Principles of Bacterial Isolation and Identification

Question 1

What are PIA plates?

Answer 1

Pseudomonas isolation agars, used to isolate pseudomonas organisms

Question 2

Describe HEK plates and their purpose.

Answer 2

HEK plates are Hektoen enteric agars that contain lactose, sucrose, salicin, and peptone. Most bacteria use the three sugars, which turn the plate yellow or red, but shigella and salmonella cannot; instead, they utilize the peptone, which alkalizes the mixture and turns it blue.

Question 3

Salmonella reduces _________, which turns a HEK plate black.

Answer 3

H2S

Question 4

Mackonkey agars are used to _________.

Answer 4

isolate Gram-negative bacteria (because the crystal violet prevents growth of Gram-positive bacteria) and to differentiate enteric bacteria; enteric bacteria can metabolize lactose, which will turn the pH indicator red

Question 5

Bacillus cereus is ________.

Answer 5

Gram-positive, rod-shaped

Question 6

Staphylococcus aureus is _________.

Answer 6

Gram-positive, coccal

Question 7

Escherichia coli is _________.

Answer 7

Gram-negative, rod-shaped

Question 8

Pseudomonas aeruginosa is ________.

Answer 8

Gram-negative, rod-shaped

Question 9

Klebsiella pneumoniae is _______.

Answer 9

Gram-negative, rod-shaped

Question 10

Proteus mirabillis is ___________.

Answer 10

Gram-negative, rod-shaped

Question 11

Salmonella is ____________.

Answer 11

Gram-negative, rod-shaped

Question 12

Enterococcus is ____________.

Answer 12

Gram-positive coccal