Characterization and sequence of the Chryseobacterium (Flavobacterium) meningosepticum carbapenemase: A new molecular class B β-lactamase showing a broad substrate profile

The metallo-β-lactamase produced by Chryseobacterium (formerly Flavobacterium) meningosepticum, which is the flavobacterial species of greatest clinical relevance, was purified and characterized. The enzyme, named BlaB, contains a polypeptide with an apparent M(r) of 26,000, and has a pI of 8.5. It hydrolyses penicillins, cephalosporins (including cefoxitin), carbapenems and 6-β-iodopenicillanate, a mechanism-based inactivator of active-site serine β-lactamases. The enzyme was inhibited by EDTA, 1-10 phenanthroline and pyridine-2,6-dicarboxylic acid, with different inactivation parameters for each chelating agent. The C. meningosepticum blaB gene was cloned and sequenced. According to the G + C content and codon usage, the blaB gene appeared to be endogenous to the species. The BlaB enzyme showed significant sequence similarity to other class B β-lactamases, being overall more similar to members of subclass B1, which includes the metallo-enzymes of Bacillus cereus (Be-II) and Bacteroides fragilis (CcrA) and the IMP-I enzyme found in various microbial species, and more distantly related to the metallo-β-lactamase of Aeromonas spp. (CphA, CphA2 and ImiS) and of Stenotrophomonas maltophilia (L1).