Antibacterial activities of erythromycins A, B, C, and 0 and some ,of their derivatives

Abstract

The MICs of erythromycins A, B, C, and J) and some of their derivatives were determined against 21 gram-positive and 15 gram-negative microorganisms, Antibacterial activity was confined to gram-poSiti,'e and very few gram-negative bacter-ia. Erythromycin U was somewhat less active than er-ythromycin A, and erythromycin C and D showed about half thaI activity or even less. Most other dcrivuti ves had negligible activity. Determination of potency by diffusion and lurhidimclJ'ic assays were in line with MICs. The cxurninatiou of the results of these assays, howevcr , revealed that there are differences between the data of different laboranu-ics , depending on the microorganisms and conditions used