Please find the following method link from the US EPA:

http://www.epa.gov/nerlcwww/1605ot01.pdf

Method 1605: Aeromonas in Finished Water by Membrane Filtration Using Ampicillin-Dextrin Agar with Vancomycin (ADA-V) (October 2001) (PDF, 26 pp., 443 KB) -

This method (EPA 821-R-01-034) describes a performance-based membrane filtration technique for the detection and enumeration of Aeromonas species. This method uses a selective medium that partially inhibits the growth of non-target bacterial species while allowing Aeromonas to grow and be detected by the production of acid from dextrin fermentation (causing a pH change producing yellow colonies). The method will be proposed for use in EPA's data gathering and monitoring programs under the Unregulated Contaminant Monitoring Rule.

Summary of Method:

The method provides a direct count of Aeromonas species in water based on the growth of yellow colonies on the surface of the membrane filter using a selective medium. A water sample is filtered through 0.45-Fm-pore-size membrane filter. The filter is placed on ampicillin-dextrin agar with vancomycin (ADA-V) and incubated at 35EC ± 0.5EC for 24 ± 2 hours. This medium uses ampicillin and vancomycin to inhibit non-Aeromonas species, while allowing most Aeromonas species to grow. The medium uses dextrin as a fermentable carbohydrate, and bromothymol blue as an indicator of acidity produced by the fermentation of dextrin. Presumptively identified yellow colonies are counted and confirmed by testing for the presence of cytochrome c (oxidase test), and the ability to ferment trehalose and produce indole.
The membrane filtration procedure provides a direct count of culturable Aeromonas in water samples that is based on the growth of bacterial colonies on the surface of the membrane filter placed on a selective medium.

Aeromonas isolates may be archived for further analysis to determine species or hybridization group by inoculating a nutrient agar slant for short term use or shipping, or nutrient broth for freezing.