Effect of gentamicin dosing interval on efficacy of penicillin or ceftriaxone treatment of experimental endocarditis due to penicillin-susceptible, ceftriaxone-tolerant viridans group streptococci.

The efficacy of ceftriaxone or penicillin alone or combined with gentamicin at different dosing intervals was evaluated in experimental endocarditis due to a penicillin-susceptible, ceftriaxone-tolerant strain of Streptococcus sanguis I. The difference between monotherapy with ceftriaxone and procaine penicillin approached statistical significance (P = 0.052). Ceftriaxone combined with gentamicin administered as a single daily dose was less effective than was procaine penicillin combined with gentamicin administered in a single daily dose or in three divided doses.