Final answer:
The rate at which an antibiotic diffuses through the agar medium in the Kirby-Bauer disk diffusion assay is controlled by the use of correct depth MH plates, and the answer is Diffusion.
Step-by-step explanation:
When interpreting antibiotic sensitivity of a pathogen through the agar medium in the Kirby-Bauer disk diffusion assay, the correct answer to what controls the rate is Diffusion.
Mueller-Hinton (MH) agar plates of the correct depth ensure a standardized rate of antibiotic diffusion which is critical to accurately measuring zones of inhibition and determining if bacteria are susceptible or resistant to the antibiotics being tested. Factors such as drug solubility, agar thickness, and drug concentration in the discs are all standardized to allow for the reliable interpretation of results.