Grepafloxacin: microbiological properties.

Grepafloxacin is a new broad-spectrum fluoroquinolone characterized by having a methyl-substituted piperazine at the 7 position. It is a water-soluble racemate with both stereoisomers having the same activity. Its mode of action involves inhibition of topoisomerases II and IV. Grepafloxacin is not recognized by the NorA efflux mechanism in Staphylococcus aureus and, thus, some strains of Staphylococcus aureus that are resistant to other fluoroquinolones remain susceptible to grepafloxacin. Grepafloxacin has potent in vitro activity against streptococci and staphylococci, respiratory Gram-negative pathogens, atypical respiratory pathogens and sexually transmitted disease pathogens. It combines the positive properties of the beta-lactams against conventional Gram-positive and Gram-negative respiratory pathogens with the activity of the macrolides against the atypical pathogens. Unlike macrolides, it is bactericidal at concentrations close to the MIC. Its in vitro activity has been reflected in animal models of respiratory tract infections. Concentrations above MICs are maintained throughout nearly all of the 24-h dosing interval. Grepafloxacin provides important improvements over older quinolones and over other classes of antibiotics.