Module Six Pre-assessment

Question 1

Some common characteristics of the Enterobacterales are Gram-positive rods that ferment glucose and most are oxidase-positive

True or False?

Answer 1

False

Members of Enterobacterales are Gram-negative rods, ferment glucose, and are oxidase-positive (except Plesiomonas).

Common genera in the order of Enterobacterales include:

Escherichia spp., Proteus spp, Klebsiella spp., Enterobacter spp., Salmonella spp., and , Shigella spp.

Question 2

Most members of Enterobacterales are motile.

True or False?

Answer 2

True

Most members of Enterobacterales are motile except for Klebsiella spp., Shigella spp., and Yersinia spp.

Question 3

Escherichia coli (E. coli) can be normal flora of the colon and it is a common cause of urinary tract infections.

True or False?

Answer 3

True

E. coli is a common resident of the GI tract and one of the most common causes of urinary tract infections.

Question 4

The Proteus spp. produces swarming colonies on blood agar plates and are strongly urease positive.

True or False?

Answer 4

True

Proteus spp. produce swarming colonies on blood agar plates. They have the ability to hydrolyze urea, thus producing a positive pink color. Most Proteus strains can also produce H2S which produces black precipitate on some differential media.

Question 5

Shigella spp. are non-lactose fermenters that can produce colonies with black centers on media that contain indicators for hydrogen sulfide production such as XLD agar and HE agar.

True or False?

Answer 5

False

Shigella spp. typically produce clear colonies that are negative for lactose fermentation. Shigella sonnei can slowly ferment lactose and thus produce a positive reaction after 48 hrs of incubation. Shigella spp. do not produce H2S so would not produce black centers on differential media such as XLD agar and HE agar.

Salmonella spp. do not ferment lactose and most species will produce H2S and thus having black centers on media such as XLD and HE agar.