Morphology

MORPHOLOGY
  • They are Gram-positive slender rods with a tendency to clubbing at one or both ends; they are non-sporing, non-motile, non-capsulated and non-acid fast.
  • They have granules composed of (high energy phosphate stores) – polymetaphosphate.
  • The granules are more strongly Gram positive than the rest of the bacterial cell.
  • Stained with Loeffler’s methylene blue, the granules take up a reddish purple color and hence they are called metachromatic granules. They are called as volutin or Babes Ernst Granules.
  • They are often situated at the poles of the bacilli and are called polar bodies.
  • Special stains, such as Albert’s, Neisser’s and Ponder’s have been devised for demonstrating the granules clearly.
  • Stained smears from animal tissues often reveal groups of cells in parallel (Palisades) or cells at sharp angles to each other (Chinese letter or Cuneiform arrangement).
  • This is due to the incomplete separation of the daughter cells after binary fission.
  • Rhodococcus equi can appear as a Gram-positive coccus or a rod or club shaped form arranged in clusters. It is capsulated and sometimes weakly acid fast.
Last modified: Monday, 4 June 2012, 5:10 AM