CHARACTERIZATION AND SEQUENCE OF THE CHRYSEOBACTERIUM (FLAVOBACTERIUM) MENINGOSEPTICUM CARBAPENEMASE - A NEW MOLECULAR CLASS-B BETA-LACTAMASE SHOWING A BROAD SUBSTRATE PROFILE

The metallo-beta-lactamase produced by Chryseobacterium (formerly Flav obacterium) meningosepticum, which is the flavo-bacterial species of g reatest clinical relevance, was purified and characterized. The enzyme , named BlaB, contains a polypeptide with an apparent M-r of 26000, an d has a pI of 8.5. It hydrolyses penicillins, cephalosporins (includin g cefoxitin), carbapenems and 6-beta-iodopenicillanate, a mechanism-ba sed inactivator of active-site serine beta-lactamases. The enzyme was inhibited by EDTA, 1-10 phenanthroline and pyridine-2,6-dicarboxylic a cid, with different inactivation parameters for each chelating agent. The C. meningosepticum blaB gene was cloned and sequenced. According t o the G+C content and codon usage, the blaB gene appeared to be endoge nous to the species. The BlaB enzyme showed significant sequence simil arity to other class B beta-lactamases, being overall more similar to members of subclass B1, which includes the metallo-enzymes of Bacillus cereus (Bc-II) and Bacteroides fragilis (CcrA) and the IMP-1 enzyme f ound in various microbial species, and mole distantly related to the m etallo-beta-lactamases of Aeromonas spp. (CphA, CphA2 and ImiS) and of Stenotrophomonas maltophilia (L1).