Liver Infusion Broth

Intended Use

Liver Infusion Broth is used for cultivating a variety of organisms, particularly Brucella and anaerobes.

Summary and Explanation

Brucellosis is a zoonotic disease with a domestic animal reservoir. Transmission by milk, milk products, meat and direct contact with infected animals is the usual route of exposure.¹

Most strains of Brucella will grow on chocolate or blood agar. However, special media such as liver infusion, tryptose, tryptone or brucella agar are preferred.² The nutritive factors of Liver Infusion media permit luxuriant growth of Brucella and other fastidious pathogens.

For isolating Brucella strains from contaminated milk, crystal violet (gentian violet) can be added to Liver Infusion Agar to suppress gram-positive organisms.³ Five percent (5%) heated horse or rabbit serum enhances growth of Brucella.⁴

Principles of the Procedure

Peptones and infusions provide the nitrogen, amino acids, vitamins and carbon sources in Liver Infusion media. Sodium chloride maintains the osmotic balance. Agar is the solidifying agent.

User Quality Control

Identity Specifications

Liver Infusion Broth
Dehydrated Appearance: Tan, free-flowing, homogeneous.
Solution:                       3.5% solution, soluble in purified water. Solution
                                    is medium to dark amber, clear to very slightly
                                    opalescent with a few particles.
Prepared Appearance:     Medium to dark amber, clear to very slightly
                                    opalescent with a few particles.
Reaction of 3.5%
Solution at 25°C:            pH 6.9 ± 0.2
Cultural Response

Liver Infusion Agar or Liver Infusion Broth
Prepare the medium per label directions. Inoculate and incubate at 35 ± 2°C for 18-48 hours, or up to 72 hours if necessary. Incubate Clostridium under anaerobic conditions. Incubate Brucella spp. and S. pneumoniae with 3-5% CO₂.

*Minimally, one strain of Brucella should be used for performance testing. These ATCC strains should be used if available

Formula

Liver Infusion Agar
Approximate Formula* Per Liter
Beef Liver, Infusion from 500 g.................................... 20.0 g
Proteose Peptone....................................................... 10.0 g
Sodium Chloride........................................................... 5.0 g
Agar.......................................................................... 20.0 g
Liver Infusion Broth
Consists of the same ingredients without the agar
*Adjusted and/or supplemented as required to meet performance criteria.

Precautions⁶

1. Biosafety Level 2 practices, containment equipment and facilities are recommended for activities with clinical specimens of human or animal origin containing or potentially containing pathogenic Brucella spp.
2. Biosafety Level 3 practices, containment equipment and facilities are recommended for all manipulations of cultures of the pathogenic Brucella spp. and for experimental animal studies.

Directions for Preparation from Dehydrated Product

1. Suspend/dissolve the powder in 1 L of purified water:
    Liver Infusion Agar – 55 g;
    Liver Infusion Broth – 35 g.
    Mix thoroughly.
2. Heat the Liver Infusion Agar with frequent agitation and boil for 1 minute to completely dissolve the powder. 3. Autoclave at 121°C for 15 minutes. 4. Test samples of the finished product for performance using stable, typical control cultures.

Procedure

For a complete discussion of the isolation and identification of Brucella, anaerobic microorganisms and other fastidious pathogens, refer to the procedures described in Bailey & Scott’s Diagnostic Microbiology,⁴ Clinical Microbiology Procedures Handbook⁷ and Manual of Clinical Microbiology.⁸

Expected Results

Refer to appropriate references and procedures for results.

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