Key tests

Question 1

Bacitracin (taxo A), Lysostaphin and Furazolidone (FX) Sensitivity key test for Staph and Micrococcus

Answer 1

Inoculate TSB w/ bacteria to match 0.5 McFarland Standard, use to streak TSA plate, place disks on lawn of streak plate, incubate 35-37*C for 18-24 hrs., note any zone around disk
suceptible: zone around disk
resistant: growth up to the edge of disk
Micrococcus: Furazolidone Resistant; Bacitracin Susceptible; Lysostaphin Resistant
Staphylococci: Furazolidone Suceptible; Bacitracin Resistant; Lysostaphin Suceptible

Question 2

Catalase key test

Answer 2

Staph/Micrococcus +
Strep/Enterococcus -
Enterococcus may give weak +

Question 3

Bile esculine/ 6.5% NaCl key test

Answer 3

-/+ : Aerococcus sp.
-/- : Viridans Streptococci group
+/- : Group D Streptococci
+/+ : Enterococcus sp.

Question 4

Optochin key test

Answer 4

Streptococcus pnemoniae is susceptible

Question 5

Coagulase key test

Answer 5

Coag. + : S. aureus

Coag - : CNS (S. saprophyticus, Micrococcus, S. epidermidis)

Question 6

Optochin (P) disk susceptibility test

Answer 6

Streptococcus pneumoniae is susceptible

P is for pneumoniae

Question 7

glucose test (GPC)

Answer 7

Staph glucose +

Micrococcus glucose -

Question 8

PYR key test (GPC)

Answer 8

PYR + : S. lugdunensis, S. pyonenes, Enterococcus

PYR - : S. aureus, S. schleiferi, S. simulans, Group D Strep

Question 9

sodium hippurate key test

Answer 9

+ : GBS

Question 10

Bacitracin A disk key test

Answer 10

GAS is suceptible

A for Group A Strep

Question 11

Enterococcus key tests

Answer 11

Catalase -
alpha/gamma hemolysis
Bile esculin/6.5%NaCl: +/+
PYR +
LAP +

Question 12

GAS key tests

Answer 12

Catalase -
beta hemolysis
bacitracin S
PYR +
LAP +

Question 13

GBS key tests

Answer 13

catalase -
beta hemolytic
sodium hippurate +
camp test +

Question 14

Streptococcus pneumoniae key tests

Answer 14

catalase-
alpha hemolytic
optochin S
sodium deoxycholate +
PYR -
LAP +
checker piece morph on plates
lancet shaped diplococci on GS

Question 15

Staphylococcus aureus key tests

Answer 15

catalase +
coagulase +
glucose fermentation +
lysostaphin S
furixolidone S
bacitracin R
GPC in clusters
DNase +
ferments mannitol
reduce nitrate-nitrite

Question 16

Micrococcus sp. key tests

Answer 16

pigmented colonies
GPC in tetrads
catalase +
coagulase -
microdase +
glucose fermentation -
glucose oxidase +
bacitracin S
lysostaphin R
furazolidone R

Question 17

Staphylococcus saprophyticus key tests

Answer 17

catalase +
coagulase -
novobiocin R (only use on urine)
reduce nitrate-nitrite

Question 18

CNS key tests

Answer 18

catalase +
coagulase -
novobiocin S (only use on urine)
ferment glucose +
reduce nitrate-nitrite

Question 19

Group D Strep key tests

Answer 19

bile esculine/6.5%NaCl: +/-
alpha/gamma hemolysis
PYR -

Question 20

Viridans Strep key tests

Answer 20

catalase -
alpha/beta/gamma hemolytic
caramel/butterscotch/honeysuckle smell
optochin R
bile esculine/6.5% NaCL: -/-
PYR -
bacitracin R
VP +
Arginine +

Question 21

Aerococcus key tests

Answer 21

optochin R
bile esculin/6.5% NaCl: -/+
alpha hemolysis
A. viridans: tetrads, PYR +, LAP - , 6.5%NaCl +
A. urinae: tetrads, PYR -, LAP +, 6.5%NaCl +

Question 22

Gemella key tests

Answer 22

catalase -
PYR +
LAP +
vancomycin R

Question 23

Pediococcus key test

Answer 23

catalase -
LAP +
PYR -
vancomycin R