In vitro activities of quinolones against enterococci resistant to penicillin-aminoglycoside synergy.
The MICs and MBCs of CI-934, ciprofloxacin, difloxacin (A-56619), A-56620, norfloxacin, enoxacin, amifloxacin, and coumermycin were determined for 43 clinical isolates of Enterococcus faecalis known to be resistant to penicillin-aminoglycoside synergy. Results were compared with those obtained for 37 synergy-susceptible E. faecalis and 22 Enterococcus faecium strains. Although no substantial differences in quinolone activities were observed between synergy-resistant and -susceptible E. faecalis strains, CI-934 and ciprofloxacin were the drugs that demonstrated the greatest bactericidal activity against both types of E. faecalis. The MBCs of the other quinolones were generally within a single twofold dilution of the MICs, but their antienterococcal activity did not approach that of CI-934 or ciprofloxacin. The MBCs for 90% of the isolates of CI-934 for synergy-resistant and -susceptible E. faecalis strains were 1 and less than or equal to 0.5 microgram/ml, respectively. The ciprofloxacin MBC for 90% of the E. faecalis strains tested was 1 microgram/ml. For E. faecium isolates the CI-934 and ciprofloxacin MBCs for 90% of the isolates were 8 and 4 micrograms/ml, respectively. Time-kill assays performed with synergy-susceptible enterococcal strains showed that the bactericidal activities of both CI-934 and ciprofloxacin were less than those of the penicillin-aminoglycoside combinations tested. However, against synergy-resistant isolates the activities of these two quinolones were comparable with and sometimes greater than those of penicillin-aminoglycoside combinations.
Sahm
D F
DF
Clinical Microbiology Laboratories, University of Chicago Medical Center, Illinois 60637.
Koburov
G T
GT
D042462:4-Quinolones; D000617:Aminoglycosides; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000890:Anti-Infective Agents / Q000494:pharmacology*; D004357:Drug Synergism; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance; D010406:Penicillins / Q000494:pharmacology; D013997:Time Factors
D042462:4-Quinolones; D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D010406:Penicillins