Micro Exam 1

Question 1

5% Sheep Blood Agar (BA/BAP)

Answer 1

Type: Enriched, Differential
Composition: 5% Sheep’s Blood
Differentiates: Hemolytic patterns from lysis of red blood cells

Question 2

Chocolate Agar (CHOC)

Answer 2

Type: Enriched
Composition: Hemin (X factor), Isovitalex (V factor or NAD), Vit B12, Fe2+, Mg2+, Cysteine
Notes: Used to grow fastidious organisms (Neisseria, Haemophilus spp.)

Question 3

MacConkey Agar (MAC)

Answer 3

Type: Selective, Differential
Composition: Bile Salts & Crystal Violet
Selects against: Gram Pos
Differentiates: Lactose fermenters grow magenta colonies (LF vs NLF)
Notes: Prevents Proteus swarming

Question 4

Sulfamethoxazole/trimethoprim Agar (SXT)

Answer 4

Type: Selective, Differential
Composition: Blood agar + SXT antimicrobial
Selects against: normal throat flora
Notes: Used to isolate GAS and GBS

Question 5

Haemophilus Isolation Medium (HIM)

Answer 5

Type: Enriched, Differential
Composition: 4 sections (Factor X, Factor V, X+V, 5% Horse blood)
Differentiates: in horse blood, demonstrates hemolysis of hemolytic Haemophilus

Question 6

Columbia Colistin-Naldixic Acid (CNA)

Answer 6

Type: Selective differential
Composition: Colistin, Naldixic Acid
Selects against: Gram Neg
Notes: Used to isolate colonies overgrown by swarming Proteus

Question 7

Phenyl Ethyl Alcohol (PEA)

Answer 7

Type: Selective
Composition: Sheep BA + Phenylethyl Alcohol
Selects against: Gram Neg Rods (like Proteus)
Notes: Used in anaerobic bacteriology

Question 8

Campy CVA Agar

Answer 8

Type: Selective
Composition: Brucella agar base (defibrinated sheep blood + yeast extract + casein), ABs against GI flora
Selects against: GNR (Cefoperzone), GP (Vancomycin), Fungi (Amphotericin B)
Notes: Incubated @ 42C in micro-aerophilic environment to isolate Campylobacter spp.

Question 9

Hektoen Agar (HEK/HEA)

Answer 9

Type: Selective, Differential
Composition: Bile salts, lactose, sucrose, salicin, Na Thiosulfate
Selects against: GNR (normal intestinal flora)
Differentiates: Enterics turn medium yellow, Salmonella/Shigella turns medium blue (Salmonella also makes black H2S)

Question 10

Xylose Lysine Desoxycholate Agar (XLD)

Answer 10

Type: Selective, Differential
Compostion: Bile salts, sugars, Na thiosulfate
Selects against: GP
Differentiates: normal enterics use sugars, make yellow colonies. Salmonella makes H2S, black colonies. Shigella makes red colonies.

Question 11

Thayer Martin Agar

Answer 11

Type: Enriched, Selective
Composition: CHOC + antibiotics
Selects against: GPC (Vancomycin), GNR (Colistin), Proteus swarming (Trimethoprim), Fungus (Nystatin)
Notes: Used to isolate Neisseria gonorrhoeae

Question 12

Martin Lewis Agar

Answer 12

Type: Enriched, Selective
Composition: CHOC + antibiotics
Selects against: GPC (Vancomycin), GNR (Colistin), Proteus swarming (Trimethoprim), Fungus (Anisomycin)
Notes: Used to isolate Neisseria gonorrhoeae

Question 13

Vaginalis Agar (V-Agar)

Answer 13

Type: Enriched
Composition: Human blood, peptones, yeast extract
Notes: Aids in isolation of Gardnerella vaginalis

Question 14

Buffered Charcoal Yeast Extract Agar (BCYE)

Answer 14

Type: Enriched, Selective
Composition: Buffer, activated charcoal, yeast extract
Notes: Used to isolate legionella spp.

Question 15

Thioglycolate broth (Thio Broth)

Answer 15

Used for wound cultures, oxygen scrubbers allow aerobic and anaerobic culture in one tube, preserves all organisms as a back-up

Question 16

GN Broth

Answer 16

Supports Salmonella and Shigella, used for subs when these are suspected

Question 17

Selenite Broth

Answer 17

Supports Salmonella and Shigella, used for subs when these are suspected

Question 18

Direct Smear Gram Stain Quant Reporting

Answer 18

R = <1 / oif
F = 1-5 / oif
M = 6-30 / oif
A = >30 / oif

Question 19

Direct Smear Cellular Elements Quant Reporting

Answer 19

R = <1 / lpf
F = 1-9 / lpf
M = 10-25 / lpf
A = >25 / lpf

Question 20

Colony Morphology Reporting Order

Answer 20

Quant/ Hemolysis, Size, Color, Texture, Notes