In vitro Etest synergy of doripenem with amikacin, colistin, and levofloxacin against Pseudomonas aeruginosa with defined carbapenem resistance mechanisms as determined by the Etest method.

The applicability of Etest for synergy testing was evaluated in 100 carbapenem-nonsusceptible Pseudomonas aeruginosa isolates. Combinations of doripenem with amikacin, colistin, or levofloxacin were synergistic or additive against 67%, 31%, and 23% of isolates, respectively. The use of Etest was practical to evaluate the synergy of doripenem with other antipseudomonal agents.