Lysine Indole Motility Medium, Modified

LYSINE INDOLE MOTILITY MEDIUM, MODIFIED

PRODUCT SUMMARY AND EXPLANATION
Lysine Indole Motility Medium, Modified is a semisolid medium used for the differentiation of Enterobacteriaceae group by lysine decarboxylation, indole production and motility.

PRINCIPLE
This medium consists of Peptone and yeast extract which supply amino acids and other complex nitrogenous substances. Dextrose (Glucose) is a source of energy. A small amount of agar is added for demonstration of motility along the stab line of inoculation. Growth of motile organisms extends out from the line of inoculation, while non-motile organisms grow only along the stab line. Bromocresol purple serves as the pH indicator. When inoculated with an organism that ferments dextrose, acids are produced that lower the pH, causing the indicator in the medium to change from purple to yellow. The acidic pH also stimulates decarboxylase enzyme activity. Organisms that possess a specific decarboxylase degrade the amino acid provided in the medium, yielding a corresponding amine. Lysine decarboxylation yields cadaverine. The production of these amines elevates the pH and causes the medium in the bottom portion of the tube to revert to a purple color. The medium in the upper portion of the tube remains acidic because of the higher oxygen tension. If the organism being tested does not produce the required decarboxylase, the medium remains yellow (acidic) throughout or yellow with a purple or red reaction near the top. Indole is produced in this medium by organisms that possess the enzyme tryptophanase. Tryptophanase degrades tryptophan, yielding indole. It can be detected in the medium by adding Kovacs reagent to the agar surface. Indole combines with the pdimethylaminobenzaldehyde of Kovacs reagent and produces a red complex.

QUALITY CONTROL SPECIFICATIONS
Appearance of Powder : Cream to greenish yellow homogeneous free flowing powder.
Appearance of prepared medium : Reddish purple coloured clear to slightly opalescent gel forms in tubes as
butts.
pH (at 25°C) : 6.7 ± 0.2