Characterization of a beta-lactamase produced by Pseudomonas paucimobilis

A novel beta-lactamase enzyme produced by a strain of Pseudomonas paucimobilis is described. The enzyme differs from other recorded beta-lactamases from Gram-negative aerobic bacteria. It was constitutive, and had the characteristics of a penicillinase. One single band of beta-lactamase activity at pI 4.6 was seen on iso-electric focusing. The enzyme had a molecular mass of 30 kDa. The beta-lactamase was strongly inhibited by tazobactam, sulbactam and clavulanic acid but not by the thiol residue inhibitors p-chloromercuribenzoate and p-chloromercuriphenylsulphonic acid, or by metallo-enzyme inhibitors. Plasmid DNA was not demonstrable, suggesting that the enzyme was chromosomally encoded.