[Studies on uptake of macrolide antibiotics by Chlamydia host cell]

Minimum inhibitory concentration (MIC) of Macrolide antibiotic (ML) against C. trachomatis was found to greatly vary with the cell culture system used for the assay. We then investigated the ability of various cell cultures to uptake MLs in the relation to MIC determination. Penetration of the 14C-labeled MLs, Erythromycin, Jasamycin and Rokitamycin into cells was quantitatively studied by measuring the radioactivity incorporated into McCoy, HeLa229W and HeLa229F cells. It was found that HeLa229W cell showed the lowest MIC for the drugs, followed by HeLa229F cell and then by McCoy cell. Reversely, McCoy cell showed the lowest intracellular concentration of an ML, followed by HeLa229F cell and then by HeLa229W cell. These results indicate that MIC of an ML significantly varies depending on the ability of the test cell to uptake the drug.