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.