Related Experiment Video

Updated: Sep 27, 2026

Use of Galleria mellonella as a Model Organism to Study Legionella pneumophila Infection
12:30

Use of Galleria mellonella as a Model Organism to Study Legionella pneumophila Infection

Published on: November 22, 2013

Development and mechanism of fluoroquinolone resistance in Legionella pneumophila

Daniel Jonas1, Inge Engels, Doris Hartung

  • 1Institute of Environmental Medicine and Hospital of Epidemiology, University Hospital of Freiburg, Hugstetter Strasse 55, D-79106 Freiburg. djonas@IUK3.UKL.uni-Freiburg.de

The Journal of Antimicrobial Chemotherapy
|February 4, 2003
PubMed

Insights

Investigating fluoroquinolone resistance in Legionella pneumophila revealed that different antibiotics vary in their ability to select for resistant mutants. The gyrA gene was identified as a potential target for fluoroquinolone action in this bacterium.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Pharmacology

Background:

  • Legionella pneumophila is a significant human pathogen.
  • Fluoroquinolones are critical antibiotics for treating Legionella infections.
  • Understanding resistance mechanisms is crucial for effective treatment.

Purpose of the Study:

  • To investigate the in vitro selection of Legionella pneumophila mutants resistant to various fluoroquinolones.
  • To determine the relative efficiency of different fluoroquinolones in selecting for resistance.
  • To identify potential genetic targets associated with fluoroquinolone resistance.

Main Methods:

  • Subculturing six clinical isolates of L. pneumophila in subinhibitory concentrations of five fluoroquinolones (ciprofloxacin, levofloxacin, clinafloxacin, trovafloxacin, moxifloxacin).
  • Determining minimum inhibitory concentrations (MICs) and the number of serial passages required for resistance development.
  • Sequencing the gyrA gene of parental and mutant strains.

Main Results:

  • Fluoroquinolones exhibited marked differences in their ability to select for resistant L. pneumophila mutants.
  • Fewer passages were required for resistance selection with clinafloxacin, ciprofloxacin, and levofloxacin compared to trovafloxacin and moxifloxacin.
  • Amino acid changes (Thr83 to Lys or Ile) in the gyrA gene were observed in mutants selected by ciprofloxacin and moxifloxacin.

Conclusions:

  • Different fluoroquinolones have varying efficacy in selecting for resistant Legionella pneumophila.
  • The gyrA gene in L. pneumophila is a likely target for fluoroquinolone activity.
  • These findings have implications for antibiotic stewardship and the development of new anti-Legionella therapies.

More Related Videos

Tractable Mammalian Cell Infections with Protozoan-primed Bacteria13:54

Tractable Mammalian Cell Infections with Protozoan-primed Bacteria

Published on: April 2, 2013

Applying Live Cell Imaging and Cryo-Electron Tomography to Resolve Spatiotemporal Features of the Legionella pneumophila Dot/Icm Secretion System09:12

Applying Live Cell Imaging and Cryo-Electron Tomography to Resolve Spatiotemporal Features of the Legionella pneumophila Dot/Icm Secretion System

Published on: March 10, 2020

Related Concept Videos

Inhibitors of Bacterial DNA Synthesis01:28

Inhibitors of Bacterial DNA Synthesis

Bacterial pathogens depend on precise and efficient DNA replication to sustain infection. Two type II topoisomerases—DNA gyrase and topoisomerase IV—are critical to this process, as they resolve DNA supercoiling and unlink chromosomes during replication. Fluoroquinolones, synthetic derivatives of quinolones, exploit this mechanism by stabilizing the transient DNA–enzyme cleavage complex, preventing strand religation, and causing lethal double-strand breaks. These antibiotics are selectively...
Mechanism of Antibiotic Resistance in MRSA01:25

Mechanism of Antibiotic Resistance in MRSA

Antibiotic resistance in bacteria arises when microorganisms evolve the ability to withstand drugs designed to kill them or inhibit their growth, rendering once-effective treatments useless. This phenomenon, driven by genetic change and selection under antibiotic exposure, poses a profound threat to modern medicine. Mechanisms include drug-inactivating enzymes (e.g., β-lactamases), efflux pumps that eject antibiotics, mutations altering antibiotic targets, decreased drug uptake, and acquisition...
Development of Antibiotic Resistance01:30

Development of Antibiotic Resistance

Antibiotic resistance is a major public health concern that arises when bacteria evolve mechanisms to withstand the effects of antibiotic treatments. This resistance can be intrinsic, acquired through genetic mutations, or transferred between bacteria via horizontal gene transfer. The development of antibiotic resistance poses significant challenges in treating bacterial infections and necessitates ongoing research to develop new therapeutic strategies.Intrinsic resistance occurs when bacterial...
Gene Regulation in Microbial Communities: Quorum Sensing01:28

Gene Regulation in Microbial Communities: Quorum Sensing

Quorum sensing is a mechanism of bacterial communication that enables coordinated gene expression in response to changes in population density. This facilitates collective behaviors that enhance survival, resource acquisition, and ecological adaptation. This process relies on small signaling molecules called autoinducers that accumulate as bacterial populations grow. When a critical threshold concentration of autoinducers is reached, bacterial cells collectively modify gene expression,...
Clinical Significance of Antibiotic Resistance01:25

Clinical Significance of Antibiotic Resistance

Methicillin-resistant Staphylococcus aureus (MRSA) presents a critical public health threat, arising from its capacity to resist β-lactam antibiotics due to acquisition of the mecA gene within the staphylococcal cassette chromosome mec (SCCmec). This gene encodes penicillin-binding protein 2a (PBP2a), which impairs binding efficacy of methicillin and other β-lactams. MRSA has evolved into distinct clonal lineages impacting humans and animals alike, reinforcing its significance within the One...