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Dissociated resistance among fluoroquinolones
1Department of Medical Microbiology, Creighton University School of Medicine, Omaha, NE 68178.
Antimicrobial Agents and Chemotherapy
|September 1, 1994
Summary
New quinolone OPC-17116 shows varied resistance in staphylococci. While generally less affected by quinolone resistance mechanisms than ciprofloxacin, some highly resistant staphylococci strains showed greater susceptibility to ciprofloxacin than OPC-17116.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Antibiotic resistance is a growing global health concern, particularly among Gram-positive and Gram-negative bacteria.
- Fluoroquinolones are a class of broad-spectrum antibiotics widely used to treat bacterial infections.
- Understanding cross-resistance patterns among different quinolone agents is crucial for effective antimicrobial stewardship.
Purpose of the Study:
- To evaluate the in vitro susceptibility of clinical bacterial isolates to five quinolones and six nonquinolone agents.
- To analyze cross-resistance patterns to OPC-17116, ofloxacin, and temafloxacin in ciprofloxacin-resistant staphylococci and Enterobacteriaceae.
- To investigate the impact of specific resistance mechanisms on the activity of different fluoroquinolones.
Main Methods:
- Agar dilution tests were performed on 190 clinical isolates, including staphylococci, enterococci, Streptococcus pneumoniae, Enterobacteriaceae, and nonfermentative gram-negative bacilli.
- Isolates were categorized into subgroups based on ciprofloxacin susceptibility.
- Cross-resistance to OPC-17116, ofloxacin, and temafloxacin was assessed, alongside single-step mutational studies in staphylococcal strains.
Main Results:
- Increasing ciprofloxacin resistance correlated with increased minimum inhibitory concentrations (MICs) for all tested quinolones.
- OPC-17116, ofloxacin, and temafloxacin showed reduced increases in MICs compared to ciprofloxacin with rising resistance, suggesting less susceptibility to common resistance mechanisms.
- An exception was observed with OPC-17116 against highly ciprofloxacin-resistant staphylococci, where some strains exhibited equal or greater resistance to OPC-17116 than to ciprofloxacin.
Conclusions:
- While OPC-17116, ofloxacin, and temafloxacin are generally less affected by quinolone resistance mechanisms than ciprofloxacin, specific resistance mechanisms in staphylococci can disproportionately impact OPC-17116 activity.
- Heterogeneity in fluoroquinolone resistance among staphylococci was observed, with some mutants showing significant decreases in susceptibility to OPC-17116.
- These findings highlight the complex nature of antibiotic resistance and the need for careful evaluation of individual agents against specific bacterial populations.