This figure shows the changes in viable bacterial count over time with this simulation system. The viable bacterial count of Pseudomonas aeruginosa was 10^6 CFU/mL at the starting point. Where no drug is present, the organisms increase to 10^10 CFU/mL after 24 hours. When levofloxacin is added as a single agent, the bacterial count first falls below the detection limit, but 24 hours later it increases to a higher count than the starting point. When meropenem is added as a single agent, the bacterial count continues to fall and rise again and exceeds the count at the starting point.
However, when these two agents are added at the same time, the viable bacterial count falls below the detection limit in 2 hours and doesn’t increase again after that.
This shows the initial bactericidal activity in each case under the same magnification.
From these results, it can be seen that a combination of levofloxacin and meropenem can be expected to exhibit high antibacterial activity where a single agent is not effective.