Ws. Champney et R. Burdine, AZITHROMYCIN AND CLARITHROMYCIN INHIBITION OF 50S RIBOSOMAL-SUBUNIT FORMATION IN STAPHYLOCOCCUS-AUREUS CELLS, Current microbiology, 36(2), 1998, pp. 119-123
The ID50 values for azithromycin and clarithromycin inhibition of tran
slation and of 50S assembly in Staphylococcus aureus cells have been m
easured. For clarithromycin, 50% inhibition of growth occurred at 0.07
5 mu g/ml, and the effects on translation and 50S formation were equiv
alent at 0.15 mu g/ml. The inhibition of these processes by azithromyc
in was less effective, with an ID50 of 2.5 mu g/ml for growth and 5 mu
g/ml for inhibition of translation and 50S formation, The additive ef
fects of each of these drugs on translation and 50S formation account
quantitatively for their observed influence on cellular growth rates,
In macrolide-treated cells, there was also a direct relationship betwe
en the loss of ribosomal RNA from the 50S subunit and its accumulation
as oligoribonucleotides. These results are compared with the previous
ly described effects of erythromycin on these same processes.