Streptococcus viridans continues to be the most frequent causal agent of
infective endocarditis. Treatment has become more complicated due to the increase in resistance to
penicillin and
cephalosporins. In order to study the possible efficacy of
teicoplanin at low and high doses, this
antibiotic was investigated in rabbits as a monotherapy and in association with
gentamicin. The effects were compared with a control group and a group given classical
penicillin-
gentamicin treatment.
Infective endocarditis was induced in 120 rabbits with a clinical isolate of Streptococcus sanguis. Treatment was started 48 h after
infection, and lasted 5 days. Animals were divided into 6 groups of 20 rabbits each: G1, untreated controls; G2, penicillin+gentamicin; G3 low-dose
teicoplanin; G4, low-dose teicoplanin+gentamicin; G5, high-dose
teicoplanin; and G6, high-dose teicoplanin+gentamicin. Response to
therapy was evaluated with mortality curves, negativization of blood cultures, concentration of S. sanguis in aortic vegetations and rate of sterilization of vegetations. Vegetation weight was significantly lower in treated groups than in controls; lower weights were found in G4, the only treatment that sterilized 65% of vegetations. Death occurred only in the control group (10% mortality). Negativization of blood cultures was greatest and most rapid in G4, followed by G6. Concentrations of S. sanguis in aortic vegetations were significantly lower in all treated groups compared with controls, with the lowest being in groups G4 and G6. Combined treatment with teicoplanin+gentamicin may be highly efficacious in patients with
endocarditis caused by
penicillin-resistant Streptococcus sanguis. High-dose teicoplanin+gentamicin does not seem to be more efficacious than low-dose teicoplanin+gentamicin.