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Diagn Microbiol Infect Dis. 1991 Mar-Apr;14(2):141-5.

The bactericidal activity of ampicillin, daptomycin, and vancomycin against ampicillin-resistant Enterococcus faecium.

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Department of Laboratories, St. Christopher's Hospital for Children, Philadelphia, PA 19134-1095.


Ampicillin, daptomycin, and vancomycin, alone and in combination with gentamicin, were examined for bactericidal effects on ampicillin-resistant Enterococcus faecium using broth dilution minimum inhibitory concentrations (MICs) and time-kill studies. We tested 12 ampicillin-resistant isolates and demonstrated the following MICs and MBCs, respectively: ampicillin, greater than or equal to 32 micrograms/ml and greater than 256 micrograms/ml; daptomycin, less than or equal to 4 micrograms/ml and less than or equal to 16 micrograms/ml; and vancomycin, less than or equal to 4 micrograms/ml and greater than 64 micrograms/ml. Time-kill studies demonstrated that daptomycin alone had marked activity against the ampicillin-resistant E. faecium and that the addition of gentamicin resulted in synergistic killing. In addition, ampicillin and vancomycin were not bactericidal for the ampicillin-resistant isolates without the addition of gentamicin. The present study supports the consideration of daptomycin alone or in combination with an aminoglycoside as an alternative therapy for ampicillin-resistant enterococci, although additional clinical experience is now necessary.

[Indexed for MEDLINE]

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