Ceftazidime-hydrolysing β-lactamase OXA-145 with impaired hydrolysis of penicillins in Pseudomonas aeruginosa
Ceftazidime-hydrolysing β-lactamase OXA-145 with impaired hydrolysis of penicillins in Pseudomonas aeruginosa
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DOI：
10.1093/jac/dkr187
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发表时间：
2011-08-01
影响因子：
5.2
通讯作者：
Meziane-Cherif, Djalal
中科院分区：
文献类型：
--
作者：
Hocquet, Didier;Colomb, Melanie;Meziane-Cherif, Djalal
目的：描述一种新的超广谱苯唑西林酶，命名为OXA-145，其与窄谱OXA-35（来自OXA-10组）的区别在于缺失了Leu-165残基。本文报道了bla（OXA-145）的遗传环境和OXA-145的生化特性。方法：采用等电聚焦电泳、PCR和DNA测序等方法，对临床分离的多重耐药铜绿假单胞菌08-056中的超广谱β-内酰胺酶OXA-145进行鉴定。采用琼脂稀释法进行药敏试验。在大肠杆菌中测定了由克隆的bla（OXA-10）、bla（OXA-35）、blaOXA-145和通过定点诱变获得的bla（OXA-10）衍生物赋予的抗性谱。OXA-35和OXA-145的动力学参数通过纯化His标记的蛋白后建立。结果：OXA-145由08-056菌株中的1类整合子携带的基因编码，其序列与窄谱青霉素酶OXA-35的序列不同，位于高度保守的omega环中的单个氨基酸缺失（Leu-165）。从OXA-35（产生OXA-145）或OXA-10（OXA-35的前身）中删除Leu-165将水解谱扩展到第三代头孢菌素和单环内酰胺类，同时降低青霉素的水解谱。OXA-145对所有受试底物均显示出双相水解曲线。结论：OXA-145是来自OXA-10组的一种新的超广谱β-内酰胺酶。Leu-165的缺失导致了从青霉素到第三代头孢菌素以及单环内酰胺类的水解谱的转变。青霉素水解的损失是由于非羧基化的Lys-73。
Objectives: To describe a novel extended-spectrum oxacillinase, named OXA-145, differing from narrow-spectrum OXA-35 (from the OXA-10 group) by deletion of residue Leu-165. The genetic environment of bla(OXA-145) and the biochemical properties of OXA-145 are reported. We also assessed the impact of the Leu-165 deletion on the hydrolysis spectrum of the ancestor OXA-10.Methods: Extended-spectrum beta-lactamase OXA-145 was identified in the multidrug-resistant clinical Pseudomonas aeruginosa 08-056, and characterized by isoelectric focusing, PCR and DNA sequencing. Antibiotic susceptibility tests were performed by agar dilution. The resistance profiles conferred by cloned bla(OXA-10), bla(OXA-35), blaOXA-145 and a bla(OXA-10) derivative obtained by site-directed mutagenesis were determined in Escherichia coli. Kinetic parameters of OXA-35 and OXA-145 were established after purification of His-tagged proteins.Results: The sequence of OXA-145, encoded by a class 1 integron-borne gene in strain 08-056, differed from that of narrow-spectrum penicillinase OXA-35 by a single amino acid deletion (Leu-165) located in the highly conserved omega loop. Deletion of Leu-165 from OXA-35 (yielding OXA-145) or OXA-10 (the progenitor of OXA-35) extended the hydrolysis spectrum to third-generation cephalosporins and to monobactams, while reducing that for penicillins. OXA-145 showed biphasic hydrolysis curves for all the substrates tested. Its activity against nitrocefin was 10-fold higher in the presence of sodium hydrogen carbonate.Conclusions: OXA-145 is a new extended-spectrum b-lactamase from the OXA-10 group. The deletion of Leu-165 is responsible for a shift in the hydrolysis spectrum from penicillins to third-generation cephalosporins, as well as monobactams. The loss of penicillin hydrolysis was due to a non-carboxylated Lys-73.