Let’s have a look at the organisms when no drugs are added.
These cells were filmed using a time lapse where 4 seconds corresponds to one hour.
The bacteria grow to fill the entire screen in about 6 hours.
Treatment with levofloxacin was started once the organisms had grown to a certain level.
Let’s first have a look at when levofloxacin is added as a single agent.
When levofloxacin is added, the organisms stop growing and undergo bacteriolysis.
Let’s see how they look under a higher magnification. Pseudomonas aeruginosa cannot undergo cell division when levofloxacin, a fluoroquinolone that inhibits bacterial DNA synthesis, is present, and the content of the elongating bacterial cells aggregate, followed by bacteriolysis.
If you zoom out again, you can see that although most organisms appear to be killed, there are still living organisms.
Twenty-four hours later, under a different view, the bacteria have gained strength and are now growing vigorously.
When meropenem is added as a single agent,
Pseudomonas aeruginosa soon start being killed after the first treatment.
When you look at them at a higher magnification, the bacterial cells swell up like tiny balloons and then burst and die in the presence of meropenem, a carbapenem that inhibits bacterial cell wall synthesis.
When you zoom out again, you see some cells starting to grow again.
Surviving cells keep growing, but the second treatment 8 hours later soon stops the growth and induces bacteriolysis.
Thirteen hours later, when you zoom out again, you can see the cells starting to grow once more. With the third treatment given 16 hours later, cell growth can be suppressed temporarily, but the cells cannot be killed completely.
In time, the cells start growing across the entire field of view.
This time, we add levofloxacin and meropenem at the same time.
You can see Pseudomonas aeruginosa are killed very quickly, much more so than when either of the drugs is used alone.
Let’s look at them using a higher magnification from the start of treatment.
When we zoom out and continue observing the bacterial cells, they do not grow again.
Twenty-four hours later, when we look at the surrounding area, we find the cells are completely eradicated with no surviving bacteria.