Performance of a commercial microdilution minimal inhibitory concentration procedure for aminoglycoside susceptibility testing of Pseudomonas aeruginosa.

The accuracy of quantitative aminoglycoside minimal inhibitory concentration (MIC) determinations was evaluated with the Micro-Media Systems microdilution MIC panel and Pseudomonas aeruginosa. Without Mg++ and Ca++ supplementation, very major interpretive discrepancies occurred. A simple, in-expensive cation supplementation procedure was evaluated to correct the discrepancies. The necessity of cation supplementation for susceptibility testing of P. aeruginosa when employing MIC procedures is stressed.