Treatment of streptococcal infective endocarditis

Patients with infective endocarditis caused by penicillin-sensitive streptococci (minimal inhibitory concentration for penicillin of 0.1 microgram/ml or less) may be treated successfully with one of the following regimens: aqueous penicillin G administered intravenously for four weeks, intravenous aqueous penicillin G for four weeks combined with streptomycin for the first two weeks of therapy, or parenterally administered penicillin plus streptomycin for two weeks. A cure rate of at least 98 percent may be anticipated with each of these regimens. During a 12-year period among 142 patients treated for two weeks with penicillin and streptomycin, one (0.7 percent) had relapse and four (3 percent) had vestibular toxicity. The major advantage of the two-week regimen is that it is more cost-effective than the four-week regimens. The major disadvantage of the use of streptomycin is the relatively low risk of vestibular toxicity. Patients with enterococcal endocarditis were treated initially for four weeks with aqueous penicillin G together with either streptomycin (streptomycin-susceptible enterococci, 36 patients) or gentamicin (streptomycin-resistant enterococci, 20 patients). Compared with patients who had symptoms for less than three months, patients with symptoms for longer than three months had a higher relapse rate (0 percent versus 44 percent; p less than 0.001) and mortality (2.5 percent versus 25 percent; p less than 0.001). Patients with mitral valve endocarditis had a significantly higher relapse rate (25 percent) than patients with aortic valve infection (0 percent; p less than 0.01]. Gentamicin-associated nephrotoxicity was more frequent (p less than 0.001) among patients treated with more than 3 mg/kg per day of gentamicin than among those treated with 3 mg/kg per day or less (100 percent versus 20 percent). Relapse and mortality rates did not differ significantly between patients treated with low-dose or high-dose gentamicin regimens. Patients who have had symptoms of enterococcal endocarditis for longer than three months or perhaps patients with mitral valve infection should receive at least six weeks of penicillin therapy together with an aminoglycoside; patients without either high-risk factor may be treated successfully for four weeks.