Which statement is characteristic of Eikenella corrodens?

• A. It is a gram-negative diplobacillus.
• B. Most isolates require both hemin and NAD.
• C. It is found in the mouth and upper respiratory tract of humans.
• D. It is often found in pure culture when causing infections.

Answer: (C)

Eikenella corrodens is a small, fastidious gram-negative rod that normally resides in the human mouth and upper respiratory tract, so its presence in these sites is a defining, characteristic feature. This organism is a common member of the oral flora and is often implicated in infections that arise from the oral cavity or human bite wounds, reflecting its natural habitat. It does not require the growth factors hem in or NAD, which are needed by Haemophilus species, so that statement is not correct for Eikenella. In infections, it is rarely found in pure culture because it typically exists as part of a mixed oral flora; its fastidious nature makes isolated, monomicrobial growth less common. Additionally, culture features such as colonies that corrode the agar and a distinctive, bleach-like odor can help identify it in the lab, reinforcing its oral-associated character.