Strep Lab

Question 1

purpose of Optochin test

Answer 1

differentiate Strep pneumoniae

Question 2

minimum zone of inhibition for sensitivity to Optochin

Answer 2

14mm

Question 3

purpose of Bile Esculin

Answer 3

differentiate Group D streptococcus

Question 4

percent of bile in bile esculin agar

Answer 4

40%

Question 5

bakit positive ang group D sa bile esculin?

Answer 5

it can hydrolyze esculin to esculetin

Question 6

reaction of esculetin with ferric citrate forms ___

Answer 6

black - brown ppt on agar

Question 7

purpose of 6.5% salt broth test

Answer 7

differentiate group D enterococci

Question 8

positive result of 6.5% salt broth test

Answer 8

turbidity in 6.5% NaCl broth = turbidity in nutrient broth

Question 9

color change @ 6.5% salt broth test when bromcresol purple is added

Answer 9

purple to yellow

Question 10

Which is resistant to both bacitracin and sulfamethoxazole-trimethoprim?

a. group A strep
b. Group B strep
c. neither

Answer 10

b. Group B strep

Question 11

Which is susceptible to bacitracin but not to sulfamethoxazole-trimethoprim?

a. group A strep
b. Group B strep
c. neither

Answer 11

a. group A strep

Question 12

True or false: In bacitracin and sulfamethoxazole-trimethoprim susceptibility test, considered susceptible if the zone of inhibition is >12 mm

Answer 12

false. susceptible pag may zone of inhibition, regardless of size

Question 13

purpose of CAMP reaction

Answer 13

differentiate group B strep

Question 14

What is CAMP factor?

Answer 14

produced by group B strep, enhances lysis of sheep red blood cells by staphylococcal beta hemolysin

Question 15

positive result for CAMP reaction

Answer 15

arrowhead-shaped area of enhanced hemolysis in junction of S.aureus streak and strep isolate