Aeromonas commonly contaminate fish and related seafood products since they occur widely in aquatic environment. Motile aeromonads have also been associated with refrigerated animal products such as chicken, beef, pork etc (1, 2, 3). The predominant organisms found in these foods are Pseudomonas species with the motile aeromonads present in low numbers (4). Glutamate Starch Phenol Red Agar Base is used for the detection of Pseudomonas and Aeromonas species in foodstuffs, waste water and equipment in the food industry. This medium is a modification of Korths Medium (5), as described by Keilwein (6).
Glutamate Starch Phenol Red Agar Base is based on the ability of Aeromonas to utilize starch with the subsequent production of acid, detected the pH indicator i.e. phenol red. Phenol red changes from red to yellow colour under acidic conditions. Pseudomonas does not utilize starch and therefore does not form yellow colonies. The medium is designed to support the growth of both Pseudomonas and Aeromonas species.
L-glutamate is a source of essential nutrients. Starch is the source of carbon. Phosphate buffers the medium whereas magnesium sulphate is a source of essential ions. Antibiotics help to improve the selectivity of the medium.
The medium may be surface inoculated or used in membrane filtration technique.
Storage and Shelf-life:
Store below 30°C in tightly closed container and prepared medium at 2-8°C. Use before expiry period on the label.
References:
1. Enfors S. O., Molin G. and Ternstrom A., 1979, J. Appl. Bacteriol., 47:197
2. Hunter P. R. and Burge S. H., 1987, Appl. Microbiol., 4:45
3. Kielwein G., Gerlach R. and Johne H., 1969, Areh Zebensmittelhyg., 20:34
4. Vanderzant C. and Splittstoesser D. (Eds.), 1992, Compendium of Methods for the Microbiological Examination of Foods, 3rd Ed., APHA, Washington, D.C.
5. Korth H., 1963, Zbl. Backt. Parasit. Hyg. Abt. 190:225
6. Kielwein G., 1971, Arch. G. Lenensmillehyg. 22:29-37.