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Widespread quinolone resistance among methicillin-resistant Staphylococcus aureus isolates in a general hospital
I Shalit1, S A Berger, A Gorea
1Department of Infectious Diseases, Tel-Aviv Medical Center, Israel.
Abstract:
Ofloxacin and ciprofloxacin resistance (MIC, greater than 4 micrograms/ml) was encountered in 45 of 50 clinical isolates of methicillin-resistant Staphylococcus aureus. None of 20 methicillin-susceptible strains was resistant to the quinolones (P less than 10(-6). Quinolone-susceptible and -resistant isolates did not differ with respect to culture source or bacteriophage type. The future usefulness of quinolones for S. aureus infection may be limited.
Insights
High rates of ofloxacin and ciprofloxacin resistance were found in methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates. This widespread quinolone resistance in MRSA may limit future treatment options for S. aureus infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of healthcare-associated infections.
- Quinolones, including ofloxacin and ciprofloxacin, are important antibiotics for treating S. aureus infections.
Purpose of the Study:
- To investigate the prevalence of ofloxacin and ciprofloxacin resistance in clinical isolates of MRSA.
- To compare quinolone resistance rates between MRSA and methicillin-susceptible Staphylococcus aureus (MSSA).
Main Methods:
- Antimicrobial susceptibility testing was performed on 50 clinical isolates of MRSA and 20 strains of MSSA.
- Minimum Inhibitory Concentrations (MICs) for ofloxacin and ciprofloxacin were determined.
Main Results:
- Resistance to ofloxacin and ciprofloxacin (MIC > 4 µg/mL) was observed in 45 out of 50 MRSA isolates (90%).
- None of the 20 MSSA strains exhibited resistance to these quinolones (P < 10^-6).
- No significant differences in culture source or bacteriophage type were found between quinolone-susceptible and -resistant MRSA isolates.
Conclusions:
- A high prevalence of quinolone resistance exists among clinical MRSA isolates.
- The findings suggest that the future clinical utility of ofloxacin and ciprofloxacin for treating S. aureus infections may be compromised by emerging resistance.