Bacillus sp. and Staphylococcus

Question 1

What differentiates B. cereus from B. thuringiensis and B. anthracis?

Answer 1

The toxin each produces is the only difference between them.

Question 2

What are the 2 types of toxins Bacillus can produce and how are they different from each other?

Answer 2

Emetic and diarrheal. See slide 6 for a chart comparing them.

Question 3

Does S. aureus cause an infection or an intoxication?

Answer 3

Intoxication.

Question 4

How are the toxins the S. aureus produces named/identified?

Answer 4

Slide 14.

Question 5

How does S. aureus toxin induce vomiting?

Answer 5

Slide 14.

Question 6

What kinds of characteristics do the foods associated with contamination by S. aureus have?

Answer 6

Slide 16.

Question 7

What is noteworthy about the oxygen requirements for Bacillus cereus, that is distinct from other pathogens we discussed this semester?

Answer 7

B. cereus is a strict aerobe

Question 8

The emetic toxin of B. cereus is also called….

Answer 8

cereulide

Question 9

What distinguishes the B. cereus emetic toxin from enterotoxin, in terms of resistance to intrinsic/extrinsic factors?

Answer 9

Cereulide is resistant to heat, pH, proteolysis; see slide 7 for specifics.

Question 10

What are three reasons that even though B. cereus is frequently found in pasteurized milk, it doesn’t cause much illness via this route?

Answer 10

see slide 9; has to do with abundance of the organism, temperatures for toxin production, and defects in product

Question 11

What are two ways heat processing selects for the growth of Bacillus in foods?

Answer 11

See slide 9; specifically, how does pasteurization affect Bacillus, and why does heat treatment impact its growth in foods such as rice?

Question 12

What is most noteworthy about S. aureus, in terms of water activity for growth?

Answer 12

It grows at the lowest water activity (low to mid 0.8’s) of any pathogen we discussed this semester)

Question 13

What Staphylococcus aureus toxin type is most associated with foodborne illness?

Answer 13

type A

Question 14

What is noteworthy about the resistance of Staphylococcus enterotoxins, compared to most enzymes?

Answer 14

Staph enterotoxin is resistant to degradation by proteolytic enzymes and to heat.

Question 15

What are the five common features of foods that are linked to Staphylococcus aureus illnesses?

Answer 15

See slide 16 for this list; one or more of these are usually found in outbreaks.

Question 16

When we say “keep hot foods hot, and cold foods cold” in order to prevent foodborne illness, how do we define “hot” and “cold”?

Answer 16

140 degrees and 40 degrees Fahrenheit