COMPARISON OF 2 TECHNIQUES FOR MEASUREMENT OF IN-VITRO KILLING KINETICS OF 5 ANTIBIOTICS AGAINST PSEUDOMONAS-AERUGINOSA

The in vitro activity of ticarcillin, imipenem, gentamicin, amikacin and ciprofloxacin against six Pseudomonas aeruginosa isolates was evaluated by two time-killing curve methods: the conventional broth technique, and another method previously described which employs a transfer filter membrane. The patterns of the killing curves obtained over a 5 h period with the two techniques were similar. In contrast to the results obtained for beta-lactam agents, the reduction of inoculum was great and increased with the concentration for aminoglycosides and ciprofloxacin. After 5 h, regrowth of the six strains tested was observed in broth with all antibiotics, whereas a bactericidal effect was observed over 24 h with the filter membrane method. Further studies are warranted to determine the reasons for this difference.