Lab exam

Question 1

What is Loffler medium used for?

Answer 1

Selective differential medium for c. diphtheria

Question 2

What is Clauberg medium used for? (What is contained in medium)

Answer 2

Selective differential medium used for c. diphtheria.

Contains potassium tellurite (colonies turn black, and has garlic smell)

Question 3

What is eosin methylene blue (EMB) differentiating agar used for? What can we see with it?

Answer 3

Used for gram negative (fecal coliforms)
[they inhibit growth of most of gram +) 
-Lactose (+) fermenter--> dark blue/purple
-Lactose (-) --> colourless
-E.coli = metallic green

Question 4

What is the selective and differentiating media Lowenstein-Jensen and Sula used for?

Answer 4

mycobacterium tuberculosis

LJ = solid slant, sula = broth

Question 5

What is the selective and differentiation media bismuth-sulphite used for? What colour and detection does it use?

Answer 5

Salmonella - appears black

It contains brilliant green, and detects H2S production

Question 6

What is the selective and differentiating medium TCBS used for?

Answer 6

Thiosulfate-citrate-bile-salt-sugar agar is used for vibrio cholera
Colonies –> yellow

Question 7

What is a transport media? List examples

Answer 7

Special type of media that tries to preserve the specimen and limit bacterial overgrowth (contaminants) until lab tests are run.
Ex. stuart - transport swabs
uricult - UTI test

Question 8

Cultivation of s. aureus and s. epidermis on agar. Result?

Answer 8

S. aureus –> Gold

s. epidermidis –> chalk white

Question 9

Cultivation of s. aureus and s. epidermis on blood agar. Result?

Answer 9

S. aureus –> Gold yellow pigment, with beta-hemolytic activity around colony
S. epidermidis –> chalk-white, NO hemolysis

Question 10

S. epidermidis and s. saphrophyticus on novobiocin disc show what result?

Answer 10

S. epidermidis –> susceptible, (circle will be visible around the disc)
S. saphrophyticus –> resistant, will not grow

Question 11

Strep. pyogenes on blood agar undergoes…

Answer 11

beta hemolysis

- no pigment is produced

Question 12

Strep mitis on blood and chocolate agar undergoes..

Answer 12

alpha-hemolysis

Question 13

Strep pneumo on blood and chocolate agar…. undergoes

Answer 13

alpha-hemolysis

–> optochin sensitive

Question 14

Proteus on agar and blood agar?

Answer 14

On agar + blood agar –> wave-like swarming pattern (no indvl colonies seen)

Question 15

Pseudomonas on agar plate…

Answer 15

• large, oval shaped colonies, that make a greenish colour, and discolour medium to gray-silver
• -> beta hemolysis

Question 16

Explain the urease test. What medium is used? Colour indicators? (+) species?

Answer 16

(+) species produces urease, and if placed in urea, it will break it down into CO2 and ammonia. Christensen medium used with phenol red indicator. 
(+) colour = purple
(-) = citric yellow 
-klebsiella
-h.pylori
-proteus

Question 17

What produces flat, jelly-fish medusa shaped colonies?

Answer 17

Bacillus cereus

Question 18

Explain what we see when using thioglycolate medium?

Answer 18

It consumes oxygen, thus we can use it for obligate anaerobes.
Ex. clostridium

Question 19

Which bacteria causes swarming?

Answer 19

Proteus species

Grown on blood agar and EMB

Question 20

Explain pseudomonas aeruginosa on agar and blood agar

Answer 20

Agar –> fluorescent greenish
Blood agar –> beta-hemolysis

sweet/grape odour