Massip Clémence, Descours Ghislaine, Ginevra Christophe, Doublet Patricia, Jarraud Sophie, Gilbert Christophe
CIRI, Centre International de Recherche en Infectiologie, "Legionella pathogenesis" team, Inserm, U1111, Université Lyon 1, CNRS, UMR5308, École Normale Supérieure de Lyon, Univ Lyon, Lyon F-69007, France.
Hospices Civils de Lyon, Groupement Hospitalier Nord, National Reference Centre of Legionella, Institute for Infectious Agents, 103 Grande rue de la Croix rousse, Lyon 69004, France.
J Antimicrob Chemother. 2017 May 1;72(5):1327-1333. doi: 10.1093/jac/dkw594.
A previous study on 12 in vitro -selected azithromycin-resistant Legionella pneumophila lineages showed that ribosomal mutations were major macrolide resistance determinants. In addition to these mechanisms that have been well described in many species, mutations upstream of lpeAB operon, homologous to acrAB in Escherichia coli , were identified in two lineages. In this study, we investigated the role of LpeAB and of these mutations in macrolide resistance of L. pneumophila .
The role of LpeAB was studied by testing the antibiotic susceptibility of WT, deleted and complemented L. pneumophila Paris strains. Translational fusion experiments using GFP as a reporter were conducted to investigate the consequences of the mutations observed in the upstream sequence of lpeAB operon.
We demonstrated the involvement of LpeAB in an efflux pump responsible for a macrolide-specific reduced susceptibility of L. pneumophila Paris strain. Mutations in the upstream sequence of lpeAB operon were associated with an increased protein expression. Increased expression was also observed under sub-inhibitory macrolide concentrations in strains with both mutated and WT promoting regions.
LpeAB are components of an efflux pump, which is a macrolide resistance determinant in L. pneumophila Paris strain. Mutations observed in the upstream sequence of lpeAB operon in resistant lineages led to an overexpression of this efflux pump. Sub-inhibitory concentrations of macrolides themselves participated in upregulating this efflux and could constitute a first step in the acquisition of a high macrolide resistance level.
先前一项针对12个体外筛选出的阿奇霉素耐药嗜肺军团菌谱系的研究表明，核糖体突变是主要的大环内酯类耐药决定因素。除了在许多物种中已被充分描述的这些机制外，在两个谱系中还鉴定出了与大肠杆菌中的acrAB同源的lpeAB操纵子上游的突变。在本研究中，我们调查了LpeAB以及这些突变在嗜肺军团菌大环内酯类耐药中的作用。
通过测试野生型、缺失型和互补型嗜肺军团菌巴黎菌株的抗生素敏感性来研究LpeAB的作用。进行了以绿色荧光蛋白（GFP）作为报告基因的翻译融合实验，以研究在lpeAB操纵子上游序列中观察到的突变的后果。
我们证明了LpeAB参与了一个外排泵，该外排泵导致嗜肺军团菌巴黎菌株对大环内酯类药物的敏感性特异性降低。lpeAB操纵子上游序列中的突变与蛋白质表达增加有关。在具有突变和野生型启动区域的菌株中，在亚抑制浓度的大环内酯类药物作用下也观察到了表达增加。
LpeAB是一个外排泵的组成部分，该外排泵是嗜肺军团菌巴黎菌株中的大环内酯类耐药决定因素。在耐药谱系中lpeAB操纵子上游序列中观察到的突变导致了该外排泵的过表达。亚抑制浓度的大环内酯类药物本身参与上调这种外排，并且可能构成获得高大环内酯类耐药水平的第一步。
