In vitro synergistic activities of tobramycin and selected beta-lactams against 75 gram-negative clinical isolates.
The microdilution checkerboard technique was utilized to distinguish synergistic activity between tobramycin and four beta-lactams: piperacillin-tazobactam, ticarcillin-clavulanate, ceftazidime, and ceftriaxone. Beta-lactam-aminoglycoside combinations were tested against 75 clinical isolates of Pseudomonas aeruginosa, Acinetobacter baumanii, Citrobacterfreundii, Serratia marcescens, and Enterobacter cloacae. Despite in vitro susceptibilities, all isolates demonstrated either synergism or indifference; no antagonism was observed. Against pathogenic gram-negative nosocomial isolates, a greater percentage of synergy was consistently observed with combination regimens containing tobramycin and piperacillin-tazobactam or ticarcillin-clavulanate than with the cephalosporin-containing regimens.
Owens
R C
RC
Department of Clinical Pharmacy Services, Medical Center of Delaware, Newark 19718, USA.
Banevicius
M A
MA
Nicolau
D P
DP
Nightingale
C H
CH
Quintiliani
R
R
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004357:Drug Synergism; D004359:Drug Therapy, Combination / Q000494:pharmacology*; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D014031:Tobramycin / Q000494:pharmacology*; D047090:beta-Lactams
D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D014031:Tobramycin