In-vitro activity of RU 28965, a new macrolide, compared to that of erythromycin.

The activity of a novel macrolide, RU 28965, was compared to that of erythromycin against Gram-positive organisms isolated mainly from cancer patients. RU 28965 was active against streptococci including Streptococcus pneumoniae and streptococcal groups A, B and G. It was also active against methicillin-susceptible staphylococci, Bacillus cereus and Listeria monocytogenes. Its activity against these organisms was generally equal to that of erythromycin. RU 28965 was moderately active against enterococci and inactive against JK diphtheroids and three different species of coagulase-negative staphylococci. Organisms resistant to erythromycin were also resistant to RU 28965.