Yersinia Selective Agar 500g

Medium proposed by SCHIEMANN (1979) for the selective cultivation of Yersinia, particularly Y. enterocolitica and Y. pseudotuberculosis, from clinical specimens, foodstuffs, water etc.

The medium complies with the recommendations of the APHA (1992) for food examination.

Principle
Microbiological method

Mode of Action
The accompanying flora is largely inhibited by a mixture of antibiotics [Yersinia Selective Supplement (CIN)], crystal violet and bile salts. The growth of Yersinia is, however, promoted by pyruvate and a superior nutrient base. Yersinia degrade the present mannitol to form acid; the colonies therefore turn red due to a change in the colour of the indicator neutral red.

Typical Composition (g/litre)
Peptone from casein 10.0; peptone from meat 10.0; yeast extract
2.0; D(-)mannitol 20.0; sodium pyruvate 2.0; sodium chloride
1.0; magnesium sulfate 0.01; bile salt mixture 1.0; neutral red
0.03; crystal violet 0.001; agar-agar 12.5.

Preparation Note

Experimental Procedure and Evaluation
Inoculate the plates with sample material from an enrichment culture, Yersinia Broth acc. to OSSMER, by the streak-plate method.
Incubation: 24-48 hours at 28 °C aerobically.
Yersinia grows to produce colonies that have a dark red centre and a transparent periphery. The size of the colonies, the width of their edges and their surface structure may vary depending on the serotype.
Certain accompanying microorganisms (e.g. some Enterobacteriaceae and Pseudomonas) may also sometimes exhibit scanty growth.