Rabbits with left-sided
endocarditis due to Pseudomonas aeruginosa were treated with a high dose (7.5 mg/kg) of
gentamicin for six days, a low dose (5 mg/kg) of
gentamicin for six days or two weeks,
carbenicillin (400 mg/kg) for six days or two weeks, or a combination of the lower dose of
gentamicin and
carbenicillin (400 mg/kg) for six days or two weeks. Sterilization of cardiac vegetations was accomplished more effectively in rabbits given the higher dose of
gentamicin for six days (44% with sterilized vegetations) or combination
therapy for 14 days (64%) than in rabbits given the lower dose of
gentamicin or
carbenicillin alone for two weeks (23.5% and none, respectively). Combination
therapy for two weeks prevented relapse in all of six treated rabbits that were followed
after treatment; in contrast, all four animals treated with
carbenicillin and four of six animals treated with the lower dose of
gentamicin relapsed after two weeks of treatment. Levels of
creatinine in serum became elevated in four of nine rabbits that received
gentamicin along for two weeks. Therapeutic success was associated with a synergistic
antibiotic combination, a peak bactericidal titer in serum of greater than or equal to 1:16, and a high level of
gentamicin in serum.