SGAP-10C agar for the isolation and quantification of Aeromonas from water

Glutamate starch penicillin (GSP) medium was used for the simultaneous isolation of Pseudomonas and Aeromonas. Modifications to reduce the number of Pseudomonas and background flora and to improve the recovery of Aeromonas from water samples are described. The original medium was modified by adding glucose and ampicillin. The addition of 10 micrograms/l of C-glucose to the medium (SGAP-10C) permitted better recuperation of stressed cells of aeromonads and the ampicillin reduced the numbers of Pseudomonas. The best temperature for the recovery of aquatic aeromonads was 28 degrees C. The recovery of different species of Aeromonas on SGAP-10C was 93%. The selectivity of the medium was validated because 95.5% of 28 colonies tested with an Aeromonas-like morphology belonged to the genus Aeromonas. Moreover, when 45 strains of different genera were cultured on the medium, only Vibrio alginolyticus presented a confusing morphology. When the SGAP-10C was compared with GSP with 45 river samples, the new medium gave a significantly better recovery of Aeromonas spp., especially when large numbers of Pseudomonas spp. were present. SGAP-10C used at 28 degrees C and 48 h was an efficient selective medium for the isolation of Aeromonas from fresh waters.