Sparfloxacin and clinafloxacin alone or in combination with gentamicin for therapy of experimental ampicillin-resistant enterococcal endocarditis in rabbits.

Sparfloxacin and clinafloxacin alone and in combination with gentamicin, were evaluated for the treatment of experimental endocarditis in rabbits caused by ampicillin-resistant enterococci. Clinafloxacin was tested against Enterococcus faecalis strain WH245, a beta-lactamase producer lacking high-level gentamicin resistance (MIC 12.5 mg/L). Sparfloxacin was tested against Enterococcus faecium strain SF2149 a non-producer of beta-lactamase (ampicillin MIC 400 mg/L, gentamicin MIC 12.5 mg/L). For strain WH245, clinafloxacin alone significantly reduced enterococcal counts in vegetations (7.7 log10 cfu/g) and for strain SF2149, sparfloxacin significantly reduced counts (7.0 log10 cfu/g) compared with untreated controls (WH245, 8.8 log10 cfu/g and SF2149, 9.3 log10 cfu) or treatment with ampicillin plus gentamicin (WH245, 9.7 log10 cfu/g). The addition of gentamicin resulted in no further reduction of bacterial counts in vegetations but resulted in an increase in sterilization of blood for strain SF2149. These results suggest that sparfloxacin and clinafloxacin and may prove useful in the therapy of infections due to ampicillin-resistant enterococci.