Characterization, cloning and sequence analysis of the inducible Ochrobactrum anthropi AmpC beta-lactamase

Abstract
Ochrobactrum anthropi is resistant to most cephalosporins and penicillins due, at least in part, to the inducible expression of a single β-lactamase. The β-lactamase gene has been cloned and sequenced. It encodes an AmpC-type class 1 serine active-site enzyme that hydrolyses mainly cephalosporins and is resistant to inhibition by clavulanic acid. Expression of the ampC gene is inducible via a typical AmpR regulator, which is encoded upstream of ampC. Inducible expression is retained following cloning of O. anthropi ampRampC into Escherichia coli, confirming that the signal for AmpR activation in O. anthropi is the same as that used in the Enterobacteriaceae. This is the first reported example of an AmpC β-lactamase outside of the γ-subdivision of the bacterial kingdom. Genomic searches of other non-γ-subdivision bacteria revealed a homologous ampRampC cluster in the plant symbiont, Sinorhizobium meliloti.

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