Descours Ghislaine, Ginevra Christophe, Jacotin Nathalie, Forey Françoise, Chastang Joëlle, Kay Elisabeth, Etienne Jerome, Lina Gérard, Doublet Patricia, Jarraud Sophie
CIRI, Centre International de Recherche en Infectiologie, Equipe Pathogénèse des Légionelles, Lyon, France
Inserm, U1111, Université Lyon 1, CNRS, UMR5308, École Normale Supérieure de Lyon, Lyon, France.
Antimicrob Agents Chemother. 2017 Feb 23;61(3). doi: 10.1128/AAC.02188-16. Print 2017 Mar.
Monitoring the emergence of antibiotic resistance is a recent issue in the treatment of Legionnaires' disease. Macrolides are recommended as first-line therapy, but resistance mechanisms have not been studied in species. Our aim was to determine the molecular basis of macrolide resistance in Twelve independent lineages from a common susceptible ancestral strain were propagated under conditions of erythromycin or azithromycin pressure to produce high-level macrolide resistance. Whole-genome sequencing was performed on 12 selected clones, and we investigated mutations common to all lineages. We reconstructed the dynamics of mutation for each lineage and demonstrated their involvement in decreased susceptibility to macrolides. The resistant mutants were produced in a limited number of passages to obtain a 4,096-fold increase in erythromycin MICs. Mutations affected highly conserved 5-amino-acid regions of L4 and L22 ribosomal proteins and of domain V of 23S rRNA (G2057, A2058, A2059, and C2611 nucleotides). The early mechanisms mainly affected L4 and L22 proteins and induced a 32-fold increase in the MICs of the selector drug. Additional mutations related to 23S rRNA mostly occurred later and were responsible for a major increase of macrolide MICs, depending on the mutated nucleotide, the substitution, and the number of mutated genes among the three copies. The major mechanisms of the decreased susceptibility to macrolides in and their dynamics were determined. The results showed that macrolide resistance could be easily selected in and warrant further investigations in both clinical and environmental settings.
监测抗生素耐药性的出现是军团病治疗中的一个新问题。大环内酯类药物被推荐作为一线治疗药物，但尚未对[具体物种]的耐药机制进行研究。我们的目的是确定[具体物种]中大环内酯类耐药性的分子基础。从一个常见的敏感祖先菌株衍生出的12个独立谱系在红霉素或阿奇霉素压力条件下传代，以产生高水平的大环内酯类耐药性。对12个选定的克隆进行了全基因组测序，我们研究了所有谱系共有的突变。我们重建了每个谱系的突变动态，并证明了它们与大环内酯类药物敏感性降低有关。耐药突变体在有限的传代次数中产生，使红霉素的最低抑菌浓度（MIC）增加了4096倍。突变影响了L4和L22核糖体蛋白以及23S rRNA结构域V（G2057、A2058、A2059和C2611核苷酸）高度保守的5个氨基酸区域。早期机制主要影响L4和L22蛋白，并使选择药物的MIC增加了32倍。与23S rRNA相关的其他突变大多在后期发生，并导致大环内酯类MIC的大幅增加，这取决于突变的核苷酸、取代情况以及三个拷贝中突变基因的数量。确定了[具体物种]中对大环内酯类药物敏感性降低的主要机制及其动态变化。结果表明，[具体物种]中很容易选择出大环内酯类耐药性，这值得在临床和环境环境中进一步研究。
