Chromosome-encoded ambler class A β-lactamase of Kluyvera georgiana, a probable progenitor of a subgroup of CTX-M extended-spectrum β-lactamases

A chromosome-encoded P-lactamase gene, cloned and expressed in Escherichia coli from Kluyvera georgiana reference strain CUETM 4246-74 (DSM 9408), encoded the extended-spectrum beta-lactamase KLUG-1, which shared 99% amino acid identity with the plasmid-mediated P-lactamase CTX-M-8. This work provides further evidence that Kluyvera spp. may be the progenitor(s) of CTX-M-type beta-lactamases.