Characterization of RASA-1, a novel class A extended-spectrum beta-lactamase from Riemerella anatipestifer.

A novel chromosomally-located β-lactamase gene, blaRASA-1, was identified in Riemerella anatipestifer RA-CH-1. The RASA-1, encoded by blaRASA-1, was a class A extended-spectrum β-lactamase (ESBL), which shared 42.7% and 40.5% identities with the RAA-1 and CGA-1 β-lactamase, respectively. Overexpression of RASA-1 in Escherichia coli confers broad resistance to β-lactams and the purified native RASA-1 revealed ESBL-like hydrolysis activity. Blasting in GenBank showed that blaRASA-1 was exclusively detected in Riemerella anatipestifer. Moreover, sequence analysis revealed that this gene was located within the multi-resistance region of Riemerella anatipestifer genome.