Babes-Ernst granules are characteristic of which organism?

Babes-Ernst granules are specific to Corynebacterium diphtheriae, the causative agent of diphtheria. These granules appear as metachromatic granules when stained with certain dyes, such as methylene blue, and are a key feature in identifying this bacterium microscopically. The presence of these granules is associated with the bacterium’s ability to store phosphate in the form of polyphosphate granules, which is vital for its metabolism and virulence.

In the context of the other organisms listed, they do not produce Babes-Ernst granules. Bacillus anthracis, while it has unique characteristics, is recognized for its protein capsule and endospores rather than granular inclusions. Listeria monocytogenes is typically known for its motility and certain pathogenic features but lacks Babes-Ernst granules. Mycobacterium tuberculosis is identified for its acid-fastness and the presence of mycolic acids in its cell wall but does not exhibit these granules. Thus, the correct association of Babes-Ernst granules with Corynebacterium diphtheriae provides a clear indication of this bacterium’s distinguishing microscopic feature.