Clinical specimens where organism may be encountered:
- CSF
- Blood
- Stool (rare)
- Vesicle fluid, skin swab, or biopsy
Gram stain morphology from clinical specimens:
- Large, gram-positive rods with square or concave ends in short chains
- Spores are usually NOT present
- Capsule may be viewed in smears from infected tissue, but this is NOT reliable
Gram stain morphology from culture material:
- Large, gram-positive rods with square or concave ends, often in long chains (more than 2-4 cells)
- Cells easily decolorize as the culture ages
- Does NOT form capsules in culture
- Central to sub-terminal, oval spores, with NO significant swelling of the cell
It must be noted that spore production increases with the age of the culture. Do NOT keep these cultures in the laboratory for longer than 24 hours for this reason!
3. CDC/Dr. James Feeley. Image #2105. Caption: "This photomicrograph of a Gram-stained culture sample, depicts chains of Gram-positive, rod-shaped, Bacillus anthracis bacteria." PHIL, 1980 public domain image. Accessed May 25, 2022. http://phil.cdc.gov/Details.aspx?pid=2105
