Comparative in vitro activity of vancomycin and levofloxacin in combination with rifampin against planktonic versus sessile cells of Staphylococcus epidermidis.
OBJECTIVE
To evaluate the activity of vancomycin and levofloxacin alone and combined with rifampin against planktonic and sessile cells.


METHODS
Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of the three drugs were determined against a clinical isolate of methicillin-resistant Staphylococcus epidermidis (MRSE 23) and a reference strain of MRSE (ATCC 35984).


RESULTS
The MICs/MBCs of vancomycin, levofloxacin, and rifampin against MRSE 23 were 0.78/0.78 microg/ml, 0.19/0.19 microg/ml or below, and 0.19/0.19 microg/ml or below, and against ATCC 35984 were 0.78/1.56 microg/ml, 0.19/0.19 microg/ml or below, and 0.19/0.19 microg/ml or below, respectively. A 99.9% killing activity was achieved with vancomycin, levofloxacin, and vancomycin-levofloxacin against planktonic cells of MRSE 23 (18.9, 21.3, and 17.5 hrs, respectively) and only with levofloxacin against ATCC 35984 (21.5 hrs). No regimen achieved 99.9% killing activity against sessile cells.


CONCLUSIONS
Adding rifampin was antagonistic against planktonic cells and had an additive effect against sessile cells. Activity typically reported using nutrient-rich, planktonic cells may not be applicable to sessile cells under environmental and growth restrictions.
Kang-Birken
S L
SL
University of the Pacific School of Pharmacy and Health Sciences, Stockton, California, USA.
D004359:Drug Therapy, Combination / Q000494:pharmacology*; D064704:Levofloxacin; D008826:Microbial Sensitivity Tests; D015242:Ofloxacin / Q000494:pharmacology*; D012293:Rifampin / Q000494:pharmacology*; D013212:Staphylococcus epidermidis / Q000187:drug effects*; D014640:Vancomycin / Q000494:pharmacology*
D064704:Levofloxacin; D014640:Vancomycin; D015242:Ofloxacin; D012293:Rifampin