Approximately 40 isolates of Aeromonas hydrophila were subjected to 67 biochemical characteristics. This data was evaluated for distribution and subsequently correlated with in vivo pathogenicity in goldfish using the Pearson, Spearman and Kendall methods.

These statistical studies indicated that 34 (50.8%) of the biochemical characteristics were not correlated with pathogenicity. Of the remaining 33 characters, 7.5% correlated at 0.6; 18% at 0.5; 37.3% at 0.4 and 11.9% correlated at 0 to 0.4 with in vivo pathogenicity.

Individual biochemical characteristics which are most closely related to in vivo pathogenicity are: 1. TSI slant reversion to alkaline reaction,  2. T. esistance to colistin, 3. fermentation of salicin, 4. presence of staphylo lytic enzyme, 5. gas production from salicin, and 6. gas production from trehalose. From a diagnostic standpoint, screening of Aeromonas hydrophila isolates utilizing colistin resistance, reversion of TSI slant and the fermentation with gas of salicin provides an easy method of selecting isolates of significance from disease processes.