Chemotherapy of experimental streptococcal endocarditis. VI. Prevention of enterococcal endocarditis
Durack, D.T.; Starkebaum, M.K.; Petersdorf, R.G.
Journal of Laboratory and Clinical Medicine 90(1): 171-179
1977
ISSN/ISBN: 0022-2143 PMID: 406336 Document Number: 111429
The ability of antibiotics to prevent experimental enterococcal endocarditis was studied in 602 rabbits with 11 strains of Streptococcus faecalis. Antibiotics were administered 1/2 h before i.v. injection of enterococci into rabbits prepared by prior insertion of a polyethylene catheter into the left heart; 48 h later intracardiac vegetations were excised and cultured. Enterococci were recovered from 97% of untreated animals. A single dose of ampicillin 30 mg/kg i.m. prevented endocarditis in 1/3 of the animals tested (67% infected). The combination of either streptomycin 15 mg/kg i.m. or gentamicin 1.5 mg/kg i.m. with ampicillin 30 mg/kg i.m. was substantially more effective than ampicillin alone (25% and 18% infected respectively P < 0.01). Vancomycin 30 mg/kg i.v. was the most effective regimen studied (13% infected), but at a lower dose (15 mg/kg) this drug was less effective. Vancomycin 15 mg/kg i.v. combined with steptomycin 15 mg/kg i.m. was highly effective against 3 of 4 strains, but, like ampicillin plus streptomycin, failed to prevent infection due to a strain that was resistant to streptomycin. Cefazolin 30 mg/kg i.m. alone or combined with gentamicin 1.5 mg/kg i.m. was ineffective when tested against 2 strains. Major variations in response to attempted prophylaxis were found among different strains of enterococci, some of which could not have been predicted from in vitro sensitivity tests. These studies may be useful in formulating recommendations for prevention of enterococcal endocarditis in patients.