Rose Bengal Chloramphenicol Agar Base

LAB 36

Description

A selective medium for the enumeration of moulds and yeasts in foods. The original formulation of Jarvis (1973) used chlortetracycline, this has been substituted by chloramphenicol because of superior selectivity. The Rose Bengal dye is taken up by the growing colonies making them easier to see and inhibiting their spreading. Rose Bengal becomes increasingly toxic on exposure to light so it is important to store plates in the dark.

Method for reconstitution

Weigh 28.5 grams of powder, disperse in 1 litre of deionised water, allow to soak for 10 minutes, swirl to mix then sterilise for 15 minutes at 121˚C. Allow to cool to 47˚C then add 2 vials of X009 (X209). Chloramphenicol (or 2 vials X089 oxytetracycline). Mix well, then pour into Petri dishes. This medium should be protected from light. Chloramphenicol may be added before autoclaving.

Appearance: Deep purple/red, clear.

pH: 7.2 ± 0.2

Minimum Q.C. organisms: Aspergillus sp. NCIMB 50097 Sacchromyces cerevisiae E. coli (inhibition) NCIMB 50034

Storage of Prepared Medium: Plates - up to 7 days at 2-8˚C in the dark. Capped Container - up to 1 month at 2-8˚C in the dark.

Inoculation: Surface spreading.

Incubation: 25˚C aerobically for 24 hours to 5 days.