In vitro activity of four fluoroquinolones against clinical isolates of Pseudomonas aeruginosa determined by the E test

Ciprofloxacin, levofloxacin, ofloxacin, and trovafloxacin were tested by th e E-test against 100 clinical isolates of Pseudomonas aeruginosa. Ciproflox acin was the most active of the tested agents with 82% of isolates having a MIC less than or equal to 1 mg/l (range: 0.094- > 8). Levofloxacin and tro vafloxacin had nearly identical potency: 75% and 76% of the isolates were i nhibited by less than or equal to 2 mg/l of these agents, respectively (ran ge: 0.125- > 8 for levofloxacin; 0.19- > 8 for trovafloxacin). Ofloxacin wa s the least active of the four quinolones, with 43% of the isolates having a MIC > 2 mg/l. All isolates resistant to ciprofloxacin were also resistant to the other agents, i.e. resistance to ciprofloxacin predicted resistance to all the quinolones tested in every case. This data demonstrates that fl uoroquinolones are active agents against P. aeruginosa. In vitro susceptibi lity testing, however, is crucial to assess the resistance pattern in any s pecific location and for each individual agent. (C) 2000 Elsevier Science B .V. and International Society of Chemotherapy. All rights reserved.