4-h Identification of Pseudomonas aeruginosa with 9-chloro-9-(4-diethylaminophenyl)-10-phenylacridan

A total of 361 gram-negative bacilli were evaluated for their ability to grow in the presence of 9-chloro-9-(4-diethylaminophenyl)-10-phenylacridan. The minimum time required for the production of visual turbidity in brain heart infusion broth was determined to be 4 h in shake cultures at 35°C. The minimal inhibitory concentration (MIC) of 9-chloro-9-(4-diethylaminophenyl)-10-phenylacridan in brain heart infusion broth was determined for 174 isolates. The MICs for all 40 Pseudomonas aeruginosa isolates tested were >50 μg/ml. The MICs for the other 53 pseudomonads tested were ≤5 μg/ml. Among 81 other gram-negative bacilli tested, the MICs for 4 were 15 μg/ml, the MICs for 15 were 10 μg/ml, the MICs for 21 were 5 μg/ml, and the MICs for 41 were ≤1 μg/ml. Based on these data, 361 gram-negative bacilli were inoculated into brain heart infusion broth containing 15 μg of 9-chloro-9-(4-diethylaminophenyl)-10-phenylacridan per ml and incubated on a shaker for 4 h. The only bacteria that produced visual turbidity were identified as P. aeruginosa (170 of 170 isolates).