The image demonstrates a Gram stain prepared from an 18-hour-old broth culture. The organism is a small, non-spore-forming bacillus measuring between 0.4 to 0.5 μm by 1.0 to 3.5 μm. Coccobacillary forms, diplobacilli, and bacilli in short chains or in diphtheroidal clusters (upper right in the image) may all be observed in Gram stain preparations. When found in the CSF, the organism may be found both intracellularly and extracellularly.
