title: Characterization of NPS-1, a novel plasmid-mediated beta-lactamase, from two Pseudomonas aeruginosa isolates.
abstract: A novel beta-lactamase, which had a pI of 6.5 and a molecular weight of 25,000, was observed in two Pseudomonas aeruginosa isolates. The enzyme, designated NPS-1, was encoded by a plasmid of molecular weight 41 X 10(6) which also encoded resistance to streptomycin and sulfonamide. This plasmid, designated pMLH50, was freely transmissible to other P. aeruginosa strains, but not to Escherichia coli K-12. The enzyme was purified partially and shown to have activity against both penicillins and cephalosporins. Vmax rates for oxacillin and carbenicillin were less than 50% of the Vmax for benzylpenicillin, and the Vmax for cephaloridine was only 3% of the Vmax for benzylpenicillin. Imipenem, aztreonam, and several antipseudomonal cephalosporins were stable to the enzyme. Hydrolysis of most substrates obeyed Michaelis-Menten kinetics, but cefsulodin induced a reversible reduction in the activity of the enzyme. Transconjugants of the beta-lactamase-producing isolates in P. aeruginosa PU21 acquired beta-lactam resistances which mirrored the hydrolytic activity of the enzyme.
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004790:Enzyme Induction / Q000187:drug effects; D007525:Isoelectric Focusing; D008826:Microbial Sensitivity Tests; D008970:Molecular Weight; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D001618:beta-Lactamases / Q000096:biosynthesis / Q000302:isolation & purification*
chemical_list: D000900:Anti-Bacterial Agents; D001618:beta-Lactamases