Molecular characterization of a novel class 1 integron containing blaGES-1 and a fused product of aac(3)-ib/Aac(6′)-Ib′ gene cassettes in Pseudomonas aeruginosa
Molecular characterization of a novel class 1 integron containing blaGES-1 and a fused product of aac(3)-ib/Aac(6′)-Ib′ gene cassettes in Pseudomonas aeruginosa
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DOI：
10.1128/aac.46.3.638-645.2002
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发表时间：
2002-03-01
影响因子：
4.9
通讯作者：
Quentin, C
中科院分区：
文献类型：
--
作者：
Dubois, W;Poirel, L;Quentin, C
纸片扩散法显示，临床分离的铜绿假单胞菌Pa695对所有的超广谱头孢菌素和氨基糖苷类药物都耐药，头孢他啶和亚胺培南具有不寻常的协同作用。该菌株产生一种等电点为5.8的超广谱β-内酰胺酶(ESBL)，似乎是染色体编码的。克隆实验表明，该ESBL由BLA(GES-1)编码，该基因以前在肺炎克雷伯菌的整合子中描述过。在铜绿假单胞菌Pa695中，头孢他啶的耐药率高于替卡西林，并且与肺炎克雷伯菌的耐药模式相反，β-内酰胺酶抑制剂与超广谱头孢菌素之间没有协同作用。进一步的序列分析表明，bla(GES-1)基因盒位于1类整合子中，含有与融合的aac(3)-Ib和aac(6‘)-Ib’基因盒对应的另一个序列。融合产物是有功能的，与单独克隆的每个基因的产物一样：aac(3)-I，尽管最后四个氨基酸缺失，但aac(6‘)，与最同源的序列相比，带有三个氨基酸的变化。Aac(3)-I蛋白对庆大霉素和福替米星产生了预期的抗性，Aac(6‘)蛋白对卡那霉素、妥布霉素和地贝卡星产生了抗性，但对奈替米星和阿米卡星略有影响，对庆大霉素没有明显影响。融合产物携带较大的抗药性，将AAC(6‘)活性与较高水平的庆大霉素耐药性结合在一起，而不伴随福替米星耐药性。
As seen by the disk diffusion method, the clinical strain of Pseudomonas aeruginosa Pa695, resistant to all extended-spectrum cephalosporins and aminoglycosides, exhibited an unusual synergistic effect between ceftazidime and imipenem. This isolate produced an extended-spectrum beta-lactamase (ESBL) with a pI of 5.8 that appeared to be chromosomally encoded. Cloning experiments revealed that this ESBL was encoded by bla(GES-1), previously described in an integron from Klebsiella pneumoniae. In P. aeruginosa Pa695, a higher level of resistance to ceftazidime than to ticarcillin was observed, and no synergy between the beta-lactamase inhibitors and extended-spectrum cephalosporins was detected, in contrast to the resistance pattern observed in K. pneumoniae. Further sequence analysis demonstrated that the bla(GES-1) gene cassette was located in a class 1 integron, which contained another sequence corresponding to the fused aac(3)-Ib and aac(6')-Ib' gene cassettes. The fusion product was functional, as was the product of each gene cloned separately: AAC(3)-I, despite the deletion of the four last amino acids, and AAC(6'), which carried three amino acid changes compared with the most homologous sequence. The AAC(3)-I protein conferred an expected gentamicin and fortimicin resistance, and the AAC(6'), despite the Leu-119-->Ser substitution, yielded resistance to kanamycin, tobramycin, and dibekacin, but slightly affected netilmicin and amikacin, and had no apparent effect on gentamicin. The fusion product conveyed a large profile of resistance, combining the AAC(6') activity with a higher level of gentamicin resistance without accompanying fortimicin resistance.