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Rapid development of ciprofloxacin resistance in methicillin-susceptible and -resistant Staphylococcus aureus
H M Blumberg1, D Rimland, D J Carroll
1Department of Medicine, Emory University School of Medicine, Atlanta, GA 30303.
Abstract:
The fluoroquinolones, particularly ciprofloxacin, have been suggested to treat methicillin-resistant Staphylococcus aureus (MRSA) infections and colonization and methicillin-susceptible S. aureus (MSSA) infections. The development of ciprofloxacin resistance in MRSA and MSSA was prospectively evaluated. After 3 months of ciprofloxacin use, high-level resistance (MIC90, 64 micrograms/ml) developed in MRSA and increased at an alarming rate, from none to 79% over a 1-year period. High-level ciprofloxacin resistance also developed in MSSA, increasing to 13.6% over the same period. Antibiograms, phage typing, and plasmid profile analysis suggest that more than one clone of MRSA developed resistance and that ciprofloxacin resistance is not associated with the acquisition of a new plasmid. Most patients had nosocomial acquisition and about one-half had a history of previous ciprofloxacin use. Ciprofloxacin resistance can develop rapidly in S. aureus; thus, ciprofloxacin appears to have limited usefulness in treating staphylococcal infections and colonization, especially those due to MRSA.
Insights
Ciprofloxacin resistance rapidly developed in both MRSA and MSSA strains. This suggests limited effectiveness of ciprofloxacin for treating staphylococcal infections, particularly MRSA.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Fluoroquinolones, like ciprofloxacin, were considered for treating Staphylococcus aureus infections, including MRSA and MSSA.
- The emergence and spread of antibiotic resistance are significant global health concerns.
Purpose of the Study:
- To prospectively evaluate the development of ciprofloxacin resistance in methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA).
- To assess the clinical implications of rapid ciprofloxacin resistance in S. aureus infections and colonization.
Main Methods:
- Prospective evaluation of ciprofloxacin resistance development over one year.
- Utilized antibiograms, phage typing, and plasmid profile analysis to investigate resistance mechanisms.
- Monitored minimum inhibitory concentration (MIC90) values for ciprofloxacin resistance.
Main Results:
- High-level ciprofloxacin resistance (MIC90, 64 µg/ml) developed in MRSA, increasing from 0% to 79% within one year.
- High-level ciprofloxacin resistance also emerged in MSSA, reaching 13.6% over the same period.
- Resistance development was not linked to new plasmid acquisition, suggesting clonal spread or intrinsic mechanisms.
Conclusions:
- Ciprofloxacin resistance can emerge rapidly in S. aureus, including MRSA and MSSA.
- The rapid development of resistance significantly limits the therapeutic utility of ciprofloxacin for staphylococcal infections and colonization.
- Particular caution is advised for using ciprofloxacin against MRSA due to high resistance rates.