Eikenella corrodens (E) belongs to the HACEK group of miscellaneous gram-negative bacilli, which includes:
- Haemophilus (H)
- Aggregatibacter (A)
- Cardiobacterium (C)
- Eikenella (E), and
- Kingella kingae (K).
Cytochrome oxidase and catalase are two rapid tests that help separate the several members of this group.
- E. corrodens shows cytochrome oxidase activity but not catalase activity.
- The positive oxidase reaction separates E. corrodens from A. aphrophilus and A. actinomycetemcomitans, both negative.
- A. actinomycetemcomitans is also catalase-positive, an additional characteristic separating it from E. corrodens, which is negative.
- As Kingella kingae is also oxidase-positive and catalase-negative, other tests are needed for differentiation. K. kingae produces acid from glucose and maltose (E. corrodens is asaccharolytic).
