Interpreting Biochemical Tests

Question 1

KIA Results

Answer 1

• Red slant/yellow butt: non-lactose fermenter
• Yellow slant/yellow butt: lactose fermenter
• H2S production: any amount
• Gas: any amount

Question 2

MIO Results

Answer 2

• Throughout media: motile
• Only on stab lines: non-motile
• Indole: Pink (+), clear (-)
• Ornithine: Purple (+), yellow (-)

Question 3

Urea

Answer 3

Pink (+), yellow/orange (-)

Question 4

Citrate

Answer 4

Blue or growth (+), no growth or color change (-)

Question 5

Fermentation Tube Test

Answer 5

All Neisseria are Glucose (+)

N. meningitides are also Maltose (+)

Question 6

O/F Glucose Tubes

Answer 6

Double stab, layer one with mineral oil, incubate at 36C in CO2

• Yellow in both: ferments glucose, open air oxidizes glucose
• No yellow in either: cannot use glucose

Question 7

API 20 Strip

Answer 7

GNRs

Boxes are filled all the way, those underlined are topped off with mineral oil

After incubation:

1. Ferric Cl to TDA
2. Potassium Hydroxide to VP sit for 10 min
3. Indole to Indole

Question 8

Proteolysis

Answer 8

Detects proteases

Positive test is appearance of clear zone around the colonies on EYA

Question 9

Reverse CAMP Test

Answer 9

Test organism streaked in the center of anaBAP and then a known GBS streaked perpendicular to test streak, arrowhead-shaped zone of hemolysis seen after 24-48 hrs.

Used for C. perfringens which is reverse CAMP (+)

Question 10

Spore Tests: Ethanol Method

Answer 10

Spores are resistant to antibacterial agents such as ethanol

Ethanol treated and untreated cultures are inoculated onto anaBAP, non-spore formers grow only in untreated cultures whereas spore formers would grow on both plates