Streptococcaceae and Related Genera PART 1

Question 1

When comparing staph and strep colonies, what are the differences?

Answer 1

Staph is opaque

Strep is “transparent” (or at least not as opaque )

Question 2

Alpha (or gamma) hemolytic Streps

Answer 2

• Group D
• S. pneumoniae
• Enterococcus spp.
• alpha Strep (not group D)

Question 3

Beta hemolytic Streps

Answer 3

• Group A
• Group B
• Group D (rarely beta hemolytic)
• Enterococcus spp. (rarely beta hemolytic
• beta Strep (not Group A, B, or D)

Question 4

Strep pneumoniae characteristic features on a plate

Answer 4

• colonies are often: depressed in center (autolysis) or mucoid ( encapsulated)

Question 5

Throat cultures ( strep screens) must be incubated ________?

Answer 5

anaerobically

Question 6

Streptolysin O is _______ ________

Answer 6

oxygen labile

Question 7

Streptolysin S is _______ ________

Answer 7

oxygen stable

Question 8

Principle of the Lancefield Grouping test

Answer 8

grouped by “ C substance” in cell wall

Question 9

Catalase test for streptococci (pos/neg?)

Answer 9

negative

Question 10

What Test?
40% bile = growth/no growth
Leads to black precipitate

Answer 10

Esculin hydrolysis

Bile Esculin Agar

Question 11

Bile Esculin Agar

what do positive / negative tests look like?

Answer 11

Pos: blackening of medium
Negative: no growth