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Material Safety Data Sheet

Organisms

Organisms this product works with:

For this Organism

Other products used in the isolation of Salmonellae:

Dehydrated Culture Media

SALMONELLA SHIGELLA AGAR (SS AGAR)

Code: CM0099

A differential selective medium for the isolation of Salmonella and some Shigella species from clinical specimens, foods etc.

Typical Formula*

gm/litre

`Lab-Lemco’ powder

5.0

Peptone

5.0

Lactose

10.0

Bile salts

8.5

Sodium citrate

10.0

Sodium thiosulphate

8.5

Ferric citrate

1.0

Brilliant green

0.00033

Neutral red

0.025

Agar

15.0

pH 7.0 ± 0.2 @ 25°C

 
* Adjusted as required to meet performance standards

Directions
Suspend 63g in 1 litre of distilled water. Bring to the boil with frequent agitation and allow to simmer gently to dissolve the agar. DO NOT AUTOCLAVE. Cool to about 50°C, mix and pour into sterile Petri dishes.

Description
SS Agar is a differential, selective medium for the isolation of Shigella and Salmonella species from pathological specimens, suspected foodstuffs, etc. Gram-positive and coliform organisms are inhibited by the action of the selective inhibitory components brilliant green, bile salts, thiosulphate and citrate.

Thiosulphate in combination with iron also acts as an indicator for sulphide production, which is indicated by blackening in the centres of the colonies.

Technique
Inoculate the medium heavily with the specimen, spreading a portion of the original inoculum in order to obtain well separated colonies on some part of the plate. Incubate for 18 to 24 hours at 35°C; non-lactose fermenters form colourless colonies, whilst occasional resistant coliforms or other lactose fermenters produce pink or red colonies.

In parallel with the SS Agar plate, inoculate a tube of Selenite Broth CM0395 enrichment medium, incubate for 12 hours at 35°C, and sub-culture on to another SS Agar plate.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C.

Appearance
Dehydrated medium: Straw pink coloured, free-flowing powder
Prepared medium: Pink-red coloured gel

Quality control

Positive controls:

Expected results

Salmonella typhimurium ATCC® 14028 *

Good growth; straw coloured colonies with black centres

Shigella sonnei ATCC® 25931 *

Good growth; straw coloured colonies

Negative control:

 

Enterococcus faecalis ATCC® 29212 *

No growth

* This organism is available as a Culti-Loop®

Precautions
This medium is highly selective and R-strains of shigellae will not grow on it. It is not recommended for the primary isolation of shigellae1,2.

References
1. Leifson E. (1935) J. Path. Bact. 40. 581-
2. Taylor W. I. and Harris B. (1965) Am. J. Clin. Path. 44. 476-

 
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