Skip Navigation


JAC Advance Access originally published online on May 27, 2009
Journal of Antimicrobial Chemotherapy 2009 64(2):284-293; doi:10.1093/jac/dkp173
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
64/2/284    most recent
dkp173v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Right arrow Disclaimer
Google Scholar
Right arrow Articles by Almahmoud, I.
Right arrow Articles by Maurin, M.
PubMed
Right arrow PubMed Citation
Right arrow Articles by Almahmoud, I.
Right arrow Articles by Maurin, M.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© The Author 2009. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

Original research

Mutational paths towards increased fluoroquinolone resistance in Legionella pneumophila

Iyad Almahmoud1,2, Elisabeth Kay1,2, Dominique Schneider1,2 and Max Maurin1,2,3,*

1 Laboratoire Adaptation et Pathogénie des Micro-organismes, Université Joseph Fourier Grenoble 1, Institut Jean Roget, Campus Santé, Domaine de la Merci, BP 170, F-38042 Grenoble cedex 9, France 2 CNRS UMR 5163, Institut Jean Roget, Campus Santé, Domaine de la Merci, BP 170, F-38042 Grenoble cedex 9, France 3 Laboratoire de Bactériologie, CHU de Grenoble, Université Joseph Fourier, BP 217, F-38043 Grenoble cedex 9, France

Received 27 January 2009; returned 24 March 2009; revised 1 April 2009; accepted 20 April 2009

* Corresponding author. CHU Grenoble, Université Joseph Fourier, BP 217, F-38043 Grenoble cedex 9, France. Tel: +33 (0) 4 76 76 54 79; Fax: +33 (0) 4 76 76 59 12; E-mail: mmaurin{at}chu-grenoble.fr

Objectives: Fluoroquinolone resistance has been poorly studied in Legionella pneumophila, an intracellular pathogen responsible for legionellosis. Our goal was to further characterize molecular mechanisms involved in fluoroquinolone resistance in this species.

Methods: Eight independent lineages were founded from a common fluoroquinolone-susceptible L. pneumophila ancestor and propagated by serial passages in moxifloxacin-containing culture medium. We identified the substituted mutations that affected the DNA topoisomerase II-encoding genes, determined the order of substitution of the mutations leading to the stepwise MIC increases of moxifloxacin over evolutionary time and demonstrated their direct involvement in the resistance process.

Results: Adaptation occurred through parallel stepwise increases in the moxifloxacin MICs up to 512-fold the MIC for the parental strain. Mutations affected the topoisomerase II-encoding genes gyrA, parC and gyrB, reflecting a high degree of genetic parallelism across the independent lineages. During evolution, the T83I change in GyrA occurred first, followed by G78D or S80R in ParC and D87N in GyrA, or S464Y or D426N in GyrB. By constructing isogenic strains, we showed that the progressive increase in resistance was linked to a precise order of mutation substitution, but also to the co-existence of several subpopulations of bacteria bearing different mutations.

Conclusions: Specific mutational trajectories were identified, strongly suggesting that intermolecular epistatic interactions between DNA topoisomerases underlie the mechanism of fluoroquinolone resistance in L. pneumophila. Our results suggest that L. pneumophila has strong potential to become resistant to fluoroquinolone compounds and warrant further investigation of resistance in clinical and environmental strains of this pathogen.

Keywords: Legionella pneumophila , resistance mechanisms , mutations , evolution


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.