Convergent evolution of TEM-26, a β-lactamase with extended-spectrum activity

Abstract

TEM-26, an extended-spectrum β-lactamase has been characterized in clinical isolates of Klebsiella pneumoniae and Escherichia coli derived from patients on the Paediatric Oncology Unit of St James's University Hospital, Leeds. The nucleotide sequence of this β-lactamase gene (bla_TEM26b) was determined, and compared with the nucleotide sequences of other TEM-type β-lactamases. The bla_TEM26b, gene was found to differ from bla_TEM12b by a single nucleotide. This difference causes the substitution of glutamic acid in bla_TEM26b for lysine in bla_TEM26b at position 102 in the predicted amino acid sequence. The bla_TEM12b gene was first described in an isolate of Klebsiella oxytoca from a patient nursed on the same unit that yielded the strains that carry bla_TEM26b However, the bla_TEM26b gene differs at no less than six nucleotides from the nucleotide sequence encoding the TEM-26 β-lactamase that was first described in isolates from cancer patients nursed in the Children's Hospital, Stanford, California, USA. This indicates that the genes encoding TEM-26 have evolved from different progenitors.