Laboratory evaluation of topically used antibiotics: framycetin MIC and extinction time data for Pseudomonas aeruginosa.

Minimum inhibitory concentration (MIC) and extinction time (ET) of framycetin (0.5% in isotonic buffer) were determined. Of 90 consecutive clinical isolates of Pseudomonas aeruginosa, obtained from patients with ear or eye infections, 88.9% were inhibited by 62.5 mg/l and 96.66% were killed within 60 min by framycetin (0.5%). Determination of ET appears to be a promising technique for quantifying the bacterial action of high drug concentrations. Further clinical and experimental studies are required to see whether the ET predicts the efficacy of topical antibacterial preparations better than the MIC.