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In Vitro Activity of Delafloxacin Against Corynebacterium spp
Montserrat Muñoz-Rosa1,2, Cristina Elías-López2,3, Rosa Pedraza1,2
1Unit of Microbiology, Reina Sofía University Hospital, 14004 Cordoba, Spain.
Antibiotics (Basel, Switzerland)
|October 28, 2025
Summary
Delafloxacin shows strong in vitro activity against Corynebacterium species, with resistance linked to gyrA gene mutations. Delafloxacin gradient strips offer a reliable alternative for clinical microbiology laboratories.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Antimicrobial resistance in Corynebacterium species is increasing, particularly to fluoroquinolones.
- This resistance is linked to the widespread use of these agents in clinical settings.
Purpose of the Study:
- To evaluate the in vitro activity of delafloxacin against clinical isolates of Corynebacterium species.
- To compare delafloxacin's efficacy with other fluoroquinolones.
- To investigate fluoroquinolone resistance mechanisms in these bacteria.
Main Methods:
- Fifty-three clinical isolates of Corynebacterium spp. were tested.
- In vitro activity was assessed using reference microdilution and delafloxacin gradient strips.
- Mechanisms of resistance were investigated by analyzing mutations in the gyrA gene's QRDR.
Main Results:
- Delafloxacin demonstrated potent activity (MIC50/MIC90: 0.5/8 mg/L).
- Resistance correlated with single or double mutations in the gyrA QRDR.
- Delafloxacin gradient strips showed high agreement (88.7%) with microdilution.
Conclusions:
- Non-conservative mutations in the gyrA QRDR are associated with increased delafloxacin MICs in Corynebacterium.
- Delafloxacin gradient strips are a viable option for routine clinical use.
- Delafloxacin may serve as an alternative treatment for Corynebacterium infections.
