In vitro activity of DC-159a, a new broad-spectrum fluoroquinolone, compared with that of other agents against drug-susceptible and -resistant pneumococci.
DC-159a yielded MICs of <or=1 mug/ml against 316 strains of both quinolone-susceptible and -resistant pneumococci (resistance was defined as a levofloxacin MIC >or=4 microg/ml). Although the MICs for DC-159a against quinolone-susceptible pneumococci were a few dilutions higher than those of gemifloxacin, the MICs of these two compounds against 28 quinolone-resistant pneumococci were identical. The DC-159a MICs against quinolone-resistant strains did not appear to depend on the number or the type of mutations in the quinolone resistance-determining region. DC-159a, as well as the other quinolones tested, was bactericidal after 24 h at 2x MIC against 11 of 12 strains tested. Two of the strains were additionally tested at 1 and 2 h, and DC-159a at 4x MIC showed significant killing as early as 2 h. Multistep resistance selection studies showed that even after 50 consecutive subcultures of 10 strains in the presence of sub-MICs, DC-159a produced only two mutants with maximum MICs of 1 microg/ml.
Clark
Catherine
C
Department of Pathology, Clinical Microbiology, Hershey Medical Center, PO Box 850, Hershey, PA 17033, USA.
Smith
Kathy
K
Ednie
Lois
L
Bogdanovich
Tatiana
T
Dewasse
Bonifacio
B
McGhee
Pamela
P
Appelbaum
Peter C
PC
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000890:Anti-Infective Agents / Q000494:pharmacology*; D003470:Culture Media; D024881:Drug Resistance, Bacterial / Q000235:genetics; D024841:Fluoroquinolones / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods / Q000592:standards; D009154:Mutation; D013296:Streptococcus pneumoniae / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development
D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D003470:Culture Media; D024841:Fluoroquinolones