After inoculating the Mueller-Hinton plates for the Kirby-Bauer susceptibility test, how long should the plates dry before adding the disk?

In the Kirby-Bauer susceptibility test, proper preparation of the Mueller-Hinton plates is crucial for obtaining reliable and reproducible results. After inoculating the plates, it is important to allow them to dry for an adequate amount of time before placing the antimicrobial disks on their surface.

Allowing the plates to dry for 3 to 15 minutes creates a balance where the moisture does not interfere with the diffusion of the antibiotics from the disks. If the plates are too wet, the antibiotics may not spread evenly, which can lead to inaccuracies in measuring the zones of inhibition. Conversely, if the plates are dried for too long, it might negatively affect the viability of the bacteria.

Thus, the correct answer encompasses both the 3 to 5 minutes and the 15-minute drying time, providing flexibility while ensuring the integrity of the test results. This method aligns with recommended practices in microbiological testing for determining antimicrobial susceptibility.