Diagnostic device > Diagnostic discs
DIAGNOSTIC DISCS 50 discs Code: DD 507
ITEST ONPG
for the rapid detection of ß-galactosidase activity
Purpose and usage:
ONPG diagnostic discs are designed for the detection of ß-galactosidase. This test serves for the differentiation for e.g. Neisseria lactamica from other Neisseriae.
Principle:
The test is based on the detection of ß-galactosidase which hydrolyses o-nitrophenyl-ß-galactopyranoside.Colored O-nitrophenol develops during this reaction.
Technique:
Prepare a dense suspension (degree No.3 of McFarland turbidity scale) from the examined strain in a test tube with 0.4 ml sterile distilled water.Put ONPG disc into the test tube with the suspension and incubate for 3 hours at 37°C. Incubate test tubes with no color changes overnight at room temperature as some strains have delayed positive reaction.
Evaluation:
The suspension with the submerged disc becomes yellow if the reaction is positive (ONPG +). No change of color appears if the reaction is negative (ONPG -).
Warning:
1. ONPG discs are designed for laboratory use only.
2. Discs should be stored in a dark place at +4°C and should not be used beyond the expiration date shown on the packing.
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