Amies Transport Medium with Charcoal

LAB 124

Description

Amies introduced his modification of Stuarts transport medium to overcome a number of problems. Stuarts transport medium suffered from overgrowth by coliforms that were capable of utilising sodium glycerophosphate. Amies replaced the problem component with an inorganic phosphate buffer system. Calcium and magnesium salts are added to control the permeability of the bacterial cell wall and thus prolong their survival. The addition of charcoal to the medium extended the survival time of Neisseria gonorrhoeae from 24 to 72 hours.

loopful of a fresh culture of the test organism. Up to 4 organisms plate can be tested.

Incubation: 37˚C anaerobically for 24-48 hours. Recognition fermentation: Remove a small plug of agar from below the grow Cover the plug with bromothymol blue indicator (0.04%). Col changes due to production of acidity will develop in a few seco and should be viewed against a white background. Comparison w controls is useful, a plug taken from an area well away from growth can be used as a negative control.

References

Phillips K.D. (1976). A Simple and sensitive technique determining the fermentation reactions of non-sporing anaero J. Appl. Bact. 41: 325-328..

Method for reconstitution

Weigh 19.75 grams of powder, disperse in 1 litre of deionised water. Allow to soak for 10 minutes, swirl to mix then bring to boil to dissolve agar. Distribute into bijou bottles filling to shoulder. Constantly mix whilst distributing. Sterilise by autoclaving at 121˚C for 15 minutes. Screw caps down after autoclaving.

Appearance: Soft gel with heavy concentration of evenly suspended charcoal.

Minimum Q.C. organisms: N. gonorrhoeae S. pyogenes

Storage of Prepared Medium: Capped containers - up to 6 months at 15-20˚C in the dark.

pH: 7.2 ± 0.2

Inoculation: Push the swab containing the sample into the gel to approximately one third of the gels depth. Cut off the unwanted swab stick then screw on the cap pushing the swab further down into the gel. Cap tightly and keep cool during transport to the laboratory.

References

Amies, C.R. (1967). Can. J. Pub. Health. 58: 296-300. A modified formula for the preparation of Stuarts Transport Medium.