Genetic characterization of resistance to extended-spectrum β-lactams in Klebsiella oxytoca isolates recovered from patients with septicemia at hospitals in the Stockholm area

Abstract

Two β-lactamase gene regions were characterized by DNA sequencing in eight clinical isolates of Klebsiella oxytoca. The bla(OXY-2a) region encoded a β-lactamase nearly identical to OXY-2 (one amino acid residue substituted) and conferred aztreonam and cefuroxime resistance on the K. oxytoca isolates. Overproduction of OXY-2a was caused by a G-to-A substitution of the fifth nucleotide in the -10 consensus sequence of bla(OXY-2a). The bla(OXY-1a) was identified in a susceptible strain, and the OXY-1a enzyme differed from OXY- 1 by two amino acid residues.