Cellulitis of the arm: Laboratory Identification

Eikenella - catalase & oxidase

  • Eikenella corrodens (E) belongs to the HACEK group of miscellaneous gram-negative bacilli which includes Haemophilus aphrophilus (H), Actinobacillus actinomycetemcometans (A), Cardiobacterium hominis (C) and Kingella kingae (K).
  • Cytochrome oxidase and catalase are two rapid tests that help separate the several members of this group.
  • Eikenella corrodens shows cytochrome oxidase activity, but not catalase activity.
  • The positive oxidase reaction separates E. corrodens from Haemophilus aphrophilus and Actinobacillus actinomycetemcomitans, which are 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).

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