Activity and diffusion of LY333328 in experimental endocarditis due to vancomycin-resistant Enterococcus faecalis

Area of Science:

• Microbiology
• Pharmacology
• Infectious Diseases

Background:

• Enterococcus faecalis is a significant cause of nosocomial infections.
• Acquired resistance to glycopeptides, such as vancomycin, is a growing clinical concern.
• Novel antimicrobial agents are needed to combat resistant enterococcal infections.

Purpose of the Study:

• To evaluate the in vitro and in vivo activity of LY333328 against glycopeptide-susceptible and resistant Enterococcus faecalis strains.
• To compare the efficacy of LY333328 with vancomycin and teicoplanin in a rabbit model of experimental endocarditis.

Main Methods:

• Minimum inhibitory concentrations (MICs) and bactericidal activity were determined in vitro.
• Protein binding and serum effects on bactericidal activity were assessed.
• Pharmacokinetic and efficacy studies were conducted in rabbits with experimental endocarditis.

Main Results:

• LY333328 exhibited potent in vitro activity against E. faecalis strains with VanA and VanB resistance phenotypes (MICs: 0.25-2 µg/ml).
• The compound was bactericidal in vitro at concentrations of 8-30 µg/ml.
• In vivo, LY333328 demonstrated significant efficacy in treating experimental endocarditis caused by all tested strains, outperforming vancomycin and teicoplanin against resistant strains.

Conclusions:

• LY333328 maintains activity against glycopeptide-resistant Enterococcus faecalis in vitro and in experimental endocarditis.
• The drug's efficacy is not significantly affected by acquired glycopeptide resistance mechanisms.
• LY333328 represents a promising therapeutic option for treating enterococcal infections, including those resistant to current glycopeptides.