Lysostaphin treatment of experimental aortic valve endocarditis caused by a Staphylococcus aureus isolate with reduced susceptibility to vancomycin

The rabbit model of endocarditis was used to test the effectiveness of vanc omycin and two different lysostaphin dosing regimens for the treatment of i nfections caused by a Staphylococcus aureus strain with reduced susceptibil ity to vancomycin (glycopeptide intermediate susceptible S. aureus [GISA]). Vancomycin was ineffective, with no evidence of sterilization of aortic va lve vegetations. However, rates of sterilization of aortic valve vegetation s were significantly better for animals treated with either a single dose o f lysostaphin (43%) or lysostaphin given twice daily for 3 days (83%) than for animals treated with vancomycin. Rabbits given a single dose of lysosta phin followed by a 3-day drug-free period had mean reductions in aortic val ve vegetation bacterial counts of 7.27 and 6.63 log(10) CFU/g compared,vith those for untreated control rabbits and the vancomycin-treated group, resp ectively. We conclude that lysostaphin is an effective alternative for the treatment of experimental aortic valve endocarditis caused by a clinical VI SA strain.