Food and Water Microbiology, ELISA Testing

Question 1

What plates were used to test for bacterial contamination on raw chicken and beef? What ingredients do the plates contain and what is the purpose of each ingredient?

Answer 1

Salmonella Shigella plates.
Lactose - differentiates for lactose fermentation
Bile salts - selective for Gram-negative organisms
Ferric citrate - acts as an indicator for hydrogen sulfide production
Neutral red - gives media pinkish-red color when lactose is fermented

Question 2

What do Escherichia coliforms look like on the SS plates?

Answer 2

pink colonies

Question 3

What does Salmonella look like on the SS plates?

Answer 3

black colonies

Question 4

What does Shigella look like on the SS plates?

Answer 4

colorless colonies

Question 5

What is the name of the broth media used to test water purity?

Answer 5

Phenol red lactose broth

Question 6

What is a Durham tube and its purpose?

Answer 6

A small tube in the broth that is used to determine the presence of gas

Question 7

Why is the MPN test considered an indirect method for quantifying bacteria?

Answer 7

It is a statistics based test