AbstractWe reported a case of abscess in whichSerratia marcescenswas isolated as the causative organism. We measured the postantibiotic effect (PAE) of dibekacin (DKB) and gentamicin (GM) againstS. marcescensand studied the relationship between the clinical effect and the PAE. The minimal inhibitory concentration (MIC) of DKB againstS. marcescenswas 6.25 μg/mL and the serum concentration 30 min after infusion of 100 mg DKB was 5.99 μg/mL. The abscess was cured by the administration of DKB every 12 h. The PAEin vivowas 2.5, 2.9 and 3.3 h when DKB was administered at 50 mg/kg, 100 mg/kg and 200 mg/kg, respectively. This PAE is one of the reasons that infection can be effectively treated with intermittent administration, even if the serum concentration is below the MI