Lab Exercise 14:
Biochemical Differentiation of some
Medically Important Gram Positive Cocci
Beta ( β ) hemolysis (blood agar around bacterial colonies is
completely clear, indicating complete breakdown and consumption
of hemoglobin)
Alpha (α) hemolysis (blood agar
around bacterial colonies looks
greenish-brown, indicating
partial breakdown and
consumption of hemoglobin)
Mixed culture from a throat
swab; note several β-hemolytic
colonies
Gamma (γ) hemolysis (really means no hemolysis; blood agar around
colonies looks normal)
Side-by-side comparisons of alpha (α), beta (β), and
gamma (γ) hemolysis
Bacitracin (Taxo A) sensitivity
+ results with a zone of inhibition
A
- Result with no zone of inhibition
Optochin (Taxo P) sensitivity
- Results with no zone of inhibition
+ results with a zone of inhibition
P
P
Coagulase Test
+
-
Carbohydrate Fermentation Tests
(Glucose and Mannitol)
+
Phenol red indicator
turns yellow at acid pH
- (same as uninoculated media)
Catalase Test
-
+
Staphylococcus
epidermidis
Enterococcus
faecalis
Use the chart on p. 146 and/or the
flow chart on p. 147 of your
labam I?
Who
manual to figure out who I am!
G
M
Answer: Streptococcus pyogenes
Use the chart on p. 146 and/or the
flow chart on p. 147 of your lab
manual to figure out who I am!
G
M
Answer: Micrococcus lutea
Use the chart on p. 146 and/or the
flow chart on p. 147 of your lab
manual to figure out who I am!
A
G
M
Answer: Enterococcus faecalis
Use the chart on p. 146 and or the
flow chart on p. 147 of your lab
manual to figure out who I am!
G
M
Answer: Staphylococcus aureus
Use the chart on p. 146 and/or the
flow chart on p. 147 of your lab
manual to figure out who I am!
G
M
Answer: Staphylococcus epidermidis
Use the chart on p. 146 and or the
flow chart on p. 147 of your lab
manual to figure out who I am!
G
M
Answer: Streptococcus pneumoniae
Use the chart on p. 146 and/or the
flow chart on p. 147 of your lab
manual to figure out who I am!
A
G
M
Answer: Streptococcus mutans