Potato Infusion Agar

Potato Infusion Agar is recommended for the isolation of Brucella species.

Composition

Final pH (at 25°C): 6.8±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 49 grams in 1000 ml distilled water containing 20 ml glycerol. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Mix well and pour into sterile Petri plates.

Principle And Interpretation

Brucella is a strictly aerobic, gram-negative coccobacilli which causes Brucellosis. This organism is sometimes carried by animals and only causes incidental infections in humans. Infection usually occurs due to consumption of contaminated milk, meat or direct contact. Potato Infusion Agar is used for the isolation of Brucella species (1). It is also used for the cultivation of Brucella species in large scale for antigen and vaccine preparation. This medium enables Brucella species to form typical colonies when isolated from infected materials.

Potato Infusion Agar medium contains infusion of potato, beef extract and peptic digest of animal tissue which provide necessary nutrients required for the growth of Brucella. Dextrose serves as source of energy and sodium chloride maintains the osmotic equilibrium of the medium.

Quality Control

Appearance: Cream to yellow homogeneous free flowing powder

Gelling: Firm, comparable with 1.5% Agar gel

Colour and Clarity of prepared medium: Yellow coloured clear to slightly opalescent gel forms in Petri plates.

Reaction: Reaction of 4.9% w/v aqueous solution (containing 2% v/v Glycerol) at 25°C.

pH: 6.60-7.00

Cultural Response: M174: Cultural characteristics observed after an incubation at 35 - 37°C for 24 - 72 hours.

Storage and Shelf Life

Store below 30°C in tightly closed container and the prepared medium at 2 - 8°C. Use before expiry date on the label.

Reference

1. Atlas R. M., 1993, Handbook of Microbiological Media, CRC Press, Inc., Boca Raton,