Microbiological techniques

Question 1

What grows and what descriptors are associated with MacConkey agar?

Answer 1

grow= gram - but not fastidious, pink colonies= lactose fermenter, colorless= nonlactose fermenter; medium normally purple agar plate

Question 2

What descriptors are associated with oxidase strip or reagent?

Answer 2

blue= positive- not enterobacteriaceae prob psuedomonas, no color change = negative

Question 3

What grows and what descriptors are associated with OF-glucose medium?

Answer 3

yellow through out= glucose ferment-eneterobacteriaceae, yellow on top only= glucose oxidizer- Psuedomonas, no change= negative; medium normally green semmisolid

Question 4

What grows and what descriptors are associated with Indole Broth?

Answer 4

after addition of Kuvac’s reagent, red surface= positive- can degrade tryptophan to indole, no change = negative; medium normally yellow broth

Question 5

What grows and what descriptors are associated with Urea agar?

Answer 5

red to pink color= positive- hydrolyze urea releasing ammonia and CO2 both react in medium forming ammonium carbonate (Proteus), no color change = negative; medium normally beige slant

Question 6

What grows and what descriptors are associated with simmon’s citrate?

Answer 6

blue slant= positive- citrate as carbon source causing alkaline products resulting in color change, no change= negative; medium normally green slant

Question 7

What descriptors are associated with Optochin Disc?

Answer 7

zone of inhibition = positive- S. Pneumoniae (from other a-hemolytic strep)

Question 8

What grows and what descriptors are associated with Bile-esculin agar?

Answer 8

black color = positive- capable of hydrolyzing esculin in bile so group D strep entero and nonentero, no change = negative; medium normally beige slant

Question 9

What descriptors are associated with BHI broth with 6.5% NaCl?

Answer 9

growth= positive- group D enterococci; medium normally tan broth

Question 10

What descriptors are associated with Coagulase test?

Answer 10

clotting of serum = positive- coagulase is enzyme causes fibrinogen to convert to fibrin, S. Aureus

Question 11

What in MacConkey agar prevents growth of gram +?

Answer 11

bile salts and crystal violet

Question 12

What is the use, what grows and what are the descriptors of catalase test?

Answer 12

catalase decomposes H2O2 into H2O and O, excluding streptococci most aerobes and facultative possess catalase; positive- lots of bubbles = staph