Microbiology

Question 1

Hektoen agar

Answer 1

selectively isolates pathogenic coliforms, especially salmonella and shigella

Question 2

MacConkey Agar

Answer 2

differentiates between lactose fermenters and non-lactose fermenters

Question 3

CNA agar

Answer 3

contains antibiotics; inhibits gram negatives; selects for gram positives

Question 4

Campy agar

Answer 4

contains antibiotics cephalothin, trimethoprim, vancomycin, polymyxin B, and amphotericin B to prevent the growth of Enterobacteriaceae, Pseudomonas spp, and fungi

Question 5

TCBS agar

Answer 5

used to grow Vibrio cholerae; grows as yellow colonies due to use of citrate and sucrose

Question 6

APW

Answer 6

enrichment broth for the growth of Vibrio

Question 7

Chocolate agar

Answer 7

used for the recovery of Haemophilus spp; provides X-factor (hemin) and V factor (NAD), both are required for the growth of Haemophilus spp.

Question 8

CCFA agar

Answer 8

used for the recovery of Clostridium difficile from stool; contains cycloserine and cefoxitin which inhibit growth of gram-negative coliforms; C. difficile ferments fructose causing colonies to grow yellow

Question 9

Deoxycholate agar (DCA)

Answer 9

used in the isolation of Enterobacteriaceae; inhibits gram positves; allows differentiation between lactose fermenters (pink) and non-lactose fermenters (colorless).

Question 10

XLD agar

Answer 10

selective for gram negative coliforms; differentiates between Shigella (red/clear colonies) and Salmonella (red colonies with black centers)