Genetic and Biochemical Characterization of FRI-1, a Carbapenem-Hydrolyzing Class A β-Lactamase from Enterobacter cloacae
Genetic and Biochemical Characterization of FRI-1, a Carbapenem-Hydrolyzing Class A β-Lactamase from Enterobacter cloacae
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DOI：
10.1128/aac.01636-15
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发表时间：
2015-12-01
影响因子：
4.9
通讯作者：
Nordmann, Patrice
中科院分区：
文献类型：
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作者：
Dortet, Laurent;Poirel, Laurent;Nordmann, Patrice
从一名曾前往瑞士的法国住院患者的直肠拭子中回收到一株阴沟肠杆菌分离株。对青霉素类、窄谱和广谱头孢菌素类、氨曲南和碳青霉烯类耐药，但对广谱头孢菌素类敏感。尽管基于PCR的最常见碳青霉烯酶基因鉴定失败，但生化Carba NP试验II鉴定了Ambler A类碳青霉烯酶。克隆实验后测序鉴定了编码全新A类碳青霉烯酶FRI-1的基因，与最接近的碳青霉烯酶序列具有51 - 55%的氨基酸序列同一性。然而，它共享保守残基作为碳青霉烯酶活性的来源。纯化的β-内酰胺酶FRI-1水解青霉素类、氨曲南和碳青霉烯类，但不水解广谱头孢菌素类。克拉维酸和他唑巴坦的50%抑制浓度（IC（50））比肺炎克雷伯菌碳青霉烯酶（KPC）、IMI和SME高10倍，导致FRI-1活性对β-内酰胺酶抑制剂的敏感性较低。bla（FRI-1）基因定位于一株CA. 110-kb不可分型、可转移和非自身接合质粒。在β-内酰胺酶基因的5'端鉴定了推定的LysR家族调节剂编码基因，导致bla（FRI-1）基因的诱导型表达。
An Enterobacter cloacae isolate was recovered from a rectal swab from a patient hospitalized in France with previous travel to Switzerland. It was resistant to penicillins, narrow-and broad-spectrum cephalosporins, aztreonam, and carbapenems but remained susceptible to expanded-spectrum cephalosporins. Whereas PCR-based identification of the most common carbapenemase genes failed, the biochemical Carba NP test II identified an Ambler class A carbapenemase. Cloning experiments followed by sequencing identified a gene encoding a totally novel class A carbapenemase, FRI-1, sharing 51 to 55% amino acid sequence identity with the closest carbapenemase sequences. However, it shared conserved residues as a source of carbapenemase activity. Purified beta-lactamase FRI-1 hydrolyzed penicillins, aztreonam, and carbapenems but spared expanded-spectrum cephalosporins. The 50% inhibitory concentrations (IC(50)s) of clavulanic acid and tazobactam were 10-fold higher than those found for Klebsiella pneumoniae carbapenemase (KPC), IMI, and SME, leading to lower sensitivity of FRI-1 activity to beta-lactamase inhibitors. The bla(FRI-1) gene was located on a ca. 110-kb untypeable, transferable, and non-self-conjugative plasmid. A putative LysR family regulator-encoding gene at the 5' end of the beta-lactamase gene was identified, leading to inducible expression of the bla(FRI-1) gene.