EBR-1, a Novel Ambler Subclass B1 β-Lactamase from Empedobacter brevis

Empedobacter brevis (formerly designated Flavobacterium breve) is a gram-negative aerobe involved in nosocomial infections. The Ambler class B β-lactamase gene bla(EBR-1) was cloned and expressed in Escherichia coli from E. brevis clinical strain ASS-1, which had reduced susceptibility to expanded-spectrum cephalosporins and carbapenems. Purified β-lactamase EBR-1 hydrolyzed penicillins, cephalosporins, and carbapenems efficiently but not aztreonam. Kinetic parameters of EBR-1 were similar to those of class B enzymes such as BlaB, IND-2, and GOB-1 identified from other Flavobacteriaceae species, except for meropenem, which was more hydrolyzed by β-lactamase GOB-1. EBR-1, with a pI of 8.0 and a relative molecular mass of ca. 25 kDa, was classified in functional subgroup 3a, which includes most of the class B β-lactamases. EBR-1, which belongs to molecular subclass B1 of metalloenzymes, shares 58, 57, and 42% amino acid identity with the most closely related β-lactamases, IND-1/IND-2 from Chryseobacterium indologenes, CGB-1 from Chryseobacterium gleum, and BlaB from Chryseobacterium meningosepticum, respectively.