidime 6.25, cefotaxime 100, and ceftriaxone 200 micrograms/ml. The CKH-1 enzyme was purified to more than 90% by ion-exchange chromatography. The molecular weight of purified CKH-1 was 30 K dalton and the isoelectric point was 8.2. Relative Vmax/Km values (cephaloridine = 100) of penicillin G, cephalothin, and oxyiminocephalosporins such as cefuroxime, ceftriaxone, and cefotaxime, were 256, 226, 116, 87, and 49, respectively. The I50 values of tazobactam, BRL-42715, and clavulanic acid against CKH-1 enzyme were 0.0011, 0.0002, and 0.097 microM respectively. The enzymatic activity of CKH-1 was not inhibited by EDTA and anti-TEM-1 serum. These findings indicate that CKH-1 is a member of the groups of class A beta-lactamases. This is the first report of a plasmid-mediated oxyiminocephalosporin hydrolyzing broad-spectrum beta-lactamase from clinical isolates of S. marcescens.
authors.affiliation: Anticancer and Antimicrobial Research Lab, Taiho Pharmaceutical Co, Ltd, Tokushima, Japan.
authors.forename: C
authors.initials: C
authors.lastname: Kunugita
authors.forename: F
authors.initials: F
authors.lastname: Higashitani
authors.forename: A
authors.initials: A
authors.lastname: Hyodo
authors.forename: N
authors.initials: N
authors.lastname: Unemi
authors.forename: M
authors.initials: M
authors.lastname: Inoue
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology; D004274:DNA, Recombinant; D004352:Drug Resistance, Microbial / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007525:Isoelectric Focusing; D008826:Microbial Sensitivity Tests; D010957:Plasmids; D012706:Serratia marcescens / Q000201:enzymology* / Q000235:genetics; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D004274:DNA, Recombinant; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases