Question 43

[dnpgr16513]

What's the difference between C & D?? I was debating back and forth on these since both seem like legitimate answers. D sounds more of a "control" definition by stating that it's purpose to eliminate any confounding factors in the bacterial growth. Can anyone clarify this for me? Thanks!

[calena7178147]

The control in this case is a “vehicle” control. Commonly, this control is used when the test substance is dissolved in a liquid or gel to make sure it does not affect the results. If bacterial growth was inhibited by the vehicle alone, then you would conclude that the water had an effect and not the antibiotic. This type of control cannot account for all other extraneous factors that can affect the growth. If extraneous factors were present, they would likely affect all of the plates, including the control.