Pseudomonas aeruginosa is an important pathogen responsible for respiratory tract infections, but there have been reports that some of these infections do not respond to antipseudomonal agents when used alone.
For the clinical isolates of Pseudomonas aeruginosa used in this study, the MIC of levofloxacin was 2 μg/mL, while the MIC of meropenem was 4 μg/mL. No synergistic activity was shown in vitro when these two antimicrobial agents were used concurrently. However, it has become evident that a combination of levofloxacin and meropenem may exhibit bactericidal activity even against these refractory bacteria.
Let’s look at the effect of levofloxacin and meropenem when used together against these clinical isolates of Pseudomonas aeruginosa in vitro, under conditions close to the clinical setting.
This is an experimental device which programs the blood levels of two antimicrobial agents in advance and can thus simulate treatment with a single agent or two agents given concomitantly.
In this system, we use a hollow fiber cartridge, which is in common use throughout the world.
So let’s look at changes in plasma levels after these drugs are administered.
When 500 mg of levofloxacin is given once a day, plasma levels reach their peak in one hour, and then decrease gradually.
When 1,000 mg of meropenem is given three times a day, plasma levels reach their peak in 30 minutes and then fall rapidly. This is repeated three times a day.
When these two agents are given at the same time, you can obtain both of these curves.