In vitro activity of six macrolides, clindamycin and tetracycline on Streptococcus pneumoniae with different penicillin susceptibilities.
A collection of 99 clinical isolates of Streptococcus pneumoniae, chosen due to their different susceptibilities to penicillin, were investigated with respect to their susceptibility to the macrolides azithromycin, clarithromycin, dirithromycin, erythromycin, roxithromycin, spiramycin, and to clindamycin and tetracycline by the agar dilution method. We found complete cross resistance among the macrolides. The pneumococci were either susceptible, MIC < or = 0.5 micrograms/ml, or resistant, MIC > or = 16 micrograms/ml, to the tested macrolides, giving a bimodal distribution. In addition, complete cross resistance was observed between clindamycin and macrolides. Pneumococci resistant to macrolides were also resistant to tetracycline, and 26% of the macrolide-susceptible strains were tetracycline resistant.
Poulsen
R L
RL
Department of Research and Development in Microbiology, Statens Seruminstitut, Copenhagen, Denmark.
Knudsen
J D
JD
Petersen
M B
MB
Fuursted
K
K
Espersen
F
F
Frimodt-Møller
N
N
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002981:Clindamycin / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D018432:Drug Resistance, Multiple; D018942:Macrolides; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance; D013296:Streptococcus pneumoniae / Q000187:drug effects*; D013752:Tetracycline / Q000494:pharmacology*; D013753:Tetracycline Resistance
D000900:Anti-Bacterial Agents; D018942:Macrolides; D002981:Clindamycin; D013752:Tetracycline