S.S. Agar 62717 63814 64514 Selective Medium for the Isolation of Salmonella and Shigella

S.S. AGAR 62717 63814 64514 SELECTIVE MEDIUM FOR THE ISOLATION OF SALMONELLA AND SHIGELLA

2014/04

1- INTENDED USE S.S. agar is a differential selective medium for the isolation of Salmonella and certain Shigella species.

2- PRINCIPLE The selectivity of this medium is based on the presence of brilliant green and bile salts which totally inhibit the growth of Gram (+) bacteria and partially inhibit the growth of Enterobacteriaceae and Proteus. The differentiation of Shigella and Salmonella is based on their ability to ferment lactose (colourless colonies) and reduce sulphates into sulphide in the presence of ferric citrate by H2S (+) Salmonella (colonies with a black centre).

3- HOW SUPPLIED  Ready to use medium: - box of 20 Petri dishes (90 mm) (SS) code 63814  Ready to use medium (to be dispensed) - 6 x 200 ml bottles (SS) code 62717  Dehydrated medium - bottle of 500 g code 64514

4- THEORETICAL COMPOSITION (g/l of distilled water) S.S. agar corresponds to an optimization of Citrate Deoxycholate medium described by Leifson (1). Peptone 5 Beef extract 5 Bile salts 4.2 Sodium citrate 10 Sodium thiosulphate 8.5 Ferric citrate 2 Lactose 10 Neutral red 0.025 Brilliant green 0.0003 Agar 12 Final pH 7.0  0.2

Preparation of the medium: Homogenize the powder contained in the bottle. Add 56.7 grams of dehydrated medium to one litre of freshly distilled water. Heat gently, shaking frequently, then heat to boiling until complete dissolution. Allow to cool to 45-50°C before dispensing into Petri dishes or bottles. DO NOT AUTOCLAVE.

5- STORAGE  Ready to use medium: at +2-8°C.  Ready to use medium (to be dispensed): at +2-25°C.  Dehydrated medium: tightly sealed bottle in a dry place at +15-25°C. The expiry date and batch number are indicated on the packaging.

6- INSTRUCTIONS Material:  Material provided: S.S. agar

Inoculation: Inoculate by streaking directly from the specimen to be examined (stool suspension, rectal swabs, food product) or an enrichment broth. For optimal detection of Salmonella and Shigella, it is recommended to inoculate an enrichment broth in parallel:  Selenite-Cystine medium (code 55746)  Muller-Kauffmann Tetrathionate medium (code 56145) Refer to current recommendations for storage of biological specimens (2).

Incubation: Incubate for 24-48 hours at 37°C.

Reading: After 24 hours of incubation, the fermentation of lactose allows differentiation of:  Enterobacter, Klebsiella: red colonies (lactose +)  Salmonella, Shigella and other Enterobacteriaceae: colourless colonies, transparent (lactose –) The production of H2S, characteristic of Salmonella, results in a black pigmentation of the centre of the colonies after 24 to 48 hours. Proteus vulgaris and Proteus mirabilis do not invade S.S. agar.

7- PERFORMANCE/QUALITY CONTROL OF THE TEST  Appearance of the ready to use medium: clear salmon-pink agar.  Appearance of the dehydrated medium: orange powder.  The growth performances of S.S. agar are verified with the following strains:

STRAINS CULTURE RESULT AFTER 24 to 48 hours at 37°C Salmonella Enteritidis ATCC 13076 Colourless colonies with a black centre Shigella sonnei ATCC 25931 Pink colonies Proteus mirabilis ATCC 25933 Colonies with a black centre Escherichia coli ATCC 25922 Partial inhibition, pinkish-red colonies Enterococcus faecalis var zymogenes ATCC 29212 Inhibition

8- QUALITY CONTROL OF THE MANUFACTURER All manufactured reagents are prepared according to our Quality System, starting from reception of raw material to the final commercialization of the product. Each lot is submitted to quality control assessments and is only released to the market, after conforming to pre-defined acceptance criteria. The records relating to production and control of each single lot are kept within Bio-Rad.

9- LIMITS OF USE  Some strains of Shigella or Salmonella from lightly contaminated specimens may not grow on this medium.  Some strains of Enterobacteriaceae and Proteus may grow on this medium. They can be differentiated by their capacity to ferment lactose (pinkish-red colonies).

10- REFERENCES 1. LEIFSON, E.1935. New culture media based on sodium desoxycholate for the isolation of intestinal pathogens and for the enumeration of colon bacilli in milk and water. J. Path. Bacteriol. 40 : 580. 2. Basic Laboratory Procedures in Clinical Bacteriology. World Health Organization. Geneva. 1991.1st edition.

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