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In vitro activity of sparfloxacin and clinafloxacin against multidrug-resistant enterococci
M B Perri1, J W Chow, M J Zervos
1Department of Internal Medicine, William Beaumont Hospital, Royal Oak, Michigan 48073.
Abstract:
We evaluated the in vitro susceptibility of 140 clinical enterococcal isolates to the quinolones sparfloxacin and clinafloxacin. Isolates included Enterococcus faecalis (107), Enterococcus faecium (29), Enterococcus raffinosus (3), and one Enterococcus gallinarum. There were 111 isolates that showed high-level [minimum inhibitory concentrations (MICs) > or = 2000 micrograms/ml] resistance to gentamicin and were resistant to high levels of all other aminoglycosides; five isolates produced beta-lactamase; 21 isolates were resistant (MIC > or = 16 micrograms/ml) to ampicillin and were not beta-lactamase producers; and 13 strains were resistant (MIC > or = 32 micrograms/ml) to vancomycin. Most strains were susceptible to low concentrations of sparfloxacin and clinafloxacin, with MIC90S of 0.6 microgram/ml and 0.5 micrograms/ml, respectively. There were no inoculum effects. Time-kill experiments were performed with 22 strains; using 2 x MIC at 24 h, a > or = 2 log10 reduction in growth was observed with sparfloxacin and clinafloxacin for 14 and 17 strains, respectively. Time-kill synergism experiments were performed with 15 strains lacking high-level aminoglycoside resistance. In vitro bacterial synergism with the combination of sparfloxacin or clinafloxacin with streptomycin or gentamicin was observed for five and 12 isolates, respectively. The bactericidal activity of sparfloxacin and clinafloxacin suggest that these antibiotics may prove useful for therapy of multidrug resistant enterococci.
Insights
Sparfloxacin and clinafloxacin show promising in vitro activity against multidrug-resistant enterococci. These fluoroquinolones demonstrate potent bactericidal effects, suggesting potential therapeutic value for challenging enterococcal infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Enterococci are significant nosocomial pathogens, often exhibiting multidrug resistance.
- High-level aminoglycoside resistance and resistance to beta-lactams and vancomycin are common in clinical enterococcal isolates.
- Novel therapeutic options are needed to combat resistant enterococcal infections.
Purpose of the Study:
- To evaluate the in vitro susceptibility of clinical enterococcal isolates to the fluoroquinolones sparfloxacin and clinafloxacin.
- To assess the bactericidal activity and synergistic potential of sparfloxacin and clinafloxacin in combination with other antibiotics.
Main Methods:
- In vitro susceptibility testing (MICs) was performed on 140 clinical enterococcal isolates.
- Time-kill experiments were conducted to determine bactericidal activity.
- Synergism studies were performed with combinations of fluoroquinolones and aminoglycosides.
Main Results:
- Most enterococcal strains were susceptible to low concentrations of sparfloxacin (MIC90 = 0.6 µg/ml) and clinafloxacin (MIC90 = 0.5 µg/ml).
- Sparfloxacin and clinafloxacin exhibited significant bactericidal activity in time-kill assays.
- Synergistic activity was observed with combinations of clinafloxacin and gentamicin.
Conclusions:
- Sparfloxacin and clinafloxacin possess potent in vitro activity against a range of multidrug-resistant enterococci.
- These fluoroquinolones demonstrate bactericidal properties and potential for synergistic effects.
- Sparfloxacin and clinafloxacin may represent valuable therapeutic options for treating infections caused by resistant enterococci.