New drugs for Gram-positive uropathogens.

Complicated urinary tract infections (UTIs) are frequent nosocomial infections. The bacterial spectrum encompasses Gram-negative but also Gram-positive pathogens in up to 30-40%. The existing treatment for Gram-positive pathogens is not always optimal. Antimicrobials for the treatment of Gram-positive uropathogens comprise older agents, such as aminopenicillins with or without beta-lactamase inhibitors and vancomycin, as well as newer fluoroquinolones, such as levofloxacin or gatifloxacin. However, resistant bacteria such as vancomycin-resistant enterococci (VRE) or methicillin-resistant Staphylococcus aureus (MRSA) (except vancomycin-resistant) are generally also not susceptible to the fluoroquinolones. Therefore new agents need to be assessed in the treatment of UTI. Daptomycin and linezolid are new antimicrobial agents with good efficacy against Gram-positive uropathogens as shown by their minimal inhibitory concentrations. In a phase II study the urinary bactericidal activity of linezolid versus ciprofloxacin in volunteers showed comparable activity of both drugs against fluoroquinolone susceptible Gram-positive uropathogens, whereas linezolid was also as active against fluoroquinolone resistant ones. The pharmacokinetics and the mode of action of these two antibiotics are discussed together with some clinical data in the context of therapeutic use in patients with complicated UTIs.