Overview
![image 28](https://usmlestrike.b-cdn.net/wp-content/uploads/2022/08/image-28.png)
- Gram stain
- Gram-positive bacteria have a thick peptidoglycan layer in their cell walls that holds the crystal violet stain
- Gram-negative bacteria cannot hold the crystal violet stain and are counterstained by safranin
- Giemsa stain
- Borrelia
- Plasmodium
- trypanosomes
- Chlamydia
- Periodic acid-Schiff stain (PAS)
- glycogen
- mucopolysaccharides
- used to diagnose Whipple’s disease (Tropheryma whippelii)
- Carbolfuscin
- acid-fast stain
- Ziehl-Neelsen
- acid-fast organisms
- Mycobacterium
- Nocardia (partially acid fast)
- Cryptosporidum oocysts
- acid-fast organisms
- India ink
- Silver stain
- fungi
- e.g. Pneumocystis, Legionella
Bugs that Gram stain poorly
- Treponema
- to thin to be visualized
- use darkfield microscopy or fluorescent antibodies
- Rickettsia
- Mycobacteria
- high-lipid-content cell wall
- Legionella pneumophila
- intracellular parasite
- use silver stain
- Mycoplasma
- Ureaplasma
- no cell wall
- Chlamydia
- intracellular parasite
- has a cell wall but the cell wall does not contain peptidoglycan