ISOLATION AND PARTIAL-PURIFICATION OF A CARBAPENEM-HYDROLYZING METALLO-BETA-LACTAMASE FROM PSEUDOMONAS-CEPACIA

A metallo-beta-lactamase has been isolated from a clinical strain of P seudomonas cepacia and partially purified using Cibacron blue F3GA cou pled agarose. The resulting preparation showed a single band of beta-l actamase activity (pI 8.45) after analytical isoelectric focusing. The enzyme was particularly effective in the hydrolysis of imipenem. Mero penem, biapenem, cephaloridine, ceftazidime, benzylpenicillin, ampicil lin and carbenicillin were also hydrolysed, although at a lower rate. An unusual inhibition profile was noted. Inhibition by the metal ion c helators ethylenediaminetetraacetic acid and o-phenanthroline was reve rsed by addition of zinc, indicating a metallo-enzyme, whilst > 90% in hibition was attainable with 0.1 mM concentrations of tazobactam and c lavulanic acid. A study of 8 other clinical isolates showed the enzyme to be present and inducible by imipenem in each case. This enzyme was assigned PCM-I (Pseudomonas cepacia metalloenzyme I).