Comparison Between Gram Stain and Acid Fast
| S.No | Characteristics | Gram Stain | Acid Fast |
| 1 | Definition | Gram stain refers to a staining technique for the preliminary identification of bacteria, in which a violet dye is applied, followed by a decolorizing agent and then a red dye. | The acid-fast stain refers to a differential stain used to identify acid-fast organisms such as members of the genus Mycobacterium. |
| 2 | Purpose | Gram stain is used to distinguish between gram-positive bacteria and gram-negative bacteria. | A cid-fast stain is used to distinguish between acid-fast bacteria and non-acid fast bacteria. |
| 3 | Type of characterization | Gram stain characterizes bacteria with different types of cell walls | Acid-fast stain characterizes bacteria with mycolic acid in the cell wall. |
| 4 | Primary Stain | Crystal violet is used as a primary stain in Gram staining. | Carbol fuchsin is used as a primary stain in Acid Fast staining. |
| 5 | Mordant | Iodine is used as mordant in Gram staining. | Phenol acts as a mordant in Acid Fast staining. |
| 6 | CounterStain | Safranin is used as a counterstain in Gram staining. | Methylene blue is used as a counterstain in Acid Fast staining. |
| 7 | Appearing | In Gram stain, Gram-positive bacteria appear in blue color while Gram-negative bacteria appear in red color. | In acid-fast stain, acid-fast bacteria appear in red color while non-acid-fast bacteria appear in blue color. |
| 8 | Microorganisms | Example of Gram-Positive Bacteria: Lactobacillus, Nocardia, Bacillus, Clostridium, Staphylococcus, Propionibacterium, Actinomyces, Streptomyces, Enterococcus, Listria,Gardnerella, Cornyebacterium, Mycoplasma, Streptococcus. Example of Gram-Negative Bacteria: Helicobcater, Escherichia, Shigella, Hemophilus, Neisseria, Pseudomonas, Klebsiella, Enterobacter, Vibrio, Chlamydia, Salmonella. | Nocardia spp (Partial Acid Fast), Rhodococcus spp (Partial Acid Fast), Legionella micdadei (Partial Acid Fast in tissue), Cyst of Cryptosporidium (Acid Fast), Cyst of Isospora (Acid Fast) |
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