Novel Ambler Class A β-Lactamase LAP-1 and Its Association with the Plasmid-Mediated Quinolone Resistance Determinant QnrS1

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Abstract
The plasmid-mediated quinolone resistance determinant QnrS1 was identified in non-clonally related Enterobacter cloacae isolates in association with a transferable narrow-spectrum β-lactam resistance marker. Cloning experiments allowed the identification of a novel Ambler class A β-lactamase, named LAP-1. It shares 62 and 61% amino acid identity with the most closely related β-lactamases, TEM-1 and SHV-1, respectively. It has a narrow-spectrum hydrolysis of β-lactams and is strongly inhibited by clavulanic acid and sulbactam and, to a lesser extent, by tazobactam. Association of the bla LAP-1 gene with the qnrS1 gene was identified in E. cloacae isolates from France and Vietnam. These genes were plasmid located and associated with similar insertion sequences but were not associated with sul1 -type class 1 integrons, as opposed to the qnrA genes.