This post was most recently updated on August 26th, 2019
Leucine Amino peptidase (LAP) Test is used to identify catalase negative gram-positive cocci.
The LAP disk is a rapid test for the detection of enzyme lucine amino peptidase.
Leucine-beta-naphthylamide impregnated disk serve as a substrate for the detection of lucine aminopeptidase. Following hydrolysis of the substrate by enzyme, the resulting beta- naphthylamineprodeces a red color upon the addition of cinnamaldehyde reagent.
- Before incubation, slightly dampen the LAP disk with reagent grade water. Do not supersaturate the disk.
- Using a wooden applicator stick, rub a small amount of several colonies of an 18 to 24 hour pure culture onto a small area of the LAP disk.
- Incubate at room temperature for 5 minutes.
- After the incubation period, add 1 drop of cinnamaldehyde reagent.
- Positive: Development of a red color within 1 minute after adding cinnamaldehyde reagent.
- Negative: No color change or development of a slight yellow color.
- Positive: Enterococcus faecalis
- Negative: Leuconostoc spp