Which of the following media allows for the microscopic examination of mycobacterial colonies?

Middlebrook 7H11 agar is specifically designed to support the growth of mycobacteria, particularly Mycobacterium tuberculosis, and allows for their subsequent microscopic examination. This medium is enriched and contains various nutrients that promote the growth of these slow-growing organisms while inhibiting the growth of many other bacteria, making it ideal for isolating mycobacterial colonies.

In addition to supporting growth, the formulation of Middlebrook 7H11 agar also aids in maintaining the characteristics of mycobacterial colonies, which can be observed microscopically. The colonies formed on this medium are often distinct and can be further examined for specific morphologies that are characteristic of mycobacteria.

Other media listed, such as MacConkey agar, blood agar, and nutrient agar, are not specifically suited for the microscopic examination of mycobacterial colonies. MacConkey agar is selective for gram-negative bacteria and does not support the growth of mycobacteria. Blood agar is used for a broad range of organisms and does not specifically enhance the growth of mycobacteria, while nutrient agar is a general-purpose medium that may not provide the necessary nutrients for optimal mycobacterial growth.