Evolution and the flanking sequences of Β-lactamase resistance gene blaOKP

Abstract

blaOKP genes are chromosomally encoded beta-lactamases that mediate several classes of antibiotics resistance. To investigate the evolution and flanking sequences of OKP beta-lactamase gene, the gene blaOKP and its flanking sequences from a newly isolated Klebsiella pneumoniae were studied using whole genome sequencing. The flanking sequences of different variant blaOKP genes and blaSHV, another plasmid-encoded beta-lactamase gene, were then compared. These studies show that the blaOKP and blaSHV genes evolve differently and belong to two different evolution branches. The blaOKP gene variants can be divided into subgroups: blaOKP-A and blaOKP-B. Although both blaOKP and blaSHV genes have no mobile genetic elements in their flanking sequences, their genetic environments are quite different. The blaOKP gene is adjacent to KdpC while blaSHV gene is flanked by RecF and ygbN-ygbM-ygbK. Furthermore, there are a variety of mobile genetic elements in the neighboring sequence plasmid-encoded blaSHV genes that are absent in blaOKP genes. These structural differences may slow the evolution of blaOKP gene. Collectively, we demonstrate that the evolution and flanking sequence of blaOKP gene are different from those of the blaSHV gene, which could be an important reason for its relatively slow evolution.