Lab Diagnostics Flashcards
Gram staining procedure…
Crystal violet for 1min Iodine for 1min Ethanol + acetone for 30secs Safranin for 1min Rinse with water and blot dry
Gram positive cells are purple
Gram negative cells are pink
What organism is acid fast staining generally used used for?
Mycobacterium
Others include nocardia and the head of sperm.
What do acid fast organisms contain?
Impermeable cell wall, mycolic acid, large amount of fatty acids
Acid fast staining procedure…
Red carbolfuchsin (contains phenol) is used as the first stain.
Heat is added.
Rinsed with strong decoloiriser, which strips stain off non-acid fast cells.
De-colourised cells take up methylene blue.
What is a spectrophotometer used for?
Used in counting bacteria. The cloudier the solution, the more bacteria are present and less light gets through, resulting in a higher reading.
Difference between a pour plate and spread plate
Pour plate contains sub surface colonies, whereas a spread plate just has colonies on the surface
Catalase test
Detects if Staphylococcus is present.
Hydrogen peroxide breakdown to water. If there are bubbles then the test is positive.
Coagulase test
Tests for Staphylococcus aureus.
Tests for coagulase enzymes (turns fibrinogen to fibrin clots).
