Yersinia Agar Base | DM252D

Yersinia Agar Base | DM252D

For the selective isolation and culture of Yersinia enterocolitica.

It is only fairly recently that the organism Y.enterocolitica has been recognised as a cause of diarrhoeal disease of man and indicated in cases of polyarthiritis, mesenteric adenitis and septicaemia. This delayed recognition is mainly attributed to the lack of appropriate isolation media and selective agents with consequent unawareness of the presence of Y.enterocolitica in clinical specimens and foods. Most routinely used enteric media are inadequate for primary isolation because of the slower growth rate and non-specific appearance on these media of colonies of Y.enterocolitica. MAST Yersinia Agar Base (DM252) is designed for use with MAST Yersinia Selectatab (MS19) to prepare the selective medium recommended by Schiemann1 for the isolation and enumeration of Y.enterocolitica from food and clinical specimens. MAST Yersinia Agar Base (DM252) has several distinct advantages over other enteric media that are commonly used for the isolation of Y.enterocolitica.
Head et al2 reported this formulation to be highly selective against the normal flora found in clinical and environmental specimens and that the colour reaction resulting from mannitol fermentation gave a characteristic appearance to colonies of Y.enterocolitica, enabling them to be easily differentiated from other Gram-negative bacteria growing on this media.
Organisms such as Citrobacter freundii, Serratia liquefaciens and Enterobacter agglomerans all have similar colonial morphology to, and may be isolated with, Y.enterocolitica but they can be easily differentiated by biochemical tests.

Technical Formula

Directions

1. Suspend 57.5g of powder in 1 litre or the contents of the sachet in the stated volume of distilled or deionised water and boil gently until completely dissolved.
2. Autoclave at 121°C (15p.s.i.) for 15 minutes.
3. Mix well before pouring.
4. The medium can be made selective by the use of MAST Yersinia Selectatab (MS19).

In Use

MAST Yersinia Agar Base (DM252) and MAST Yersinia Selectatab (MS19) have been specifically formulated to overcome these problems and give the optimum growth and recovery of Y.enterocolitica.
Specimens may be directly cultured onto plates of MAST Yersinia Agar Base (DM252) containing MAST Yersinia Selectatab (MS19) and incubated at 32°C for 24hrs.
A typical colony of Y.enterocolitica will produce a dark red "bullseye" surrounded by a transparent border. Colony size and the ratio of the border to centre diameter will vary considerably amongst serotypes.