Gram negative rods
occuring singly or in long wavy chains or filaments (up to 150 µm).

Some may be highly pleomorphic.

Singly rods may show central swelling.

Chains or filaments may have a series of swellings (1-3 µm wide) resulting in a "string of beads" appearance.

0.1-0.7 x 1.0-5.0 µm with rounded or pointed ends.

L-forms
are coccobacillary or bipolar-staining coccoid forms, usually a special stain is required because of their lack of cell wall

(Giemsa, acridine orange)

Facultative anaerobic (capnophilic)

They require serum, ascitic fluid and blood for growth and incubated with 5-10% CO2

BA: they grow slowly (2-3 days) and that may take as long as 7 days.

The colonies are small, circular, convex, grayish, smooth, and glistening.

L-forms: may develop in the same culture (after 5 days) are considered not pathogenic

These colonies are embedded in the agar and may also have a “fried egg” appearance, with a dark center and a flattened lacy edge.

They have undergone spontaneous transformation to the L-form.

McC: no growth

Thioglycollate broth + 10-30% ascitic fluid:
Growing colonies as "bread crumbs" on the bottom of the tube.

Blood Culture Media with SPS inhibits the growth

James Versalovic et al.(2011) Manual of Clinical Microbiology 10th Edition