Biochemical Testing Flashcards
Catalase Test
-formation of bubbles indicates a positive test where the catalase enzyme breaks down hydrogen peroxide into water and oxygen
-typically present in all orgamosms that grow in the presence of oxygen
-Gram + and gram -
oxygen requirement test
-differentiates bacteria based on requirement for oxygen
-thioglycollate reduces oxygen to water and permits the growth of obligate anaerobes, combines with diffusion of oxygen from the top of the broth this produces a range of oxygen concentrations down the length of the tube
-pink when oxidized
-Gram + and gram -
oxidase test
-gram negative organisms
-the oxidase test uses TMPD as an artificial electron carrier to provide electrons to cytochrome C
-in its reduced form TMPD is colorless but in its oxidized form it is blue/purple
-if cytocrhome c oxidase is present it will be in its oxidized form and the dot should turn blue
ONPG
-differentiate bacteria based on their ability to hydrolyze lactose
-Uses ONPG as a substrate for betagalactosidase which is present in cells that use lactose as carbon source
-changes from colourless to yellow
tests for gram pos and neg
catalase and oxygen requirement
tests for gram neg
-Oxidase
-ONPG
-Urease
-Indole
-Carbohydrate fermentation
Urease
-gram negative and only if oxidase test is negative
-assess urease present
-presence of urease hydrolyzes urea for use as a nitrogen source and produces alkaline product ammonia
-ammonia diffuses from the cell into the medium and pH of medium rises as ammonia dissolves inw ater to produce ammonium and hydroxide ions, phenol red then turns to a vivid pinkish purplea
Indole Test
-gram negative
-test detects for tryptophanase
-as celsls that produce tryptophanse grow they metabolize tryptophan from the growth medua for energy and convert it to indole, pyruvic acid and ammonia
-when the cells are mixed with DMACA the strong acid present in the reagent lyses the cells and releases indole, indole reacts with DMACA to produce a blue green complex
Carbohydrate fermentation
-production of acids that produce characteristics on the EMB or MAC agar
-carbohydrate/lactose fermentation
Bile esculin test
-gram positive
-assess the abilityy of an organism to grow in the presence of bile and hydrolyze exculin
-esculin hydrolysis produces glucose and esculetin reacts with iron salts in the agar to rpoduce a dark brown black colour
tests for gram positive
-bile esculin
-blood hemolysis
-mannitol salt agar
-starch hydrolysis (gram pos bacilli)
BAP
-gram positive
-test for hemolysins that lyse red blood cells
-medium containing sheep RBCs
MSA
-gram positive
-used for gram pos staphylococci based on tolerance to high salt concentrations and abbility to ferment the carbohydrate mannitol
starch hydrolysis
-bacteria grown as a smear on the surface of a complex nutrient rich medium containing start
-after grwoth thr presence of starch surrounding the bacterial growth is detected by applying iodine. If starch is present idoine reacts with it in the medium resulting in a noticable blue black or dark brwon colour change
