This post was most recently updated on August 26th, 2019
Morphological characteristics of pathogenic bacteria helps us to identify them, when we stain microbiological specimens and view them under microscope.
In this blog post, i am going to share some of the distinguishing characteristics shapes of pathogenic bacteria.
- Vibrio cholerae: Comma “Curved” Shaped Gram negative rod
- Campylobacter: Curved Gram negative rods that appear either comma or S shaped
- H. Influenzae: Small, Gram negative coccobacilli
- Staphylococci: Spherical, gram positive cocci arranged in irregular, grape like clusters
Streptococci: Spherical, Gram positive cocci arranged in chains or pairs
- Streptococcus pneumoniae (pneumococci): Gram positive lancet-shaped cocci arranged in pairs (diplococci) or short chains.
- Neisseria (N. gonorrhoeae and N. meningitidis): Gram negative cocci that resemble paired kidney bean shaped
- Bacillus anthracis: Large, Gram positive rod with square ends, frequently found in chains
- Clostridium tetani: Gram positive rod with characteristics “tennis racket shaped” or “Drum stick appearance” (because of terminal spore)
- Clostridium perfringens: Large, Gram positive, “boxcar” shaped rods
- Fusobacterium spp: These pleomorphic, long Gram negative rods often with tapered “pointy” ends
- Corynebacteria: Gram positive rods that appear club shaped and are arranged in palisades or in V or L shaped formations (“Chinese-Letter” appearance)
- Listeria monocytogenes: It is a small Gram positive rods arranged in V or L shaped formations similar to corynebacteria
- Spirochetes (Treponema, Leptospira, and Borrelia): Thin walled, flexible, spiral rods (Corkscrew shaped) seen only by darkfield microscope and generally not seen in standard light microscope.
- Borrelia: They are corkscrew shaped and are larger than the Treponema, they can be viewed under a light microscope with Giemsa or Wright stains.