Biochemical characters, resistance and antigens and toxins

BIOCHEMICAL CHARACTERS, RESISTANCE AND ANTIGENS AND TOXINS

Biochemical characters

  • They are catalase positive, oxidase negative. Except Corynebacterium bovis others are urease positive.
  • The renale group is very strong urease positive (less than one hour).
  • All diptheroids ferments sugar except Rhodococcus equi. Corynebacterium bovis and Corynebacterium renale ferments both glucose and maltose.
  • Two biotypes of Corynebacterium ovis are recognized.
  • The ovine/caprine strains lack nitrate-reducing capacity, while the equine/bovine strains usually reduce nitrate.

Resistance

  • Diptheroids are readily destroyed by heat, 60ºC for one hour.
  • They are highly susceptible to disinfectants.
  • It is more resistant to the action of light, dessication and freezing.
  • Rhodococcus equi is resistant to 2.5% oxalic acid for one hour.

Antigens and toxins

  • The diphtheroid antigen and toxins are not well documented.
  • Corynebacterium ovis produces a filterable toxin similar to that produced by Corynebacterium diphtheriae.
  • It is a haemolytic toxin, which has phospholipase activity to the cell wall lipids.
  • In Corynebacterium renale, the pili is antigenic, Renalin- a Corynebacterium renale extracellular protein may play a role in lysis of cell membranes.
  • Rhodococcus equi produces diffusible Rhodococcus equi factors (Phospholipase C and Cholesterol oxidase) and these as well as the capsule and cell wall constituents probably play a major role.
Last modified: Monday, 4 June 2012, 5:11 AM