(3b) API-20 E Interpretation of results

Orange

Any shade of ? within 24 hours should be interpreted as a positive result in the ADH, LDC, ODC tube

ONPG

Any shade of Yellow = POSITIVE Colorless = NEGATIVE

H2S

Black deposit = POSITIVE No Black deposit = NEGATIVE

GEL

Diffusion of pigment = POSITIVE No diffusion = NEGATIVE

TDA

Immediate Brown to red = POSITIVE Yellow = NEGATIVE **Add 1 drop 10% FeCl3

capule area

In the CIT tube the reaction is read in the ? area of the micro tube

negative reaction

In the GEL tube the solid gelatin particles may spread throughout the tube after inoculation; this is a

VP

Red color throughout = Positive Colorless = negative ** 1 drop 5% alpha-naphthol (VP-A) & 1 drop 40% KOH (VP-B)

URE

Red or Orange = POSITIVE Yellow = NEGATIVE

ADH, LDC, ODC

Red or orange = POSITIVE Yellow = NEGATIVE

IND

Red ring = POSITIVE No red ring or yellow = negative **1 drop Kovac's reagent (2min)

CIT

Turquoise or dark blue = POSITIVE Light green or yellow = NEGATIVE

negative control

Use the VP tube (before the addition of reagents) as a ? for the ONPG tube

GLU, MAN, INO, SOR, RHA, SAC, MEL, AMY, ARA

Yellow = POSITIVE Blue to blue green = NEGATIVE

Negative result

You have to wait 10 minutes in order to read a ? result in a VP tube

Carbohydrates fermentation

begins in the bottom of the tube so reactions should be read from the bottom to the top

H2S Production

may range from a heavy black deposit to a thin black line around the tube bottom