Identification of a chromosome-borne expanded-spectrum class a beta-lactamase from Erwinia persicina

Abstract

From whole-cell DNA of an enterobacterial Erwinia persicina reference strain that displayed a penicillinase-related antibiotic-resistant phenotype, a beta-lactamase gene was cloned and expressed in Escherichia coli. It encoded a clavulanic-acid-inhibited Ambler class A beta-lactamase, ERP-1, with a pI value of 8.1 and a relative molecular mass of ca. 28 kDa. ERP-1 shared 45 to 50% amino acid identity with the most closely related enzymes, the chromosomally encoded enzymes from Citrobacter koseri, Kluyvera ascorbata, Kluyvera cryocrescens, Klebsiella oxytoca, Proteus vulgaris, Proteus penneri, Rahnella aquatilis, Serratia fonticola, Yersinia enterocolitica, and the plasmid-mediated enzymes CTX-M-8 and CTX-M-9. The substrate profile of the noninducible ERP-1 was similar to that of these beta-lactamases. ERP-1 is the first extended-spectrum beta-lactamase from an enterobacterial species that is plant associated and plant pathogenic.

FIG. 1.

Alignment of the ERP-1 amino acid sequence with those of the most closely related enzymes: CTX-M-9 from E. coli (28), CTX-M-8 from Enterobacter cloacae (5), KLUA-1 from K. ascorbata (GenBank accession no. CAB59824), and YENT from Yersinia enterocolitica (30). Numbering is according to Ambler et al. (1). Dashes represent identical amino acid residues. The vertical arrow is the cleavage site of the leader peptide of the mature β-lactamase ERP-1. Structural elements characteristic of class A β-lactamases and of serine β-lactamases are shaded. The amino acids of the omega loop are underlined.