Comparative in vitro activity of ABT-773 and two macrolides against staphylococci

The anti-staphylococcal activity of ABT-773, a new member of the ketolides, was examined and compared with those of erythromycin and clarithromycin using the agar dilution method. A total of 336 well-defined clinical isolates of staphylococci, including a large number of clonally different methicillin-resistant strains with defined macrolide-lincosamide-streptogramin B (MLSB) resistance phenotypes were tested. The novel ketolide exhibited broad-spectrum anti-staphylococcal activity against both methicillin-susceptible and methicillin-resistant strains. Apart from strains with constitutive expression of MLSB resistance, all staphylococcal strains tested were inhibited by less than or equal to0.063 mg/L of ABT-773, irrespective of the resistance phenotype for methicillin.