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Time-kill profiles of Enterococcus to antibiotics used for intravitreal therapy
R P Kowalski1, L M Karenchak, B B Warren
1University of Pittsburgh, PA, USA.
Background And Objective:
To determine and then compare the time-kill profiles of Enterococcus to antibiotics used for intravitreal therapy.
Patients And Methods:
The time-kill profiles of four endophthalmitis isolates of Enterococcus faecalis, one vancomycin-resistant E. faecalis isolate, and three vancomycin-resistant isolates of E. faecium were determined against vancomycin, amikacin, cefazolin, gentamicin, ampicillin, ciprofloxacin, ceftazidime, clindamycin, and the combinations of vancomycin and amikacin, vancomycin and ceftazidime, vancomycin and gentamicin, vancomycin and ampicillin, cefazolin and gentamicin, and ampicillin and gentamicin.
Results:
No single antibiotic or combination was bactericidal (defined as 99.9% kill) to all isolates of Enterococcus. Gentamicin was bactericidal to all E. faecalis isolates. None of the tested antibiotics were bactericidal to vancomycin-resistant E. faecium.
Conclusions:
The time-kill profiles demonstrated that vancomycin and ceftazidime did not produce a 99.9% kill for E. faecalis in this small study. Gentamicin combined with either cefazolin or ampicillin had somewhat better bactericidal activity and should be considered as an alternative therapy. Novel therapy may be necessary to treat endophthalmitis because of vancomycin-resistant Enterococcus, depending on the susceptibility patterns of the individual isolate and the response to initial therapy.