Lab: Enteric Unknown I

Question 1

What is the utility of the MacConkey agar?

Answer 1

It selects for Gram-negative bacteria only, and lactose-fermenting bacteria grow pink due to the presence of lactose. Non-fermenters grow golden.

Question 2

What is a SMAC agar?

Answer 2

MacConkey agar with sorbitol instead of lactose. Most strains of lactose can ferment sorbitol and will turn pink after growth, but O157:H7 cannot and thus will not turn pink.

Question 3

Fecal leukocytes are typically found in ______________ diarrheal illnesses.

Answer 3

invasive/inflammatory