Younes A, Hamouda A, Amyes S G B
Centre for Infectious Diseases, University of Edinburgh, 49 Little France Crescent, Edinburgh, UK.
J Chemother. 2011 Jun;23(3):127-30. doi: 10.1179/joc.2011.23.3.127.
Klebsiella oxytoca strains MU946294N and MB193997E were isolated from patients in Scotland. Strain MU946294N was resistant to pencillins, monbactams and cephalosporins. Isolate MB193997E displayed a β-lactam resistance phenotype consistent with chromosomal β-lactamase overproduction. No bla(TEM), bla(SHV) or bla(CTX-M) genes could be amplified in either strain; however, amplification by PCR was found with primers for the bla(OXY-2) gene. This β-lactamase gene in MU946294N differed by one mutation from the all other bla(OXY) genes previously reported, with an amino acid substitution Alanine237 Threonine enhancing the binding of cefotaxime. Strain MB193997E showed mutations at positions 255 and 283, neither of which affect function. Based on rpoB and gyrA characterization, both strains were assigned to the KoII phylogenic group but they were completely dissimilar from each other by PFGE. This study is the first to report the substitution of Alanine to Threonine at position 237 in a OXY- 2 β-lactamase and this enhances resistance to cefotaxime.
产酸克雷伯菌菌株MU946294N和MB193997E是从苏格兰的患者中分离出来的。菌株MU946294N对青霉素、单环β-内酰胺类抗生素和头孢菌素耐药。分离株MB193997E表现出与染色体β-内酰胺酶过量产生一致的β-内酰胺耐药表型。在这两种菌株中均未扩增出bla(TEM)、bla(SHV)或bla(CTX-M)基因；然而，使用bla(OXY-2)基因的引物通过聚合酶链反应（PCR）扩增到了该基因。MU946294N中的这种β-内酰胺酶基因与先前报道的所有其他bla(OXY)基因有一个突变差异，丙氨酸237到苏氨酸的氨基酸取代增强了头孢噻肟的结合。菌株MB193997E在第255和283位显示出突变，这两个突变均不影响功能。基于rpoB和gyrA特征分析，这两种菌株均被归为KoII系统发育组，但通过脉冲场凝胶电泳（PFGE）分析它们彼此完全不同。本研究首次报道了OXY-2β-内酰胺酶第237位的丙氨酸被苏氨酸取代，这增强了对头孢噻肟的耐药性。
