Related Experiment Video
Updated: Jun 25, 2026
09:03
Forward Genetic Approaches in Chlamydia trachomatis
Published on: October 23, 2013
Fluoroquinolone-resistant Brucella melitensis mutants obtained in vitro
Francisco García Lázaro1, R Elisa Rodríguez-Tarazona, José Angel García-Rodríguez
1Departamento de Microbiología, Hospital Universitario de Salamanca, Paseo de San Vicente 58-182, 37007 Salamanca, Spain.
International Journal of Antimicrobial Agents
|February 27, 2009
Summary
Researchers developed fluoroquinolone-resistant Brucella melitensis mutants. These mutants exhibited specific gyrA gene mutations, indicating potential efflux mechanisms contributing to resistance.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Brucella melitensis is a significant zoonotic pathogen.
- Fluoroquinolone antibiotics are crucial for treating brucellosis.
- Emergence of antibiotic resistance in Brucella poses a therapeutic challenge.
Purpose of the Study:
- To investigate the genetic basis of fluoroquinolone resistance in Brucella melitensis.
- To characterize the mutations conferring resistance to fluoroquinolones.
Main Methods:
- Induction of resistance through successive passages on norfloxacin-containing agar.
- Genomic analysis to identify mutations in resistance-associated genes (gyrA, gyrB, parC).
- Determination of Minimum Inhibitory Concentrations (MICs) for various fluoroquinolones.
Main Results:
- Three fluoroquinolone-resistant Brucella melitensis mutants were successfully generated.
- Mutants consistently displayed a gyrA Ala71Ser mutation and an Ala340 insertion.
- No mutations were detected in parC or gyrB genes.
- Progressive increase in MICs for norfloxacin, ciprofloxacin, levofloxacin, and moxifloxacin was observed, with later-step mutants showing increased resistance primarily to norfloxacin and ciprofloxacin.
Conclusions:
- The gyrA gene is a primary target for fluoroquinolone resistance development in Brucella melitensis.
- The observed resistance patterns suggest the potential involvement of efflux mechanisms in higher-level resistance.
Related Concept Videos
01:16In vitro Mutagenesis
To learn more about the function of a gene, researchers can observe what happens when the gene is inactivated or “knocked out,” by creating genetically engineered knockout animals. Knockout mice have been particularly useful as models for human diseases such as cancer, Parkinson’s disease, and diabetes.
01:16In-vitro Mutagenesis
To learn more about the function of a gene, researchers can observe what happens when the gene is inactivated or “knocked out,” by creating genetically engineered knockout animals. Knockout mice have been particularly useful as models for human diseases such as cancer, Parkinson’s disease, and diabetes.
01:28Inhibitors 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...