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C-L-E-A-R bacteria: small gram-positive rods

These organisms are the C-L-E-A-R bacteria: Corynebacterium, Listeria, Erysipelothrix, Arcanobacterium and Rhodococcus. They are small Gram-positive rods similar to those seen in this slide. The specific pathogenic species of veterinary significance in the CLEAR group are:

- Coyrnbacterium pseudotuberculosis
- Listeria monocytogenes
- Erysipelothrix rhusiopathiae
- Arcanobacterium pyogenes
- Rhodococcus equi.


When Gram staining these agents, be careful. Students often over-decolorize them making them appear Gram-negative. Also, the rods can be very short, plump or pleomorphic, making their shape hard to determine.