Culture Mediums

Question 1

MacConkey agar

Answer 1

bile salts and crystal violet inhibits G+ and some G- –> selective for G-
Lactose only
Fermentation –> pink
No fermentation –> colorless

Question 2

Cetrimide agar

Answer 2

Isolation of Pseudomonas aeruginosa

Mg/K –> pyocyanin (blue/green) and fluoroescein (yellow/green)

Question 3

Thayer Martin agar

Answer 3

Selective CAP for Neisseria gonorrhea

Question 4

Mannitol salt agar

Answer 4

High salt limits growth to osmotolerant
Selective for staphylococci
Ferment mannitol –> yellow (diff for S aureus)

Question 5

Hektoen Enteric agar

Answer 5

Bile salts inhibit G+
Ferment lactose –> yellow/orange
No ferm –> green or transparent
H2S producing organisms –> black precip

Question 6

Bile Esculin agar

Answer 6

Bile salts inhibit G+ except:

Group D Streptococcus and Enterococcus hydrolyze esculin –> black FeSO4 precipitate

Question 7

Tellurite agar

Answer 7

Isolation of Corynebacterium diphtheriae
Potassium tellurite inhibits G-
Colonies - black w/brown halo

Question 8

Blood agar

Answer 8

differential medium
sheep blood
determining hemolysis

Question 9

Chocolate agar (CAP)

Answer 9

heat lysed RBCs
good for organisms w/difficult nut requirements
Haemophilus and Neisseria

Question 10

Triple Sugar Ion agar

Answer 10

Lactose, sucrose, glucose
No ferm --> red
Ferm --> yellow
     full tube: ferment multiple sugars
     bottom: glucose only
H2S --> black

Question 11

Selective agents

Answer 11

Inhibit growth of specific organisms

Question 12

Sabouraud Dextrose agar

Answer 12

All fungal growth

Question 13

Eosin Methylene Blue agar

Answer 13

Eosin and meth blue inhibit G+
Lactose ferm –> blue/black
Strong ferm –> shiny green
No ferm –> clear

Question 14

Differential agents

Answer 14

distinguish between types

Question 15

Chromogenic agar

Answer 15

Differentiate through colony color

SA, MRSA, MSSA