In Vitro Activities of the New Ketolide Antibiotics HMR 3004 and HMR 3647 against Streptococcus pneumoniae in Germany

The comparative in vitro activity of HMR 3004 and HMR 3647, new ketolide antibiotics, was tested by a standard agar dilution technique against 221 pneumococcal strains, including isolates with intermediate levels of resistance to penicillin and erythromycin-resistant isolates. The ketolides were more active than other macrolides and showed excellent activity against erythromycin-resistant strains. All the strains were inhibited by ≤2 μg of HMR 3004/ml or by ≤0.5 μg of HMR 3647/ml.