Which statement about Eikenella corrodens is not characteristic?

• A. It is a thin, gram-negative bacillus.
• B. Colonies sometimes pit the surface of the agar medium.
• C. It is found in the mouth and upper respiratory tract of humans.
• D. It is often found in pure culture when recovered from infections.

Answer: (D)

Eikenella corrodens is a slender, gram-negative bacillus that is a normal inhabitant of the human mouth and upper respiratory tract, and it is notorious for causing infections in mixed, often polymicrobial, flora such as bite wounds and periodontal infections. It grows slowly on standard media and can produce small, gray colonies that may pit the agar, a distinctive sign of its activity. Because it tends to be part of a mixed microbial community in infections and is slow-growing, it is rarely recovered as a pure culture. That makes the statement about it being often found in pure culture not characteristic, while the other statements describe its real traits accurately.