In vitro activity of midecamycin, a new macrolide antibiotic.

Midecamycin, an acetoxy-substituted macrolide antibiotic, was tested against gram-positive and gram-negative bacteria. It inhibited the majority of streptococci, staphylococci, and strains of Haemophilus and Listeria at concentrations of less than 3.1 micrograms/ml. It was less active than erythromycin, and it failed to inhibit erythromycin-resistant isolates.