Levinthal’s Medium- Composition, Principle, Preparation, Results, Uses

Levinthal’s Medium is used for the cultivation of Haemophilus species. The genus Haemophilus includes a number of species that cause a wide variety of infections but share a common morphology and a requirement for blood-derived factors during growth that has given the genus its name. The Haemophilus genus represents a large group of gram-negative rods that grow on agar-containing blood. The blood provides two factors, which many Haemophilus species require for growth: factor-X and factor-V.

Table of Contents

Composition of Levinthal’s Medium

Ingredients	Gms/liter
Peptic digest of animal tissue	10.000
Beef extract	10.000
Sodium chloride	5.000
Bacitracin	0.300
Agar	20.000

Final pH (at 25°C): 7.6±0.2

Principle of Levinthal’s Medium

Whole blood of rabbit or human blood contains two important factors viz factor-X and factor-V, which are necessary for the growth of type species of influenzae.
Factor-X is a heat stable substance, the hemin associated with hemoglobin, whereas factor-V is a heat labile coenzyme Nicotinamide Adenine Dinucleotide (NAD).
Other nutrients such as nitrogen compounds are supplied by a peptic digest of animal tissue and beef extract incorporated in the medium.
Sodium chloride helps to maintain the osmotic balance of the medium.
The bacitracin added inhibits normal flora, which enhances the recovery of Haemophilus species.
Pathogenic Haemophilus species may be presumptively identified by determining in vitro growth requirements for X and V factors and by hemolytic reactions on the agar.

Preparation of Levinthal’s Medium

Suspend 45 grams in 1000 ml distilled water.
Heat to boiling to dissolve the medium completely.
Dispense in 100 ml amounts and sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes.
Cool to 50°C and add 5 ml sterile rabbit or human blood to 100 ml medium.
Heat the mixture in boiling water bath.
Allow the deposits to settle and dispense clear supernatant.
Pour into sterile petriplates.

Result Interpretation on Levinthal’s Medium

Organisms	Growth
Haemophilus influenza	Luxuriant growth; capsulated strains show translucent colonies with distinctive iridescence; non-capsulated strains are transparent, bluish, and non-iridescent.
Staphylococcus aureus	Luxuriant growth
Streptococcus pyogenes	Luxuriant growth

Uses of Levinthal’s Medium

Levinthal’s Medium Base with the addition of blood is used for cultivation of Haemophilus species.
It can be used for cultivating a variety of fastidious organisms.

Limitation of Levinthal’s Medium

It is recommended that biochemical, immunological, molecular, or mass spectrometry testing be performed on colonies from pure culture for complete identification.

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