Molecular and Biochemical Characterization of Ambler Class A Extended-Spectrum β-Lactamase CGA-1 from Chryseobacterium gleum

Antibiotic susceptibility testing by disk diffusion of a Chryseobacterium gleum isolate, strain CIP 103039, showed a typical synergy image between clavulanic acid and expanded-spectrum cephalosporins. Shotgun cloning gave a recombinant plasmid in Escherichia coli that produced a β-lactamase, CGA-1, with a pI value of 8.9 that conferred resistance to most penicillins (except ureidopenicillins) and narrow-spectrum cephalosporins and an intermediate susceptibility to expanded-spectrum cephalosporins and aztreonam. The CGA-1 amino acid sequence shared only 60% amino acid identity with CME-1 and CME-2 from Chryseobacterium meningosepticum, the most closely related β-lactamases. CGA-1 was very likely chromosome encoded. It is a novel member of the PER subgroup of Ambler class A β-lactamases (Bush functional group 2be).