Pyelonephritis. XVII. Comparison of Combinations of Vancomycin, Ampicillin, Streptomycin, and Gentamicin in the Treatment of Enterococcal Infection in Rats
Vancomycin has been proposed as the drug of choice in the treatment of serious enterococcal infection when penicillin cannot be used. We have studied rats with enterococcal pyelonephritis to evaluate in vivo the effectiveness of vancomycin alone or with streptomycin or gentamicin, compared to ampicillin plus streptomycin or gentamicin. Rats were infected iv with Streptococcus faecalis. Kidneys of 10 rats from each therapeutic group were cultured after one, two, four, and six weeks of therapy and one week after treatment stopped. Comparing the log of cfu of S. faecalis recovered per g of kidney tissue, all treated groups had significantly lower numbers than controls (P < 0.001). Vancomycin plus gentamicin was most active, significantly more so than vancomycin alone or vancomycin plus streptomycin. After one week ampicillin plus streptomycin was equally effective, while ampicillin plus gentamicin was noticeably less so. The combination of vancomycin with gentamicin, though potentially toxic, may be the most effective alternative therapy for serious enterococcal infection when penicillins cannot be used.