Genetic Basis for In Vitro and In Vivo Resistance to Lincosamides, Streptogramins A, and Pleuromutilins (LSAP Phenotype) in Enterococcus faecium
Genetic Basis for In Vitro and In Vivo Resistance to Lincosamides, Streptogramins A, and Pleuromutilins (LSAP Phenotype) in Enterococcus faecium
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DOI：
10.1128/aac.01030-13
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发表时间：
2013-09-01
影响因子：
4.9
通讯作者：
Cattoir, Vincent
中科院分区：
文献类型：
--
作者：
Isnard, Christophe;Malbruny, Brigitte;Cattoir, Vincent
与粪肠球菌相反，粪肠球菌通过产生ABC蛋白Lsa(A)对lincosamides， streptogramins A和胸膜多素（LSAP表型）具有内在抗性，而粪肠球菌天然易感。由于这种表型可能被奎奴普司汀-达福普司汀（Q-D）在体内选择，因此本研究的目的是探讨粪肠杆菌获得性LSAP耐药的分子机制。研究了6个对lsap耐药的粪肠杆菌HM1070体外突变体以及3对不同的临床分离株（暴露于Q-D前和暴露于Q-D后）。采用454测序技术测定了体外突变株E. faecium UCN90B的全基因组序列，并与亲本菌株进行了比较。进行了单核苷酸替换以确认该突变的作用。通过比较基因组分析，在编码ABC同源物的1,503 bp基因中发现一个点突变，该基因与Lsa(a)的氨基酸同源性为66%。该突变（C1349T）导致一个氨基酸取代（Thr450Ile）。在所有体外和体内耐药菌株中发现了相同的突变，但在敏感菌株中不存在。该野生型等位基因命名为eat(A)（ABC肠球菌转运体），其突变等位基因变体命名为eat(A)(v)。从UCN90B导入的eat(A)(v)赋予了LSAP表型，而从HM1070导入的eat(A)则完全恢复了对UCN90B的易感性。这是首次描述粪肠杆菌获得性LSAP耐药的分子机制。抗性的生化机制及该ABC蛋白的生理作用有待进一步研究。
As opposed to Enterococcus faecalis, which is intrinsically resistant to lincosamides, streptogramins A, and pleuromutilins (LSAP phenotype) by production of the ABC protein Lsa(A), Enterococcus faecium is naturally susceptible. Since this phenotype may be selected for in vivo by quinupristin-dalfopristin (Q-D), the aim of this study was to investigate the molecular mechanism of acquired LSAP resistance in E. faecium. Six LSAP-resistant in vitro mutants of E. faecium HM1070 as well as three different pairs of clinical isolates (pre- and postexposure to Q-D) were studied. The full genome sequence of an in vitro mutant (E. faecium UCN90B) was determined by using 454 sequencing technology and was compared with that of the parental strain. Single-nucleotide replacement was carried out to confirm the role of this mutation. By comparative genomic analysis, a point mutation was found within a 1,503-bp gene coding for an ABC homologue showing 66% amino acid identity with Lsa(A). This mutation (C1349T) led to an amino acid substitution (Thr450Ile). An identical mutation was identified in all in vitro and in vivo resistant strains but was not present in susceptible strains. The wild-type allele was named eat(A) (for Enterococcus ABC transporter), and its mutated allelic variant was named eat(A)(v). The introduction of eat(A)(v) from UCN90B into HM1070 conferred the LSAP phenotype, whereas that of eat(A) from HM1070 into UCN90B restored susceptibility entirely. This is the first description of the molecular mechanism of acquired LSAP resistance in E. faecium. Characterization of the biochemical mechanism of resistance and the physiological role of this ABC protein need further investigations.