In vitro activity of U-57930E, a new clindamycin analog, against aerobic gram-positive bacteria.

The in vitro activity of U-57930E, a new clindamycin analog, against aerobic gram-positive cocci was studied by microdilution broth susceptibility tests and compared with the activities of clindamycin, vancomycin, oxacillin, and ampicillin. U-57930E inhibited methicillin-susceptible Staphylococcus aureus, Streptococcus pyogenes, Streptococcus agalactiae, and Streptococcus viridans at concentrations of less than or equal to 1 microgram/ml. This degree of activity was generally slightly less than that of the other antimicrobial agents tested. Methicillin-resistant Staphylococcus aureus, coagulase-negative staphylococci, penicillin-resistant Streptococcus pneumoniae, and enterococci were resistant to U-57930E. At the concentrations used, U-57930E exhibited bactericidal activity against most susceptible organisms, and a minimal effect of inoculum size was noted.