Semisolid Nutrient Agar

Semisolid Nutrient Agar is used for the detection of Salmonellae on the basis of motility and hydrogen sulphide production.

Composition**

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 12 grams in 1000 ml distilled water. Heat to boiling to dissolve the medium completely. Dispense in tubes. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Allow the tubes to cool in an upright position.

Principle And Interpretation

Semisolid Nutrient Agar is recommended for detection of Salmonellae on the basis of motility and hydrogen sulphide (H2S) production(2,3). Nutrient Agar is a basic culture medium used in water and food studies. It is generally used for maintenance purpose or to check the purity of subcultures(1). It is recommended for isolation of Salmonella (2,3). Peptic digest of animal tissue and meat extract provide essential growth nutrients. The motile cultures grow away from the stab line while non-motile grow along the stabline. Lead acetate strip incorporation helps to detect H2S production.

Quality Control

Appearance Cream to yellow homogeneous free flowing powder

Gelling Semisolid, comparable with 0.4% Agar gel.

Colour and Clarity of prepared medium Light yellow coloured clear gel forms in tube as butts.

Reaction Reaction of 1.2% w/v aqueous solution at 25°C. pH : 7.0±0.2

pH 6.80-7.20

Cultural Response

M1191S: Cultural characteristics observed after an incubation at 35-37°C for 18-24 hours

Storage and Shelf Life

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

Reference

1. Lappage S.P Shelton J.E. and Mitchelle T.G., 1970, Methods in Microbiology, Norris J.R. and Ribbons D.W. (Eds). Vol. 3A, Academic Press, London.
2. International Organization for Standardization(ISO), 1993, Draft ISO/DIS 6579.
3. Bureau of Indian Standards, IS:5887, (Part 3) 1999.