BRILLIANT GREEN AGAR (ORIGINAL)

 

Selective media for the isolation of Salmonellae from pathological specimens, dairy and food products.

 

Code: CB1/1012

 

Original formula g/l

 

Beef extract	5.0
Yeast extract	3.0
Sodium di-hydrogen orthophosphate	0.6
Sucrose	10.0
Brilliant green	0.0032
Peptone mix	10.0
Disodium hydrogen orthophosphate	1.0
Lactose	10.0
Phenol red	0.09
Agar	12.5

    

pH approx.6.9

 

Directions

 

Suspend by swirling 52.2g in 1 litre or the contents of the sachet in the stated volume of distilled or deionised water. Allow to stand for 15 minutes.  Heat gently with occasional mixing until the medium is completely dissolved.  DO NOT AUTOCLAVE. Cool to 50ºC, mix well and pour plates.

 

Description

 

In 1925 Kristensen et al. first showed the value of incorporating phenol red as an indicator in a brilliant green selective medium for Salmonella spp.  A more recent survey, however, showed wide variations in plating efficiency between laboratories, and further comparative study showed the value of standardised techniques.

 

In Use

 

Inoculate either directly from the specimen or after enrichment in  Selenite F Broth, onto a dried plate of Brilliant Green Agar formulation.  Incubate at 37ºC for 18-48 hours.  Salmonella spp. appear as red colonies surrounded by a bright red halo but Shigella spp.  are inhibited.  If the latter are sought,  XLD Agar should be used in parallel.  Pseudomonas spp. grow as crenated, red colonies and Proteus spp. are either inhibited or grow as red non-swarming colonies.  Most lactose and sucrose fermenting organisms are also inhibited, but occasionally grow as yellow/orange colonies.

 

References

 

1. Kristensen M, Lester V, Jurgens A. Br J Exp Pathol 1952; 6: 291-3.