title: Ribosomal Mutations Conferring Macrolide Resistance in Legionella pneumophila.
abstract: 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 inLegionellaspecies. Our aim was to determine the molecular basis of macrolide resistance inL. pneumophilaTwelve independent lineages from a common susceptibleL. pneumophilaancestral 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 threerrlcopies. The major mechanisms of the decreased susceptibility to macrolides inL. pneumophilaand their dynamics were determined. The results showed that macrolide resistance could be easily selected inL. pneumophilaand warrant further investigations in both clinical and environmental settings.
authors.affiliation: CIRI, Centre International de Recherche en Infectiologie, Equipe Pathogénèse des Légionelles, Lyon, France ghislaine.descours@univ-lyon1.fr.|Inserm, U1111, Université Lyon 1, CNRS, UMR5308, École Normale Supérieure de Lyon, Lyon, France.|Univ Lyon, F-69007, Lyon, France.|Hospices Civils de Lyon, Groupement Hospitalier Nord, National Reference Centre of Legionella, Institute for Infectious Agents, Lyon, France.
authors.forename: Ghislaine
authors.initials: G
authors.lastname: Descours
authors.affiliation: 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.|Univ Lyon, F-69007, Lyon, France.|Hospices Civils de Lyon, Groupement Hospitalier Nord, National Reference Centre of Legionella, Institute for Infectious Agents, Lyon, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Ginevra
authors.affiliation: Hospices Civils de Lyon, Groupement Hospitalier Nord, National Reference Centre of Legionella, Institute for Infectious Agents, Lyon, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Jacotin
authors.affiliation: Hospices Civils de Lyon, Groupement Hospitalier Nord, National Reference Centre of Legionella, Institute for Infectious Agents, Lyon, France.
authors.forename: Françoise
authors.initials: F
authors.lastname: Forey
authors.affiliation: Hospices Civils de Lyon, Groupement Hospitalier Nord, National Reference Centre of Legionella, Institute for Infectious Agents, Lyon, France.
authors.forename: Joëlle
authors.initials: J
authors.lastname: Chastang
authors.affiliation: 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.|Univ Lyon, F-69007, Lyon, France.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kay
authors.affiliation: Inserm, U1111, Université Lyon 1, CNRS, UMR5308, École Normale Supérieure de Lyon, Lyon, France.|Univ Lyon, F-69007, Lyon, France.|Hospices Civils de Lyon, Groupement Hospitalier Nord, National Reference Centre of Legionella, Institute for Infectious Agents, Lyon, France.
authors.forename: Jerome
authors.initials: J
authors.lastname: Etienne
authors.affiliation: Inserm, U1111, Université Lyon 1, CNRS, UMR5308, École Normale Supérieure de Lyon, Lyon, France.|Univ Lyon, F-69007, Lyon, France.|Hospices Civils de Lyon, Groupement Hospitalier Nord, National Reference Centre of Legionella, Institute for Infectious Agents, Lyon, France.
authors.forename: Gérard
authors.initials: G
authors.lastname: Lina
authors.affiliation: 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.|Univ Lyon, F-69007, Lyon, France.
authors.forename: Patricia
authors.initials: P
authors.lastname: Doublet
authors.affiliation: 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.|Univ Lyon, F-69007, Lyon, France.|Hospices Civils de Lyon, Groupement Hospitalier Nord, National Reference Centre of Legionella, Institute for Infectious Agents, Lyon, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Jarraud
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017963:Azithromycin / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002999:Clone Cells; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004917:Erythromycin / Q000494:pharmacology; D059014:High-Throughput Nucleotide Sequencing; D016952:Legionella pneumophila / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D008826:Microbial Sensitivity Tests; D009154:Mutation; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012338:RNA, Ribosomal, 23S / Q000235:genetics* / Q000378:metabolism; D012269:Ribosomal Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D020033:Protein Isoforms; D012338:RNA, Ribosomal, 23S; D012269:Ribosomal Proteins; D004917:Erythromycin; D017963:Azithromycin
keywords: 23S rRNA; Legionella pneumophila; macrolide; resistance; ribosomal mutations; ribosomal proteins