What is phenol & what is its usual application?
Phenol in low concentrations is used as a disinfectant in household cleaners and mouthwash. Phenol used as a slimicide (a chemical toxic to bacteria and fungi characteristic of aqueous slimes) is a type of disinfectant. The largest single use of phenol is as an intermediate in the production of phenolic resins.
What is the purpose of the acid-fast stain?
The acid-fast stain is a laboratory test that determines if a sample of tissue, blood, or other body substance is infected with the bacteria that causes tuberculosis (TB) and other illnesses.
What diseases are diagnosed using acid-fast procedure?
An acid-fast bacteria (AFB) culture is done to find out if you have tuberculosis (TB) or another mycobacterial infection. Besides TB, the other main mycobacterial infections are leprosy and a TB-like disease that affects people with HIV/AIDS.
Which of the following is a decolorizing agent for acid fast staining?
Ziehl Neelsen Acid-fast stain
|ACID-FAST STAIN||Cell Color|
What is the role of phenol carbolic acid in acid fast staining?
Strong carbol fuchsin solution is basic fuchsin dissolved in phenol (carbolic acid). Heating the slide helps to soften the waxy material on the bacterial cell wall. … Hence strong carbol fuchsin is able to stain the cell. Upon staining, they tend to resist decolourization by 20% H2SO4 (sulphuric acid).
What is the role of phenol in acid fast staining?
In acid fast stains, the phenol allows the stain to pen- etrate, even after exposure to decolourisors. If an organism is to be termed Acid Fast, it must resist decolourisation by acid-alcohol. A counterstain is then used to emphasise the stained organism.
What is the purpose of the reagents used in Gram stain?
The first reagent is called the primary stain. Its function is to impart its color to all cells. The second stain is a mordant used to in- tensify the color of the primary stain. In order to es- tablish a color contrast, the third reagent used is the decolorizing agent.
Why is acid alcohol used as a decolorizing agent?
Acid alcohol is used as a decolorizing agent because of its interaction with the bacterial cell wall.
What is the purpose of steaming the stain while applying malachite green?
The presence of endospores in a bacterial culture can be detected by staining with malachite green. Because the endospore coat is so tough, steam is used to enable dye penetration. After washing, only the endospores will retain the primary stain Malachite green.
What are the 4 reagents used in Gram stain?
- Crystal violet (primary stain)
- Iodine solution/Gram’s Iodine (mordant that fixes crystal violet to cell wall)
- Decolorizer (e.g. ethanol)
- Safranin (secondary stain)
- Water (preferably in a squirt bottle)
What is the application of selective medium?
Selective media are used for the growth of only selected microorganisms. For example, if a microorganism is resistant to a certain antibiotic, such as ampicillin or tetracycline, then that antibiotic can be added to the medium to prevent other cells, which do not possess the resistance, from growing.
What is the most important reagent in the Gram stain method?
The primary stain of the Gram’s method is crystal violet. Crystal violet is sometimes substituted with methylene blue, which is equally effective. The microorganisms that retain the crystal violet-iodine complex appear purple brown under microscopic examination.
Why do we use 95% alcohol in Gram staining?
Either acetone or ethyl alcohol can be used as the decolorizing agent. The alcohol dissolves lipids found in the outer cell membrane of Gram-negative bacteria, allowing the crystal violet-iodine complex to leak out of the thinner peptidoglycan layer.
Why 95 Ethanol is used in Gram staining?
Gram-negative cell walls contain a high concentration of lipids which are soluble in alcohol. The decolorizer dissolves the lipids, increasing cell-wall permeability and allowing the crystal violet-iodine complex to flow out of the cell. The color of the counterstain must contrast with that of the primary stain.
Which is applied last in Gram staining?
After decolorization, the gram-positive cell remains purple and the gram-negative cell loses its purple color. Counterstain, which is usually positively charged safranin or basic fuchsine, is applied last to give decolorized gram-negative bacteria a pink or red color.
Why is the decolorization important in Gram staining?
The Gram stain is the most important staining procedure in microbiology. … This layer makes up 60-90% of the gram positive cell wall. Decolorizing the cell causes this thick cell wall to dehydrate and shrink, which closes the pores in the cell wall and prevents the stain from exiting the cell.
What is the mordant used in Gram staining?
The mordant is Gram’s Iodine. This binds to the crystal violet making a large complex that adheres to the cell membrane.
What is Safranin used for in Gram staining?
Safranin is used as a counterstain in some staining protocols, colouring cell nuclei red. This is the classic counterstain in both Gram stains and endospore staining. It can also be used for the detection of cartilage, mucin and mast cell granules.