Characteristics Shape of Pathogenic Bacteria

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.

1. Vibrio cholerae: Comma “Curved” Shaped Gram negative rod
2. Campylobacter:  Curved Gram negative rods that appear either comma or S shaped
3. H. Influenzae: Small, Gram negative coccobacilli
4. Staphylococci: Spherical, gram positive cocci arranged in irregular, grape like clusters

5. 

   Streptococci: Spherical, Gram positive cocci arranged in chains or pairs

6. Streptococcus pneumoniae (pneumococci): Gram positive lancet-shaped cocci arranged in pairs (diplococci) or short chains.
7. Neisseria (N. gonorrhoeae and N. meningitidis): Gram negative cocci that resemble paired kidney bean shaped
8. Bacillus anthracis: Large, Gram positive rod with square ends, frequently found in chains
9. Clostridium tetani: Gram positive rod with characteristics “tennis racket shaped” or “Drum stick appearance” (because of terminal spore)
10. Clostridium perfringens: Large, Gram positive, “boxcar” shaped rods
11. Fusobacterium spp: These pleomorphic, long Gram negative rods often with tapered “pointy” ends

    

12. Corynebacteria: Gram positive rods that appear club shaped and are arranged in palisades or in V or L shaped formations (“Chinese-Letter” appearance) 
13. Listeria monocytogenes: It is a small Gram positive rods arranged in V or L shaped formations similar to corynebacteria
14. 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.
15. Borrelia: They are corkscrew shaped and are larger than the Treponema, they can be viewed under a light microscope with Giemsa or Wright stains.