Biological properties of new acyl derivatives of tylosin.

Abstract
The antibacterial activity of acyl derivatives of tylosin were examined in vitro and in vivo. The 4"-acyl group in the acylated tylosins enhanced the antibacterial activity and antimycoplasmal activity against some macrolide-resistant strains. The orally administered 3-acetyl-4" -isovaleryltylosin produced a higher blood level in mice and rabbits than tylosin and a good therapeutic effect on the infection of Staphylococcus aureus Smith in mice.