micro unit 3

Question 1

Blood Agar (BA)

Answer 1

non selective, differential medium — grows most bacteria; used to detect hemolysis (α, β, γ). sheep’s blood

Question 2

CAP

Answer 2

non selective Enriched medium for fastidious organisms (e.g., Neisseria, Haemophilus). sheep blood that is lysed

Question 3

MAC

Answer 3

Selective for Gram-negative bacteria; differential for lactose fermenters (pink) vs non-fermenters (colorless). lactose fermenters include E. coli, Klebsiella, Enterobacter

Question 4

Thio broth

Answer 4

nonselective, differential, enriched. differentiates respiration

Question 5

Mannitol salt agar

Answer 5

selective for staphylococcus, differential for coagulase (coagulase positive for S. aureus)

Question 6

BEA bile esculin agar

Answer 6

selective for streptococcus, differential for enterococcus (black if so)

Question 7

Hektoen Enteric media

Answer 7

selective for Gram-negative enteric bacteria, differential for samonella and shigella.

Salmonella: Non-fermenter, H₂S positive → blue-green with black center
Shigella: Non-fermenter, H₂S negative → blue-green

Question 8

xylose lysine deoxycholate

Answer 8

selective for Gram-negative enteric bacteria, differential for samonella and shigella.

Salmonella: Red with black center (non-fermenter after lysine decarboxylation, H₂S positive)
Shigella: Red colonies (non-fermenter, H₂S negative)

Question 9

MAC w/ sorbitol

Answer 9

selective for gram neg. rods, differential for sorbitol fermentation. E. coli O157:H7 is sorbitol negative

Question 10

salmonella shigella agar

Answer 10

Selective for: Gram-negative enteric bacteria, differential for salmonella (clear with black center) and shigella (clear)

Question 11

selenite F broth

Answer 11

enriched, selective for samonella

Question 12

Tryptose Cycloserine Dextrose Sulfite (TCDS)

Answer 12

selective for vibrio species (differential for sucrose, vibrio chlorae is yellow)

Question 13

cetrimide

Answer 13

selective-Cetrimide
differential-enhances pigment Pseudomonas aeruginosa

Question 14

BCYE ( buffer CHARCOAL yeast extract)

Answer 14

selective for legionella.

Question 15

bordet gengou

Answer 15

selective for bordetella pertussis

Question 16

CIN

Answer 16

selective -Yersinia ( grows at room temp)
differential- Mannitol fermentation and colony morphology