Synergistic effect of ampicillin or vancomycin in combination with decreasing concentrations of streptomycin against enterococci.
The extent of synergistic killing and duration of the post-antibiotic effect (PAE) was evaluated in streptomycin-susceptible strains of Streptococcus faecalis and Streptococcus faecium with 20 mcg/ml of ampicillin or 10 mcg/ml of vancomycin in combination with decreasing concentrations of streptomycin (20, 10, 5, 2, 1, 0.5 mcg/ml). The bactericidal activity or duration in recovery period declined progressively in a linear pattern with decreasing concentrations of streptomycin. One log10 or greater reduction in viable counts was seen with streptomycin concentrations of 2 mcg/ml or higher with both ampicillin and vancomycin. A synergistic increase in recovery period (PAE greater than or equal to 0.5 h) of ampicillin or vancomycin was observed with concentrations of streptomycin in excess of 2 mcg/ml and 1 mcg/ml, respectively. These results suggest that lower dosage of streptomycin in the therapy of enterococcal infections will probably result in a higher relapse rate.
D000667:Ampicillin / Q000494:pharmacology*; D004357:Drug Synergism; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000254:growth & development; D013291:Streptococcus / Q000187:drug effects* / Q000254:growth & development; D013307:Streptomycin / Q000494:pharmacology*; D014640:Vancomycin / Q000494:pharmacology*
D014640:Vancomycin; D000667:Ampicillin; D013307:Streptomycin