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首页> 外文期刊>Antimicrobial agents and chemotherapy. >Carbapenem resistance in Escherichia coli associated with plasmid-determined CMY-4 beta-lactamase production and loss of an outer membrane protein.
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Carbapenem resistance in Escherichia coli associated with plasmid-determined CMY-4 beta-lactamase production and loss of an outer membrane protein.

机译：大肠杆菌对碳青霉烯的耐药性与质粒确定的CMY-4β-内酰胺酶的产生和外膜蛋白的损失有关。

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Three cefoxitin-resistant Escherichia coli isolates from stool specimens of a patient with leukemia were either resistant, intermediate, or sensitive to imipenem. Conjugation experiments showed that cefoxitin resistance, but not imipenem resistance, was transferable. All isolates were shown by isoelectric focusing to produce two beta-lactamases with isoelectric points of 5.4 (TEM-1, confirmed by sequencing of a PCR product) and >8.5 (consistent with a class C beta-lactamase). The gene coding for the unknown beta-lactamase was cloned and sequenced and revealed an enzyme which had 99.9% sequence identity with the plasmid-determined class C beta-lactamase CMY-2. The cloned beta-lactamase gene differed from blaCMY-2 at one nucleotide position that resulted in an amino acid change, tryptophan to arginine at position 221. We propose that this enzyme be designated CMY-4. Both the imipenem-resistant and -intermediate isolates lacked a 38-kDa outer membrane protein (OMP) that was present in the imipenem-sensitive isolate. The lack of an OMP alone did not explain the difference in carbapenem susceptibilities observed. However, measurement of beta-lactamase activities (including measurements under conditions where TEM-1 beta-lactamase was inhibited) indicated that the imipenem-intermediate isolate expressed six- to eightfold less beta-lactamase than did the other isolates. This study illustrates that carbapenem resistance in E. coli can arise from high-level expression of plasmid-mediated class C beta-lactamase combined with an OMP deficiency. Furthermore, in the presence of an OMP deficiency, the level of expression of a plasmid-mediated class C beta-lactamase is an important factor in determining whether E. coli isolates are fully resistant to carbapenems.
机译：从白血病患者粪便标本中分离出的三种耐头孢西丁的大肠杆菌对亚胺培南具有抗性，中度或敏感性。缀合实验表明，头孢西丁耐药性是可转移的，但亚胺培南耐药性却是不可转移的。通过等电聚焦显示所有分离物产生两种β-内酰胺酶，其等电点分别为5.4（TEM-1，通过PCR产物测序确认）和> 8.5（与C类β-内酰胺酶一致）。克隆编码未知的β-内酰胺酶的基因并进行测序，揭示出一种与质粒确定的C类β-内酰胺酶CMY-2具有99.9％序列同一性的酶。克隆的β-内酰胺酶基因在一个核苷酸位置不同于blaCMY-2，导致一个氨基酸改变，从221位色氨酸变为精氨酸。我们建议将该酶命名为CMY-4。耐亚胺培南的分离株和对亚胺培南的分离株均缺乏在亚胺培南敏感的分离株中存在的38 kDa外膜蛋白（OMP）。单独缺乏OMP不能解释观察到的碳青霉烯敏感性的差异。然而，对β-内酰胺酶活性的测量（包括在TEM-1β-内酰胺酶被抑制的条件下的测量）表明，亚胺培南中间体分离物表达的β-内酰胺酶比其他分离物少六至八倍。这项研究表明，大肠杆菌中的碳青霉烯耐药性可能是由质粒介导的C类β-内酰胺酶的高水平表达与OMP缺乏引起的。此外，在OMP缺乏的情况下，质粒介导的C类β-内酰胺酶的表达水平是确定大肠杆菌分离株是否对碳青霉烯类药物完全耐药的重要因素。

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