Efficacy of a novel tetracycline derivative, glycylcycline, against penicillin-resistant Streptococcus pneumoniae in a mouse model of pneumonia

The MIC90 of glycylcycline (< or =0.06 mg/L) against 55 strains of Streptococcus pneumoniae was 100-fold lower than that of minocycline or tetracycline. In a mouse model of penicillin-resistant S. pneumoniae (PRSP) pneumonia, glycylcycline (10 mg/kg) decreased bacterial counts in the lungs from 10(6) cfu to <10(2) cfu, whereas no apparent reduction of bacterial numbers was observed with minocycline or penicillin G. Pharmacokinetic studies showed that the half-life and area under the curve of glycylcycline were superior to those of minocycline and penicillin G in the lungs. These results show a preferential distribution of glycylcycline in the lungs and potent in vivo bactericidal activity in PRSP pneumonia.